A
rocket is a
missileThough a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
,
spacecraftA spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
,
aircraftAn aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
or other
vehicleA vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
which obtains
thrustThrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
from a
rocket engineA rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...
. In all rockets, the exhaust is formed entirely from
propellantA propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
s carried within the rocket before use. Rocket engines work by
action and reactionThe third of Newton's laws of motion of classical mechanics states that forces always occur in pairs. Every action is accompanied by a reaction of equal magnitude but opposite direction. This principle is commonly known in the Latin language as actio et reactio. The attribution of which of the two...
. Rocket engines push rockets forwards simply by throwing their exhaust backwards extremely fast.
Rockets for military and recreational uses date back to at least 13th century
ChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. Significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry was the enabling technology of the
Space AgeThe Space Age is a time period encompassing the activities related to the Space Race, space exploration, space technology, and the cultural developments influenced by these events. The Space Age is generally considered to have begun with Sputnik...
, including
setting foot on the moonIn early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...
.
Rockets are used for
fireworksFireworks are a class of explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices...
,
weaponA weapon, arm, or armament is a tool or instrument used with the aim of causing damage or harm to living beings or artificial structures or systems...
ry, ejection seats,
launch vehicleIn spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from the Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure....
s for artificial satellites,
human spaceflightHuman spaceflight is spaceflight with humans on the spacecraft. When a spacecraft is manned, it can be piloted directly, as opposed to machine or robotic space probes and remotely-controlled satellites....
and
space explorationSpace exploration is the use of space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
. While comparatively inefficient for low speed use, they are very lightweight and powerful, capable of generating large accelerations and of attaining
extremely high speedsIn physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...
with reasonable efficiency.
Chemical rockets are the most common type of rocket and they typically create their exhaust by the combustion of
rocket propellantRocket propellant is mass that is stored in some form of propellant tank, prior to being used as the propulsive mass that is ejected from a rocket engine in the form of a fluid jet to produce thrust. A fuel propellant is often burned with an oxidizer propellant to produce large volumes of very hot...
. Chemical rockets store a large amount of energy in an easily released form, and can be very dangerous. However, careful design, testing, construction and use minimizes risks.
History of rockets
In antiquity
The availability of black powder (
gunpowderGunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...
) to propel projectiles was a precursor to the development of the first solid rocket. Ninth century
ChineseThe term Chinese people may refer to any of the following:*People with Han Chinese ethnicity ....
Taoist
alchemistsAlchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...
discovered black powder while searching for the
elixir of lifeThe elixir of life, also known as the elixir of immortality and sometimes equated with the philosopher's stone, is a legendary potion, or drink, that grants the drinker eternal life and or eternal youth. Many practitioners of alchemy pursued it. The elixir of life was also said to be able to create...
; this accidental discovery led to experiments as weapons such as
bombA bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy...
s,
cannonA cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...
, incendiary
fire arrowFire arrows are an early form of gun powder rocket which were attached to a stick. The Chinese are credited with the first use of fire arrows in a military application, they may have developed fire arrows from their use of fireworks.- Design :...
s and rocket-propelled fire arrows. The discovery of gunpowder was probably the product of centuries of alchemical experimentation.
Exactly when the first
flightFlight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....
s of rockets occurred is contested. A common claim is that the first recorded use of a rocket in battle was by the Chinese in 1232 against the Mongol hordes at
Kai Feng FuKaifeng , known previously by several names , is a prefecture-level city in east-central Henan province, Central China. Nearly 5 million people live in the metropolitan area...
. This is based on an old Mandarin civil service examination question which reads "Is the defense of Kai Feng Fu against the Mongols (1232) the first recorded use of cannon?". Another question from the examinations read "Fire-arms began with the use of rockets in the dynasty of Chou (B. C. 1122-255)--in what book do we first meet with the word p'ao, now used for cannon?". The first reliable scholarly reference to rockets in China occurs in the Ko Chieh Ching Yuan (The Mirror of Research) which states that in 998 A.D. a man named Tang Fu invented a rocket of a new kind having an iron head. There were reports of fire arrows and 'iron pots' that could be heard for 5
leaguesA league is a unit of length . It was long common in Europe and Latin America, but it is no longer an official unit in any nation. The league originally referred to the distance a person or a horse could walk in an hour...
(25 km, or 15 miles) when they exploded upon impact, causing devastation for a radius of 600 meters (2,000 feet), apparently due to shrapnel. The lowering of the iron pots may have been a way for a besieged army to blow up invaders. The fire arrows were either arrows with explosives attached, or arrows propelled by gunpowder, such as the Korean
HwachaHwacha or Hwach'a is the world's first multiple rocket launcher developed and used in Joseon Korea. It had the ability to fire up to 100 steel-tipped rockets, or 200 Singijeon flaming arrow projectiles from a range of 500 yards in multiple salvos...
.
Less controversially, one of the earliest devices recorded that used internal-combustion rocket propulsion, was the 'ground-rat,' a type of firework recorded in 1264 as having frightened the Empress-Mother Kung Sheng at a feast held in her honor by her son the Emperor Lizong.
Subsequently, one of the earliest texts to mention the use of rockets was the
HuolongjingThe Huolongjing is a 14th century military treatise that was compiled and edited by Jiao Yu and Liu Ji of the early Ming Dynasty in China...
, written by the Chinese artillery officer
Jiao YuJiao Yu was a Chinese military officer loyal to Zhu Yuanzhang , the founder of the Ming Dynasty . He was entrusted by Emperor Hongwu as a leading artillery officer for the rebel army that overthrew the Mongol Yuan Dynasty, and established the Ming Dynasty...
in the mid-14th century. This text also mentioned the use of the first known
multistage rocketA multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...
, the 'fire-dragon issuing from the water' (huo long chu shui), used mostly by the Chinese navy.
Spread of rocket technology
Rocket technology first became known to
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
ans following its use by the Mongols
Genghis KhanGenghis Khan , born Temujin and occasionally known by his temple name Taizu , was the founder and Great Khan of the Mongol Empire, which became the largest contiguous empire in history after his death....
and
Ögedei KhanÖgedei Khan, born Ögedei was the third son of Genghis Khan and second Great Khan of the Mongol Empire by succeeding his father...
when they conquered parts of Russia, Eastern, and Central Europe. The Mongolians had acquired the Chinese technology by conquest of the northern part of China and by the subsequent employment of Chinese rocketry experts as mercenaries for the Mongol military. Reports of the
Battle of MohiThe Battle of Mohi , or Battle of the Sajó River, was the main battle between the Mongol Empire and the Kingdom of Hungary during the Mongol invasion of Europe. It took place at Muhi, Southwest of the Sajó River. After the invasion, Hungary lay in ruins. Nearly half of the inhabited places had...
in the year 1241 describe the use of rocket-like weapons by the Mongols against the Magyars. Rocket technology also spread to
KoreaKorea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
, with the 15th century wheeled
hwachaHwacha or Hwach'a is the world's first multiple rocket launcher developed and used in Joseon Korea. It had the ability to fire up to 100 steel-tipped rockets, or 200 Singijeon flaming arrow projectiles from a range of 500 yards in multiple salvos...
that would launch
singijeonSingijeon or Shinkichon is a multi-launch rocket invented by Korean general Choe Mu-seon in 1377, during the Goryeo Dynasty under King U...
rockets.
Additionally, the spread of rockets into Europe was also influenced by the
OttomansThe Ottoman EmpireIt was usually referred to as the "Ottoman Empire", the "Turkish Empire", the "Ottoman Caliphate" or more commonly "Turkey" by its contemporaries...
at the siege of
ConstantinopleConstantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...
in 1453, although it is very likely that the Ottomans themselves were influenced by the Mongol invasions of the previous few centuries. In their history of rockets published on the Internet,
NASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
says "Rockets appear in Arab literature in 1258 A.D., describing Mongol invaders' use of them on February 15 to capture the city of Baghdad."
Between 1270 and 1280, Hasan al-Rammah wrote
al-furusiyyah wa al-manasib al-harbiyya (
The Book of Military Horsemanship and Ingenious War Devices), which included 107 gunpowder recipes, 22 of which are for rockets. According to
Ahmad Y HassanAhmad Yusuf Al-Hassan is a historian of Arabic and Islamic science and technology, educated in Jerusalem, Cairo and London with a Ph.D. in Mechanical engineering from University College London. He was Dean of Engineering and later President of the University of Aleppo where he founded the...
, al-Rammah's recipes were more explosive than rockets used in China at the time.
The name
Rocket comes from the
ItalianItalian is a Romance language spoken mainly in Europe: Italy, Switzerland, San Marino, Vatican City, by minorities in Malta, Monaco, Croatia, Slovenia, France, Libya, Eritrea, and Somalia, and by immigrant communities in the Americas and Australia...
Rocchetta (i.e.
little fuse), a name of a small firecracker created by the Italian artificer Muratori in 1379.
Konrad KyeserKonrad Kyeser was a German military engineer, author of Bellifortis , a book on siege engines popular throughout the 15th century...
described rockets in his famous military treatise
BellifortisBellifortis is the first fully illustrated manual of military technology, dating from the start of the 15th century...
around 1405.
Between 1529 and 1556
Conrad HaasConrad Haas was a military engineer of the Holy Roman Empire, who is believed to be the first person to describe a multistage rocket in writing.Haas was perhaps born in Dornbach...
wrote a book in which he described rocket technology, involving the combination of
fireworksFireworks are a class of explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices...
and weapons technologies. This manuscript was discovered in 1961, in the Sibiu public records (Sibiu public records
Varia II 374). His work dealt with the theory of motion of multi-stage rockets, different fuel mixtures using liquid fuel, and introduced
deltaDelta is the fourth letter of the Greek alphabet. In the system of Greek numerals it has a value of 4. It was derived from the Phoenician letter Dalet...
-shape
finA fin is a surface used for stability and/or to produce lift and thrust or to steer while traveling in water, air, or other fluid media, . The first use of the word was for the limbs of fish, but has been extended to include other animal limbs and man-made devices...
s and bell-shaped
nozzleA nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....
s.
