Apollo 13

From Academic Kids

This article is about the Moon mission. There is also a movie by the name of Apollo 13.
Apollo 13
Mission insignia
Apollo 13 insignia
Mission statistics
Mission name:Apollo 13
Call sign:Command module: Odyssey
Lunar module: Aquarius
Number of
Launch:April 11, 1970
19:13:00 UTC
Kennedy Space Center
LC 39A
Lunar flyby:
April 15, 1970
00:21:00 UTC
254.3 km from Moon
400,171 km from Earth
Splashdown:April 17, 1970
18:07:41 UTC
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
Crew picture
Apollo 13 crew portrait (L-R: Lovell, Swigert, and Haise)
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.



Backup crew

Support crew

Mission parameters

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).

See also


Famous misquote: "Houston, we have a problem"
Actual quote: "Okay, Houston, we've had a problem here" [1] (http://www.hq.nasa.gov/office/pao/History/Timeline/apollo13chron.html), uttered by Swigert to ground. Lovell then uttered this similar phrase: "Houston, we've had a problem."

Mission highlights

The crew's understated radio message to Mission Control was "Okay, Houston, we've had a problem here." When Apollo 13 was 321,860 kilometers from 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. However, because their command/service module "Odyssey" was severely damaged, 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. Damaged wires powering 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 the CSM meant that the CSM had to be completely shut down. The CM contained batteries for use during re-entry, after the Service Module was jettisoned, but these would only last about ten hours, and needed to be saved for re-entry. The crew survived by using the Lunar Module (still attached to the Command Module) as a "lifeboat".

Missing image
Apollo 13 damaged Service Module (NASA)

The loss of electrical power in the CSM meant that the Moon-landing mission (originally intended to land at the Fra Mauro Highlands) 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. One of the major stumbling blocks in this was that the LM "lifeboat" 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.

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 discussion, engineers on the ground found it was possible. The maneuver to a free return trajectory was made within hours of the accident. The descent engine was fired again 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.

As re-entry to Earth's atmosphere approached, NASA took the unusual step of jettisoning the Service Module first, while the Lunar Module was still attached to the Command Module. The LM thrusters were used to maneuver the CM/LM stack to point its windows at the departing SM, and photos were taken. 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.

There was some fear that the extensive condensation in the CM, due to reduced temperatures during the return leg, could seriously damage the electronics of the Command Module upon activation. In the event, the equipment worked perfectly, at least in part due to the extensive design modifications made to the CM after the Apollo 1 fire.

Missing image
A successful splashdown (NASA)

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.

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 LM had been jettisoned, it is not likely that the crew would have survived.

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.

Jim Lovell and Jeffrey Kluger's book about the mission, Lost Moon, was later turned into a successful movie, Apollo 13, starring Tom Hanks and Kevin Bacon.

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 28 volt supply that would be used in the command module. However, the specification for the tank was changed so that it had to handle 65 volts 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 80 degrees, 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 80 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. The current recorder in the power supply showed that the heater was not cycling on and off, but no-one noticed it at the time. 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 "cryo 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.

Mission notes

  • 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.
  • 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.
  • Superstitious people have often associated the belief that 13 is an unlucky number to the mission, especially due to the fact that the mission began at 13:13, and the problems began on April 13.


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. It is one of two Apollo insignias (the other being Apollo 11's) not to include the names of the crew.


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 a radioisotope thermoelectric generator (RTG) on board (had the mission proceeded as planned, the RTG would have been used to power the Apollo Lunar Surface Experiment Package, and then remained on the Moon). The RTG survived reentry (as designed) and landed in the Tonga Trench. While it will remain radioactive for approximately 2000 years, it does not appear to be releasing radioactive material.


Board game

External link



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