SpaceX’s first cargo delivery to the International Space Station (ISS) in October was troubled by several anomalies, including the failure of one of the nine Falcon 9 engines. Mike Suffredini, NASA’s space station program manager, released some comments during the NASA Advisory Council’s Human Exploration and Operations Committee of November 14 and 15.
According to SpaceX, the rocket’s computer shut down one of the first stage’s Merlin 1C engines 79 seconds into the flight following a sudden loss in pressure in the combustion chamber. The accident has been investigated jointly by NASA and SpaceX, and a fault tree analysis is underway, but the root cause of the problem has not been determined yet. The engine underwent extensive testing, but according to Suffredini, “[the engine] was never tested beyond any of its limits.”
While berthed to the ISS, one of Dragon’s three flight computers failed, possibly following a radiation hit. According to Suffredini, the flight computers of Dragon are not radiation hardened, but the spacecraft is designed to operate with two computers, so SpaceX decided proceed with the two remaining units, without fixing the third one.
Radiation may have also been the cause for anomalies on one of three GPS units, the Propulsion and Trunk computers and Ethernet switch. All units recovered after been reset. According to Suffredini, SpaceX did not use radiation-hardened parts because of cost and performance, but he also noted that the company may consider using rad-hardened components in the future.
The Dragon capsule suffered problems with one of the Draco thrusters during reentry. It also suffered a loss of all three coolant pumps after splashdown, a failure that affected the Glacier freezer used to return scientific samples, like urine and blood, from the ISS. The temperature rose from -95 degrees Centigrade (C) up to -65 degrees C, exceeding the temperature limits for some sample.”It wasn’t a severe impact in terms of the temperature increase,” said Josh Byerly, a NASA official. After the retirement of the Space Shuttle, Dragon is the only spacecraft with significant return capability. “We’re working our way through this,” said Suffredini about future flights, “we may limit the cold stowage coming home.”
Responding to a question, Suffredini commented that if NASA is not sufficiently confident that the system works, they may chose not to fly their cargo in it and SpaceX “[doesn’t] get paid if I don’t fly.”
The next SpaceX mission to ISS is scheduled for March 2013, followed in April by the first flight of Orbital Science’s Cygnus cargo spacecraft.
Below, a slow motion video of the launch ascent rocket engine failure: