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Apollo Command/Service Module

Apollo Command/Service Module

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Apollo CSM

The Apollo 15 CSM in lunar orbit
Description
Role: Earth and Lunar Orbit
Crew: 3; CDR, CM pilot, LM pilot
Dimensions
Height: 36.2 ft 11.03 m
Diameter: 12.8 ft 3.9 m
Volume: 218 ft3 6.17 m3
Mass
Command module: 12,807 lb 5,809 kg
Service module: 54,064 lb 24,523 kg
Total: 66,871 lb 30,332 kg
Rocket engines
CM RCS (UDMH/N2O4) x 12: 92 lbf ea 409 N
SM RCS (MMH
Monomethylhydrazine
Monomethylhydrazine is a volatile hydrazine chemical with the chemical formula CH3 NH2. It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as nitrogen tetroxide and nitric acid...

/N2O4) x 16:
100 lbf ea 445 N
Service Propulsion System
(Aerozine 50
Aerozine 50
Aerozine 50 is a 50/50 mix of hydrazine and unsymmetrical dimethylhydrazine . Originally developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines, Aerozine continues in wide use as a rocket fuel, typically with...

/N2O4) x 1:
20,500 lbf 91,000 N
Performance
Endurance: 14 days
Max delta v: 9,200 ft/s 2,800 m/s
Apollo CSM diagram

Apollo Block II CSM diagram (NASA)


The Command/Service Module (CSM) was one of two spacecraft, along with the Lunar Module
Apollo Lunar Module
The Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman to carry a crew of two from lunar orbit to the surface and back...

, used for the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 Apollo program which landed astronauts on the Moon
Moon
The 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...

. It was built for NASA
NASA
The 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...

 by North American Aviation
North American Aviation
North American Aviation was a major US aerospace manufacturer, responsible for a number of historic aircraft, including the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F-86 Sabre jet fighter, the X-15 rocket plane, and the XB-70, as well as Apollo Command and Service...

. It was launched by itself into suborbital
Sub-orbital spaceflight
A sub-orbital space flight is a spaceflight in which the spacecraft reaches space, but its trajectory intersects the atmosphere or surface of the gravitating body from which it was launched, so that it does not complete one orbital revolution....

 and low Earth orbit
Low Earth orbit
A 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...

 test missions with the Saturn IB
Saturn IB
The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration for use in the Apollo program...

 launch vehicle, and three times by itself and nine times with the Lunar Module as part of the Apollo spacecraft assembly on the larger Saturn V
Saturn V
The 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 vehicle, which was capable of sending it to the Moon.

After the Apollo lunar program, the CSM saw manned service as a crew shuttle for the Skylab
Skylab
Skylab was a space station launched and operated by NASA, the space agency of the United States. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V rocket, with a mass of...

 program, and the Apollo-Soyuz Test Project
Apollo-Soyuz Test Project
-Backup crew:-Crew notes:Jack Swigert had originally been assigned as the command module pilot for the ASTP prime crew, but prior to the official announcement he was removed as punishment for his involvement in the Apollo 15 postage stamp scandal.-Soyuz crew:...

 in which an American crew rendezvoused
Space rendezvous
A space rendezvous is an orbital maneuver during which two spacecraft, one of which is often a space station, arrive at the same orbit and approach to a very close distance . Rendezvous requires a precise match of the orbital velocities of the two spacecraft, allowing them to remain at a constant...

 and docked with a Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 Soyuz spacecraft
Soyuz spacecraft
Soyuz , 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...

 in Earth orbit.

The CSM consisted of two segments: the Command Module, a cabin which housed a crew of three and equipment needed for re-entry
Re-Entry
"Re-Entry" was the second album released by UK R&B / Hip Hop collective Big Brovaz. After the album was delayed in May 2006, the band finally release the follow-up to "Nu Flow" on 9 April 2007...

 and splashdown
Splashdown (spacecraft landing)
Splashdown is the method of landing a spacecraft by parachute in a body of water. It was used by American manned spacecraft prior to the Space Shuttle program. It is also possible for the Russian Soyuz spacecraft and Chinese Shenzhou spacecraft to land in water, though this is only a contingency...

; and a Service Module that provided propulsion, electrical power and storage for various consumables required during a mission. The Service Module was cast off and allowed to burn up in the atmosphere before the Command Module re-entered and brought the crew home.

The CSM was initially designed to return all three astronauts from the lunar surface on a direct-descent mission which would not use a separate Lunar Module, and thus had no provisions for docking with another spacecraft. This, plus other required design changes led to the decision to design two versions of the CSM: Block I was to be used for unmanned missions and a single manned Earth orbit flight (Apollo 1
Apollo 1
Apollo 1 was scheduled to be the first manned mission of the Apollo manned lunar landing program, with a target launch date of February 21, 1967. A cabin fire during a launch pad test on January 27 at Launch Pad 34 at Cape Canaveral killed all three crew members: Command Pilot Virgil "Gus"...

), while the more advanced Block II was designed for use with the Lunar Module. But the Apollo 1 flight was cancelled by a cabin fire which killed the crew and destroyed the Command Module during a launch rehearsal test. Corrections of the problems which caused the fire were applied to the Block II spacecraft, which was used for all manned missions.

Development history


In 1964, NASA decided to build the Command/Service Module in two versions:
  • Block I to be used for early low earth orbit test flights only. This version of the spacecraft contained no capability for rendezvous and docking with the Lunar Module.
  • Block II, the lunar-capable version which included rendezvous and docking capability.


Block I spacecraft were used for all unmanned Saturn 1B and Saturn V test flights. Initially two manned flights were planned, but this was reduced to one in late 1966. This mission, designated AS-204 but named Apollo 1
Apollo 1
Apollo 1 was scheduled to be the first manned mission of the Apollo manned lunar landing program, with a target launch date of February 21, 1967. A cabin fire during a launch pad test on January 27 at Launch Pad 34 at Cape Canaveral killed all three crew members: Command Pilot Virgil "Gus"...

 by its flight crew, was planned for launch on February 21, 1967. But during a dress rehearsal for the launch on January 27, all three astronauts (Virgil I. "Gus" Grissom
Gus Grissom
Virgil Ivan Grissom , , better known as Gus Grissom, was one of the original NASA Project Mercury astronauts and a United States Air Force pilot...

, Edward H. White, II
Edward Higgins White
Edward Higgins White, II was an engineer, United States Air Force officer and NASA astronaut. On June 3, 1965, he became the first American to "walk" in space. White died along with fellow astronauts Gus Grissom and Roger Chaffee during a pre-launch test for the first manned Apollo mission at...

 and Roger Chaffee
Roger B. Chaffee
Roger Bruce Chaffee was an American aeronautical engineer and a NASA astronaut in the Apollo program. Chaffee died along with fellow astronauts Gus Grissom and Ed White during a pre-launch test for the Apollo 1 mission at Cape Kennedy...

), were killed in a cabin fire which revealed serious design, construction and maintenance shortcomings in Block I, many of which were carried over into Block II.

After a thorough investigation by the Apollo 204 Review Board, it was decided to terminate the manned Block I phase and redefine Block II to incorporate the review board's recommendations. Block II incorporated a revised CM heat shield design, which was tested on the unmanned Apollo 4 and Apollo 6 flights, so the first all-up Block II spacecraft flew on the first manned mission, Apollo 7
Apollo 7
Apollo 7 was the first manned mission in the American Apollo space program, and the first manned US space flight after a cabin fire killed the crew of what was to have been the first manned mission, AS-204 , during a launch pad test in 1967...

.

