SpaceX cargo flight overcomes engine mishap
BY STEPHEN CLARK
Posted: October 8, 2012
One of the Falcon 9 rocket's nine Merlin first stage engines suddenly lost pressure and shut down during Sunday's launch of a commercial resupply craft to the International Space Station, but the engine did not explode and the launcher successfully placed its Dragon payload in the correct orbit, SpaceX said in a statement Monday.
The Falcon 9 rocket lifted off at 8:35 p.m. EDT Sunday (0035 GMT Monday) from Cape Canaveral Air Force Station, Fla., and reached orbit about 10 minutes later, deploying the privately-built Dragon spacecraft to begin a 59-hour chase of the space station.
Although NASA and SpaceX commentators did not acknowledge the mishap in live coverage of the launch, an engine on the Falcon 9's first stage unexpectedly shut down seconds before the rocket passed through Max Q, engineering shorthand for the moment of peak mechanical stress on the vehicle.
"Approximately one minute and 19 seconds into last night's launch, the Falcon 9 rocket detected an anomaly on one first stage engine," SpaceX said in a statement issued Monday. "Initial data suggests that one of the rocket's nine Merlin engines, Engine 1, lost pressure suddenly and an engine shutdown command was issued immediately."
Views from optical tracking cameras around Cape Canaveral showed a noticeable change in color and shape of the exhaust plume from the Falcon 9 first stage. Footage showed what appeared to be debris falling away in the wake of the rocket.
But SpaceX says telemetry data indicate the engine remained intact.
"We know the engine did not explode, because we continued to receive data from it," SpaceX said in a statement. "Our review indicates that the fairing that protects the engine from aerodynamic loads ruptured due to the engine pressure release, and that none of Falcon 9's other eight engines were impacted by this event."
SpaceX has long touted the Falcon 9 rocket's ability to lose a first stage engine and still achieve a successful mission.
Sunday's launch was the fourth flight of a Falcon 9 rocket. All have been successful.
The Merlin 1C engine burns kerosene and liquid oxygen propellants. The nine first stage engines were designed to burn for three minutes on Sunday's launch, but the stage's eight remaining engines fired nearly 30 seconds longer than planned to compensate for the lost engine.
The Falcon 9's second stage, powered by a single Merlin engine optimized for performance in vacuum, accelerated into orbit and deployed the Dragon spacecraft 10 minutes and 24 seconds after liftoff, about 38 seconds later than planned.
"As designed, the flight computer then recomputed a new ascent profile in real time to ensure Dragon's entry into orbit for subsequent rendezvous and berthing with the ISS," the statement said. "This was achieved, and there was no effect on Dragon or the cargo resupply mission."
Two launches of the Saturn 5 rocket lost engines during ascent and still reached orbit, including Apollo 13, which was later struck by an unrelated problem requiring the mission's famous aborted moon landing and risky return to Earth.
One space shuttle flight in 1985 experienced a premature engine shutdown during launch, and it safely reached orbit and accomplished its mission.
"We will continue to review all flight data in order to understand the cause of the anomaly, and will devote the resources necessary to identify the problem and apply those lessons to future flights," SpaceX's statement said. "We will provide additional information as it becomes available."
The Dragon spacecraft is on course to reach the space station Wednesday, with grapple by the robot arm expected at 7:22 a.m. EDT (1122 GMT).
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