Apollo (spaceship)

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North American Apollo CSM
Apollo-15 (CSM-112) in orbit
Apollo CSM-112 ( Apollo 15 ) in orbit
Use: Earth and lunar orbit
Crew: 3 (commander, CSM pilot, LM pilot)
Height: 11.03 m
Diameter: 3.90 m
Volume: 6.17 m³
CM: 5,809 kg
SM: 24,523 kg (full tank)
Total: 30,332 kg
CM control nozzles (N 2 O 4 / UDMH) 12 × 412 N
SM control nozzles (N 2 O 4 / UDMH) 16 × 441 N
Main drive
(N 2 O 4 / UDMH)
1 × 97.86 kN
Mission data
Mission duration: 14 days (200 orbits)
Apogee: 386.242 km
Perigee: 160 km
Delta v: 2804 m / s
Apollo CSM diagram
CSM with rescue rocket (LES) (NASA)
CSM with rescue rocket (NASA)
North American Apollo CSM

Apollo was a spaceship developed by North American Aviation as part of the Apollo program in the mid-1960s . It consisted of two components: the command module (CM) and the service module (SM). The combination (CSM) was only separated shortly before re-entry into the earth's atmosphere . Only the CM with the three astronauts on board was equipped with a heat shield and equipped for re-entry into the earth's atmosphere and a splashdown .

The Apollo CSM spacecraft was launched into orbit by Saturn launch vehicles .

Command module (CM)

The CM had a mass of 5900 kg, a height of 3.23 m and a diameter of 3.91 m. In addition to numerous technical systems, it contained the astronauts' lounge area. When they returned from space, it served as a landing capsule.

Front part

Stabilization chutes ( drogue chutes ) and three large main parachutes were housed in the front part . The latter opened after re-entry at a height of 2.5 km. Two umbrellas were sufficient for a safe dive. At Apollo 15 , one of the three screens failed without causing damage or injury. Furthermore, two control nozzles of the attitude control system for re-entry as well as the coupling system and the hatch for the lunar module were installed in the upper area . In addition, there were antennas and signal lights that made it easier to recover at sea, as well as inflatable balloons that set the system upright if the landing capsule floated with the tip down after the ditch.

Middle part

Sectional view of the Apollo-CM

In the middle part of the spaceship there was a pressure-resistant cabin for the astronauts. This housed the main instrument panel for the control and steering of the spaceship , life support systems and some material lockers. There were five small windows and a hatch on the side for entry and exit. The life support systems controlled the cabin atmosphere and kept the temperature at 22 ° C. During the flight, the cabin air consisted of pure oxygen at a third of the pressure on earth. Only during the start-up phase, after the painful findings from the disaster with Apollo 1 , 40% nitrogen was added. On board were also maps of the moon and the earth , star maps for navigation and orbit maps for each of the individual phases of the mission.

The CM offered each astronaut about two cubic meters of space.


In the stern of the CM, ten additional control nozzles of the attitude control system for re-entry, their fuel and helium and water tanks were housed. The structure here consisted of triangular ribs that were designed to be deformable on the side opposite the parachutes and, in the event of a landing on land, acted as a crumple zone and thus cushioned the impact.

Instruments of the CM

Most of the instruments were on the main control panel , across from three couches for the astronauts. The life support systems were on the left side of the module, the disposal systems on the right side. The astronauts were able to control and stabilize the spaceship using hand controllers ( flysticks ) attached to two of the three couches . The main control console was divided into three areas. The controls were designed in such a way that the astronauts could operate them with gloves.

  • The controls were on the left, the commander's seat . This included instruments for stabilization, steering, thrust and landing; furthermore the emergency systems as well as one of the control units ( DSKY - Display & Keyboard ) for the control and navigation computer ( AGC - Apollo Guidance Computer ). Another identical control panel was attached to the navigation telescope. The two docking maneuvers in the lunar transfer orbit and in the lunar orbit were carried out from this place, with a window in the docking (= flight) direction in the commander's line of sight.
  • The pilot of the command module sat in the middle . In its area were warning systems and control instruments for the life support system and the tanks . At the foot of the seat there were optical navigation instruments that are used several times in flight to adjust the gyro compass ( IMU - Inertial Measurement Unit ) before course corrections . This included a permanently installed space sextant for determining position and a telescope . A second control unit for the computer was also located at this workstation.
  • The lunar module pilot sat on the right . The control systems for communication , electrics , data storage and fuel cells were installed in its segment .

Navigation and communication

The CM was equipped with its own computer, the Apollo Guidance Computer, and two operating consoles for independent navigation. The sextant was connected directly to the computer via an angle encoder, which differed from the design of normal sextants. (Without this sextant, Apollo 16 would have got into serious trouble, as the electronic navigation system had failed on this mission.) The radio communication took place in the S-band , in particular via the large, swiveling, clover-leaf-shaped directional antenna at the rear of the service module. In addition, a VHF connection with an omnidirectional antenna was available for the landing and recovery phases.

Landing capsule heat shield

The landing capsule was equipped with an ablative heat shield made of epoxy resin for re-entry into the earth's atmosphere at about escape speed .