The two blocks were essentially similar in overall dimensions, but several design improvements resulted in weight reduction in Block II. The Apollo 1 spacecraft weighed 45,000 lb (20,412 kg), while Apollo 7 weighed only 36,993 lb. (16,520 kg.) Also, the Block I Service Module propellant tanks were slightly larger than in Block II. In the specifications given below, unless otherwise noted, all weights given are for the Block II spacecraft.

Command Module (CM)


The Command Module was a truncated cone (frustum) measuring 10 feet 7 inches (3.2 m) tall and having a diameter of 12 feet 10 inches (3.9 m) across the base. The forward compartment contained two reaction control engines
Reaction control system
A reaction control system is a subsystem of a spacecraft whose purpose is attitude control and steering by the use of thrusters. An RCS system is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is also capable of providing torque to allow...

, the docking tunnel, and the components of the Earth Landing System. The inner pressure vessel housed the crew accommodations, equipment bays, controls and displays, and many spacecraft
Spacecraft
A 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....

 systems. The last section, the aft compartment, contained 10 reaction control engines and their related propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...

 tanks, fresh water tanks, and the CSM umbilical cables.

Construction


The command module's inner structure was an aluminum "sandwich" consisting of a welded aluminum inner skin, a thermally bonded honeycomb core, and a thin aluminum "face sheet". The central heat shield
Heat shield
A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat...

 consisted of 40 individual panels interspersed with several holes and openings for the reaction control engines and after-compartment equipment access. The central compartment structure consisted of an inner aluminum face sheet with a steel honeycomb core, a glass-phenolic ablative honeycomb heat shield, a layer of q-felt fibrous insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...

, a pore seal, a moisture barrier, and a layer of aluminized PET film thermal strips.

The aft heat shield consisted of four brazed honeycomb panels, four spot-welded sheet metal fairings, and a circumferential ring. The fairing segments were attached to the honeycomb panels and ring with conventional fasteners. The steel honeycomb core and outer face sheets were then thermally bonded to the inner skin in a giant autoclave
Autoclave
An autoclave is an instrument used to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C for around 15–20 minutes depending on the size of the load and the contents. It was invented by Charles Chamberland in 1879, although a precursor known as the...

. The aft heat shield is nearly identical to the central, with the exception of the outer alluminized PET film layer.

Earth landing system


The components of the ELS were housed around the forward docking tunnel. The forward compartment was separated from the central by a bulkhead and was divided into four 90-degree wedges. The ELS consisted of three main parachute
Parachute
A 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, three pilot parachutes, two drogue parachute motors, three upright bags, a sea recovery cable, a dye marker, and a swimmer umbilical.

The Command Module's center of mass was offset a foot or so from the center of pressure (along the symmetry axis). This provided a rotational moment during reentry, angling the capsule and providing some lift (a lift to drag ratio of about 0.368). The capsule was then steered by rotating the capsule using thrusters; when no steering was required, the capsule was spun slowly, and the lift effects cancelled out. This system greatly reduced the g-force
G-force
The 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...

 experienced by the astronauts, permitted a reasonable amount of directional control and allowed the capsule's splashdown point to be targeted within a few miles.

At 24000 feet (7.3 km) the forward heat shield was jettisoned using four pressurized-gas compression springs. The drogue parachutes were then deployed and slowed the spacecraft to 125 miles per hour (201 km/h). At 10700 feet (3.3 km) the drogue's were jettisoned and the pilot parachutes, which pulled out the mains, were deployed. These slowed the CM to 22 miles per hour (35 km/h) for splashdown. The portion of the capsule which first contacted the water surface was built with crushable ribs to further mitigate the force of impact. The Apollo Command Module could safely parachute to an ocean landing with at least two parachutes (as occurred on Apollo 15
Apollo 15
Apollo 15 was the ninth manned mission in the American Apollo space program, the fourth to land on the Moon and the eighth successful manned mission. It was the first of what were termed "J missions", long duration stays on the Moon with a greater focus on science than had been possible on previous...

), the third parachute being a safety precaution.

Reaction Control System


The Command Module attitude control system consisted of twelve 93 pound-forces (413.7 N) attitude control jets; ten were located in the aft compartment, and two pitch motors in the forward compartment. Four tanks stored 270 pounds (122.5 kg) of mono-methyl hydrazine
Monomethylhydrazine
Monomethylhydrazine is a volatile hydrazine chemical with the chemical formula CH3 NH2. It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as nitrogen tetroxide and nitric acid...

 fuel and nitrogen tetroxide oxidizer. They were pressurized by 1.1 pound (0.498951607 kg) of helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

 stored at 4150 pound per square inches (28.6 MPa) in two tanks.

Hatches


The forward docking hatch was mounted at the top of the docking tunnel. It was 30 inch (0.762 m) in diameter and weighed 80 pounds (36.3 kg). It was constructed from two machined rings that were weld-joined to a brazed honeycomb panel. The exterior side was covered with a 0.5 inches (12.7 mm) of insulation and a layer of aluminum foil. It was latched in six places and operated by a pump handle. At the center was a pressure equalization
Equalization
Equalization, is the process of adjusting the balance between frequency components within an electronic signal. The most well known use of equalization is in sound recording and reproduction but there are many other applications in electronics and telecommunications. The circuit or equipment used...

 valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...

, used to equalize the pressure in the tunnel and lunar module before the hatch was removed.

The Unified Crew Hatch (UCH) measured 29 inches (73.7 cm) high, 34 inches (864 mm) wide, and weighed 225 pounds (102.1 kg). It was operated by a pump handle, which drove a ratchet
Ratchet (device)
A ratchet is a device that allows continuous linear or rotary motion in only one direction while preventing motion in the opposite direction. Because most socket wrenches today use ratcheting handles, the term "ratchet" alone is often used to refer to a ratcheting wrench, and the terms "ratchet"...

 mechanism to open or close fifteen latches simultaneously.

Docking assembly


The Apollo spacecraft docking mechanism was a non-androgynous system, consisting of a probe located in the nose of the CSM, which connected to the drogue, a truncated cone located on the Lunar Module. The probe was extended like a scissor jack to capture the drogue on initial contact, known as "soft docking". Then the probe was retracted to pull the vehicles together and establish a firm connection, known as "hard docking". The mechanism was specified by NASA to have the following functions:
  • Allow the two vehicles to connect, and attenuate excess movement and energy caused by docking
  • Align and center the two vehicles and pull them together for capture
  • Provide a rigid structural connection between both vehicles, and be capable of removal and re-installation by a single crewman
  • Provide a means of remote separation of both vehicles for the return to Earth, using pyrotechnic fastener
    Pyrotechnic fastener
    A pyrotechnic fastener is a fastener, usually a nut or bolt, that incorporates a pyrotechnic charge that can be initiated remotely. One or more explosive charges embedded within the bolt are typically activated by an electric current, and the charge breaks the bolt into two or more pieces...

    s at the circumference of the CSM docking collar
  • Provide redundant power and logic circuits for all electrical and pyrotechnic components.

Coupling


The probe head located in the CSM was self-centering and gimbal-mounted to the probe piston. As the probe head engaged in the opening of the drogue socket, three spring-loaded latches depressed and engaged. These latches allowed a so called 'soft dock' state and enabled the pitch and yaw movements in the two vehicles to subside. Excess movement in the vehicles during the 'hard dock' process could cause damage to the docking ring and put stress on the upper tunnel. A depressed locking trigger link at each latch allowed a spring-loaded spool to move forward, maintaining the toggle linkage in an over-center locked position. In the upper end of the Lunar Module tunnel, the drogue, which was constructed of 1-inch-thick aluminum honeycomb core, bonded front and back to aluminum face sheets, was the receiving end of the probe head capture latches.

