A
relativistic kill vehicleKill vehicle is a term from space weapon development and science fiction which denotes either a or an explosive warhead supposed to impact on or near a target...
(RKV) or
relativistic bomb is a hypothetical weapon system sometimes found in
science fictionScience fiction is a genre of fiction. It differs from fantasy in that, within the context of the story, its imaginary elements are largely possible within scientifically-established or scientifically-postulated laws of nature...
. The details of such systems vary widely, but the key common feature is the use of a massive impactor traveling at a significant fraction of light speed to strike the target. Therefore the weapon would be an extreme example of the real-life concept of a
kinetic bombardmentA kinetic bombardment is the act of attacking a planetary surface with an inert projectile, where the destructive force comes from the kinetic energy of the projectile impacting at very high velocities. The resulting extreme force can be explained by the formula EK = , where...
.
RKVs have been proposed as a method of
interstellar warIn fiction, an interstellar war is a war between combatants whose respective headquarters lie in different planetary systems. It is a popular plot device in science fiction, especially in the space opera subgenre. An intergalactic war refers to war between combatants of different galaxies...
fare, especially in settings where faster than light travel or sensors are impossible.
A
relativistic kill vehicleKill vehicle is a term from space weapon development and science fiction which denotes either a or an explosive warhead supposed to impact on or near a target...
(RKV) or
relativistic bomb is a hypothetical weapon system sometimes found in
science fictionScience fiction is a genre of fiction. It differs from fantasy in that, within the context of the story, its imaginary elements are largely possible within scientifically-established or scientifically-postulated laws of nature...
. The details of such systems vary widely, but the key common feature is the use of a massive impactor traveling at a significant fraction of light speed to strike the target. Therefore the weapon would be an extreme example of the real-life concept of a
kinetic bombardmentA kinetic bombardment is the act of attacking a planetary surface with an inert projectile, where the destructive force comes from the kinetic energy of the projectile impacting at very high velocities. The resulting extreme force can be explained by the formula EK = , where...
.
RKVs have been proposed as a method of
interstellar warIn fiction, an interstellar war is a war between combatants whose respective headquarters lie in different planetary systems. It is a popular plot device in science fiction, especially in the space opera subgenre. An intergalactic war refers to war between combatants of different galaxies...
fare, especially in settings where faster than light travel or sensors are impossible. By traveling near the speed of light an RKV could substantially limit the amount of early warning detection time. Furthermore, since the destructive effects of the RKV are carried by its kinetic energy, destroying the vehicle near its target would do little to reduce the damage; the cloud of particles or vapor would still be traveling at nearly the same speed and would have little time to disperse. Indeed, some versions of the RKV concept call for the RKV to explode shortly before impact to shower a wide region of space.
As providing terminal guidance for such a high-speed object would likely be difficult, RKVs are usually proposed as a strategic weapon targeted against large and predictable targets such as
planetA planet , is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s. However, they can still be used against smaller targets like spaceships, by aiming the weapons in the area they are in, and detonating a fuse in advance to shatter the mass into swarms of smaller particles, all traveling at nearly the same speed. This would cover a much larger area, and destroy smaller targets in space. Accelerating a mass to such velocities in the first place will likely require vast amounts of energy and large, unwieldy accelerators.
An RKV could theoretically be launched using any of the
spacecraft propulsionSpacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by exhausting a gas from the...
techniques that are capable of accelerating
starshipA starship is a theoretical spacecraft designed for traveling between the stars, as opposed to a vehicle designed for orbital spaceflight or interplanetary travel....
s to relativistic velocities, such as
antimatter rocketAn antimatter rocket is a proposed class of rockets that use antimatter as their power source. There are several types of design that attempt to accomplish this goal...
s,
Bussard ramjetThe Bussard ramjet is a theoretical method of spacecraft propulsion proposed in 1960 by the physicist Robert W. Bussard, popularized by Larry Niven in his Known Space series of books, and referred to by Carl Sagan in the television series and book Cosmos....
systems, or
nuclear pulse propulsionNuclear pulse propulsion is a proposed method of spacecraft propulsion that uses nuclear explosions for thrust. It was first developed as Project Orion by DARPA, after a suggestion by Stanislaw Ulam in 1947...
(see also
relativistic rocketA relativistic rocket is any spacecraft that is travelling at a velocity close enough to light speed for relativistic effects to become significant. What "significant" means is a matter of context, but generally speaking a velocity of at least 50% of the speed of light is required...
s). Since an RKV would be unmanned, higher accelerations could be used (though with most propulsion methods high acceleration may not be the most efficient approach).
