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The Space Shuttle Landed with its APU on Fire – and No One Knew!

STS-9 orbiter suffered two near-catastrophic failures on reentry and landing

STS-9 was the ninth NASA Space Shuttle mission, and the sixth flight of Space Shuttle Columbia. It was launched in November 1983 on a nine-day mission carrying the first Spacelab laboratory module into orbit.

STS-9 was notable for its “firsts.” While this was not Commander John Young’s first Shuttle flight, he was the commander of STS-1, the first Shuttle flight.

STS-9 was a mission of many firsts

sts-9-patch-2This was the first time the Shuttle orbiter flew with six crew members.

It was the first flight for a member of the European Space Agency.

It was the first Spacelab laboratory module mission.

The mission went so well, the mission was extended to 10 days, making STS-9 the longest duration Shuttle flight at that time.

The flight events progressed smoothly. The six astronauts, working in teams of three, worked 12-hour shifts in the Spacelab. Work in the Spacelab went so well that the mission was extended to 10 days, making it the longest-duration shuttle flight at that time.

The Spacelab 1 mission was highly successful, proving the feasibility of the concept of carrying out complex experiments in space using non-NASA persons trained as payload specialists in collaboration with a Payload Operations Control Center (POCC).

Some firsts were not positive

Four hours before scheduled re-entry, one of the flight control computers crashed when the Reaction Control System (RCS) maneuvering thrusters were fired. A few minutes later, a second computer crashed in a similar fashion, but it was successfully rebooted. Young delayed re-entry and allowed the Shuttle to drift in orbit for several hours, double checking their systems.

Re-entry went smoothly and all systems appeared normal throughout the descent and landing.

Then a fire…

What no one knew was that about two minutes before touchdown, two of the three APUs caught fire in the APU compartment in the rear of the Shuttle. The APUs provide hydraulic pressure to operate the orbiter’s flight controls and landing gear.

Unaware of the fire, the crew landed the orbiter without difficulty. The fire continued after the wheels stopped, eventually burning itself out, causing major damage to the compartment. The fact that there had been a fire was not discovered, however, until the APU compartment was opened during post-flight inspections.

Post-flight analysis revealed the first computer failed when the RCS thruster motion knocked a piece of solder loose and shorted the CPU board.

The fire in the APU compartment was caused by a hydrazine fuel leak. Hydrazine is used as a fuel for the RCS thrusters.

During a post-flight press conference, Young remarked that when the first computer failed “…my knees started shaking. When the next computer failed I turned to jelly.” (John Young – Mission Report STS-9)