Retraction


After the initial capture and stabilization of the vehicles, the probe was capable of exerting a closing force of 1000 pound-forces (4.4 kN) to draw the vehicles together. This force was generated by gas pressure acting on the center piston within the probe cylinder. Piston retraction compressed the probe and interface seals and actuated the 12 automatic ring latches which were located radially around the inner surface of the CSM docking ring. The latches were manually re-cocked in the docking tunnel by an astronaut after each hard docking event (lunar missions required two dockings).

Separation


An automatic extension latch attached to the probe cylinder body engaged and retained the probe center piston in the retracted position. Before vehicle separation in lunar orbit, manual cocking of the twelve ring latches was accomplished. The separating force from the internal pressure in the tunnel area was then transmitted from the ring latches to the probe and drogue.
In undocking, the release of the capture latches was accomplished by electrically energizing tandem-mounted DC torque motors located in the center piston. In a temperature degraded condition, a single motor release operation was done manually in the Lunar Module by depressing the locking spool through an open hole in the probe heads, while release from the CSM was done by rotating a release handle at the back of the probe to rotate the motor torque shaft manually.
When the Command and Lunar Modules separated for the last time just before re-entry, the probe and forward docking ring were pyrotechnically separated, leaving all docking equipment attached to the lunar module. In the event of an abort during launch from Earth, the same system would have explosively jettisoned the docking ring and probe from the CM as it separated from the boost protective cover.

Cabin interior arrangement


The central pressure vessel of the command module was its sole habitable compartment. It had an interior volume of 210 ft3 and housed the main control panels, crew seats, guidance and navigation systems, food and equipment lockers, the waste management system, and the docking tunnel.

Dominating the forward section of the cabin was the crescent-shaped main display panel measuring nearly seven feet (2.1 m) wide and three feet (0.9 m) tall. It was arranged into three panels, each emphasizing the duties of each crew member. The mission commander’s panel (left side) included the velocity
Velocity
In 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 ...

, attitude, and altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...

 indicators, the primary flight controls, and the main FDAI (Flight Director Attitude Indicator).

The CM pilot served as navigator, so his control panel (center) included the Guidance and Navigation computer
Apollo Guidance Computer
The Apollo Guidance Computer provided onboard computation and control for guidance, navigation, and control of the Command Module and Lunar Module spacecraft of the Apollo program...

 controls, the caution and warning indicator panel, the event timer, the Service Propulsion System and RCS controls, and the environmental control system controls.

The LM pilot served as systems engineer, so his control panel (right-hand side) included the fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...

 gauges and controls, the electrical and battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

 controls, and the communications controls.

Flanking the sides of the main panel were sets of smaller control panels. On the left side were a circuit breaker
Circuit breaker
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow...

 panel, audio controls, and the SCS power controls. On the right were additional circuit breakers and a redundant audio control panel, along with the environmental control switches. In total, the command module panels included 24 instruments, 566 switches, 40 event indicators, and 71 lights.

The three crew couches were constructed from hollow steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 tubing and covered in a heavy, fireproof cloth known as Armalon. The leg pans of the two outer couches could be folded in a variety of positions, while the hip pan of the center couch could be disconnected and laid on the aft bulkhead. One rotation
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

 and one translation
Translation (physics)
In physics, translation is movement that changes the position of an object, as opposed to rotation. For example, according to Whittaker:...

 hand controller was installed on the armrests of the left-hand couch. The translation controller was used by the crew member performing the LM docking maneuver, usually the CM Pilot. The center and right-hand couches had duplicate rotational controllers. The couches were supported by eight shock-attenuating struts, designed to ease the impact of touchdown on water or, in case of an emergency landing, on solid ground.

The contiguous cabin space was organized into six equipment bays:
  • The lower equipment bay, which housed the Guidance and Navigation computer
    Apollo Guidance Computer
    The Apollo Guidance Computer provided onboard computation and control for guidance, navigation, and control of the Command Module and Lunar Module spacecraft of the Apollo program...

    , sextant
    Sextant
    A sextant is an instrument used to measure the angle between any two visible objects. Its primary use is to determine the angle between a celestial object and the horizon which is known as the altitude. Making this measurement is known as sighting the object, shooting the object, or taking a sight...

    , telescope
    Telescope
    A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

    , and Inertial Measurement Unit
    Inertial measurement unit
    An inertial measurement unit, or IMU, is an electronic device that measures and reports on a craft's velocity, orientation, and gravitational forces, using a combination of accelerometers and gyroscopes. IMUs are typically used to maneuver aircraft, including UAVs, among many others, and...

    ; various communications beacons; medical stores; an audio center; the S-band power amplifier; etc. There was also an extra rotation hand controller mounted on the bay wall, so the CM Pilot/navigator could rotate the spacecraft as needed while standing and looking through the telescope to find stars to take navigational measurements with the sextant. This bay provided a significant amount of room for the astronauts to move around in, unlike the cramped conditions which existed in the previous Mercury
    Project Mercury
    In 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,...

     and Gemini
    Project Gemini
    Project 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....

     spacecraft.
  • The left-hand forward equipment bay, which contained four food storage compartments, the cabin heat exchanger
    Heat exchanger
    A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

    , pressure suit
    Pressure suit
    A pressure suit is a protective suit worn by high-altitude pilots who may fly at altitudes where the air pressure is too low for an unprotected person to survive, even breathing pure oxygen at positive pressure. Such suits may be either full-pressure or partial-pressure...

     connector, potable water
    Water
    Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

     supply, and G&N telescope eyepiece
    Eyepiece
    An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device. The objective lens or mirror collects light and brings...

    s.
  • The right-hand forward equipment bay, which housed two survival kit
    Survival kit
    A survival kit is a package of basic tools and supplies prepared in advance as an aid to survival in an emergency. Military aircraft, lifeboats, and spacecraft are equipped with survival kits....

     containers, a data card kit, flight data books and files, and other mission documentation.
  • The left hand intermediate equipment bay, housing the oxygen
    Oxygen
    Oxygen 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...

     surge tank, water delivery system, food supplies, the cabin pressure relief valve controls, and the ECS package.
  • The right hand intermediate equipment bay, which contained the bio instrument kits, waste management system, food and sanitary supplies, and a waste storage compartment.
  • The aft storage bay, behind the crew couches. This housed the 70 mm camera
    Camera
    A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...

     equipment, the astronaut’s garments, tool sets, storage bags, a fire extinguisher
    Fire extinguisher
    A fire extinguisher or extinguisher, flame entinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations...

    , CO2
    Carbon dioxide
    Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

     absorbers, sleep restraint ropes, spacesuit maintenance kits, 16mm camera equipment, and the contingency lunar sample container.


The CM had five windows. The two side windows measured 13 inches (330 mm) square next to the left and right-hand couches. Two forward-facing triangular rendezvous windows measured 8 by 13 inches (204 by 330 mm), used to aid in rendezvous
Space rendezvous
A space rendezvous is an orbital maneuver during which two spacecraft, one of which is often a space station, arrive at the same orbit and approach to a very close distance . Rendezvous requires a precise match of the orbital velocities of the two spacecraft, allowing them to remain at a constant...

 and docking with the LM. The hatch window was 10 5/8 in. diameter (27 cm)
and was directly over the center couch. Each window assembly consisted of three thick panes of glass. The inner two panes, which were made of aluminosilicate, made up part of the module's pressure vessel. The fused silica outer pane served as both a debris shield and as part of the heat shield. Each pane had an anti-reflective coating and a blue-red reflective coating on the inner surface.