For over two centuries, the work of
Polish-Lithuanian CommonwealthThe Polish–Lithuanian Commonwealth was a dualistic state of Poland and Lithuania ruled by a common monarch. It was the largest and one of the most populous countries of 16th- and 17th‑century Europe with some and a multi-ethnic population of 11 million at its peak in the early 17th century...
noblemanThe szlachta was a legally privileged noble class with origins in the Kingdom of Poland. It gained considerable institutional privileges during the 1333-1370 reign of Casimir the Great. In 1413, following a series of tentative personal unions between the Grand Duchy of Lithuania and the Kingdom of...
Kazimierz SiemienowiczKazimierz Siemienowicz , was a Polish-Lithuanian general of artillery, gunsmith, military engineer, artillery specialist and pioneer of rocketry. Born in the Grand Duchy of Lithuania, he served the armies of the Polish-Lithuanian Commonwealth, a federation of Poland and the Grand Duchy, and in the...
"
Artis Magnae Artilleriae pars prima" ("Great Art of Artillery, the First Part", also known as "The Complete Art of Artillery"), was used in
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
as a basic artillery manual. First printed in
AmsterdamAmsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...
in 1650 it was translated to
FrenchFrench is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
in 1651,
GermanGerman is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
in 1676,
EnglishEnglish is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
and
DutchDutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...
in 1729 and
PolishPolish is a language of the Lechitic subgroup of West Slavic languages, used throughout Poland and by Polish minorities in other countries...
in 1963. The book provided the standard designs for creating rockets,
fireballsIncendiary weapons, incendiary devices or incendiary bombs are bombs designed to start fires or destroy sensitive equipment using materials such as napalm, thermite, chlorine trifluoride, or white phosphorus....
, and other pyrotechnic devices. It contained a large chapter on caliber, construction, production and properties of rockets (for both military and civil purposes), including
multi-stageA multistage rocket is a rocket that usestwo or more stages, each of which contains its own engines and propellant. A tandem or serial stage is mounted on top of another stage; a parallel stage is attached alongside another stage. The result is effectively two or more rockets stacked on top of or...
rockets, batteries of rockets, and rockets with
delta wingThe delta wing is a wing planform in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta .-Delta-shaped stabilizers:...
stabilizerIn aviation, a stabilizer provides stability when the aircraft is flying straight, and the airfoil of the horizontal stabilizer balances the forces acting on the aircraft....
s (instead of the common guiding rods).
Metal-cylinder rocket artillery
In 1792, the first
iron-cased rocketsMysorean rockets were the first iron-cased rockets that were successfully deployed for military use. Hyder Ali, the 18th century ruler of Mysore, and his son and successor, Tipu Sultan used them effectively against the British East India Company...
were successfully developed and used by
Hyder AliHyder Ali was the de facto ruler of the Kingdom of Mysore in southern India. Born Hyder Naik, he distinguished himself militarily, eventually drawing the attention of Mysore's rulers...
and his son
Tipu SultanTipu Sultan , also known as the Tiger of Mysore, was the de facto ruler of the Kingdom of Mysore. He was the son of Hyder Ali, at that time an officer in the Mysorean army, and his second wife, Fatima or Fakhr-un-Nissa...
, rulers of the
Kingdom of MysoreThe Kingdom of Mysore was a kingdom of southern India, traditionally believed to have been founded in 1399 in the vicinity of the modern city of Mysore. The kingdom, which was ruled by the Wodeyar family, initially served as a vassal state of the Vijayanagara Empire...
in
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
against the larger
British East India CompanyThe East India Company was an early English joint-stock company that was formed initially for pursuing trade with the East Indies, but that ended up trading mainly with the Indian subcontinent and China...
forces during the
Anglo-Mysore WarsThe Anglo-Mysore Wars were a series of wars fought in India over the last three decades of the 18th century between the Kingdom of Mysore and the British East India Company, represented chiefly by the Madras Presidency...
. The British then took an active interest in the technology and developed it further during the 19th century. The Mysore rockets of this period were much more advanced than the British had previously seen, chiefly because of the use of iron tubes for holding the propellant; this enabled higher thrust and longer range for the missile (up to 2 km range). After Tipu's eventual defeat in the
Fourth Anglo-Mysore WarThe Fourth Anglo-Mysore War was a war in South India between the Sultanate of Mysore and the British East India Company under the Earl of Mornington....
and the capture of the Mysore iron rockets, they were influential in British rocket development, inspiring the
Congreve rocketThe Congreve Rocket was a British military weapon designed and developed by Sir William Congreve in 1804.The rocket was developed by the British Royal Arsenal following the experiences of the Second, Third and Fourth Mysore Wars. The wars fought between the British East India Company and the...
, which was soon put into use in the
Napoleonic WarsThe Napoleonic Wars were a series of wars declared against Napoleon's French Empire by opposing coalitions that ran from 1803 to 1815. As a continuation of the wars sparked by the French Revolution of 1789, they revolutionised European armies and played out on an unprecedented scale, mainly due to...
.
Accuracy of early rockets
William CongreveSir William Congreve, 2nd Baronet was an English inventor and rocket artillery pioneer distinguished for his development and deployment of Congreve rockets.-Biography:...
, son of the Comptroller of the Royal Arsenal, Woolwich, London, became a major figure in the field. From 1801, Congreve researched on the original design of
Mysore rocketsMysorean rockets were the first iron-cased rockets that were successfully deployed for military use. Hyder Ali, the 18th century ruler of Mysore, and his son and successor, Tipu Sultan used them effectively against the British East India Company...
and set on a vigorous development program at the Arsenal's laboratory. Congreve prepared a new propellant mixture, and developed a rocket motor with a strong iron tube with conical nose. This early
Congreve rocketThe Congreve Rocket was a British military weapon designed and developed by Sir William Congreve in 1804.The rocket was developed by the British Royal Arsenal following the experiences of the Second, Third and Fourth Mysore Wars. The wars fought between the British East India Company and the...
weighed about 32 pounds (14.5 kilograms). The Royal Arsenal's first demonstration of solid fuel rockets was in 1805. The rockets were effectively used during the Napoleonic Wars and the War of 1812. Congreve published three books on rocketry.
From there, the use of military rockets spread throughout the western world. At the
Battle of BaltimoreThe Battle of Baltimore was a combined sea/land battle fought between British and American forces in the War of 1812. It was one of the turning points of the war as American forces repulsed sea and land invasions of the busy port city of Baltimore, Maryland, and killed the commander of the invading...
in 1814, the rockets fired on
Fort McHenryFort McHenry, in Baltimore, Maryland, is a star-shaped fort best known for its role in the War of 1812, when it successfully defended Baltimore Harbor from an attack by the British navy in Chesapeake Bay...
by the
rocket vesselA rocket vessel was a ship equipped with rockets as a weapon. The most famous ship of this type was HMS Erebus, which at the Battle of Baltimore in 1814 provided the "rockets' red glare" that was memorialized by Francis Scott Key in The Star-Spangled Banner.Rocket vessels were also used by the...
HMS ErebusHMS Erebus was originally built as a Royal Navy fireship, but served as a sloop and was re-rated as such in March 1808. She served in the Baltic during the Gunboat and Anglo-Russian Wars, where in 1809 she was briefly converted to a fireship, and then served in the War of 1812. In 1814 she was...
were the source of the
rockets' red glare described by
Francis Scott KeyFrancis Scott Key was an American lawyer, author, and amateur poet, from Georgetown, who wrote the lyrics to the United States' national anthem, "The Star-Spangled Banner".-Life:...
in
The Star-Spangled Banner"The Star-Spangled Banner" is the national anthem of the United States of America. The lyrics come from "Defence of Fort McHenry", a poem written in 1814 by the 35-year-old lawyer and amateur poet, Francis Scott Key, after witnessing the bombardment of Fort McHenry by the British Royal Navy ships...
. Rockets were also used in the
Battle of WaterlooThe Battle of Waterloo was fought on Sunday 18 June 1815 near Waterloo in present-day Belgium, then part of the United Kingdom of the Netherlands...
.
Early rockets were very inaccurate. Without the use of spinning or any
gimbalA gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of two gimbals, one mounted on the other with pivot axes orthogonal, may be used to allow an object mounted on the innermost gimbal to remain immobile regardless of the motion of its support...
ling of the thrust, they had a strong tendency to veer sharply off course. The early
Mysorean rocketsMysorean rockets were the first iron-cased rockets that were successfully deployed for military use. Hyder Ali, the 18th century ruler of Mysore, and his son and successor, Tipu Sultan used them effectively against the British East India Company...
and their successor British
Congreve rocketThe Congreve Rocket was a British military weapon designed and developed by Sir William Congreve in 1804.The rocket was developed by the British Royal Arsenal following the experiences of the Second, Third and Fourth Mysore Wars. The wars fought between the British East India Company and the...
s reduced this somewhat by attaching a long stick to the end of a rocket (similar to modern bottle rockets) to make it harder for the rocket to change course. The largest of the Congreve rockets was the 32-pound (14.5 kg) Carcass, which had a 15-foot (4.6 m) stick. Originally, sticks were mounted on the side, but this was later changed to mounting in the center of the rocket, reducing drag and enabling the rocket to be more accurately fired from a segment of pipe.
The accuracy problem was greatly improved in 1844 when
William HaleWilliam Hale , was a British inventor and rocket pioneer.- Biography :Hale was born in Colchester, England in 1797. He was self-taught although his grandfather, the educator William Cole, is believed to have tutored him...
modified the rocket design so that thrust was slightly
vectoredThrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....
, causing the rocket to spin along its axis of travel like a bullet. The Hale rocket removed the need for a rocket stick, travelled further due to reduced air resistance, and was far more accurate.
Theories of interplanetary rocketry
At the beginning of the 20th Century, there was a burst of scientific investigation into interplanetary travel, largely driven by the inspiration of fiction by writers such as
Jules VerneJules Gabriel Verne was a French author who pioneered the science fiction genre. He is best known for his novels Twenty Thousand Leagues Under the Sea , A Journey to the Center of the Earth , and Around the World in Eighty Days...
and H.G.Wells. Scientists seized on the rocket as a technology that was able to achieve this in real life.
In 1903, high school mathematics teacher
Konstantin TsiolkovskyKonstantin Eduardovich Tsiolkovsky was an Imperial Russian and Soviet rocket scientist and pioneer of the astronautic theory. Along with his followers the German Hermann Oberth and the American Robert H. Goddard, he is considered to be one of the founding fathers of rocketry and astronautics...