Service module (SM)

Exploded view of the service module
Control nozzles (RCS) on the service module

The SM contained the systems that were needed for a longer stay in space and for maneuvering. It consisted of a cylindrical , 7.50 m long and 3.91 m diameter construction. It contained electrical life support and communication systems. It was divided into a central section and another six outer sections. This contained tanks for propulsion, attitude control, power generation and life support systems as well as the control engines and the main engine. On the outside there are four modules, each with four were steering jets , navigation lights , three antennas and four parabolic antennas for communication and radar - transponders .


Connection of the CM with the SM at Apollo 6

The structure of the service module consisted of an inner cylinder with a diameter of about one meter, surrounded by an outer cylinder with a diameter of 3.91 m. Partition walls divided the space between the inner and outer cylinder into six unequal-sized sectors. The cylinders were closed at the front and rear by bulkheads. All parts were made from milled aluminum plates. The inner cylinder contained two spherical tanks with helium under high pressure.

The six sectors were occupied as follows (counting starting at the top left and counterclockwise, viewed from the CM):

  • Sector 1 was a 50 ° segment and was initially unused. After the near-catastrophe of Apollo 13, a third oxygen tank was installed in the upper part. During the flights of Apollo 15 , Apollo 16 and Apollo 17 , there were also scientific instruments for exploring the lunar surface from the lunar orbit, such as cameras, altimeters and radiation detectors; the outer panel was blown off during these missions (as shown in the above picture of the CSM-112).
  • Sector 2 spanned 70 ° and was used for the first, larger oxidizer tank. This was called the " sump tank ". The tank was 3.90 m high with a diameter of 1.30 m and contained 6315 kg of the oxidizer.
  • Sector 3 was a 60 ° segment, and contained the second oxidizer, the "storage tank" ( storage tank ). The oxidizer from this tank first got into the collecting tank and from there to the engine. This tank was 3.92 m long, 1.14 m in diameter and held another 5118 kg of oxidizer.
  • Sector 4 was again a 50 ° segment. In the upper part there were three fuel cells , including two tanks with supercritical oxygen for the fuel cells and the life support systems. At the very bottom were two tanks with supercritical hydrogen for the fuel cells.
  • Sector 5, a 70 ° segment, contained the fuel holding tank. The same two-step concept was used. With the same size as its opposite counterpart, this tank contained 3950 kg of fuel.
  • Sector 6 was another 60 ° segment for the fuel storage tank. It contained another 3200 kg of fuel.

All tanks were made of titanium sheet 1.36 mm thick.

The electrical system was mainly on the front bulkhead. Overall, the arrangement of the systems took the center of gravity into account. Since it was not possible to achieve complete compensation, the engine was installed in such a way that the zero position deviates by 1.5 ° from the geometric axis.


Scheme of the drive

The engine of the SM, the AJ10-137 developed by the Aerojet-General Corporation , generated a thrust of 97.5  kN and was designed for a maximum of 50 ignition processes. As fuel was aerozine 50 used a mixture of 50% hydrazine and 50% unsymmetrical dimethylhydrazine as oxidizer was dinitrogen tetroxide is used, a storable hypergolic propellant combination. Ignition in the strict sense of the word by means of sparks did not take place; the two liquids ignite on contact with one another. The engine had no pump ; rather, the fuel and the oxidizer were forced out of their tanks into the combustion chamber using helium as a propellant . The construction became simple and reliable at the expense of performance. The entire engine and the engine nozzle were 3.90 m long and weighed 293 kg together. The nozzle alone was 2.80 m long and had a diameter of 2.10 m.


Two fuel tanks with a total capacity of 7.2 t and two oxidizer tanks with a total capacity of 11.4 t (see above) supplied the engine. These fuels alone made up about 75% of the total mass of the SM. There were two spherical helium tanks in the middle of the module for pumping compressed gas. Two further tanks with a volume of 144 l each provided the oxygen for the fuel cells and life support. There were also two hydrogen tanks with a volume of 13 l each for the fuel cells. A defective heating element in one of the oxygen tanks caused the accident on the Apollo 13 mission . It had previously been used in a spaceship, but was removed before the launch of the earlier spaceship and, despite a defect, was used on Apollo 13.

Power supply of the CSM

In addition to electrical energy , three alkaline fuel cells also provided heat and drinking water. Furthermore, silver oxide-zinc batteries delivered 1.5 kW of power and ensured the supply during re-entry and landing. Two further silver-zinc oxide batteries in the CM delivered 28 watts and released the explosive bolts for the separation of the third rocket stage, for the separation of CM and SM and that of the rescue rocket (LES). They were also responsible for deploying the parachutes. Overall, the CSM required an electrical output of 2000 watts.

