Apollo 13 Command and Service Module (CSM)

Description

Apollo 13 was intended to be the third mission to carry humans to the surface of the Moon, but an explosion of one of the oxygen tanks and resulting damage to other systems resulted in the mission being aborted before the planned lunar landing could take place. The crew, commander James A. Lovell, Jr., command module pilot John L. Swigert, Jr., and lunar module pilot Fred W. Haise Jr., were returned safely to Earth on 17 April 1970.

Mission Profile

Apollo 13 was launched on Saturn V SA-508 on 11 April 1970 at 19:13:00 UT (02:13:00 p.m. EST) from pad 39A at Kennedy Space Center. During second stage boost the center engine of the S-II stage cut off 132 seconds early, causing the remaining four engines to burn 34 seconds longer than normal. The velocity after S-II burn was still lower than planned by 68 m/sec, so the S-IVB orbital insertion burn at 19:25:40 was 9 seconds longer than planned. Translunar injection took place at 21:54:47 UT, CSM/S-IVB separation at 22:19:39 UT, and CSM-LM docking at 22:32:09 UT. The S-IVB auxilliary propulsive system burned at 01:13 UT on 12 April for 217 seconds to put the S-IVB into a lunar impact trajectory. (It impacted the lunar surface on 14 April at 01:09:41.0 at 2.75 S, 27.86 W with a velocity of 2.58 km/s at a 76 degrees angle from horizontal.) A 3.4 second mid-course correction was made at 01:27 UT on 13 April.

A television broadcast was made from Apollo 13 from 02:24 UT to 02:59 UT on 14 April and a few minutes later, at 03:06:18 UT Jack Swigert turned the fans on to stir oxygen tanks 1 and 2 in the service module. The Accident Review Board concluded that wires which had been damaged during pre-flight testing in oxygen tank no. 2 shorted and the teflon insulation caught fire. The fire spread within the tank, raising the pressure until at 3:07:53 UT on 14 April (10:07:53 EST 13 April; 55:54:53 mission elapsed time) oxygen tank no. 2 exploded, damaging oxygen tank no. 1 and the interior of the service module and blowing off the bay no. 4 cover. With the oxygen stores depleted, the command module was unusable, the mission had to be aborted, and the crew transferred to the lunar module and powered down the command module.

At 08:43 UT a mid-course maneuver (11.6 m/s delta V) was performed using the lunar module descent propulsion system (LMDPS) to place the spacecraft on a free-return trajectory which would take it around the Moon and return to Earth, targeted at the Indian Ocean at 03:13 UT 18 April. After rounding the Moon another LMDPS burn at 02:40:39 UT 15 April for 263.4 seconds produced a differential velocity of 262 m/s and shortened the estimated return time to 18:06 UT 17 April with splashdown in the mid-Pacific. To conserve power and other consumables the lunar module was powered down except for environmental control, communications, and telemetry, and passive thermal control was established. At 04:32 UT on 16 April a 15 second LMDPS burn at 10% throttle produced a 2.3 m/s velocity decrease and raised the entry flight path angle to -6.52 degrees. Following this the crew partially powered up the CSM. On 17 April at 12:53 UT a 22.4 second LMDPS burn put the flight path entry angle at -6.49 degrees.

The service module, which had been kept attached to the command module to protect the heat shield, was jettisoned on 17 April at 13:15:06 UT and the crew took photographs of the damage. The command module was powered up and lunar module was jettisoned at 16:43:02 UT. Any parts of the lunar module which survived atmospheric re-entry, including the SNAP-27 generator, planned to power the ALSEP apparatus on the lunar surface and containing 3.9 kg of plutonium, fell into the Pacific Ocean northeast of New Zealand. Apollo 13 splashed down in the Pacific Ocean on 17 April 1970 at 18:07:41 UT (1:07:41 p.m. EST) after a mission elapsed time of 142 hrs, 54 mins, 41 secs. The splashdown point was 21 deg 38 min S, 165 deg 22 min W, SE of American Samoa and 6.5 km (4 mi) from the recovery ship USS Iwo Jima.

The spacecraft was the second of the Apollo H-series. The purposes of the mission were (1) to explore the hilly upland Fra Mauro region of the moon, (2) to perform selenological inspection, survey, and sampling of material in the Fra Mauro formation, (3) to deploy and activate an Apollo lunar surface experiments package (ALSEP), (4) to further develop man's capability to work in the lunar environment, and (5) to obtain photographs of candidate lunar exploration sites. These goals were to be carried out from a near-circular lunar orbit and on the lunar surface at 3 deg S latitude, 17 deg W longitude. Although the planned mission objectives were not realized, a limited amount of photographic data was obtained. Lovell was a Navy captain on his fourth spaceflight (he'd flown previously on Gemini 7, Gemini 12, and Apollo 8), Haise and Swigert were both civilians on their first spaceflights. The backup crew was John Young, Charles Duke, and John Swigert (who replaced Thomas Mattingly on the prime crew after the crew was exposed to German measles). The Apollo 13 Command Module "Odyssey" is now at the Kansas Cosmosphere and Space Center, Hutchinson, Kansas. It was originally on display at the Musee de l'Air, Paris, France.