(1857–1935), published
Исследование мировых пространств реактивными приборами (
The Exploration of Cosmic Space by Means of Reaction Devices), the first serious scientific work on space travel. The
Tsiolkovsky rocket equationThe Tsiolkovsky rocket equation, or ideal rocket equation is an equation that is useful for considering vehicles that follow the basic principle of a rocket: where a device that can apply acceleration to itself by expelling part of its mass with high speed and moving due to the conservation of...
—the principle that governs rocket propulsion—is named in his honor (although it had been discovered previously). He also advocated the use of liquid hydrogen and oxygen for propellant, calculating their maximum exhaust velocity. His work was essentially unknown outside the Soviet Union, but inside the country it inspired further research, experimentation and the formation of the
Society for Studies of Interplanetary TravelThe Society for Studies of Interplanetary Travel was founded in Moscow in May 1924. It was a spin off of a military science society at the Zhukovsky Airforce Academy, and was chaired by Grigory Kramarov. Its 200 charter members included important Soviet space-exploration and rocketry experts such...
in 1924.
In 1912,
Robert Esnault-PelterieRobert Albert Charles Esnault-Pelterie was a pioneering French aircraft designer and spaceflight theorist. He was born in Paris, the son of a textile industrialist...
published a lecture on rocket theory and interplanetary travel. He independently derived Tsiolkovsky's rocket equation, did basic calculations about the energy required to make round trips to the Moon and planets, and he proposed the use of atomic power (i.e. Radium) to power a jet drive.
In 1912 Robert Goddard, inspired from an early age by H.G.Wells, began a serious analysis of rockets, concluding that conventional solid-fuel rockets needed to be improved in three ways.
First, fuel should be burned in a small combustion chamber, instead of building the entire propellant container to withstand the high pressures. Second, rockets could be arranged in stages. Finally, the exhaust speed (and thus the efficiency) could be greatly increased to beyond the speed of sound by using a
De Laval nozzleA de Laval nozzle is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass-shape...
. He patented these concepts in 1914. He, also, independently developed the mathematics of rocket flight.
In 1920, Goddard published these ideas and experimental results in
A Method of Reaching Extreme Altitudes. The work included remarks about sending a solid-fuel rocket to the Moon, which attracted worldwide attention and was both praised and ridiculed. A New York Times editorial suggested:
In 1923,
Hermann OberthHermann Julius Oberth was an Austro-Hungarian-born German physicist and engineer. He is considered one of the founding fathers of rocketry and astronautics.- Early life :...
(1894–1989) published
Die Rakete zu den Planetenräumen ("The Rocket into Planetary Space"), a version of his doctoral thesis, after the University of Munich rejected it.
In 1924, Tsiolkovsky also wrote about multi-stage rockets, in 'Cosmic Rocket Trains'
Pre–World War II
Modern rockets were born when Goddard attached a supersonic (
de LavalA de Laval nozzle is a tube that is pinched in the middle, making a carefully balanced, asymmetric hourglass-shape...
) nozzle to a liquid-fueled rocket engine's combustion chamber. These nozzles turn the hot gas from the combustion chamber into a cooler,
hypersonicIn aerodynamics, a hypersonic speed is one that is highly supersonic. Since the 1970s, the term has generally been assumed to refer to speeds of Mach 5 and above...
, highly directed jet of gas, more than doubling the thrust and raising the engine efficiency from 2% to 64%. In 1926, Robert Goddard launched the world's first liquid-fueled rocket in
AuburnAuburn is a town in Worcester County, Massachusetts, United States. The population was 16,188 at the 2010 census.- History :Auburn was first settled in 1789 and was officially incorporated in 1808 as the town of Ward, in honor of American Revolution General Artemas Ward...
, Massachusetts.
During the 1920s, a number of rocket research organizations appeared worldwide. In 1927 the German car manufacturer
OpelAdam Opel AG, generally shortened to Opel, is a German automobile company founded by Adam Opel in 1862. Opel has been building automobiles since 1899, and became an Aktiengesellschaft in 1929...
began to research rocket vehicles together with Mark Valier and the solid-fuel rocket builder Friedrich Wilhelm Sander. In 1928, Fritz von Opel drove with a rocket car, the
Opel-RAKOpel-RAK were a series of rocket vehicles produced by Fritz von Opel, of the Opel car company, in association with others, including Max Valier and Friedrich Wilhelm Sander largely as publicity stunts....
.1 on the Opel raceway in Rüsselsheim, Germany. In 1928 the
Lippisch Ente flew, rocket power was used to launch the manned glider, although it was destroyed on its second flight. In 1929 von Opel started at the Frankfurt-Rebstock airport with the
Opel-Sander RAK 1-airplaneThe Opel RAK.1 was the world's first purpose-built rocket-powered aircraft. It was designed and built by Julius Hatry under commission from Fritz von Opel who flew it on September 30, 1929 in front of a large crowd at Rebstock airport near Frankfurt-am-Main.During the late 1920s, von Opel had...
, which was damaged beyond repair during a hard landing after its first flight.
In the mid-1920s,
GermanThe Weimar Republic is the name given by historians to the parliamentary republic established in 1919 in Germany to replace the imperial form of government...
scientists had begun experimenting with rockets which used liquid propellants capable of reaching relatively high altitudes and distances. In 1927 and also in Germany, a team of amateur rocket engineers had formed the
Verein für RaumschiffahrtThe Verein für Raumschiffahrt was a German amateur rocket association prior to World War II that included members outside of Germany...
(German Rocket Society, or VfR), and in 1931 launched a liquid propellant rocket (using
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and gasoline).
From 1931 to 1937 in Russia, extensive scientific work on rocket engine design occurred in
LeningradLeningrad is the former name of Saint Petersburg, Russia.Leningrad may also refer to:- Places :* Leningrad Oblast, a federal subject of Russia, around Saint Petersburg* Leningrad, Tajikistan, capital of Muminobod district in Khatlon Province...
at the Gas Dynamics Laboratory there. Well-funded and staffed, over 100 experimental engines were built under the direction of
Valentin GlushkoValentin Petrovich Glushko or Valentyn Petrovych Hlushko was a Soviet engineer, and the principal Soviet designer of rocket engines during the Soviet/American Space Race.-Biography:...
. The work included regenerative cooling, hypergolic propellant ignition, and fuel injector designs that included swirling and bi-propellant mixing injectors. However, the work was curtailed by Glushko's arrest during
Stalinist purgesThe Great Purge was a series of campaigns of political repression and persecution in the Soviet Union orchestrated by Joseph Stalin from 1936 to 1938...
in 1938. Similar work was also done by the Austrian professor
Eugen SängerEugen Sänger was an Austrian-German aerospace engineer best known for his contributions to lifting body and ramjet technology.-Early career:...
who worked on rocket-powered spaceplanes such as Silbervogel (sometimes called the 'antipodal' bomber.)
On November 12, 1932 at a farm in Stockton NJ, the American Interplanetary Society's attempt to static fire their first rocket (based on German Rocket Society designs) failed in a fire.
In 1930s, the
ReichswehrThe Reichswehr formed the military organisation of Germany from 1919 until 1935, when it was renamed the Wehrmacht ....
(which in 1935 became the
WehrmachtThe Wehrmacht – from , to defend and , the might/power) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the Heer , the Kriegsmarine and the Luftwaffe .-Origin and use of the term:...
) began to take an interest in rocketry. Artillery restrictions imposed by the
Treaty of VersaillesThe Treaty of Versailles was one of the peace treaties at the end of World War I. It ended the state of war between Germany and the Allied Powers. It was signed on 28 June 1919, exactly five years after the assassination of Archduke Franz Ferdinand. The other Central Powers on the German side of...
limited Germany's access to long distance weaponry. Seeing the possibility of using rockets as long-range
artilleryOriginally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
fire, the Wehrmacht initially funded the VfR team, but because their focus was strictly scientific, created its own research team. At the behest of military leaders,
Wernher von BraunWernher Magnus Maximilian, Freiherr von Braun was a German rocket scientist, aerospace engineer, space architect, and one of the leading figures in the development of rocket technology in Nazi Germany during World War II and in the United States after that.A former member of the Nazi party,...
, at the time a young aspiring rocket scientist, joined the military (followed by two former VfR members) and developed long-range weapons for use in
World War IIWorld War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
by
Nazi GermanyNazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...
.
World War II
In 1943, production of the
V-2 rocketThe V-2 rocket , technical name Aggregat-4 , was a ballistic missile that was developed at the beginning of the Second World War in Germany, specifically targeted at London and later Antwerp. The liquid-propellant rocket was the world's first long-range combat-ballistic missile and first known...
began in Germany. It had an operational range of 300 km (186.4 mi) and carried a 1000 kg (2,204.6 lb) warhead, with an
amatolAmatol is a highly explosive material made from a mixture of TNT and ammonium nitrate. Its name originates from the words ammonium and toluene...
explosive charge. It normally achieved an operational maximum altitude of around 90 km (55.9 mi), but could achieve 206 km (128 mi) if launched vertically. The vehicle was similar to most modern rockets, with
turbopumpA turbopump is a gas turbine that comprises basically two main components: a rotodynamic pump and a driving turbine, usually both mounted on the same shaft, or sometimes geared together...
s,
inertial guidanceA guidance system is a device or group of devices used to navigate a ship, aircraft, missile, rocket, satellite, or other craft. Typically, this refers to a system that navigates without direct or continuous human control...
and many other features. Thousands were fired at various
AlliedThe Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...
nations, mainly Belgium, as well as England and France. While they could not be intercepted, their guidance system design and single conventional warhead meant that it was insufficiently accurate against military targets. A total of 2,754 people in England were killed, and 6,523 were wounded before the launch campaign was ended. There were also 20,000 deaths of slave labour during the construction of V-2s. While it did not significantly affect the course of the war, the V-2 provided a lethal demonstration of the potential for guided rockets as weapons.
In parallel with the guided missile programme in
Nazi GermanyNazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...
, rockets were also used on aircraft, either for assisting horizontal take-off (
JATOJATO is an acronym for jet-fuel assisted take off. It is a system for helping overloaded aircraft into the air by providing additional thrust in the form of small rockets....