Specifications


  • Crew: 3
  • Crew cabin volume: 218 ft3 living space, pressurized 366 cu ft (10,3 m3)
  • Length: 11.4 ft (3.5 m)
  • Diameter: 12.8 ft (3.9 m)
  • Mass: 12250 lb (5,556.5 kg)
  • Structure mass: 3450 lb (1,564.9 kg)
  • Heat shield mass: 1870 lb (848.2 kg)
  • RCS engine mass: 880 lb (399.2 kg)
  • Recovery equipment mass: 540 lb (244.9 kg)
  • Navigation
    Navigation
    Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...

     equipment mass: 1110 lb (503.5 kg)
  • Telemetry
    Telemetry
    Telemetry 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...

     equipment mass: 440 lb (199.6 kg)
  • Electrical equipment mass: 1500 lb (680.4 kg)
  • Communications systems mass: 220 lb (99.8 kg)
  • Crew couches and provisions mass: 1200 lb (544.3 kg)
  • Environmental Control System mass: 440 lb (199.6 kg)
  • Misc. contingency mass: 440 lb (199.6 kg)
  • RCS thrust: two x 93 lbf (413.7 N)
  • RCS propellants: UDMH/N2O4
  • RCS propellant mass: 270 lb (122.5 kg)
  • Drinking water capacity: 33 lb (15 kg)
  • Waste water capacity: 58 lb (26.3 kg)
  • CO2 scrubber: lithium hydroxide
    Lithium hydroxide
    Lithium hydroxide is an inorganic compound with the formula LiOH. It is a white hygroscopic crystalline material. It is soluble in water and slightly soluble in ethanol...

  • Odor absorber: activated charcoal
    Activated carbon
    Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...

  • Electric system batteries: three 40 ampere-hour silver-zinc batteries
    Silver-oxide battery
    A silver oxide battery , not to be confused with a similar but different silver–zinc battery, which is a secondary cell, is a primary cell with relatively very high energy/weight ratio. They are costly due to the high price of silver...

    ; two 0.75 ampere-hour silver-zinc pyrotechnic batteries
  • Parachutes: two 16 feet (4.9 m) conical ribbon drogue parachutes; three 7.2 feet (2.2 m) ringshot pilot parachutes; three 83.5 feet (25.5 m) ringsail main parachutes

Construction


The Service Module was an unpressurized cylindrical structure, measuring 24 feet 7 inches (7.5 m) long and 12 feet 10 inches (3.9 m) in diameter.
The interior was a simple structure consisting of a central tunnel section 44 inches (1.1 m) in diameter, surrounded by six pie-shaped sectors. The sectors were topped by a forward bulkhead and fairing, separated by six radial beams, covered on the outside by four honeycomb panels, and supported by an aft bulkhead and engine heat shield. The sectors were not all equal 60° angles, but varied according to required size.
  • Sector 1 (50°) was originally unused, so it was filled with ballast
    Sailing ballast
    Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...

     to maintain the SM's center-of gravity. On the last three lunar landing (I-J class) missions, it carried the Scientific Instrument Module (SIM) which contained a package of lunar orbital sensors and a subsatellite.
  • Sector 2 (70°) contained the Service Propulsion System (SPS) oxidizer sump
    Sump
    A sump is a low space that collects any often-undesirable liquids such as water or chemicals. A sump can also be an infiltration basin used to manage surface runoff water and recharge underground aquifers....

     tank, so called because it directly fed the engine and was kept continuously filled by a separate storage tank, until the latter was empty. The sump tank was a cylinder with hemispherical ends, 153.8 inches (3.9 m) high, 51 inches (1.3 m) in diameter, and contained 13923 pounds (6,315.4 kg) of oxidizer.
  • Sector 3 (60°) contained the SPS oxidizer storage tank, which was the same shape as the sump tank but slightly smaller at 154.47 inches (3.9 m) high and 44 inches (1.1 m) in diameter, and held 11284 pounds (5,118.3 kg) of oxidizer.
  • Sector 4 (50°) contained the Electrical Power System (EPS) fuel cells with their hydrogen and oxygen reactants.
  • Sector 5 (70°) contained the SPS fuel sump tank. This was the same size as the oxidizer sump tank and held 8708 pounds (3,949.9 kg) of fuel.
  • Sector 6 (60°) contained the SPS fuel storage tank, also the same size as the oxidizer storage tank. It held 7058 pounds (3,201.5 kg) of fuel.


The forward fairing measured 2 feet 10 inches (864 mm) long and included the Reaction Control System (RCS) computer, umbilical connection, power distribution block, ECS controller, separation controller, components for the high-gain antenna, and eight EPS radiators. The umbilical housing contained the main electrical and plumbing connections to the CM.
The fairing externally contained a retractable forward-facing spotlight
Searchlight
A searchlight is an apparatus that combines a bright light source with some form of curved reflector or other optics to project a powerful beam of light of approximately parallel rays in a particular direction, usually constructed so that it can be swiveled about.-Military use:The Royal Navy used...

; an EVA floodlight
High-intensity discharge lamp
High-intensity discharge lamps are a type of electrical lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with both gas and metal salts. The gas facilitates the...

 to aid the Command Module pilot in SIM film retrieval; and a flashing rendezvous beacon
Beacon
A beacon is an intentionally conspicuous device designed to attract attention to a specific location.Beacons can also be combined with semaphoric or other indicators to provide important information, such as the status of an airport, by the colour and rotational pattern of its airport beacon, or of...

 visible from 54 nautical miles (100 km) away as a navigation aid for rendezvous with the Lunar Module (LM).

The SM was connected to the CM using three tension ties and six compression pads. The tension ties were stainless steel straps bolted to the CM's aft heat shield. It remained attached to the Command Module throughout most of the mission, until being jettisoned just prior to re-entry into the Earth's atmosphere. At jettison, the CM umbillical connections were cut using a pyrotechnic-activated guillotine
Guillotine
The guillotine is a device used for carrying out :executions by decapitation. It consists of a tall upright frame from which an angled blade is suspended. This blade is raised with a rope and then allowed to drop, severing the head from the body...

 assembly. Following jettison, the SM aft translation thrusters automatically fired continuously to distance it from the CM, until either the RCS fuel or the fuel cell power was depleted. The roll thrusters were also fired for five seconds to make sure it followed a different trajectory from the CM and faster break-up on re-entry.

Service Propulsion System


The 20500 pound-forces (91,188.5 N) SPS engine was used to place the Apollo spacecraft into and out of lunar orbit, and for mid-course corrections between the Earth and Moon. The engine used was an AJ10-137
AJ-10
The AJ-10 or AJ10 is a hypergolic rocket engine. It has been used to propel the upper stages of several carrier rockets, including the Delta II and Titan III. It will also be used as the main engine of the Orion Crew Exploration Vehicle for NASA's Project Constellation.It was first used in the Able...

 engine using Aerozine 50
Aerozine 50
Aerozine 50 is a 50/50 mix of hydrazine and unsymmetrical dimethylhydrazine . Originally developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines, Aerozine continues in wide use as a rocket fuel, typically with...

 as fuel and nitrogen tetroxide (N2O4) as oxidizer. The propellants were pressure-fed to the engine by 39.2 ft3 of gaseous helium at 3600 pound per square inches (24.8 MPa), carried in two 40 inches (1 m) diameter spherical tanks.

The engine measured 152.82 inches (3.9 m) long and 98.48 inches (2.5 m) wide at the base. It was mounted on two gimbal
Gimbal
A 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 to provide pitch and yaw control in lieu of the RCS during SPS firings. The combustion chamber and pressurant tanks were housed in the central tunnel.