In some science fiction smaller relativistic projectiles can sometimes be found depending on the technologies imagined in any particular scenario. In the movie
Eraser, for example, characters used man-portable "gauss rifles" that were able to fire bullets at relativistic velocities. Man-portable weapons of this type would have extreme issues with recoil, however; accelerating a 1 gram projectile up to a mere 1% of light speed would produce enough force to send a 100 kg (220 pound) man flying backward at 30 meters per second (98 feet per second or 67 miles per hour). A further difficulty is reaching such high speeds over such a short distance; to reach 1% of light speed over the length of a one-meter accelerator would require (or over 450 billion
gThe g-force experienced by an object is its acceleration relative to free-fall. The term g-force is considered a misnomer, as g-force is not a force but an acceleration....
) of acceleration. Space-based RKVs have the advantage of being able to accelerate over a vastly longer distance and period of time.
Calculating energy content
Newton'sSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
formula for
kinetic energyThe kinetic energy of an object is the extra 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 current velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its...
, given as , is only an approximation for the kinetic energy of an object, reasonably accurate for speeds well below
cIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
, approximately 3 × 10
8 m s
-1. For higher speeds,
Einstein'sAlbert Einstein was a theoretical physicist. His many contributions to physics include the special and general theories of relativity, the founding of relativistic cosmology, the first post-Newtonian expansion, explaining the perihelion advance of Mercury, prediction of the deflection of...
formula for kinetic energy,
Ek, must be used.
Where:
m is the object's mass in kg,
cIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
is the speed of light in m s
-1,
is the
Lorentz factorThe Lorentz factor or Lorentz term appears in several equations in special relativity, including time dilation, length contraction, and the relativistic mass formula. Because of its ubiquity, physicists generally represent it with the shorthand symbol γ. It gets its name from its earlier...
, given by:
Where
v is the velocity of the object in question.
Therefore, expanded our equation is:
Example
A 1 kg mass traveling at 99% of the speed of light would have a kinetic energy of 5.47×10
17 joules. In explosive terms, it would be equal to 132 megatons of TNT or approximately 32 megatons more than the theoretical max yield of the
tsar bombaTsar Bomba , literally "Tsar-bomb", is the nickname for the AN602 hydrogen bomb — the largest, most powerful nuclear weapon ever detonated, and currently the most powerful explosive ever detonated in human history.Developed by the Soviet Union, the bomb was originally designed to have a yield of...
, the most powerful nuclear weapon ever detonated. 1 kg of mass-energy is 8.99×10
16 joules or about 21.5 megatons of TNT.
Examples of RKVs in fiction
A good example of RKV use in science fiction novels is in
Charles R. PellegrinoCharles R. Pellegrino is a renowned and sometimes controversial author of several books relating to archaeology, including Return to Sodom and Gomorrah, Ghosts of the Titanic , Unearthing Atlantis and Ghosts of Vesuvius.From the inside cover of Ghosts of Vesuvius: Charles Pellegrino has been known...
and
George ZebrowskiGeorge Zebrowski is a science fiction author and editor who has written and edited a number of books...
's
The Killing StarThe Killing Star is a Hard science fiction novel by Charles R. Pellegrino and George Zebrowski, published in April, 1995. It covers several familiar speculative fiction ideas such as sublight interstellar travel, genetic cloning, virtual reality, advanced robotics, alien contact, and interstellar...
and
Flying to Valhalla, wherein aliens exterminate all human life on Earth by kinetic weapons traveling at relativistic velocities called "R-bombs".
W. Michael GearW. Michael Gear is an American writer, and archaeologist born in Colorado Springs, Colorado on May 20, 1955. He is perhaps best known for his First North Americans series, co-authored with wife Kathleen O'Neal Gear.-Biography:...
's "Forbidden Borders" trilogy,
Requiem for the Conqueror-Plot introduction:Set in a future when humanity has forgotten its origins in earth, the novel describes the political equations and power struggle between the emperor, a quasireligious group, a pre-sentient computer named the Magcomm and the Lord Commander....
,
Relic of Empire-Plot introduction:Set in a future when humanity has forgotten its origins in Earth, the novel describes the political equations and power struggle between the emperor, a quasi-religious group, a pre-sentient computer named the Mag Comm and the Lord Commander....
and
Countermeasures also include RKVs. In
A Fire Upon the DeepA Fire Upon the Deep is a science fiction novel written by Vernor Vinge, an award-winning space opera involving superhuman intelligences, aliens, variable physics, space battles, love, betrayal, genocide, and a conversation medium resembling Usenet...
by
Vernor VingeVernor Steffen Vinge is a retired San Diego State University Professor of Mathematics, computer scientist, and science fiction author...