), vertical take-off (
Bachem Ba 349The Bachem Ba 349 Natter was a World War II German point-defence rocket powered interceptor, which was to be used in a very similar way to a manned surface-to-air missile. After vertical take-off, which eliminated the need for airfields, the majority of the flight to the Allied bombers was to be...
"Natter") or for powering them (Me 163, etc.). During the war Germany also developed several guided and unguided air-to-air, ground-to-air and ground-to-ground missiles (see
list of World War II guided missiles of Germany).
The Allies rocket programs were much less sophisticated, relying mostly on unguided missiles like the Soviet Katyusha rocket.
Post World War II
At the end of World War II, competing Russian, British, and US military and scientific crews raced to capture technology and trained personnel from the German rocket program at
PeenemündeThe Peenemünde Army Research Center was founded in 1937 as one of five military proving grounds under the Army Weapons Office ....
. Russia and Britain had some success, but the United States benefited the most. The US captured a large number of German rocket scientists (many of whom were members of the
Nazi PartyThe National Socialist German Workers' Party , commonly known in English as the Nazi Party, was a political party in Germany between 1920 and 1945. Its predecessor, the German Workers' Party , existed from 1919 to 1920...
, including von Braun) and brought them to the United States as part of Operation Overcast. In America, the same rockets that were designed to rain down on
BritainThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
were used instead by scientists as research vehicles for developing the new technology further. The V-2 evolved into the American Redstone rocket, used in the early space program.
After the war, rockets were used to study high-altitude conditions, by radio
telemetryTelemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...
of temperature and pressure of the atmosphere, detection of cosmic rays, and further research; notably for the
Bell X-1The Bell X-1, originally designated XS-1, was a joint NACA-U.S. Army/US Air Force supersonic research project built by Bell Aircraft. Conceived in 1944 and designed and built over 1945, it eventually reached nearly 1,000 mph in 1948...
to break the sound barrier. This continued in the US under von Braun and the others, who were destined to become part of the US scientific community.
Independently, in the
Soviet Union's space programThe Soviet space program is the rocketry and space exploration programs conducted by the former Union of Soviet Socialist Republics from the 1930s until its dissolution in 1991...
research continued under the leadership of the chief designer Sergei Korolev. With the help of German technicians, the V-2 was duplicated and improved as the R-1, R-2 and R-5 missiles. German designs were abandoned in the late 1940s, and the foreign workers were sent home. A new series of engines built by Glushko and based on inventions of
Aleksei Mihailovich IsaevAleksei Mikhailovich Isaev was a Russian rocket engineer.Aleksei Isaev began work under Leonid Dushkin during World War II, on an experimental rocket-powered interceptor plane. In 1944 he formed his own design bureau to engineer liquid-propellant engines...
formed the basis of the first ICBM, the R-7. The R-7 launched the first satellite-
Sputnik 1Sputnik 1 ) was the first artificial satellite to be put into Earth's orbit. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957. The unanticipated announcement of Sputnik 1s success precipitated the Sputnik crisis in the United States and ignited the Space...
, and later
Yuri GagarinYuri Alekseyevich Gagarin was a Soviet pilot and cosmonaut. He was the first human to journey into outer space, when his Vostok spacecraft completed an orbit of the Earth on April 12, 1961....
-the first man into space, and the first lunar and planetary probes. This rocket is still in use today. These prestigious events attracted the attention of top politicians, along with additional funds for further research.
One problem that had not been solved was
atmospheric reentryAtmospheric entry is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line,...
. It had been shown that an orbital vehicle easily had enough kinetic energy to vaporize itself, and yet it was known that meteorites can make it down to the ground. The mystery was solved in the US in 1951 when H. Julian Allen and
A. J. Eggers, Jr.Alfred J. Eggers, Jr. was NASA's Assistant Administrator for Policy and devoted efforts to determine the influence of aviation technology in world peace and lectured widely....
of the
National Advisory Committee for AeronauticsThe National Advisory Committee for Aeronautics was a U.S. federal agency founded on March 3, 1915 to undertake, promote, and institutionalize aeronautical research. On October 1, 1958 the agency was dissolved, and its assets and personnel transferred to the newly created National Aeronautics and...
(NACA) made the counterintuitive discovery that a blunt shape (high drag) permitted the most effective heat shield. With this type of shape, around 99% of the energy goes into the air rather than vehicle, and this permitted safe recovery of orbital vehicles.
The Allen and Eggers discovery, though initially treated as a military secret, was eventually published in 1958. The Blunt Body Theory made possible the heat shield designs that were embodied in the
MercuryMercury Program might refer to:*the first successful American manned spaceflight program, Project Mercury*an American post-rock band, The Mercury Program...
and all other space capsules and space planes, enabling astronauts to survive the fiery re-entry into Earth's atmosphere.
Cold war
Rockets became extremely important militarily as modern intercontinental ballistic missiles (ICBMs) when it was realized that nuclear weapons carried on a rocket vehicle were essentially impossible for existing defense systems to stop once launched, and ICBM/Launch vehicles such as the R-7,
AtlasAtlas is a family of U.S. space launch vehicles. The original Atlas missile was designed in the late 1950s and produced by the Convair Division of General Dynamics, to be used as an intercontinental ballistic missile...
and
TitanTitan was a family of U.S. expendable rockets used between 1959 and 2005. A total of 368 rockets of this family were launched, including all the Project Gemini manned flights of the mid-1960s...
became the delivery platform of choice for these weapons.
Fueled partly by the
Cold WarThe Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
, the 1960s became the decade of rapid development of rocket technology particularly in the Soviet Union (
VostokVostok was a family of rockets derived from the Soviet R-7 Semyorka ICBM designed for the human spaceflight programme. This family of rockets launched the first artificial satellite and the first manned spacecraft in human history...
, Soyuz,
ProtonProton is an expendable launch system used for both commercial and Russian government space launches. The first Proton rocket was launched in 1965 and the launch system is still in use as of 2011, which makes it one of the most successful heavy boosters in the history of spaceflight...
) and in the United States (e.g. the X-15 and
X-20 Dyna-SoarThe X-20 Dyna-Soar was a United States Air Force program to develop a spaceplane that could be used for a variety of military missions, including reconnaissance, bombing, space rescue, satellite maintenance, and sabotage of enemy satellites...
aircraft). There was also significant research in other countries, such as Britain, Japan, Australia, etc., and a growing use of rockets for
Space explorationSpace exploration is the use of space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
, with pictures returned from the far side of the
MoonThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and unmanned flights for Mars exploration.
In America the manned programmes,
Project MercuryIn January 1960 NASA awarded Western Electric Company a contract for the Mercury tracking network. The value of the contract was over $33 million. Also in January, McDonnell delivered the first production-type Mercury spacecraft, less than a year after award of the formal contract. On February 12,...
,
Project GeminiProject Gemini was the second human spaceflight program of NASA, the civilian space agency of the United States government. Project Gemini was conducted between projects Mercury and Apollo, with ten manned flights occurring in 1965 and 1966....
and later the Apollo programme culminated in 1969 with the first manned
landing on the moonA moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both manned and unmanned missions. The first human-made object to reach the surface of the Moon was the Soviet Union's Luna 2 mission on 13 September 1959. The United States's Apollo 11 was the first manned...
via the
Saturn VThe Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...
, causing the New York Times to retract their earlier editorial implying that spaceflight couldn't work:
In the 1970s America made further lunar landings, before cancelling the Apollo programme in 1975. The replacement vehicle, the partially reusable '
Space ShuttleThe Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
' was intended to be cheaper, but this large reduction in costs was largely not achieved. Meanwhile in 1973, the expendable
ArianeAriane is a series of a European civilian expendable launch vehicles for space launch use. The name comes from the French spelling of the mythological character Ariadne....
programme was begun, a launcher that by the year 2000 would capture much of the
geosatA geosynchronous Satellite is a satellite whose orbit on the Earth repeats regularly over points on the Earth over time. If such a satellite's orbit lies over the equator, the orbit is circular and its angular velocity is the same as the earth's, then it is called a geostationary satellite...
market.
Current day
Rockets remain a popular military weapon. The use of large battlefield rockets of the V-2 type has given way to guided missiles. However rockets are often used by
helicopterA helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
s and light aircraft for ground attack, being more powerful than
machine gunA machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....
s, but without the recoil of a heavy
cannonA cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...
and by the early 1960s
air-to-air missileAn air-to-air missile is a missile fired from an aircraft for the purpose of destroying another aircraft. AAMs are typically powered by one or more rocket motors, usually solid fuelled but sometimes liquid fuelled...
s became favored. Shoulder-launched rocket weapons are widespread in the anti-tank role due to their simplicity, low cost, light weight, accuracy and high level of damage. Current artillery systems such as the MLRS or BM-30 Smerch launch multiple rockets to saturate battlefield targets with munitions.
Economically, rocketry is the enabler of all
space technologiesSpace technology is technology that is related to entering, and retrieving objects or life forms from space."Every day" technologies such as weather forecasting, remote sensing, GPS systems, satellite television, and some long distance communications systems critically rely on space infrastructure...
particularly
satelliteIn the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s, many of which impact people's everyday lives in almost countless ways.
Scientifically, rocketry has opened a window on the universe, allowing the launch of
space probeA robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...
s to explore the
solar systemThe Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
and space-based telescopes to obtain a clearer view of the rest of the
universeThe Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...
.
However, it is probably manned spaceflight that has predominantly caught the imagination of the public. Vehicles such as the
Space ShuttleThe Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
for scientific research, the
SoyuzSoyuz , Union) is a series of spacecraft initially designed for the Soviet space programme by the Korolyov Design Bureau in the 1960s, and still in service today...
increasingly for orbital tourism and
SpaceShipOne for suborbital tourism may show a trend towards greater commercialisation of manned rocketry.
Types
Vehicle configurations
Rocket vehicles are often constructed in the archetypal tall thin "rocket" shape that takes off vertically, but there are actually many different types of rockets including:
- tiny models such as balloon rocket
A balloon rocket is a balloon filled with air. Besides being simple toys, balloon rockets are a widely used teaching device to demonstrate physical principles and the functioning of a rocket....
s, water rocketA water rocket is a type of model rocket using water as its reaction mass. The pressure vessel—the engine of the rocket—is usually a used plastic soft drink bottle. The water is forced out by a pressurized gas, typically compressed air...
s, skyrocketA skyrocket is a type of firework that uses a solid rocket motor to rise quickly into the sky. At the apex of its ascent, it is usual for a variety of effects to be emitted...
s or small solid rocketsA model rocket is a small rocket that is commonly advertised as being able to be launched by anybody, to, in general, low altitudes and recovered by a variety of means....
that can be purchased at a hobby storeA hobby store sells recreational modelling and craft supplies and specialty magazines for model airplanes , train models, ship models, house and building models. Some hobby shops may also sell dolls, and collectible coins and stamps. A subtype of hobby store is a game store, which sells board...
- missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
s
- space rocket
In spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from the Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure....
s such as the enormous Saturn VThe Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...
used for the Apollo program
- rocket car
A rocket car is a land rocket vehicle powered by a rocket engine. A rocket dragster is a rocket car used for competing in drag racing, and this type holds the unofficial world record for the 1/4 mile....
s
- rocket bike
- rocket-powered aircraft
A rocket-powered aircraft or rocket plane is an aircraft that uses a rocket for propulsion, sometimes in addition to airbreathing jet engines. Rocket planes can achieve much higher speeds than similarly sized jet aircraft, but typically for at most a few minutes of powered operation, followed by a...
(including rocket assisted takeoff of conventional aircraft- JATOJATO is an acronym for jet-fuel assisted take off. It is a system for helping overloaded aircraft into the air by providing additional thrust in the form of small rockets....
)
- rocket sled
A rocket sled is a test platform that slides along a set of rails, propelled by rockets.As its name implies, a rocket sled does not use wheels. Instead, it has sliding pads, called "slippers", which are curved around the head of the rails to prevent the sled from flying off the track...
s
- rocket train
Opel-RAK were a series of rocket vehicles produced by Fritz von Opel, of the Opel car company, in association with others, including Max Valier and Friedrich Wilhelm Sander largely as publicity stunts....
s
- rocket torpedo
The VA-111 Shkval torpedo and its descendants are supercavitating torpedoes developed by the Soviet Union. They are capable of speeds in excess of 200 knots .-Design and capabilities:...
s
- rocket-powered jet pack
Jet pack, rocket belt, rocket pack, and similar names are various types of devices, usually worn on the back, that are propelled by jets of escaping gases so as to allow a single user to fly....
s
- rapid escape systems such as ejection seats and launch escape system
A Launch Escape System is a top-mounted rocket connected to the crew module of a crewed spacecraft and used to quickly separate the crew module from the rest of the rocket in case of emergency. Since the escape rockets are above the crew module, an LES typically uses separate nozzles which are...
s
- space probe
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...
s
Design
A rocket design can be as simple as a cardboard tube filled with black powder, but to make an efficient, accurate rocket or missile involves overcoming a number of difficult problems. The main difficulties include cooling the combustion chamber, pumping the fuel (in the case of a liquid fuel), and controlling and correcting the direction of motion.
Components
Rockets consist of a
propellantRocket propellant is mass that is stored in some form of propellant tank, prior to being used as the propulsive mass that is ejected from a rocket engine in the form of a fluid jet to produce thrust. A fuel propellant is often burned with an oxidizer propellant to produce large volumes of very hot...
, a place to put propellant (such as a
propellant tankA propellant tank is a container which is part of a vehicle, where propellant is stored prior to use. Propellant tanks vary in construction, and may be a fuel tank in the case of many aircraft....
), and a nozzle. They may also have one or more
rocket engineA rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...
s, directional stabilization device(s) (such as
finsFINS is a network protocol used by Omron PLCs, over different physical networks like Ethernet, Controller Link, DeviceNet and RS-232C....
, vernier engines or engine
gimbalA gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of two gimbals, one mounted on the other with pivot axes orthogonal, may be used to allow an object mounted on the innermost gimbal to remain immobile regardless of the motion of its support...
s for
thrust vectoringThrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....
,
gyroscopeA gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...
s) and a structure (typically
monocoqueMonocoque is a construction technique that supports structural load by using an object's external skin, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork...
) to hold these components together. Rockets intended for high speed atmospheric use also have an aerodynamic fairing such as a
nose coneThe term nose cone is used to refer to the forwardmost section of a rocket, guided missile or aircraft. The cone is shaped to offer minimum aerodynamic resistance...
, which usually holds the payload.
As well as these components, rockets can have any number of other components, such as wings (rocketplanes),
parachuteA parachute is a device used to slow the motion of an object through an atmosphere by creating drag, or in the case of ram-air parachutes, aerodynamic lift. Parachutes are usually made out of light, strong cloth, originally silk, now most commonly nylon...
s, wheels (
rocket carA rocket car is a land rocket vehicle powered by a rocket engine. A rocket dragster is a rocket car used for competing in drag racing, and this type holds the unofficial world record for the 1/4 mile....
s), even, in a sense, a person (rocket belt). Vehicles frequently possess
navigation systemAn automotive navigation system is a satellite navigation system designed for use in automobiles. It typically uses a GPS navigation device to acquire position data to locate the user on a road in the unit's map database. Using the road database, the unit can give directions to other locations...
s and
guidance systemA guidance system is a device or group of devices used to navigate a ship, aircraft, missile, rocket, satellite, or other craft. Typically, this refers to a system that navigates without direct or continuous human control...
s which typically use satellite navigation and
inertial navigation systemAn inertial navigation system is a navigation aid that uses a computer, motion sensors and rotation sensors to continuously calculate via dead reckoning the position, orientation, and velocity of a moving object without the need for external references...
s.
Engines
Rocket engines employ the principle of
jet propulsionA jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
. The rocket engines powering rockets come in a great variety of different types, a comprehensive list can be found in
rocket engineA rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...
. Most current rockets are chemically powered rockets (usually internal combustion engines, but some employ a decomposing
monopropellantMonopropellants are propellants composed of chemicals or mixtures of chemicals which can be stored in a single container with some degree of safety. While stable under defined storage conditions, they react very rapidly under certain other conditions to produce a large volume of energetic gases...
) that emit a hot
exhaust gasExhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel oil or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack or propelling nozzle.It often disperses...
. A rocket engine can use gas propellants, solid propellant,
liquid propellantA liquid-propellant rocket or a liquid rocket is a rocket engine that uses propellants in liquid form. Liquids are desirable because their reasonably high density allows the volume of the propellant tanks to be relatively low, and it is possible to use lightweight pumps to pump the propellant from...
, or a
hybrid mixture of both solid and liquidA hybrid rocket is a rocket with a rocket motor which uses propellants in two different states of matter - one solid and the other either gas or liquid. The Hybrid rocket concept can be traced back at least 75 years....
. Some rockets use heat or pressure that is supplied from a source other than the chemical reaction of propellant(s), such as steam rockets,
solar thermal rocketSolar thermal propulsion is a form of spacecraft propulsion that makes use of solar power to directly heat reaction mass, and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. A solar thermal rocket only has to carry the means of capturing solar...
s,
nuclear thermal rocketIn a nuclear thermal rocket a working fluid, usually liquid hydrogen, is heated to a high temperature in a nuclear reactor, and then expands through a rocket nozzle to create thrust. In this kind of thermal rocket, the nuclear reactor's energy replaces the chemical energy of the propellant's...
engines or simple pressurized rockets such as
water rocketA water rocket is a type of model rocket using water as its reaction mass. The pressure vessel—the engine of the rocket—is usually a used plastic soft drink bottle. The water is forced out by a pressurized gas, typically compressed air...
or
cold gas thrusterA cold gas thruster is a rocket engine/thruster that uses a gas as the reaction mass.A cold gas thruster usually simply consists of a pressurized tank containing gas, a valve to control its release and a nozzle, and plumbing connecting them...
s. With combustive propellants a chemical reaction is initiated between the
fuelFuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
and the oxidizer in the
combustionCombustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
chamber, and the resultant hot gases accelerate out of a rocket engine nozzle (or
nozzleA nozzle is a device designed to control the direction or characteristics of a fluid flow as it exits an enclosed chamber or pipe via an orifice....
s) at the rearward-facing end of the rocket. The
accelerationIn physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
of these gases through the engine exerts force ("thrust") on the combustion chamber and nozzle, propelling the vehicle (according to Newton's Third Law).
Propellant
Rocket propellant is mass that is stored, usually in some form of
propellantA propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
tank or casing, prior to being used as the propulsive mass that is ejected from a
rocket engineA rocket engine, or simply "rocket", is a jet engineRocket Propulsion Elements; 7th edition- chapter 1 that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law...
in the form of a
fluidIn physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
jetA jet is an efflux of fluid that is projected into a surrounding medium, usually from some kind of a nozzle, aperture or orifice. Jets can travel long distances without dissipating...
to produce
thrustThrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
. For chemical rockets often the propellants are a fuel such as
liquid hydrogenLiquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be...
or
keroseneKerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
which is burned with an oxidizer such as
liquid oxygenLiquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.-Physical properties:...
or
nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
to produce large volumes of very hot gas. The oxidiser is either kept separate and mixed in the combustion chamber, or comes premixed, as with solid rockets.
Sometimes the propellant is not burned but still undergoes a chemical reaction, and can be a 'monopropellant' such as
hydrazineHydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...
,
nitrous oxideNitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
or
hydrogen peroxideHydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
that can be catalytically decomposed to hot gas.
Alternatively, an inert propellant can be used that can be externally heated, such as in steam rocket,
solar thermal rocketSolar thermal propulsion is a form of spacecraft propulsion that makes use of solar power to directly heat reaction mass, and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. A solar thermal rocket only has to carry the means of capturing solar...
or
nuclear thermal rocketIn a nuclear thermal rocket a working fluid, usually liquid hydrogen, is heated to a high temperature in a nuclear reactor, and then expands through a rocket nozzle to create thrust. In this kind of thermal rocket, the nuclear reactor's energy replaces the chemical energy of the propellant's...
s.
For smaller, low performance, rockets such as attitude control thrusters where high performance is less necessary, a pressurised fluid is used as propellant that simply escapes the spacecraft through a propelling nozzle.
Uses
Rockets or other similar
reaction devicesA reaction engine is an engine or motor which provides propulsion by expelling reaction mass, in accordance with Newton's third law of motion...
carrying their own propellant must be used when there is no other substance (land, water, or air) or force (gravity,
magnetismMagnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
,
lightLight or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
) that a
vehicleA vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
may usefully employ for propulsion, such as in space. In these circumstances, it is necessary to carry all the
propellantA propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
to be used.