The thrust level was twice what was needed to accomplish the lunar orbit rendezvous
Lunar orbit rendezvous
Lunar orbit rendezvous is a key concept for human landing on the Moon and returning to Earth.In a LOR mission a main spacecraft and a smaller lunar module travel together into lunar orbit. The lunar module then independently descends to the lunar surface. After completion of the mission there, a...

 (LOR) mission mode, because the engine was originally sized to lift the CM with a much larger SM off of the lunar surface in the direct ascent
Direct ascent
Direct ascent was a proposed method for a mission to the Moon. In the United States, direct ascent proposed using the enormous Nova rocket to launch a spacecraft directly to the Moon, where it would land tail-first and then launch off the Moon back to Earth...

 mode assumed in original planning (see Choosing a mission mode.) A contract was signed in April 1962 for the Aerojet-General company to start developing the engine, before the LOR mode was officially chosen in July of that year.

Reaction Control System


Four clusters of four reaction control system
Reaction control system
A reaction control system is a subsystem of a spacecraft whose purpose is attitude control and steering by the use of thrusters. An RCS system is capable of providing small amounts of thrust in any desired direction or combination of directions. An RCS is also capable of providing torque to allow...

 (RCS) thrusters were installed around the upper section of the SM every 90°. The sixteen-thruster arrangement provided rotation
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

 and translation
Translation (geometry)
In Euclidean geometry, a translation moves every point a constant distance in a specified direction. A translation can be described as a rigid motion, other rigid motions include rotations and reflections. A translation can also be interpreted as the addition of a constant vector to every point, or...

 control in all three spacecraft axes. Each thruster generated 100 pounds (45.4 N) of thrust, and used mono-methyl hydrazine
Monomethylhydrazine
Monomethylhydrazine is a volatile hydrazine chemical with the chemical formula CH3 NH2. It is used as a rocket propellant in bipropellant rocket engines because it is hypergolic with various oxidizers such as nitrogen tetroxide and nitric acid...

 (MMH) as fuel and nitrogen tetroxide as oxidizer. Each quad assembly measured 8 feet (2.4 m) by 3 foot (0.9144 m) and had its own fuel tank, oxidizer tank, helium pressurant tank, and associated valves and regulators.

The Lunar Module used a similar four-quad arrangement of the identical thruster engines for its RCS.

Electrical power system



Electrical power was produced by three fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...

s, each measuring 44 inches (1.1 m) tall by 22 inch (0.5588 m) in diameter and weighing 245 pounds (111.1 kg). These combined hydrogen and oxygen to generate electrical power, along with some of the water used for drinking and other purposes. The cells were fed by two hemispherical-cylindrical 31.75 inch (0.80645 m) diameter tanks, each holding 29 pounds (13.2 kg) of liquid hydrogen
Liquid hydrogen
Liquid 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 two spherical 26 inch (0.6604 m) diameter tanks, each holding 326 pounds (147.9 kg) of liquid oxygen
Liquid oxygen
Liquid oxygen — abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries — is one of the physical forms of elemental oxygen.-Physical properties:...

 (which also supplied the environmental control system).

On the flight of Apollo 13
Apollo 13
Apollo 13 was the seventh manned mission in the American Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, at 13:13 CST. The landing was aborted after an oxygen tank exploded two days later, crippling the service module upon which the Command...

, the EPS was disabled by an explosive rupture of one oxygen tank, which punctured the second tank and led to the loss of all oxygen. After the accident, a third oxygen tank was added to prevent operation below 50% tank capacity which allowed removal of the tank's internal stirring fan equipment, which had contributed to the failure.

Also starting with Apollo 14, a 400 Ah auxiliary battery was added to the SM for emergency use. Apollo 13 had drawn heavily on its entry batteries in the first hours after the explosion, and while this new battery could not power the CM for more than 5–10 hours it would buy time in the event of a temporary loss of all three fuel cells. Such an event occurred when Apollo 12 was struck twice by lightning shortly after launch.

Environmental control system


Storage tanks were carried for water and oxygen.
Waste heat from the CM cabin was dumped to space by two 30 ft2 radiators located on the lower section of the exterior walls, one covering sectors 2 and 3, and the other covering sectors 5 and 6.

Communications system


Short-range communications with the Lunar Module employed two VHF scimitar antenna
Scimitar antenna
A scimitar antenna is a radio antenna so named because its shape resembles a talon-shaped curved sword of the same name. It was invented in 1958 by Edwin M. and William P. Turner. It is essentially a flat metal plate in a semi-circular or semi-elliptical shape with a wide end at one side and a...

s mounted on the SM just above the ECS radiators.

A steerable S-band
Unified S-Band
The Unified S-band system was a tracking and communication system developed for the Apollo program by NASA and the Jet Propulsion Laboratory . It operated in the S band portion of the microwave spectrum, combining voice communications, television, telemetry, command, tracking and ranging into a...

 high-gain antenna for earth communications was mounted on the aft bulkhead. This was an array of four 31 inch (0.7874 m) diameter reflectors surrounding a single 11 inch (0.2794 m) square reflector. During launch it was folded down parallel to the main engine to fit inside the Spacecraft-to-LM Adapter (SLA). After CSM separation from the SLA, it deployed at a right angle to the SM.

Two omnidirectional S-band antennas antennas on the CM were used when the attitude of the CSM kept the high gain antenna from being pointed at earth. These antennas were also used between SM jettison and landing.

Specifications

  • Length: 24.8 ft (7.6 m)
  • Diameter: 12.8 ft (3.9 m)
  • Mass: 54060 lb (24,521.2 kg)
  • Structure mass: 4200 lb (1,905.1 kg)
  • Electrical equipment mass: 2600 lb (1,179.3 kg)
  • RCS thrust: two or four x 100 lbf (444.8 N)
  • RCS Propellants: MMH/N2O4
  • Service Propulsion (SPS) engine mass: 6600 lb (2,993.7 kg)
  • SPS engine thrust: 20500 lbf (91,188.5 N)
  • SPS engine propellants: (UDMH/N2H4)/N2O4
  • SPS engine propellants: 40590 lb (18,411.3 kg)
  • SPS ISP: 314 s (3,100 N·s/kg)
  • Spacecraft delta v: 9200 ft/s (2,804.2 m/s)
  • Electrical System: three 1.4 kW DC/30-volt fuel cells

Modifications for Saturn IB missions


The Low Earth Orbit payload capability of the Saturn IB
Saturn IB
The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration for use in the Apollo program...

 booster used to launch the Low Earth Orbit missions (Apollo 1
Apollo 1
Apollo 1 was scheduled to be the first manned mission of the Apollo manned lunar landing program, with a target launch date of February 21, 1967. A cabin fire during a launch pad test on January 27 at Launch Pad 34 at Cape Canaveral killed all three crew members: Command Pilot Virgil "Gus"...

 (planned), Apollo 7
Apollo 7
Apollo 7 was the first manned mission in the American Apollo space program, and the first manned US space flight after a cabin fire killed the crew of what was to have been the first manned mission, AS-204 , during a launch pad test in 1967...

, Skylab 2
Skylab 2
-Backup crew:-Support crew:*Robert L. Crippen*Richard H. Truly*Henry W. Hartsfield, Jr*William E. Thornton-Mission parameters:*Mass: 19,979 kg*Maximum Altitude: 440 km*Distance: 18,536,730.9 km...

