Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

8.2.2.2 - Apollo 13

 

· a definitive example of failure management

 

· the mission objective was to land on the surface of the moon, and return.

 

· the mission had four major components,

  1. 1. The booster (a saturn V rocket) was used for the initial launch, and was discarded after use.
  2. 2. The lunar module (dubbed Aquarius) was to be used for descent and ascent from the lunar surface, and to be discarded after use.
  3. 3. The service module was to be used for the trip to and from the moon.
  4. 4. The command module was equipped with a heat shield, and would be the only module to return to earth.

 

· In basic terms the mission had to be aborted as a result of an oxygen tank rupture. The fact that the astronauts managed to return back safely is a tribute to the quality of design in the space program.

 

· The events are chronicled below,

 

  1. PRELAUNCH
  2. - during a test the booster oxygen tank drains (causing fires in nearby automobiles, sparked by ignition systems)
  3. - a helium tank on the lunar module is found to have excessive pressure a number of times
  4. - oxygen tanks that supplied breathing air and fuel cells were not draining properly. This was overcome by turning on heat, and redraining the tanks. No action was taken because the performance was adequate. It is believed that a problem arose at this point where insulation on wires inside the tank was worn down because of overheating, and the slower drain of oxygen from the tank.
  5.  
  6. T-5 DAYS
  7. - one of the backup crew (Charles Duke) got german measles, and had exposed one of the crew (Thomas Mattingly). He was replaced by Jack Swigert as the command module pilot. This crew had not had any experience together in critical situations.
  8.  
  9. LAUNCH
  10. - The Saturn V rocket burn is cut off 2 minutes early, requiring additional fuel to be burned to reach earth orbit. Fuel level were now lower, but not critical.
  11.  
  12. T+0 TO 55 HOURS
  13. - one of the oxygen tank pressure gauges had gone off the scale and ground control had requested several times that the oxygen be stirred by a small fan in the tank.
  14. - there were also pressure problems in a lunar module helium tank, and a hydrogen tank.
  15.  
  16. 56 HOURS
  17. - a warning light indicates low pressure in a hydrogen tank in the service module. Fans in the tanks were turned on to stir up the hydrogen.
  18.  
  19. 56 HOURS + 16 SECONDS
  20. - an arc between two wires starts a fire in an oxygen tank fueled by the insulators. The pressure in the oxygen tank builds, and warnings are not sounded because they are overridden by the hydrogen tank warning. The fire spreads through the service module bay.
  21.  
  22. 56 HOURS + 5 MINUTES
  23. - a bang is heard, crew assumes it is a noisy valve actuation, and that it might have been done as a practical joke.
  24. - the pressure has built enough to blow out an outer panel on the service module bay.
  25. - the master power alarm sounds as power on a master bus is lost. This was caused by damaged oxygen lines to the fuel cells. It turns out that 2 of the 3 were off line.
  26. - hatch to lunar module is closed.
  27. - Huston is informed of the problem.
  28. - readings are scrambled, pressures and temperatures appeared erratic. Oxygen pressure in one tank was zero, and dropping in another.
  29. - a cloud is observed outside the service module
  30. - the venting of gases causes the craft to drift off course, the guidance system fails, and the craft begins to wobble, interrupting communications with the ground.
  31. - Huston is still taken by surprise, assuming that four failures indicated could not be related, and almost impossible independently, and they began looking for instrumentation problems.
  32. - a battery for reentry was connected to the power bus, but disconnected to reduce power drain.
  33. - Huston suggests disconnecting the 3rd fuel cell to check to see if oxygen loss was caused by the fuel cell. This operation could not be reversed.
  34. - the goal of landing on the moon is no longer assumed possible, but the lunar module is kept intact for its supply of water and oxygen.
  35. - the reentry battery is recharged and the command module is shut down, as the astronauts move to the lunar module. This is done acknowledging that the effects of the cold on the electronics is not known, and may affect earth reentry.
  36. - it was decided to continue the flight path, and use the moons gravity to get back (with no lunar landing) for a total flight time of 100 hours.
  37. THE NEXT 3 AND A HALF DAYS
  38. - the remainder of the trip was punctuated by,
    1. - cold (minimal power for heating left temperatures about 10°C)
    2. - stress
    3. - fatigue (standing room only, or sleeping in the cold service module)
    4. - hunger (the food was meant to be mixed with hot water)
    5. - thirst (water was generated by the fuel cells)
  39. - the CO2 was normally absorbed by filters. With the extra use the filters in the lunar module were exhausted. The filters from the service module were not the correct shape to fit, requiring a jury rigged arrangement using duct tape.
  40. - a new reentry procedure was devised and had to be relayed verbally to the crew and written on paper (not plentiful). This checklist took 2 hours to transmit verbally.
  41. DESCENT
  42. - The astronauts moved back to the command module, powered up the equipment (luckily the effects of the cold did not cause any malfunctions). There was a new concern that the heat shield was still intact. No instruments allowed this to be checked. The other modules were jettisoned.
  43. - the spacecraft landing began, and finished safely, with one of the fastest recoveries.

 

· In retrospect the accident was reviewed, and the causes for this accident were believed to be,

  1. - budget pressures, morale problems, and schedule pressures encouraged the use of the damaged oxygen tank.
  2. - the estimates of failure effects had been incomplete because of assumptions of adequacy.
  3. - emergency plans were available but not practiced.