Un problème de court-circuit électrique … entre la terre et la lune

Au cours de la mission Appolo 13, voilà 43 ans, lire (en anglais)



11 avril 1970

En route to the Moon, approximately 200,000 miles (320,000 km) from Earth, Mission Control asked Swigert to turn on the hydrogen and oxygen tank stirring fans, which were designed to destratify the cryogenic contents and increase the accuracy of their quantity readings. Approximately 93 seconds later, just under 56 hours since launch, the astronauts heard a “loud bang”, accompanied by fluctuations in electrical power and firing of the attitude control thrusters.[6] The crew initially thought that a meteoroid might have struck the Lunar Module (LM).

In fact, the number-2 oxygen tank, one of two in the Service Module (SM), had exploded.[11] Damaged Teflon insulation on the wires to the stirring fan inside oxygen tank 2 allowed the wires to short-circuit and ignite this insulation. The resulting fire rapidly increased pressure beyond its 1,000 pounds per square inch (6.9 MPa) limit and the tank dome failed, filling the fuel cell bay (Sector 4) with rapidly expanding gaseous oxygen and combustion products. It is also possible some combustion occurred of the Mylar/Kapton thermal insulation material used to line the oxygen shelf compartment in this bay.[12]

The resulting pressure inside the compartment popped the bolts attaching the 13-foot Sector-4 outer aluminum skin panel, which as it blew off probably caused minor damage to the nearby high-gain S-band antenna used for translunar communications. Communications and telemetry to Earth were lost for 1.8 seconds, until the system automatically corrected by switching the antenna from narrow-band to wide-band mode.

Mechanical shock forced the oxygen valves closed on the number-1 and number-3 fuel cells, leaving them operating for only about three minutes on the oxygen in the feed lines. The shock also either partially ruptured a line from the number-1 oxygen tank, or caused its check or relief valve to leak, causing its contents to leak out into space over the next 130 minutes, entirely depleting the SM’s oxygen supply.[12]

Because the fuel cells combined hydrogen and oxygen to generate electricity and water, the remaining fuel cell number 2 finally shut down and left the Command Module (CM) on limited-duration battery power. The crew was forced to shut down the CM completely and to use the LM as a “lifeboat”.[13] This situation had been suggested during an earlier training simulation, but had not been considered a likely scenario.[14] Without the LM, the accident would certainly have been fatal.[15]




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