Apollo 13 (AS-508): Houston, we have a problem.


The Apollo 13 mission was launched at 2:13 p.m. EST, April 11, 1970 from
launch complex 39A at Kennedy Space Center. The space vehicle crew consisted of
James A. Lovell, Jr. commander, John L. Swigert, Jr., command module pilot and
Fred W. Haise, Jr. lunar module pilot.
The Apollo 13 Mission was planned as a lunar landing mission but was
aborted en route to the moon after about 56 hours of flight due to loss of
service module cryogenic oxygen and consequent loss of capability to generate
electrical power, to provide oxygen and to produce water.
Spacecraft systems performance was nominal until the fans in cryogenic
oxygen tank 2 were turned on at 55:53:18 ground elapsed time (GET). About 2
seconds after energizing the fan circuit, a short was indicated in the current
from fuel cell 3, which was supplying power to cryogenic oxygen tank 2 fans.
Within several additional seconds, two other shorted conditions occurred.
Electrical shorts in the fan circuit ignited the wire insulation, causing
temperature and pressure to increase within cryogenic oxygen tank 2. When
pressure reached the cryogenic oxygen tank 2 relief valve full-flow conditions
of 1008 psi, the pressure began decreasing for about 9 seconds, at which time
the relief valve probably reseated, causing the pressure to rise again
momentarily. About a quarter of a second later, a vibration disturbance was
noted on the command module accelerometers.
The next series of events occurred within a fraction of a second between
the accelerometer disturbances and the data loss. A tank line burst, because of
heat, in the vacuum jacket pressurizing the annulus and, in turn, causing the
blow-out plug on the vacuum jacket to rupture. Some mechanism in bay 4 combined
with the oxygen buildup in that bay to cause a rapid pressure rise which
resulted in separation of the outer panel. The panel struck one of the dishes of
the high-gain antenna. The panel separation shock closed the fuel cell 1 and 3
oxygen reactant shut-off valves and several propellant and helium isolation
valves in the reaction control system. Data were lost for about 1.8 seconds as
the high-gain antenna switched from narrow beam to wide beam, because of the
antenna being hit and damaged.
As a result of these occurrences, the CM was powered down and the LM was
configured to supply the necessary power and other consumables.
The CSM was powered down at approximately 58:40 GET. The surge tank and
repressurization package were isolated with approximately 860 psi residual
pressure (approx. 6.5 lbs of oxygen total). The primary water glycol system was
left with radiators bypassed.
All LM systems performed satisfactorily in providing the necessary power
and environmental control to the spacecraft. The requirement for lithium
hydroxide to remove carbon dioxide from the spacecraft atmosphere was met by a
combination of the CM and LM cartridges since the LM cartridges alone would not
satisfy the total requirement. The crew, with direction from Mission Control,
built an adapter for the CM cartridges to accept LM hoses.
The service module was jettisoned at approximately 138 hours GET, and
the crew observed and photographed the bay-4 area where the cryogenic tank
anomaly had occurred. At this time, the crew remarked that the outer skin
covering for bay-4 had been severely damaged, with a large portion missing.
The LM was jettisoned about 1 hour before entry, which was performed
nominally using primary guidance and navigation system.

Category: Science