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Apollo 13

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This article is about the Moon mission. For the film, see Apollo 13 (film).
Apollo 13
Mission insignia
Apollo 13 insignia
Mission statistics
Mission name: Apollo 13
Call sign: Command module: Odyssey
Lunar module: Aquarius
Number of
crew:		 3
Launch: April 11, 1970
19:13:00 UTC
Kennedy Space Center
LC 39A
Lunar flyby:
(Pericynthion)		 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 the third American manned lunar landing mission, part of the Apollo program. Two days after launch, the Apollo Spacecraft was crippled by an explosion, causing the Service Module portion of the Apollo Command/Service Module to lose its oxygen and electrical power. The crew used the Lunar Module as a lifeboat in space. The command module systems remained functional but were deactivated to preserve its capability to re-enter earth's atmosphere upon return to the earth. The crew endured difficult conditions due to severe constraints on power, cabin heat, and drinkable water, but successfully returned to Earth.

Crew

Backup Crew

Support crew

Changes

Ken Mattingly, who was slated to be command module pilot, was grounded shortly before launch due to exposure to Rubella, which he was not immune to (yet never ended up contracting). He was replaced by John Swigert, for Apollo 13 and he later flew with Young and Duke (Apollo 13 back-up crew) as command module pilot on Apollo 16.

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

Quote

Famous misquote: "Houston, we have a problem"
Actual quote: "Okay, Houston, we've had a problem here" [1], uttered by Swigert to ground. Lovell then uttered this similar phrase: "Houston, we've had a problem."

Mission highlights

The Apollo 13 mission began with a lesser-known malfunction. During the second stage burn the center engine shut down prematurely. Engineers later discovered that this was due to dangerous pogo oscillations which might have torn the second stage apart; the engine was experiencing 68g vibrations at 16 hertz, flexing the thrust frame by 3 inches. Luckily the oscillations caused a low pressure reading to register, and the computer shut the engine down automatically. This was later traced to amplification of the pogo that had occurred on previous flights by an unexpected interaction with the cavitation in the turbopumps. Later missions had anti-pogo devices, as had already been planned since before Apollo 13, which solved the problem.

Problem

As the spacecraft was on its way to the Moon, at a distance of 321,860 kilometers (199,990 mi) from Earth, the number two oxygen tank in the Service Module (SM) exploded. Mission Control requested that the crew stir the oxygen tanks, a task required to prevent the oxygen "slush" from stratifying. Damaged Teflon-insulated electrical wires powering the stirrer motor caught fire when power was applied. The fire caused a pressure increase above the tank's nominal 1,000 lbf/in² (7 MPa), causing the tank to explode. The true cause of the explosion was unknown at the time. One conjecture was that a meteoroid had impacted the SM.

This explosion damaged other parts of the service module, primarily the number one oxygen tank. As a result the Command/Service Modules (CSM) lost its entire oxygen supply. The oxygen in the service module was required to create electrical power for the CSM, meaning that after the explosion very little power was available for the spacecraft. The Command Module (CM) contained batteries for use during re-entry, after the Service Module was jettisoned, but these would only last about ten hours. Because this power needed to be saved for re-entry, the crew survived by using the Lunar Excursion Module (LEM) - still attached to the CSM - as a "lifeboat". The LEM "lifeboat" procedure had actually been worked on/created during a training simulation (in the simulator) not long before the flight of Apollo 13.[1](Lovell and Kluger 83-87)

Apollo 13 damaged Service Module (NASA)

The damage to the CSM meant that the Moon-landing mission (originally intended to land at the Fra Mauro Highlands) had to be aborted. In order to return the crew as quickly and safely as possible, only a single pass around the Moon was made in what is called a free return trajectory, which uses the Moon's gravity to effectively "slingshot" the spacecraft back to Earth. To enter this trajectory, a significant course correction was required. This would normally be a simple procedure using the service module propulsion engine. However, the flight 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 initial maneuver to change to a free return trajectory was made within hours of the accident. After passage around the moon, the descent engine was fired again for a PC+2 (PeriCynthion + 2 hours) burn in order to accelerate the spacecraft's return to Earth. Only one more descent engine burn was required later, for a minor course correction.

Considerable ingenuity under extreme pressure was required from both the crew and the flight controllers to figure out how to jury rig the craft for the crew's safe return, with much of the world watching the developing drama on television. One of the major stumbling blocks in this was that the LEM "lifeboat" was only equipped to sustain two people for two days, yet it would now be required to sustain three people for four days. One of the most critical problems was that the lithium hydroxide carbon dioxide filters in the LEM would not last for all four days. Adding to the problem, the CM's spare filters were the wrong shape for the LEM's filter receptacle; an adapter had to be fabricated from materials in the spacecraft.

As re-entry to Earth's atmosphere approached, NASA took the unusual step of jettisoning the Service Module before the Lunar Module, so pictures of the SM could be taken for later analysis. When the crew saw the damaged service module, they reported that the access panel covering the oxygen tanks and fuel cells—which extended the entire length of the Service Module's body—had been blown off.