, Skylab 3
Skylab 3
Skylab 3 was the second manned mission to Skylab. The Skylab 3 mission started July 28, 1973, with the launch of three astronauts on the Saturn IB rocket, and lasted 59 days, 11 hours and 9 minutes...

, Skylab 4
Skylab 4
Skylab 4 was the fourth Skylab mission and placed the third and final crew on board the space station. The mission started November 16, 1973 with the launch of three astronauts on a Saturn IB rocket, and lasted 84 days, 1 hour and 16 minutes...

, and Apollo-Soyuz
Apollo-Soyuz Test Project
-Backup crew:-Crew notes:Jack Swigert had originally been assigned as the command module pilot for the ASTP prime crew, but prior to the official announcement he was removed as punishment for his involvement in the Apollo 15 postage stamp scandal.-Soyuz crew:...

) could not handle the 66900 pounds (30,345.3 kg) mass of the fully fueled CSM. This was not a problem because the delta-V
Delta-v
In 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....

 requirement of these missions was much smaller than that of the lunar mission, therefore they were launched with less than half of the full SPS propellant load. The CSMs launched in orbit on Saturn IB ranged from 32558 pounds (14,768.1 kg) (Apollo-Soyuz), to 46000 pounds (20,865.2 kg) (Skylab 4).

The omnidirectional antennas sufficed for ground communications during the earth orbital missions so the high gain S-band antenna on the SM was omitted from Apollo 1, Apollo 7, and the three Skylab flights. It was restored for the Apollo-Soyuz mission to communicate through the ATS-6
ATS-6
ATS-6 was a NASA experimental satellite, built by Fairchild Space and Electronics Division It has been called the world's first educational satellite as well as world's first experimental Direct Broadcast Satellite as part of the Satellite Instructional Television Experiment between NASA and ISRO...

 satellite in geostationary orbit, an experimental precursor to the current TDRSS system.

On the Skylab and Apollo-Soyuz missions, some additional dry weight was saved by removing the otherwise empty fuel and oxidizer storage tanks (leaving the partially filled sump tanks), along with one of the two helium pressurant tanks.
This permitted the addition of some extra RCS propellant to allow for use as a backup for the deorbit burn in case of possible SPS failure.

Since the spacecraft for the Skylab missions would not be occupied for most of the mission, there was lower demand on the power system and one of the three fuel cells was deleted from these SMs.

Command Module


  • The Block II used a one-piece, quick-release, outward opening hatch instead of the two-piece plug
    Plug door
    A plug door is a door designed to seal itself by taking advantage of pressure difference on its two sides and is typically used on pressurised aircraft...

     hatch used on Block I, in which the inner piece had to be unbolted and placed inside the cabin in order to enter or exit the spacecraft. The Block II hatch could be opened quickly in case of an emergency. (Both hatch versions were covered with an extra, removable section of the Boost Protective Cover which surrounded the CM to protect it in case of a launch abort.)
  • The Block I forward access tunnel was smaller than Block II, and intended only for emergency crew egress after splashdown in case of problems with the main hatch. It was covered with a removable plug in the nose of the forward heat shield. Block II contained a shorter forward heat shield with a flat removable hatch, beneath a docking ring and probe mechanism which captured and held the LM.
  • The aluminized PET film layer, which gave the Block II heat shield a shiny mirrored appearance, was absent on Block I, exposing the light gray fiberglass material, which on some flights was painted white.
  • The Block I VHF scimitar antenna
    Scimitar antenna
    A scimitar antenna is a radio antenna so named because its shape resembles a talon-shaped curved sword of the same name. It was invented in 1958 by Edwin M. and William P. Turner. It is essentially a flat metal plate in a semi-circular or semi-elliptical shape with a wide end at one side and a...

    s were located in two semicircular strakes
    Strake (aviation)
    In aviation, a strake is an aerodynamic surface generally mounted on the fuselage of an aircraft to improve the airflow and hence the flight characteristics.In general a strake is longer than it is wide, in contrast to a winglet or a moustache....

     originally thought necessary to help stabilize the CM during reentry. However, the unmanned reentry tests proved these to be unnecessary for stability, and also aerodynamically ineffective at high simulated lunar reentry speeds. Therefore the strakes were removed from Block II and the antennas were moved to the Service Module.
  • The Block I CM/SM umbillical connector was smaller than on Block II, located near the crew hatch instead of nearly 180 degrees away from it. The separation point was between the modules, instead of the larger hinged arm mounted on the Service Module, separating at the CM sidewall on Block II.
  • The two negative pitch RCS engines located in the forward compartment were arranged vertically on Block I, and horizontally on Block II.

Service Module


  • On most unmanned Block I flights, the SM was painted white to match the Command Module's appearance, but on Apollo 1, Apollo 4, and all the Block II spacecraft, the SM walls were left unpainted except for the EPS and ECS radiators, which were white.
  • The EPS and ECS radiators were redesigned for Block II. Block I had three larger EPS radiators located on Sectors 1 and 4. The ECS radiators were located on the aft section of Sectors 2 and 5.
  • The Block I fuel cells were located at the aft bulkhead in Sector 4, and their hydrogen and oxygen tanks were located in Sector 1.
  • Block I had slightly longer SPS fuel and oxidizer tanks which carried more propellant than Block II.
  • The Block II aft heat shield was a rectangular shape with slightly rounded corners at the propellant tank sectors. The Block I shield was the same basic shape, but bulged out slightly near the ends more like an hourglass or figure eight, to cover more of the tanks.

CSMs produced

Block I
Serial number Use Launch date Current location
CSM-001 systems compatibility test vehicle
CSM-002 A-004
A-004
A-004 was the sixth and final test of the Apollo launch escape vehicle and the first flight of a Block I production-type spacecraft.-Objectives:...

 flight
January 20, 1966 Command Module on display at Cradle of Aviation, Long Island
Long Island
Long Island is an island located in the southeast part of the U.S. state of New York, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City , and two of which are mainly suburban...

, New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

CSM-004 static and thermal structural ground tests scrapped
CSM-006 scrapped
CSM-007 various tests including acoustic vibration and drop tests, and water egress training. CM was refit with Block II improvements. Underwent testing for Skylab
Skylab
Skylab was a space station launched and operated by NASA, the space agency of the United States. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V rocket, with a mass of...

 at the McKinley Climatic Laboratory, Eglin AFB, Florida, 1971-1973.
Command Module on display at Museum of Flight
Museum of Flight
The Museum of Flight is a private non-profit air and space museum at King County International Airport , south of downtown Seattle, Washington. It was established in 1965 and is fully accredited by the American Association of Museums...

, Seattle, Washington
CSM-008 complete systems spacecraft used in thermal vacuum tests scrapped
CSM-009 AS-201
AS-201
AS-201 , flown February 26, 1966, was the first unmanned test flight of an entire production Block I Apollo Command/Service Module and the Saturn IB launch vehicle. The spacecraft consisted of the second Block I command module and the first Block I service module...

 flight and drop tests
February 26, 1966 Command Module on display at Strategic Air and Space Museum
Strategic Air and Space Museum
The Strategic Air and Space Museum is a museum focusing on United States Air Force military aircraft and nuclear missiles located near Ashland, Nebraska, along Interstate 80 southwest of Omaha, Nebraska. The objective of the museum is to preserve and display historic aircraft, missile, and space...

, Ashland, Nebraska
Ashland, Nebraska
Ashland is a city in Saunders County, Nebraska, United States. The population was 2,262 at the 2000 census.- History :Ashland is located at the site of a low-water limestone ledge along the bottom of Salt Creek, an otherwise mud-bottomed stream that was a formidable obstacle for wagon trains on the...

