Science Fair Project Encyclopedia
- This article is about the Moon mission. There is also a movie by the name of Apollo 13.
|Mission name:||Apollo 13|
|Call sign:||Command module: Odyssey|
Lunar module: Aquarius
|Launch:||April 11, 1970|
Kennedy Space Center
|April 15, 1970|
254.3 km from Moon
400,171 km from Earth
|Splashdown:||April 17, 1970|
21° 38' 24" S - 165° 21' 42" W
|Duration:||5 d 22 h 54 min 41 s|
|Mass:||CSM 28,945 kg;|
LM 15,235 kg
Apollo 13 crew portrait
(L-R: Lovell, Swigert, and Haise)
|Apollo 13 Crew|
Apollo 13 was an American space mission, part of the Apollo program. It was intended to be the third mission to land on the Moon, but instead is famous for the critical malfunction it suffered and its difficult but successful return home.
- James Lovell (4), commander
- John Swigert (1), command module pilot
- Fred Haise (1), lunar module pilot
- Mass: CM 28,945 kg; LM 15,235 kg
- Perigee: 181.5 km
- Apogee: 185.6 km
- Inclination: 33.5°
- Period: 88.07 min
Oxygen tank explosion
Closest approach to Moon
- April 15, 1970, 00:21:00 UTC
- 254.3 km above far side of Moon;
- 400,171 km from Earth (possibly a record distance, see below).
Famous misquote: "Houston, we have a problem"
Actual quote: "Okay, Houston, we've had a problem here" , uttered by Swigert to ground. Lovell then uttered this similar phrase: "Houston, we've had a problem."
The crew's understated radio message to Mission Control was "Okay, Houston, we've had a problem here." Within 321,860 kilometers of Earth, an oxygen tank in the service module exploded. The only solution was for the crew to cancel their planned landing, swing around the Moon and return on a trajectory back to Earth. Since their command/service module "Odyssey" was severely damaged, however, the three astronauts had to use the lunar module "Aquarius" as a crowded lifeboat for the return home. The four-day return trip was cold, uncomfortable, and tense. But Apollo 13 proved the program's ability to weather a major crisis and bring the crew back home safely.
As the spacecraft was on its way to the Moon, the number two oxygen tank in the Service Module exploded when Mission Control requested that the crew perform a "cryo stir", in which the oxygen "slush" is stirred to prevent it from stratifying. Faulty wires connecting to the stirrer motor caught fire when power was applied. The fire caused a pressure increase above the tank's nominal 1,000 lb/in² (7 MPa), and the tank exploded. The explosion damaged other parts of the service module, including the number 1 oxygen tank. At the time of the explosion, however, the true cause was not known, and was conjectured to be a meteoroid impact.
The loss of both Service Module oxygen tanks and the oxygen required to create electrical power for much of the spacecraft meant that the Moon-landing mission had to be aborted; a single pass around the Moon was made and the spacecraft returned to Earth. Considerable ingenuity under extreme pressure was required from both the crew and the ground controllers to figure out how to jury rig the craft for the crew's safe return, with much of the world watching the drama on television. Central to the survival of the crew was the use of the Lunar Module (still attached to the Command Module) as a "lifeboat". One of the major stumbling blocks in this was that the LM was equipped to sustain two people for two days, and it would now have to sustain three people for four days. The carbon dioxide filters in the LM could not handle the extra load and the CM's spare filters were the wrong shape for the LM's filter receptacle; an adapter had to be fabricated from materials in the spacecraft. The crew had to use the LM as a lifeboat because the explosion had damaged the craft's electrical systems, precluding the generation of enough power to keep the Command Module operational. The emergency batteries would only last about ten hours, and needed to be saved for re-entry.
In order to accomplish a safe return to Earth, a significant course correction to place the spacecraft on a free return trajectory was required. This would normally be a simple procedure using the service module propulsion engine. However, the mission's ground controllers did not know the extent of the damage the service module had suffered and did not want to risk firing the main engine. Instead, the course correction would have to be performed by firing the lunar module's descent engine. After extensive thought and discussion, engineers on the ground found it was possible. The descent engine was fired after passage around the Moon in order to accelerate the spacecraft's return to Earth, and once again for a minor course correction. This created concern, as the LM was designed to be fired once and permanently shut down.