However, they are also useful in other situations:
Military
Some military weapons use rockets to propel
warheadThe term warhead refers to the explosive material and detonator that is delivered by a missile, rocket, or torpedo.- Etymology :During the early development of naval torpedoes, they could be equipped with an inert payload that was intended for use during training, test firing and exercises. This...
s to their targets. A rocket and its payload together are generally referred to as a
missileThough a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
when the weapon has a
guidance systemA guidance system is a device or group of devices used to navigate a ship, aircraft, missile, rocket, satellite, or other craft. Typically, this refers to a system that navigates without direct or continuous human control...
(not all missiles use rocket engines, some use other engines such as
jetA jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
s) or as a
rocketA rocket is a self propelled, unguided weapon system powered by a rocket motor.- Categorisation :In military parlance, powered munitions are broadly categorised as follows:* A powered, unguided munition is known as a rocket....
if it is unguided. Anti-tank and anti-aircraft missiles use rocket engines to engage targets at high speed at a range of several miles, while intercontinental ballistic missiles can be used to deliver multiple nuclear warheads thousands of miles, and anti-ballistic missiles try to stop them.
Science & research
Sounding rocketA sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The origin of the term comes from nautical vocabulary, where to sound is to throw a weighted line from a ship into...
s are commonly used to carry instruments that take readings from 50 kilometres (31.1 mi) to 1500 kilometres (932.1 mi) above the surface of the Earth, the altitudes between those reachable by
weather balloonA weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde...
s and satellites.
Rocket engines are also used to propel
rocket sledA rocket sled is a test platform that slides along a set of rails, propelled by rockets.As its name implies, a rocket sled does not use wheels. Instead, it has sliding pads, called "slippers", which are curved around the head of the rails to prevent the sled from flying off the track...
s along a rail at extremely high speed. The world record for this is Mach 8.5.
Spaceflight
Larger rockets are normally launched from a
launch padA launch pad is the area and facilities where rockets or spacecraft lift off. A spaceport can contain one or many launch pads. A typical launch pad consists of the service and umbilical structures. The service structure provides an access platform to inspect the launch vehicle prior to launch....
which serves as stable support until a few seconds after ignition. Due to their high exhaust velocity—2500 m/s (9,000 km/h; 5,592.3 mph) (
MachMach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...
~10+)—rockets are particularly useful when very high speeds are required, such as orbital speed (Mach 24+). Spacecraft delivered into orbital trajectories become artificial satellites which are used for many commercial purposes. Indeed, rockets remain the only way to launch
spacecraftA spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....
into orbit and beyond. They are also used to rapidly accelerate spacecraft when they change orbits or de-orbit for
landingthumb|A [[Mute Swan]] alighting. Note the ruffled feathers on top of the wings indicate that the swan is flying at the [[Stall |stall]]ing speed...
. Also, a rocket may be used to soften a hard parachute landing immediately before touchdown (see
retrorocketA retrorocket is a rocket engine providing thrust opposing the motion of a spacecraft, thereby causing it to decelerate.-History:...
).
Rescue
Rockets were used to propel a line to a stricken ship so that a
Breeches buoyA breeches buoy is a crude rope-based rescue device used to extract people from wrecked vessels, or to transfer people from one location to another in situations of danger. The device resembles a round emergency personal flotation device with a leg harness attached...
can be used to
rescueRescue refers to responsive operations that usually involve the saving of life, or prevention of injury during an incident or dangerous situation....
those on board. Rockets are also used to launch emergency flares.
Some crewed rockets, notably the
Saturn VThe Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...
and
SoyuzThe Soyuz was a Soviet expendable carrier rocket designed by OKB-1 and manufactured by State Aviation Plant No. 1 in Samara, Russia. It was used to launch Soyuz spacecraft as part of the Soyuz programme, initially on unmanned test flights, followed by the first 19 manned launches of the...
have
launch escape systemA Launch Escape System is a top-mounted rocket connected to the crew module of a crewed spacecraft and used to quickly separate the crew module from the rest of the rocket in case of emergency. Since the escape rockets are above the crew module, an LES typically uses separate nozzles which are...
s. This is a small, usually solid rocket that is capable of pulling the crewed capsule away from the main vehicle towards safety at a moments notice. These types of systems have been operated several times, both in testing and in flight, and operated correctly each time.
Solid rocket propelled ejection seats are used in many military aircraft to propel crew away to safety from a vehicle when flight control is lost.
Hobby, sport and entertainment
Hobbyists build and fly a wide variety of
model rocketA model rocket is a small rocket that is commonly advertised as being able to be launched by anybody, to, in general, low altitudes and recovered by a variety of means....
s. Many companies produce model rocket kits and parts but due to their inherent simplicity some hobbyists have been known to make rockets out of almost anything. Rockets are also used in some types of consumer and professional
fireworksFireworks are a class of explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices...
.
Hydrogen peroxideHydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
rockets are used to power jet packs, and have been used to power
carsA rocket car is a land rocket vehicle powered by a rocket engine. A rocket dragster is a rocket car used for competing in drag racing, and this type holds the unofficial world record for the 1/4 mile....
and a rocket car holds the all time (albeit unofficial)
drag racingDrag racing is a competition in which specially prepared automobiles or motorcycles compete two at a time to be the first to cross a set finish line, from a standing start, in a straight line, over a measured distance, most commonly a ¼-mile straight track....
record.
Noise
For all but the very smallest sizes, rocket exhaust compared to other engines is generally very noisy. As the
hypersonicIn aerodynamics, a hypersonic speed is one that is highly supersonic. Since the 1970s, the term has generally been assumed to refer to speeds of Mach 5 and above...
exhaust mixes with the ambient air,
shock waveA shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
s are formed. The
sound intensitySound intensity or acoustic intensity is defined as the sound power Pac per unit area A. The usual context is the noise measurement of sound intensity in the air at a listener's location.-Acoustic intensity:...
from these shock waves depends on the size of the rocket as well as the exhaust speed. The sound intensity of large, high performance rockets could potentially kill at close range.
The
Space ShuttleThe Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
generates over 200 dB(A) of noise around its base. A
Saturn VThe Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...
launch was detectable on
seismometerSeismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources...
s a considerable distance from the launch site.
Noise is generally most intense when a rocket is close to the ground, since the noise from the engines radiates up away from the plume, as well as reflecting off the ground. This noise can be reduced somewhat by flame trenches with roofs, by water injection around the plume and by deflecting the plume at an angle.
For crewed rockets various methods are used to reduce the sound intensity for the passengers, and typically the placement of the astronauts far away from the rocket engines helps significantly. For the passengers and crew, when a vehicle goes
supersonicSupersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...
the sound cuts off as the sound waves are no longer able to keep up with the vehicle.
Operation
The
actionThe third of Newton's laws of motion of classical mechanics states that forces always occur in pairs. Every action is accompanied by a reaction of equal magnitude but opposite direction. This principle is commonly known in the Latin language as actio et reactio. The attribution of which of the two...
of the rocket engine's
combustion chamberA combustion chamber is the part of an engine in which fuel is burned.-Internal combustion engine:The hot gases produced by the combustion occupy a far greater volume than the original fuel, thus creating an increase in pressure within the limited volume of the chamber...
s and expansion nozzles on a high pressure fluid is able to accelerate the fluid to extremely high speed, and conversely this exerts a large reactive thrust on the rocket (an equal and opposite reaction according to Newton's third law) which propels the rocket forwards.
In a closed chamber, the pressures are equal in each direction and no acceleration occurs. If an opening is provided in the bottom of the chamber then the pressure is no longer acting on the missing section. This opening permits the exhaust to escape. The remaining pressures give a resultant thrust on the side opposite the opening, and these pressures are what push the rocket along.
Using a nozzle gives more force as well since the exhaust also presses on it as it expands outwards, roughly doubling the total force. If propellant gas is continuously added to the chamber then these pressures can be maintained for as long as propellant remains.
As a side effect, these pressures on the rocket also act on the exhaust in the opposite direction and accelerate this to very high speeds (according to Newton's Third Law). From the principle of conservation of momentum the speed of the exhaust of a rocket determines how much momentum increase is created for a given amount of propellant. This is called the rocket's
specific impulseSpecific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
. Because a rocket, propellant and exhaust in flight, without any external perturbations, may be considered as a closed system, the total momentum is always constant. Therefore, the faster the net speed of the exhaust in one direction, the greater the speed of the rocket can achieve in the opposite direction. This is especially true since the rocket body's mass is typically far lower than the final total exhaust mass.
As the remaining propellant decreases, rocket vehicles become lighter and their acceleration tends to increase until the propellant is exhausted. This means that much of the speed change occurs towards the end of the burn when the vehicle is much lighter.
Forces on a rocket in flight
The general study of the
forceIn physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
s on a rocket or other spacecraft is part of
ballisticsBallistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...
and is called
astrodynamicsOrbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion and Newton's law of universal gravitation. It...
.
Flying rockets are primarily affected by the following:
- Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
from the engine(s)
- Gravity from celestial bodies
- Drag
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
if moving in atmosphere
- Lift
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
; usually relatively small effect except for rocket-powered aircraftA rocket-powered aircraft or rocket plane is an aircraft that uses a rocket for propulsion, sometimes in addition to airbreathing jet engines. Rocket planes can achieve much higher speeds than similarly sized jet aircraft, but typically for at most a few minutes of powered operation, followed by a...
In addition, the inertia and centrifugal pseudo-force can be significant due to the path of the rocket around the center of a celestial body; when high enough speeds in the right direction and altitude are achieved a stable
orbitIn physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
or
escape velocityIn physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...
is obtained.
These forces, with a stabilizing tail (the
empennageThe empennage , also known as the tail or tail assembly, of most aircraft gives stability to the aircraft, in a similar way to the feathers on an arrow...
) present will, unless deliberate control efforts are made, naturally cause the vehicle to follow a roughly
parabolicIn mathematics, the parabola is a conic section, the intersection of a right circular conical surface and a plane parallel to a generating straight line of that surface...
trajectory termed a
gravity turnA gravity turn or zero-lift turn is a maneuver used in launching a spacecraft into, or descending from, an orbit around a celestial body such as a planet or a moon. This launch trajectory offers two main advantages over a thrust-controlled trajectory where the rocket's own thrust steers the vehicle...