CSM-010 Command Module on display at U.S. Space & Rocket Center, Huntsville, Alabama
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....

CSM-011 AS-202
AS-202
AS-202 was the second unmanned, suborbital test flight of a production Block I Apollo Command/Service Module launched with the Saturn IB launch vehicle. It launched August 25, 1966 and was the first flight which included the spacecraft Guidance and Navigation Control system and fuel cells...

 flight
August 25, 1966 Command Module on display on the USS Hornet
USS Hornet (CV-12)
USS Hornet is a United States Navy aircraft carrier of the Essex class. Construction started in August 1942; she was originally named , but was renamed in honor of the , which was lost in October 1942, becoming the eighth ship to bear the name.Hornet was commissioned in November 1943, and after...

 museum, in Alameda, California
Alameda, California
Alameda is a city in Alameda County, California, United States. It is located on Alameda Island and Bay Farm Island, and is adjacent to Oakland in the San Francisco Bay. The Bay Farm Island portion of the city is adjacent to the Oakland International Airport. At the 2010 census, the city had a...

CSM-012 Apollo 1
Apollo 1
Apollo 1 was scheduled to be the first manned mission of the Apollo manned lunar landing program, with a target launch date of February 21, 1967. A cabin fire during a launch pad test on January 27 at Launch Pad 34 at Cape Canaveral killed all three crew members: Command Pilot Virgil "Gus"...

; the Command Module was severely damaged in the Apollo 1 fire
Command Module in storage at the Langley Research Center
Langley Research Center
Langley Research Center is the oldest of NASA's field centers, located in Hampton, Virginia, United States. It directly borders Poquoson, Virginia and Langley Air Force Base...

, Hampton, Virginia
Hampton, Virginia
Hampton is an independent city that is not part of any county in Southeast Virginia. Its population is 137,436. As one of the seven major cities that compose the Hampton Roads metropolitan area, it is on the southeastern end of the Virginia Peninsula. Located on the Hampton Roads Beltway, it hosts...

CSM-014 Command Module disassembled as part of Apollo 1 investigation. Service Module (SM-014) used on Apollo 6
Apollo 6
Apollo 6, launched on April 4, 1968, was the Apollo program's second and last A type mission—unmanned test flight of its Saturn V launch vehicle. It was intended to demonstrate full lunar injection capability of the Saturn V, and the capability of the Command Module's heat shield to withstand a...

 mission
April 4, 1968
CSM-017 Apollo 4
Apollo 4
Apollo 4, , was the first unmanned test flight of the Saturn V launch vehicle, which was ultimately used by the Apollo program to send the first men to the Moon...

November 9, 1967 Command Module on display at Stennis Space Center, Bay St. Louis, Mississippi
Bay St. Louis, Mississippi
Bay Saint Louis is a city located in Hancock County, Mississippi. It is part of the Gulfport–Biloxi, Mississippi Metropolitan Statistical Area. As of the 2000 census, the city had a total population of 8,209. It is the county seat of Hancock County...

CSM-020 CM-020 flew on Apollo 6
Apollo 6
Apollo 6, launched on April 4, 1968, was the Apollo program's second and last A type mission—unmanned test flight of its Saturn V launch vehicle. It was intended to demonstrate full lunar injection capability of the Saturn V, and the capability of the Command Module's heat shield to withstand a...

 with SM-014 after SM-020 was destroyed in an explosion
April 4, 1968 Command Module on display at Fernbank Science Center
Fernbank Science Center
The Fernbank Science Center is a museum, classroom, and woodland complex located in Atlanta. It is owned and operated by DeKalb County School System...

, Atlanta
Block II
Serial number Use Launch date Current location
CSM-098 used in thermal vacuum test CSM on display at Academy of Science Museum, Moscow, Russia
CSM-099 static structural testing scrapped
CSM-100 static structural testing unknown
CSM-101 Apollo 7
Apollo 7
Apollo 7 was the first manned mission in the American Apollo space program, and the first manned US space flight after a cabin fire killed the crew of what was to have been the first manned mission, AS-204 , during a launch pad test in 1967...

October 11, 1968 Command Module was on display at National Museum of Science & Technology
Canada Science and Technology Museum
The Canada Science and Technology Museum is located in Ottawa, Ontario, on St. Laurent Boulevard, to the south of the Queensway .-Mission:...

, Ottawa, Canada from 1974 until 2004, now at the Frontiers of Flight Museum
Frontiers of Flight Museum
The Frontiers of Flight Museum is an aerospace museum located in Dallas, Texas. The museum was founded in November 1988 by William E. Cooper, Kay Bailey Hutchison and Jan Collmer. Originally located within a terminal at Dallas Love Field, the museum now occupies a building at the Southeast corner...

, Dallas, TX
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

 after 30 years of being on loan.
CSM-102 Launch Complex 34 checkout vehicle Service Module is at JSC on top of the Little Joe II in Rocket Park. The command module is Boiler Plate 22.
CSM-103 Apollo 8
Apollo 8
Apollo 8, the second manned mission in the American Apollo space program, was the first human spaceflight to leave Earth orbit; the first to be captured by and escape from the gravitational field of another celestial body; and the first crewed voyage to return to Earth from another celestial...

December 21, 1968 Command Module on display at the Museum of Science and Industry
Museum of Science and Industry (Chicago)
The Museum of Science and Industry is located in Chicago, Illinois, USA in Jackson Park, in the Hyde Park neighborhood adjacent to Lake Michigan. It is housed in the former Palace of Fine Arts from the 1893 World's Columbian Exposition...

 in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

CSM-104
Gumdrop
Apollo 9
Apollo 9
Apollo 9, the third manned mission in the American Apollo space program, was the first flight of the Command/Service Module with the Lunar Module...

March 3, 1969 Command Module on display at San Diego Aerospace Museum
San Diego Aerospace Museum
San Diego Air & Space Museum is an aviation and space exploration museum in San Diego, California, USA...

CSM-105 acoustic tests Command Module on display at National Air & Space Museum, Washington DC as part of the Apollo Soyuz Test Project display. (Photo)
CSM-106
Charlie Brown
Apollo 10
Apollo 10
Apollo 10 was the fourth manned mission in the American Apollo space program. It was an F type mission—its purpose was to be a "dry run" for the Apollo 11 mission, testing all of the procedures and components of a Moon landing without actually landing on the Moon itself. The mission included the...

May 18, 1969 Command Module on display at Science Museum
Science Museum (London)
The Science Museum is one of the three major museums on Exhibition Road, South Kensington, London in the Royal Borough of Kensington and Chelsea. It is part of the National Museum of Science and Industry. The museum is a major London tourist attraction....

, London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

CSM-107
Columbia
Apollo 11
Apollo 11
In 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...

July 16, 1969 Command Module on display at National Air & Space Museum, Washington DC
CSM-108
Yankee Clipper
Apollo 12
Apollo 12
Apollo 12 was the sixth manned flight in the American Apollo program and the second to land on the Moon . It was launched on November 14, 1969 from the Kennedy Space Center, Florida, four months after Apollo 11. Mission commander Charles "Pete" Conrad and Lunar Module Pilot Alan L...

November 14, 1969 Command Module on display at Virginia Air & Space Center, Hampton, Virginia
Hampton, Virginia
Hampton is an independent city that is not part of any county in Southeast Virginia. Its population is 137,436. As one of the seven major cities that compose the Hampton Roads metropolitan area, it is on the southeastern end of the Virginia Peninsula. Located on the Hampton Roads Beltway, it hosts...