, the destruction of a human civilization is preceded by an RKV assault.
In
Iron SunriseIron Sunrise is a 2004 hard science fiction novel by author Charles Stross, which follows the events in Singularity Sky. The book was nominated for both the Hugo and Locus Awards in 2005....
by
Charles StrossCharles David George "Charlie" Stross is a writer based in Edinburgh, Scotland. His works range from science fiction and Lovecraftian horror to fantasy. Stross was born in Leeds....
, attempts are made to obtain the deactivation codes which will stop a destroyed planet's automated RKV retaliation from destroying another world.
In
David WeberDavid Mark Weber is an American science fiction and fantasy author. He was born in Cleveland, Ohio. Weber and his wife Sharon live in Greenville, South Carolina with their three children and "a passel of dogs"....
's
Honor HarringtonHonor Stephanie Alexander-Harrington is a fictional character, the eponymous heroine of a series of military science fiction books set in the "Honorverse", written by David Weber and published by Baen Books....
series, RKVs are mentioned as a historical weapon, later banned as uncivilized.(see Eridani Edict)
In
Joe HaldemanJoe William Haldeman is an American science fiction author.-Life and work:Haldeman was born June 9, 1943 in Oklahoma City, Oklahoma. His family traveled and he lived in Puerto Rico, New Orleans, Washington, D.C., Bethesda, Maryland and Anchorage, Alaska as a child. Haldeman married Mary Gay...
's
The Forever WarThe Forever War is a 1974 science fiction novel by Joe Haldeman. It won the Nebula Award in 1975, and both the Hugo and Locus Awards in 1976...
, a drone traveling at relativistic speeds changes the outcome of a battle by destroying a much larger enemy battlecruiser as well as, accidentally, part of a moon.
In
Larry NivenLaurence van Cott Niven is a US science fiction author. Perhaps his best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics. It also often includes elements of detective...
's '
Known SpaceKnown Space is the fictional setting of several science fiction novels and short stories written by author Larry Niven. It has also in part been used as a shared universe in the Man-Kzin Wars spin-off anthologies sub-series....
' setting (specifically the '
Man-Kzin WarsThe Man-Kzin Wars is a series of military science fiction short story collections , as well as the eponymous conflicts between mankind and the Kzinti that they detail...
' shared-world series), RKVs were used as part of the counterattack against the Kzinti occupation of the Alpha Centauri system, impacting against the planet Wunderland with a combined energy release equaling 12 gigatons of TNT.
In issue 18 of Marvel Comics'
Supreme PowerThe Squadron Supreme is a fictional superhero team that appears in publications under the mature-audience Marvel MAX imprint by Marvel Comics. The team first appears in Supreme Power #1 and was created by writer J...
series, the main character Hyperion uses his indestructible body as an RKV, slamming himself into the far Northern Hemisphere with enough force to generate a one
teratonA teraton is the equivalent, in SI terms, of being 1.00×1012 tons; 1,000 gigatons; 1,000,000 megatons; 1,000,000,000 kilotons; or 1,000,000,000,000 tons in its entirely expanded form....
explosion.
The
Jack WilliamsonJohn Stewart Williamson , who wrote as Jack Williamson was a U.S. writer often referred to as the "Dean of Science Fiction" following the death in 1988 of Robert A...
story "Nowhere Near" features robots of a defunct alien race that defend their derelict spaceships with
BBBB may refer to:*BB , ammunition for a BB gun-Transportation:*Toyota bB, a car sold in Japan*NZR Bb class, a New Zealand locomotive class*Seaborne Airlines' IATA airline code*Buckingham Branch Railroad's reporting mark...
sized "micro missiles" launched at a substantial fraction of light speed.
In the webcomic
Schlock MercenarySchlock Mercenary is a comedic webcomic written and drawn by Howard Tayler. It follows the tribulations of a star-travelling mercenary company in a satiric, mildly dystopian 31st-century space opera setting...
, RKVs of various sorts are used, such as the cee-sabots deployed by the Partnership Collective fleet and the Tohdfraug assault on the planet Qlaviql.
In the video game series
Halo, over three hundred orbital defense platforms have been positioned by the United Nations Space Command in defense of Earth. These Super-MAC stations fire
magnetically acceleratedA mass driver or electromagnetic catapult is a proposed method of non-rocket spacelaunch that would use a linear motor to accelerate and catapult payloads up to high speeds. All existing and contemplated mass drivers use coils of wire energized by electricity to make electromagnets. Sequential...
projectiles which weigh hundreds of tons and travel at approximately 40% of the speed of light.