, and this trajectory is often used at least during the initial part of a
launchA rocket launch is the takeoff phase of the flight of a rocket. Launches for orbital spaceflights, or launches into interplanetary space, are usually from a fixed location on the ground, but may also be from a floating platform such as the San Marco platform, or the Sea Launch launch...
. (This is true even if the rocket engine is
mounted at the nosePendulum rocket fallacy is a common fundamental misunderstanding of the mechanics of rocket flight and how rockets remain on a stable trajectory. The first liquid-fuel rocket, constructed by Robert Goddard in 1926, differed significantly from modern rockets in that the rocket engine was at the top...
.) Vehicles can thus maintain low or even zero
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...
which minimizes transverse
stressIn continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...
on the launch vehicle; permitting a weaker, and hence lighter, launch vehicle.
Net thrust
A typical rocket engine can handle a significant fraction of its own mass in propellant each second, with the propellant leaving the nozzle at several kilometres per second. This means that the
thrust-to-weight ratioThrust-to-weight ratio is a ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine. It is a dimensionless quantity and is an indicator of the performance of the engine or vehicle....
of a rocket engine, and often the entire vehicle can be very high, in extreme cases over 100. This compares with other jet propulsion engines that can exceed 5 for some of the better engines.
The propellant flow rate of a rocket is often deliberately varied over a flight, to provide a way to control the thrust and thus the airspeed of the vehicle. This, for example, allows minimization of aerodynamic losses and can limit the increase of
g-forcesThe g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
due to the reduction in propellant load.
It can be shown that the net thrust of a rocket is:
where:
propellant flow (kg/s or lb/s)
the effective exhaust velocity (m/s or ft/s)
The effective exhaust velocity
is more or less the speed the exhaust leaves the vehicle, and in the vacuum of space, the effective exhaust velocity is often equal to the actual average exhaust speed along the thrust axis. However, the effective exhaust velocity allows for various losses, and notably, is reduced when operated within an atmosphere.
Impulse
The total impulse of a rocket burning its propellant is simply:
When there is fixed thrust, this is simply:
Specific impulse
As can be seen from the thrust equation the effective speed of the exhaust controls the amount of thrust produced from a particular quantity of fuel burnt per second.
An equivalent measure, the net thrust-seconds (impulse) per weight unit of propellant expelled is called
specific ImpulseSpecific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
"
" and this is one of the most important figures that describes a rocket's performance. It is defined such that it is related to the effective exhaust velocity by:
where:
has units of seconds
is the acceleration at the surface of the Earth
Thus, the greater the specific impulse, the greater the net thrust and performance of the engine.
is determined by measurement while testing the engine. In practice the effective exhaust velocities of rockets varies but can be extremely high, ~4500 m/s, about 15 times the sea level speed of sound in air.
Delta-v (rocket equation)
The
delta-vIn astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....
capacity of a rocket is the theoretical total change in velocity that a rocket can achieve without any external interference (without air drag or gravity or other forces).
When
is constant, the delta-v that a rocket vehicle can provide can be calculated from the
Tsiolkovsky rocket equationThe Tsiolkovsky rocket equation, or ideal rocket equation is an equation that is useful for considering vehicles that follow the basic principle of a rocket: where a device that can apply acceleration to itself by expelling part of its mass with high speed and moving due to the conservation of...
:
where:
is the initial total mass, including propellant, in kg (or lb)
is the final total mass in kg (or lb)
is the effective exhaust velocity in m/s or (ft/s)
is the delta-v in m/s (or ft/s)
When launched from the Earth practical delta-v's for a single rockets carrying payloads can be a few km/s. Some theoretical designs have rockets with delta-v's over 9 km/s.
The required delta-v can also be calculated for a particular manoeuvre; for example the delta-v to launch from the surface of the Earth to
Low earth orbitA low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
is about 9.7 km/s, which leaves the vehicle with a sideways speed of about 7.8 km/s at an altitude of around 200 km. In this manoeuvre about 1.9 km/s is lost in air drag,
gravity dragIn astrodynamics and rocketry, gravity drag is a measure of the loss in the net performance of a rocket while it is thrusting in a gravitational field...
and
gaining altitudeIn physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
.
The ratio
is sometimes called the
mass ratio.
Mass ratios
Persons not familiar with spaceflight rarely realize that almost all of a launch vehicle's mass consists of propellant. Mass ratio is, for any 'burn', the ratio between the rocket's initial mass and the mass after. Everything else being equal, a high mass ratio is desirable for good performance, since it indicates that the rocket is lightweight and hence performs better, for essentially the same reasons that low weight is desirable in sports cars.
Rockets as a group have the highest
thrust-to-weight ratioThrust-to-weight ratio is a ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine. It is a dimensionless quantity and is an indicator of the performance of the engine or vehicle....
of any type of engine; and this helps vehicles achieve high
mass ratioIn aerospace engineering, mass ratio is a measure of the efficiency of a rocket. It describes how much more massive the vehicle is with propellant than without; that is, it is the ratio of the rocket's wet mass to its dry mass...
s, which improves the performance of flights. The higher the ratio, the less engine mass is needed to be carried. This permits the carrying of even more propellant, enormously improving the delta-v. Alternatively, some rockets such as for rescue scenarios or racing carry relatively little propellant and payload and thus need only a lightweight structure and instead achieve high accelerations. For example, the Soyuz escape system can produce 20g.
Achievable mass ratios are highly dependent on many factors such as propellant type, the design of engine the vehicle uses, structural safety margins and construction techniques.
The highest mass ratios are generally achieved with liquid rockets, and these types are usually used for orbital launch vehicles, a situation which calls for a high delta-v. Liquid propellants generally have densities similar to water (with the notable exceptions of
liquid hydrogenLiquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be...
and liquid
methaneMethane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
), and these types are able to use lightweight, low pressure tanks and typically run high-performance turbopumps to force the propellant into the combustion chamber.
Some notable mass fractions are found in the following table (some aircraft are included for comparison purposes):
Staging
Often, the required velocity (delta-v) for a mission is unattainable by any single rocket because the
propellantA propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
, tankage, structure,
guidanceA guidance system is a device or group of devices used to navigate a ship, aircraft, missile, rocket, satellite, or other craft. Typically, this refers to a system that navigates without direct or continuous human control...
, valves and engines and so on, take a particular minimum percentage of take-off mass that is too great for the propellant it carries to achieve that delta-v.
For example the first stage of the Saturn V, carrying the weight of the upper stages, was able to achieve a
mass ratioIn aerospace engineering, mass ratio is a measure of the efficiency of a rocket. It describes how much more massive the vehicle is with propellant than without; that is, it is the ratio of the rocket's wet mass to its dry mass...
of about 10, and achieved a specific impulse of 263 seconds. This gives a delta-v of around 5.9 km/s whereas around 9.4 km/s delta-v is needed to achieve orbit with all losses allowed for.
This problem is frequently solved by staging — the rocket sheds excess weight (usually empty tankage and associated engines) during launch. Staging is either
serial where the rockets light after the previous stage has fallen away, or
parallel, where rockets are burning together and then detach when they burn out.
The maximum speeds that can be achieved with staging is theoretically limited only by the speed of light. However the payload that can be carried goes down geometrically with each extra stage needed, while the additional delta-v for each stage is simply additive.
Acceleration and thrust-to-weight ratio
From Newton's second law, the acceleration,
, of a vehicle is simply:
Where m is the instantaneous mass of the vehicle and
is the net force acting on the rocket (mostly thrust but air drag and other forces can play a part.)
Typically, the acceleration of a rocket increases with time (if the thrust stays the same) as the weight of the rocket decreases as propellant is burned, but the thrust can be throttled to offset or vary this if needed. Discontinuities in acceleration will also occur when stages burn out, often starting at a lower acceleration with each new stage firing.
Peak accelerations can be increased by designing the vehicle with a reduced mass, usually achieved by a reduction in the fuel load and tankage and associated structures, but obviously this reduces range, delta-v and burn time. Still, for some applications that rockets are used for, a high peak acceleration applied for just a short time is highly desirable.
The minimal mass of vehicle consists of a rocket engine with minimal fuel and structure to carry it. In that case the
thrust-to-weight ratioThrust-to-weight ratio is a ratio of thrust to weight of a rocket, jet engine, propeller engine, or a vehicle propelled by such an engine. It is a dimensionless quantity and is an indicator of the performance of the engine or vehicle....
of the rocket engine limits the maximum acceleration that can be designed. It turns out that rocket engines generally have truly excellent thrust to weight ratios (137 for the
NK-33The NK-33 and NK-43 are rocket engines designed and built in the late 1960s and early 1970s by the Kuznetsov Design Bureau. They were intended for the ill-fated Soviet N-1 rocket moon shot. The NK-33 engine achieves the highest thrust-to-weight ratio of any Earth-launchable rocket engine, whilst...
engine, some solid rockets are over 1000), and nearly all really
high-gThe g-force associated with an object is its acceleration relative to free-fall. This acceleration experienced by an object is due to the vector sum of non-gravitational forces acting on an object free to move. The accelerations that are not produced by gravity are termed proper accelerations, and...
vehicles employ or have employed rockets.
The high accelerations that rockets naturally possess means that rocket vehicles are often capable of
vertical takeoffA vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...
; this can be done provided the vehicles engines provide more than the local gravitational acceleration away from the Earth or gravity source.
Drag
Drag is a force which acts opposite to the direction of the rocket's motion. This will cause a decrease in the acceleration of the vehicle whilst also producing structural loads. The deceleration force for fast-moving rockets can be calculated using the
drag equationIn fluid dynamics, the drag equation is a practical formula used to calculate the force of drag experienced by an object due to movement through a fully enclosing fluid....
.
Drag can be minimised by an aerodynamic
nose coneThe term nose cone is used to refer to the forwardmost section of a rocket, guided missile or aircraft. The cone is shaped to offer minimum aerodynamic resistance...
and by using a shape with a high ballistic coefficient (the "classic" rocket shape—long and thin), and by keeping the rocket's
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...
as low as possible.