Re-entry in Earth's atmosphere required the unusual step of undocking and jettisoning the lunar module, which had been retained for the flight back to Earth, in addition to the separation of the damaged service module. There was some fear the reduced temperatures during the return leg would cause condensation that could seriously damage the electronics of the Command Module upon activation, but the equipment worked perfectly under the circumstances.
The crew returned unharmed to Earth, although Haise had a urinary tract infection resulting from the scarcity of potable water on the damaged ship and the difficulty of disposing of urine, and had to be treated in an infirmary. When the crew saw the damaged service module, they reported that the access panel covering the O2 tanks and fuel cells had been blown off.
It was noted later that while the crew was unfortunate to have this kind of major malfunction, they were still extremely lucky that it occurred on the first leg of the mission when they had a maximum of supplies, equipment, and power to use in the emergency. If the explosion had occurred on the return leg after the Moon landing, it is unlikely that they would have survived, especially if the LEM had already been jettisoned.
After the completion of the mission, there was a full investigation of the incident and the craft was modified to prevent future occurrences of the fault.
Cause of the accident
The explosion on Apollo 13 led to a lengthy investigation of the underlying cause. Thanks to detailed manufacturing records and logs of mission problems, the failure of the faulty oxygen tank was tracked to multiple faults that were not problems individually, but nearly led to disaster on this mission.
Liquid gases are very difficult to handle, and most storage containers holding them are unsealed so that pressure from expanding gas will not cause the container to fail (much like freezing water in even the strongest sealed container will shatter it). Apollo's liquid oxygen tank was a marvel of engineering, able to hold several hundred pounds of highly pressurized liquid gas to supply the craft with oxygen, fuel for electricity (along with hydrogen) and water from the by-product of the fuel cells. Left alone, the tank was capable of safely holding liquid oxygen under high pressure for years before it evaporated because of its design and insulation. Unfortunately, the very characteristic that made the tank useful made internal inspection impossible.
The tank was made of several basic components that were relevant to the accident:
- A thermostat to control the heater within the tank that sped the evaporation of the liquid into gaseous oxygen;
- A thermometer to determine the temperature of the heater;
- Valves and piping that were designed to allow the tank to be completely emptied of liquid by forcing gas into the tank;
- An interior coating of teflon that protected the wiring from the extremely cold gas; and
- An internal fan to stir the liquid oxygen (liquid oxygen will turn into a "slush" at these pressures if it is allowed to sit for a long period of time).
These were the basic design, manufacturing and operational problems that led to the accident.
- The thermostat was originally designed to handle the 24 volt current that would be used in the command module. However, the specification for the tank was changed so that it had to handle 120 volt current on the launch pad. Most of the wiring was changed to handle the higher voltage, but the thermostat was not.
- The thermometer was designed to read out at the highest operational temperature of the heater, about 100 degrees Fahrenheit. Higher temperatures registered at 100, but the thermostat was supposed to cut out at that temperature, making higher temperatures impossible.
- During assembly, the structure carrying the tank that failed was dropped about 2 inches (5 cm). The exterior was undamaged, but the pipes that directed flow within the tank became misaligned.
- For ground testing the tank was filled. However, when it came time to empty it, the problem with the piping was discovered. As such, the tank could not be properly emptied except for running the heater to evaporate the liquid gas. There was no alternative tank available, and trashing this tank would have delayed the mission. Lovell was in on the decision to use the heater to evaporate the oxygen, which was calculated to take a few days at the highest operational temperature of 100 degrees.
- However, when the heater was turned on continuously, the higher voltage fused the thermostat, which allowed the heater to keep heating up. Because the thermostat did not register temperatures higher than 100 degrees, the monitoring equipment did not pick this up. Instead of taking several days, the gas evaporated in hours, and the interior of the tank kept heating up, reaching an estimated 800 degrees. This burned off the teflon coating, leaving the wires inside the tank exposed.