Spacecraft and Subsystems

As the name implies, the Command and Service Module (CSM) comprised two distinct units: the Command Module (CM), which housed the crew, spacecraft operations systems, and re-entry equipment, and the Service Module (SM) which carried most of the consumables (oxygen, water, helium, fuel cells, and fuel) and the main propulsion system. The total length of the two modules attached was 11.0 meters with a maximum diameter of 3.9 meters. Block II CSM's were used for all the crewed Apollo missions. The Apollo 13 CSM mass of 28,881 kg was the launch mass including propellants and expendables, of this the Command Module (CM 109) had a mass of 5703 kg and the Service Module (SM 109) 23,178 kg.

Telecommunications included voice, television, data, and tracking and ranging subsystems for communications between astronauts, CM, LM, and Earth. Voice contact was provided by an S-band uplink and downlink system. Tracking was done through a unified S-band transponder. A high gain steerable S-band antenna consisting of four 79-cm diameter parabolic dishes was mounted on a folding boom at the aft end of the SM. Two VHF scimitar antennas were also mounted on the SM. There was also a VHF recovery beacon mounted in the CM. The CSM environmental control system regulated cabin atmosphere, pressure, temperature, carbon dioxide, odors, particles, and ventilation and controlled the temperature range of the electronic equipment.

Command Module

The CM was a conical pressure vessel with a maximum diameter of 3.9 m at its base and a height of 3.65 m. It was made of an aluminum honeycomb sandwhich bonded between sheet aluminum alloy. The base of the CM consisted of a heat shield made of brazed stainless steel honeycomb filled with a phenolic epoxy resin as an ablative material and varied in thickness from 1.8 to 6.9 cm. At the tip of the cone was a hatch and docking assembly designed to mate with the lunar module. The CM was divided into three compartments. The forward compartment in the nose of the cone held the three 25.4 m diameter main parachutes, two 5 m drogue parachutes, and pilot mortar chutes for Earth landing. The aft compartment was situated around the base of the CM and contained propellant tanks, reaction control engines, wiring, and plumbing. The crew compartment comprised most of the volume of the CM, approximately 6.17 cubic meters of space. Three astronaut couches were lined up facing forward in the center of the compartment. A large access hatch was situated above the center couch. A short access tunnel led to the docking hatch in the CM nose. The crew compartment held the controls, displays, navigation equipment and other systems used by the astronauts. The CM had five windows: one in the access hatch, one next to each astronaut in the two outer seats, and two forward-facing rendezvous windows. Five silver/zinc-oxide batteries provided power after the CM and SM detached, three for re-entry and after landing and two for vehicle separation and parachute deployment. The CM had twelve 420 N nitrogen tetroxide/hydrazine reaction control thrusters. The CM provided the re-entry capability at the end of the mission after separation from the Service Module.

Service Module

The SM was a cylinder 3.9 meters in diameter and 7.6 m long which was attached to the back of the CM. The outer skin of the SM was formed of 2.5 cm thick aluminum honeycomb panels. The interior was divided by milled aluminum radial beams into six sections around a central cylinder. At the back of the SM mounted in the central cylinder was a gimbal mounted re-startable hypergolic liquid propellant 91,000 N engine and cone shaped engine nozzle. Attitude control was provided by four identical banks of four 450 N reaction control thrusters each spaced 90 degrees apart around the forward part of the SM. The six sections of the SM held three 31-cell hydrogen oxygen fuel cells which provided 28 volts, two cryogenic oxygen and two cryogenic hydrogen tanks, four tanks for the main propulsion engine, two for fuel and two for oxidizer, and the subsystems the main propulsion unit. Two helium tanks were mounted in the central cylinder. Electrical power system radiators were at the top of the cylinder and environmental control radiator panels spaced around the bottom.

Apollo Program

The Apollo program included a large number of uncrewed test missions and 12 crewed missions: three Earth orbiting missions (Apollo 7, 9 and Apollo-Soyuz), two lunar orbiting missions (Apollo 8 and 10), a lunar swingby (Apollo 13), and six Moon landing missions (Apollo 11, 12, 14, 15, 16, and 17). Two astronauts from each of these six missions walked on the Moon (Neil Armstrong, Edwin Aldrin, Charles Conrad, Alan Bean, Alan Shepard, Edgar Mitchell, David Scott, James Irwin, John Young, Charles Duke, Gene Cernan, and Harrison Schmitt), the only humans to have set foot on another solar system body. Total funding for the Apollo program was approximately $20,443,600,000.