During a rocket launch, as the vehicle speed increases, and the atmosphere thins, there is a point of maximum aerodynamic drag called
Max QIn aerospace engineering, the maximum dynamic pressure, often referred to as maximum Q or max Q, is the point at which aerodynamic stress on a vehicle in atmospheric flight is maximized...
. This determines the minimum aerodynamic strength of the vehicle, as the rocket must avoid
bucklingIn science, buckling is a mathematical instability, leading to a failure mode.Theoretically, buckling is caused by a bifurcation in the solution to the equations of static equilibrium...
under these forces.
Energy efficiency
Rocket launch vehicles take-off with a great deal of flames, noise and drama, and it might seem obvious that they are grievously inefficient. However, while they are far from perfect, their energy efficiency is not as bad as might be supposed.
The energy density of a typical rocket propellant is often around one-third that of conventional hydrocarbon fuels; the bulk of the mass is (often relatively inexpensive) oxidizer. Nevertheless, at take-off the rocket has a great deal of energy in the fuel and oxidizer stored within the vehicle. It is of course desirable that as much of the energy of the propellant end up as
kineticThe kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
or
potential energyIn physics, potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. The SI unit of measure for energy and work is the Joule...
of the body of the rocket as possible.
Energy from the fuel is lost in air drag and
gravity dragIn astrodynamics and rocketry, gravity drag is a measure of the loss in the net performance of a rocket while it is thrusting in a gravitational field...
and is used for the rocket to gain altitude and speed. However, much of the lost energy ends up in the exhaust.
In a chemical propulsion device, the engine efficiency is simply the ratio of the kinetic power of the exhaust gases and the power available from the chemical reaction:
100% efficiency within the engine (engine efficiency
) would mean that all the heat energy of the combustion products is converted into kinetic energy of the jet. This is not possible, but the near-adiabatic high expansion ratio nozzles that can be used with rockets come surprisingly close: when the nozzle expands the gas, the gas is cooled and accelerated, and an energy efficiency of up to 70% can be achieved. Most of the rest is heat energy in the exhaust that is not recovered. The high efficiency is a consequence of the fact that rocket combustion can be performed at very high temperatures and the gas is finally released at much lower temperatures, and so giving good Carnot efficiency.
However, engine efficiency is not the whole story. In common with the other
jet-based enginesA jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
, but particularly in rockets due to their high and typically fixed exhaust speeds, rocket vehicles are extremely inefficient at low speeds irrespective of the engine efficiency. The problem is that at low speeds, the exhaust carries away a huge amount of
kinetic energyThe kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
rearward. This phenomenon is termed
propulsive efficiencyIn aircraft and rocket design, overall propulsive efficiency \eta is the efficiency, in percent, with which the energy contained in a vehicle's propellant is converted into useful energy, to replace losses due to air drag, gravity, and acceleration. It can also be stated as the proportion of the...
(
).
However, as speeds rise, the resultant exhaust speed goes down, and the overall vehicle energetic efficiency rises, reaching a peak of around 100% of the engine efficiency when the vehicle is travelling exactly at the same speed that the exhaust is emitted. In this case the exhaust would ideally stop dead in space behind the moving vehicle, taking away zero energy, and from conservation of energy, all the energy would end up in the vehicle. The efficiency then drops off again at even higher speeds as the exhaust ends up travelling forwards- trailing behind the vehicle.
From these principles it can be shown that the propulsive efficiency
for a rocket moving at speed
with an exhaust velocity
is:
And the overall energy efficiency
is:
For example, from the equation, with an
of 0.7, a rocket flying at Mach 0.85 (which most aircraft cruise at) with an exhaust velocity of Mach 10, would have a predicted overall energy efficiency of 5.9%, whereas a conventional, modern, air-breathing jet engine achieves closer to 35% efficiency. Thus a rocket would need about 6x more energy; and allowing for the specific energy of rocket propellant being around one third that of conventional air fuel, roughly 18x more mass of propellant would need to be carried for the same journey. This is why rockets are rarely if ever used for general aviation.
Since the energy ultimately comes from fuel, these considerations mean that rockets are mainly useful when a very high speed is required, such as ICBMs or
orbital launchAn orbital spaceflight is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altitude at perigee above...
. For example
NASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's
space shuttleThe Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
fires its engines for around 8.5 minutes, consuming 1,000 tonnes of solid propellant (containing 16% aluminium) and an additional 2,000,000 litres of liquid propellant (106,261 kg of
liquid hydrogenLiquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be...
fuel) to lift the 100,000 kg vehicle (including the 25,000 kg payload) to an altitude of 111 km and an orbital
velocityIn physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
of 30,000 km/h. At this altitude and velocity, the vehicle has a kinetic energy of about 3 TJ and a potential energy of roughly 200 GJ. Given the initial energy of 20 TJ, the Space Shuttle is about 16% energy efficient at launching the orbiter.
Thus jet engines which have a better match between speed and jet exhaust speed such as turbofans (in spite of their worse
) dominate for subsonic and supersonic atmospheric use while rockets work best at hypersonic speeds. On the other hand rockets do also see many short-range
relatively low speed military applications where their low-speed inefficiency is outweighed by their extremely high thrust and hence high accelerations.
Oberth effect
One subtle feature of rockets relates to energy. A rocket stage, while carrying a given load, is capable of giving a particular
delta-vIn astrodynamics a Δv or delta-v is a scalar which takes units of speed. It is a measure of the amount of "effort" that is needed to change from one trajectory to another by making an orbital maneuver....
. This delta-v means that the speed will increase (or decrease) by a particular amount, which is independent of the initial speed. However, because
kinetic energyThe kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
is a square law on speed, this means that the faster the rocket is travelling before the burn the more orbital energy it gains or loses.
This fact is used in interplanetary travel. It means that the amount of delta-v to reach other planets, over and above that to reach escape velocity can be much less if the delta-v is applied when the rocket is travelling at high speeds, close to the Earth or other planetary surface; whereas waiting till the rocket has slowed at altitude multiplies up the effort required to achieve the desired trajectory.
Safety, reliability and accidents
The reliability of rockets, as for all physical systems, is dependent on the quality of engineering design and construction.
Because of the enormous chemical energy in
rocket propellantRocket propellant is mass that is stored in some form of propellant tank, prior to being used as the propulsive mass that is ejected from a rocket engine in the form of a fluid jet to produce thrust. A fuel propellant is often burned with an oxidizer propellant to produce large volumes of very hot...
s (greater energy by weight than explosives, but lower than
gasolineGasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
), consequences of accidents can be severe. Most space missions have some issues. In 1986, following the
Space Shuttle Challenger DisasterThe Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft disintegrated over the Atlantic Ocean, off the coast of central Florida at 11:38 am EST...
, Richard Feynmann estimated that the chance of an unsafe condition for a launch of the Shuttle was very roughly 1%; more recently the historical per person-flight risk in orbital spaceflight has been calculated to be around 2% or 4%.
Costs and economics
The costs of rockets can be roughly divided into propellant costs, the costs of obtaining and/or producing the 'dry mass' of the rocket and the costs of any required support equipment and facilities.
Most of the takeoff mass of a rocket is normally propellant. However propellant is seldom more than a few times more expensive than gasoline per kg (as of 2009 gasoline is about $1/kg or less), and although substantial amounts are needed, for all but the very cheapest rockets it turns out that the propellant costs are usually comparatively small, although not completely negligible. With liquid oxygen costing $0.15 per kilogram and liquid hydrogen $2.20 per kilogram, the
Space ShuttleThe Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
has a liquid propellant expense of approximately $1.4 million for each launch that costs $450 million from other expenses (with 40% of the mass of propellants used by it being liquids in the external fuel tank, 60% solids in the
SRBsThe Space Shuttle Solid Rocket Boosters were the pair of large solid rockets used by the United States' NASA Space Shuttle during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or...
).
Even though a rocket's non-propellant, dry mass is often only between 1/5th and 1/20th of total mass, nevertheless this cost dominates. For hardware with the performance used in orbital
launch vehiclesIn spaceflight, a launch vehicle or carrier rocket is a rocket used to carry a payload from the Earth's surface into outer space. A launch system includes the launch vehicle, the launch pad and other infrastructure....
, expenses of $2000–$10,000+ per kilogram of
dry weightDry weight is the weight of a vehicle without any consumables, passengers, or cargo.It is one of the two common weight measurements included in road vehicle specifications, the other one being curb weight....
are common, primarily from engineering, fabrication, and testing; raw materials amount to typically around 2% of total expense.
Extreme performance requirements for rockets reaching orbit correlate with high cost, including intensive quality control to ensure reliability despite the limited safety factors allowable for weight reasons. Components produced in small numbers if not individually machined can prevent
amortization of R&D and facility costs over mass production to the degree seen in more pedestrian manufacturing. Amongst liquid-fueled rockets, complexity can be influenced by how much hardware must be lightweight, like pressure-fed engines can have two orders of magnitude lesser part count than pump-fed engines but lead to more weight by needing greater tank pressure, most often used in just small maneuvering thrusters as a consequence.
To change the preceding factors for orbital launch vehicles, proposed methods have included mass-producing simple rockets in large quantities or on large scale, or developing
reusable rocketsA reusable launch system is a launch system which is capable of launching a launch vehicle into space more than once. This contrasts with expendable launch systems, where each launch vehicle is launched once and then discarded.No true orbital reusable launch system is currently in use. The...
meant to fly very frequently to amortize their up-front expense over many payloads, or
reducing rocket performance requirements by constructing a hypothetical
non-rocket spacelaunchNon-rocket space launch is a launch into space where some or all needed speed and altitude is provided by non-rocket means, rather than simply using conventional chemical rockets from the ground. A number of alternatives to rockets have been proposed...
system for part of the velocity to orbit (or all of it but with
most methods involving some rocket use).
The costs of support equipment, range costs and launch pads generally scale up with the size of the rocket, but vary less with launch rate, and so may be considered to be approximately a fixed cost.
Rockets in applications other than launch to orbit (such as military rockets and
rocket-assisted take offJATO is an acronym for jet-fuel assisted take off. It is a system for helping overloaded aircraft into the air by providing additional thrust in the form of small rockets....
), commonly not needing comparable performance and sometimes mass-produced, are often relatively inexpensive.
External links
Governing agencies
Information sites