CSM-109
Odyssey
Apollo 13
Apollo 13
Apollo 13 was the seventh manned mission in the American Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, at 13:13 CST. The landing was aborted after an oxygen tank exploded two days later, crippling the service module upon which the Command...

April 11, 1970 Command Module on display at Kansas Cosmosphere and Space Center
Kansas Cosmosphere and Space Center
The Kansas Cosmosphere and Space Center is a museum and educational facility in Hutchinson, Kansas that is best known for the display and restoration of spaceflight artifacts and educational camps...

CSM-110
Kitty Hawk
Apollo 14
Apollo 14
Apollo 14 was the eighth manned mission in the American Apollo program, and the third to land on the Moon. It was the last of the "H missions", targeted landings with two-day stays on the Moon with two lunar EVAs, or moonwalks....

January 31, 1971 Command Module on display at the Kennedy Space Center
Kennedy Space Center
The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

CSM-111 Apollo Soyuz Test Project July 15, 1975 Command Module currently on display at California Science Center
California Science Center
The California Science Center is a state agency and museum located in Exposition Park, Los Angeles. Billed as the West Coast's largest hands-on science center, the California ScienCenter is a public-private partnership between the State and the California Science Center Foundation...

 in Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...

, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 (formerly displayed at the Kennedy Space Center
Kennedy Space Center
The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

's Visitor's Complex)
CSM-112
Endeavour
Apollo 15
Apollo 15
Apollo 15 was the ninth manned mission in the American Apollo space program, the fourth to land on the Moon and the eighth successful manned mission. It was the first of what were termed "J missions", long duration stays on the Moon with a greater focus on science than had been possible on previous...

July 26, 1971 Command Module on display at National Museum of the United States Air Force
National Museum of the United States Air Force
The National Museum of the United States Air Force is the official museum of the United States Air Force located at Wright-Patterson Air Force Base northeast of Dayton, Ohio. The NMUSAF is the world's largest and oldest military aviation museum with more than 360 aircraft and missiles on display...

, Wright-Patterson Air Force Base
Wright-Patterson Air Force Base
Wright-Patterson Air Force Base is a United States Air Force base in Greene and Montgomery counties in the state of Ohio. It includes both Wright and Patterson Fields, which were originally Wilbur Wright Field and Fairfield Aviation General Supply Depot. Patterson Field is located approximately...

, Dayton, Ohio
Dayton, Ohio
Dayton is the 6th largest city in the U.S. state of Ohio and the county seat of Montgomery County, the fifth most populous county in the state. The population was 141,527 at the 2010 census. The Dayton Metropolitan Statistical Area had a population of 841,502 in the 2010 census...

CSM-113
Casper
Apollo 16
Apollo 16
Young and Duke served as the backup crew for Apollo 13; Mattingly was slated to be the Apollo 13 command module pilot until being pulled from the mission due to his exposure to rubella through Duke.-Backup crew:...

April 16, 1972 Command Module on display at U.S. Space & Rocket Center, Huntsville, Alabama
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....

CSM-114
America
Apollo 17
Apollo 17
Apollo 17 was the eleventh and final manned mission in the American Apollo space program. Launched at 12:33 a.m. EST on December 7, 1972, with a three-member crew consisting of Commander Eugene Cernan, Command Module Pilot Ronald Evans, and Lunar Module Pilot Harrison Schmitt, Apollo 17 remains the...

December 7, 1972 Command Module on display at Space Center Houston
Space Center Houston
Space Center Houston is the official visitors' center of the Lyndon B. Johnson Space Center—the National Aeronautics and Space Administration's center for human spaceflight activities—located in Houston...

, Houston, Texas
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...

CSM-115 canceled Never fully completed – service module does not have its SPS nozzle installed. On display as part of the Saturn V display at Johnson Space Center, Houston, Texas
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...

; command module restored in 2005 prior to the dedication of the JSC Saturn V Center
CSM-115a canceled never completed
CSM-116 Skylab 2
Skylab 2
-Backup crew:-Support crew:*Robert L. Crippen*Richard H. Truly*Henry W. Hartsfield, Jr*William E. Thornton-Mission parameters:*Mass: 19,979 kg*Maximum Altitude: 440 km*Distance: 18,536,730.9 km...

May 25, 1973 Command Module on display at National Museum of Naval Aviation
National Museum of Naval Aviation
The National Museum of Naval Aviation is a military and aerospace museum located at Naval Air Station Pensacola, Florida. The museum opened in 1962....

, Pensacola, Florida
Pensacola, Florida
Pensacola is the westernmost city in the Florida Panhandle and the county seat of Escambia County, Florida, United States of America. As of the 2000 census, the city had a total population of 56,255 and as of 2009, the estimated population was 53,752...

CSM-117 Skylab 3
Skylab 3
Skylab 3 was the second manned mission to Skylab. The Skylab 3 mission started July 28, 1973, with the launch of three astronauts on the Saturn IB rocket, and lasted 59 days, 11 hours and 9 minutes...

July 28, 1973 Command Module on display at Great Lakes Science Center
Great Lakes Science Center
The Great Lakes Science Center is a museum and educational facility in downtown Cleveland, Ohio, United States.The center's exhibits focus on helping visitors to understand science, technology, and their interdependence with the environment. Many of the exhibits document the features of the natural...

, current location of the NASA Glenn Research Center
Glenn Research Center
NASA John H. Glenn Research Center at Lewis Field is a NASA center, located within the cities of Brook Park, Cleveland and Fairview Park, Ohio between Cleveland Hopkins International Airport and the Cleveland Metroparks's Rocky River Reservation, and has other subsidiary facilities in Ohio...

 Visitor Center, Cleveland, Ohio
Cleveland, Ohio
Cleveland is a city in the U.S. state of Ohio and is the county seat of Cuyahoga County, the most populous county in the state. The city is located in northeastern Ohio on the southern shore of Lake Erie, approximately west of the Pennsylvania border...

CSM-118 Skylab 4
Skylab 4
Skylab 4 was the fourth Skylab mission and placed the third and final crew on board the space station. The mission started November 16, 1973 with the launch of three astronauts on a Saturn IB rocket, and lasted 84 days, 1 hour and 16 minutes...

November 16, 1973 Command Module on display at National Air & Space Museum, Washington DC
CSM-119 Skylab Rescue
Skylab Rescue
Brand flew in 1975 during the Apollo-Soyuz Test Project as command module pilot, later commanding three Space Shuttle missions . Lind would wait another decade before he flew as a mission specialist on STS-51-B in 1985.-External links:* * * * * * *...

 and ASTP backup
On display at the Kennedy Space Center
Kennedy Space Center
The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...


See also

  • Orbital module
    Orbital module
    The orbital module is a portion of spacecraft used only in orbit. These have developed from the Soviet Soyuz spacecraft.-Soyuz orbit module:The orbit module is a spherical part of Soviet-Russian Soyuz space ship series...

  • Reentry module
  • Space capsule
    Space capsule
    A space capsule is an often manned spacecraft which has a simple shape for the main section, without any wings or other features to create lift during atmospheric reentry....

  • Space suit
    Space suit
    A space suit is a garment worn to keep an astronaut alive in the harsh environment of outer space. Space suits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, and are necessary for extra-vehicular activity , work done outside spacecraft...

  • Space exploration
    Space exploration
    Space 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....

  • U.S. Space Exploration History on U.S. Stamps
    U.S. space exploration history on U.S. stamps
    With the advent of unmanned and manned space flight a whole new era of American history had presented itself. Keeping with the tradition of honoring the country's history on the face of U.S. postage stamps, the U.S. Post Office began honoring the various events with its commemorative postage stamp...