Modifications for Skylab

In order to take into account the significantly changed requirements for the flight to the Skylab space station and in particular the fact that the CSM remained docked at the station for several months, the last four CSMs CSM-116 to CSM-119 were extensively modified and the following equipment added or added:

  • a device for power transmission between Skylab and the CSM
  • Backflow-free discharge valves ('non-propulsive vent') for hydrogen and oxygen
  • additional insulation and heater for thermal control
  • Batteries and fuel
  • Racks for experiments
  • changed software and improvements to the erection system

In return:

  • a helium pressure tank and the two storage tanks of the drive (the drive requirement was considerably lower)
  • a large part of the storage space for waste (Skylab provided enough space for this)
  • the swiveling S-band directional antenna at the rear
  • one of the three fuel cells

A CSM could have been further modified for a rescue mission and equipped for five astronauts. The rear cupboards would have been exchanged for two more couches and the life support system would have been added accordingly. A two-man crew could have flown to Skylab and picked up the crew.

The individual Apollo spaceships

Block I.
serial number used for Start date Whereabouts
CSM-001 Test device probably scrapped
CSM-002 A-004 20th January 1966 Command capsule on display in the Cradle of Aviation , Long Island , New York
CSM-004 static tests, heat tests scrapped
CSM-006 scrapped
CSM-007 various tests, etc. a. acoustic vibrations and drop tests Command capsule on display in the Museum of Flight , Seattle , Washington
CSM-008 for heat and vacuum tests scrapped
CSM-009 AS-201 and drop tests February 26, 1966 Command capsule on display at the Strategic Air and Space Museum , Ashland , Nebraska
CSM-010 Command capsule on display at the US Space & Rocket Center , Huntsville , Alabama
CSM-011 AS-202 August 25, 1966 Command capsule on display at the National Air & Space Museum , Washington, DC
CSM-012 Apollo 1 ; Command capsule destroyed by fire Command capsule kept at Langley Research Center , Hampton , Virginia
CSM-014 Command capsule dismantled as part of the Apollo 1 investigation. Service Module (SM-014) flew with Apollo 6 4th April 1968
CSM-017 Apollo 4 November 9, 1967 Command capsule on display at the Stennis Space Center , Bay St. Louis , Mississippi
CSM-020 CM-020 was used together with SM-014 for Apollo 6 after SM-020 was destroyed by an explosion 4th April 1968 Command Module on display at the Fernbank Science Center , Atlanta
Block II
serial number used for Start date Whereabouts
CSM-098 for heat and vacuum tests Spaceship exhibited in the Academy of Science Museum , Moscow (but there may only be one model)
CSM-099 Stress tests possibly scrapped, but maybe also dismantled in the National Air & Space Museum , Washington, DC
CSM-100 Stress tests possibly kept in the National Air & Space Museum , Washington, DC
CSM-101 Apollo 7 October 11, 1968 Command capsule on display at the National Museum of Science & Technology , Ottawa , Canada
CSM-102 Test device in the Kennedy Space Center possibly kept in the National Air and Space Museum , Washington, DC
CSM-103 Apollo 8 December 21, 1968 Command capsule on display at the Museum of Science and Industry in Chicago
Apollo 9 March 3, 1969 Command capsule on display at the San Diego Aerospace Museum
CSM-105 Vibration tests and demonstration for the Apollo-Soyuz test project Command capsule on display at the National Air and Space Museum , Washington, DC as the Apollo-Soyuz Test Project
Charlie Brown
Apollo 10 May 18, 1969 Command capsule on display in the Science Museum , London
Apollo 11 July 16, 1969 Command capsule on display at the National Air & Space Museum , Washington, DC
Yankee Clipper
Apollo 12 November 14, 1969 Command Module on display at the Virginia Air & Space Center , Hampton , Virginia
Apollo 13 April 11, 1970 Command capsule on display at the Kansas Cosmosphere and Space Center
Kitty Hawk
Apollo 14 January 31, 1971 Command capsule on display at the Saturn V Center at the Kennedy Space Center in Florida . She was previously a member of the United States Astronaut Hall of Fame , Titusville , Florida .
CSM-111 Apollo Soyuz Test Project 15th July 1975 Command capsule on display at the Kennedy Space Center Visitor's Complex
Apollo 15 July 26, 1971 Command capsule on display at the National Museum of the United States Air Force , Wright-Patterson Air Force Base , Dayton , Ohio
Apollo 16 April 16, 1972 Command capsule on display at the US Space & Rocket Center , Huntsville , Alabama
Apollo 17 7th December 1972 Command Module on display at the Lyndon B. Johnson Space Center , Houston , Texas
CSM-115 - Not completed. On display as part of the Saturn V at Lyndon B. Johnson Space Center , Houston
CSM-115a - not completed
CSM-116 Skylab 2 May 25, 1973 Command capsule on display at the National Museum of Naval Aviation on Naval Air Station Pensacola , Florida
CSM-117 Skylab 3 July 28, 1973 Command Module on display at the Glenn Research Center , Cleveland , Ohio
CSM-118 Skylab 4 November 16, 1973 Command capsule on display at the National Air & Space Museum , Washington, DC
CSM-119 Maintained as a rescue spaceship for Skylab and as a reserve for the Apollo-Soyuz test project Exhibited at the Kennedy Space Center

See also

Web links