- The rest was inevitable. When the tank was re-filled with oxygen, it became a bomb waiting to go off. The order to run the "cyro stir" to run the fans set off sparks inside the tank which led to the explosion.
- However, disaster could have been averted if it had not been for the fact that both oxygen tanks were next to each other in the assembly. Although the second tank survived the explosion, its valves were damaged which allowed the oxygen within to leak out. In future Apollo missions, the two oxygen tanks were put in different parts of the craft.
- Swigert was a replacement for Ken Mattingly, who later flew to the Moon aboard Apollo 16. Mattingly was reportedly exposed to German measles prior to the mission, and NASA officials insisted upon removing him from the flight so as not to endanger the mission. He never contracted the sickness and played a critical role in the crisis working on the simulator to help devise a means for the crew to return home safely.
- As a result of following the free return trajectory, the altitude of Apollo 13 over the lunar far side was approximately 100 km greater than the corresponding orbital altitude on the remaining Apollo lunar missions. This could mean an all-time altitude record for human spaceflight—not even superseded as of 2005—but this may well not be the case: the variation in distance between Earth and the Moon owing to the eccentricity of the Moon's orbit about Earth is much larger than this 100 km.
- The splashdown point was 21° 38′ S, 165° 22′ W, SE of American Samoa and 6.5 km (4 mi) from the recovery ship, USS Iwo Jima.
- There was another not quite so famous failure on this mission which could have been equally catastrophic. During second stage burn the center engine shut down. It was later discovered that this was due to dangerous pogo oscillations which might have torn the second stage apart. Luckily the oscillations caused a low pressure reading to register, and the computer shut the engine down automatically.
The Apollo 13 logo featured three flying horses, and the motto Ex luna, scientia (from the Moon, knowledge), and the number of the mission in Roman numerals.
- Launched: April 11, 1970 from Pad 39A
- Returned: April 17, 1970
- Crew members: Jim Lovell, commander; Jack Swigert, command module pilot; Fred Haise, lunar module pilot.
- Command module: Odyssey
- Lunar module: Aquarius
- Intended lunar landing site: Fra Mauro highlands
The command module is currently displayed at the Kansas Cosmosphere and Space Center, Hutchinson, Kansas. It was formerly at the Musee de l'Air , Paris. The lunar module burned up in Earth's atmosphere 17 April, 1970, having been targeted to enter over the Pacific Ocean to reduce the possibility of contamination from radioactive material on board.
- Apollo 13 - the 1995 movie directed by Ron Howard and starring, as the astronauts, Tom Hanks, Bill Paxton, and Kevin Bacon, with Ed Harris, Kathleen Quinlan, and Gary Sinise in supporting roles.
- Apollo 13 - a 1995 board game released by Universal Games and based on the popular 1986 space-age Monopoly variant, Solarquest. Sega also produced an Apollo 13 pinball machine, featuring a 13-ball multiball.
- NASA NSSDC Master Catalog
- APOLLO BY THE NUMBERS: A Statistical Reference by Richard W. Orloff (NASA)
- The Apollo Spacecraft: A Chronology
- Apollo Program Summary Report
- Apollo 13 Characteristics - SP-4012 NASA HISTORICAL DATA BOOK
- Original Apollo 13 Lunar Exploration and Photography Summary Plan (PDF), February 1970
- Apollo 13 Spacecraft Incident Investigation, (PDF) NASA June 1970
- Report of Apollo 13 Review Board, (PDF) NASA June 1970
- Apollo 13 Technical Air-to-Ground Voice Transcription, April 1970, 765 pages (PDF, 20.4 MB)
- Apollo 13, We Have a Solution: Rather than hurried improvisation, saving the crew of Apollo 13 took years of preparation
- Lovell, Jim; Kluger, Jeffrey (1994). Lost Moon: The Perilous Voyage of Apollo 13. Houghton Mifflin. ISBN 0395670292.
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