There was some fear that the extensive condensation in the CM, due to reduced temperatures during the return leg, might have seriously damaged the electronics of the Command Module, which would only become apparent upon activation. But the equipment worked perfectly when activated, at least partly due to the extensive design modifications made to the CM after the Apollo 1 fire.

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 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 while in orbit around the moon, or on the return leg after the LM had been jettisoned, the crew probably would not 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.

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. Individually, these faults were not problems, but together they nearly led to disaster for Apollo 13.

Liquid gases—such as liquid oxygen or liquid hydrogen—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 will shatter even the strongest sealed container). Apollo's liquid oxygen tanks, though, were capable of safely holding liquid oxygen at supercritical pressures for years before it evaporated because of their design and insulation. Each tank was able to hold several hundred pounds of highly pressurized liquid gas to supply the craft with oxygen, fuel for electricity, and water from the by-products of the fuel cells. Unfortunately, the very characteristics 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, used to speed the evaporation of the liquid into gas;
  • 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. Engineers at Saturn V subcontractor Beechcraft, later admitted they knew they had put 65 volts through a line designed for only 28 volts. The tank then made it into the Apollo 13 Service Module which crippled the mission.
  • The thermometer was designed to read out at the highest operational temperature of the heater, about 100 degrees Fahrenheit. As a result, higher temperatures registered at only 100 °F. At the time this was not an issue, because the thermostat was supposed to cut out at 80 °F (27 °C), 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 by running the heater to evaporate the liquid gas. Not using this tank would have delayed the mission and there was no alternate tank available. Lovell was aware of 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 °F (27 °C).
  • However, when the heater was turned on continuously, the higher 65-volt supply fused the thermostat, which was only wired to handle 28 volts. This malfunction eliminated the thermostat's ability to switch off the heater, which in turn allowed the heater to keep heating up past 80 °F (27 °C), eventually past 100 °F. The current recorder in the power supply showed that the heater was not cycling on and off, as it should have if the thermostat was functioning correctly, but no-one noticed it at the time. Because the thermometer did not register temperatures higher than 100 degrees Fahrenheit (38 degrees Celsius), the monitoring equipment did not register the true tempature inside the tank—an estimated 800 degrees Fahrenheit (430 °C). Instead of taking several days, the gas evaporated in hours. The high temperatures burned off the teflon coating, leaving the wires inside the tank exposed.
  • The rest was inevitable. When the tank was refilled with oxygen, it became a bomb waiting to go off. During the "cryo stir" procedure, the electricity to run the fans ran through the exposed wires inside the tank, setting off sparks which led to the explosion.
  • The close proximity of the two oxygen tanks exacerbated the situation. 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 situated farther apart.

Mission notes

  • There was no time to properly replace the original lunar plaque on Aquarius (which bore Mattingly's name), so Jim Lovell was given a replacement (with Swigert's name) to place over the original plaque once they landed on the moon. However, because the lunar landing was never made, Lovell kept the plaque, which is one of the few mementos from the mission that he has on display at his home.
  • 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 2006—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 Guinness Book of Records listed this flight as having the absolute altitude record for a manned spacecraft, and Lovell should have received a certificate from them attesting to this record (Lovell stated in the book Lost Moon that apart from the plaque and a couple of other pieces of salvage, the only other item he has regarding this mission was a letter from Charles Lindbergh).
  • The splashdown point was 21°38′S 165°22′W / 21.633°S 165.367°W / -21.633; -165.367, SE of American Samoa and 6.5 km (4 mi) from the recovery ship, USS Iwo Jima.
  • When the Apollo 13 Command Module was examined after its return, it was found that the crew had tried to wire up a manual deployment switch for the recovery parachutes. However - they had in fact wired the switch to the parachute jettison control. If they had decided to use their jury-rigged manual override they would have in reality released the parachutes from the command module and plunged to their deaths in the ocean below.
  • The Apollo 13 mission has been called "A Successful Failure" from the fact that it was successful in bringing the astronauts home, but it failed to land on the moon.

Insignia

The Apollo 13 logo featured three flying horses of Apollo's chariot across the sky, 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 (which was fortunate, considering one of the original crew was replaced not long before the mission began). It was designed by artist Lumen Winter. He based it on a mural he had done for the St. Regis Hotel in New York; the mural was later purchased by actor Tom Hanks, who portrayed Lovell in the movie Apollo 13, and now is on a wall of a restaurant in Chicago owned by Lovell's son.

Relics

The command module shell was formerly at the Musée de l'Air et de l'Espace, Paris. The interior components were removed during the investigation of the accident and reasembled into BP-1102A, the water egress training module, and were subsequently on display at the Museum of Natural History and Science in Louisville, Kentucky until 2000. The command module and the internal components were reasembled, and Odyssey is currently on display at the Kansas Cosmosphere and Space Center, Hutchinson, Kansas.

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 any of its 3.9 kg of radioactive plutonium. [2] NASA has expressed a wish that the RTG be recovered.

Dramatization

Games

External links

References

Wikimedia Commons has media related to Apollo 13.
  1. ^ Lovell, Jim, and Jeffrey Kluger. Apollo 13. Boston: Houghton Mifflin, 2000.
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