It’s been 18 days since SpaceX’s Dragon capsules splashed from its latest mission to the International Space Station. The mission, the first in the commercial resupply contract the company holds with NASA, was a major step. SpaceX CEO Elon Musk said the recent flight “signifies the restoration of America’s ability to deliver and return critical space station cargo,” adding that “the reliability of SpaceX’s technology and the strength of our partnership with NASA provide[s] a strong foundation for future missions and achievements to come.”
But the mission wasn’t a complete success. As those who watched the launch will remember, one of the Falcon 9‘s first stage Merlin 1C engines shut down early when the computer detected a loss in pressure in the combustion chamber just 79 seconds after lift off. The failure put the Dragon in a lower than expected orbit. An Orbcomm satellite, the secondary payload on the mission, failed to reach orbit entirely and fell back to Earth less than a week later. Orbcomm declared the mission a total loss.
Now, as engineers from NASA and SpaceX continue to analyze the flight data to determine the cause of the engine loss – no smoking gun yet – it seems there were more problems on the flight than the launch anomaly.
ISS program manager Mike Suffredini, speaking to the NASA Advisory Council’s Human Exploration and Operations Committee on Wednesday, made the scope of problems on the mission clear.
There were problems while the Dragon was berthed to the ISS. One of the capsule’s three computers failed. Flight Computer-B “de-synched” from the other two due to what Suffrendini suspects was a radiation hit. Like the Falcon 9 losing an engine, the Dragon can still function with two computers so SpaceX opted to proceed with only two active units. The third was rebooted after the anomaly, but SpaceX opted no to “re-synch” it with the other two.
Radiation took other victims on the flight. One of the Dragon’s three GPS units, its Propulsion and Trunk computers, and the Ethernet switch all malfunctioned likely due to radiation. Lucky for the mission, these units were rebooted and recovered in short order.
The radiation is a serious issue; it’s an inescapable part of spaceflight. Suffredini said that SpaceX is now facing the decision of whether or not it needs to use radiation-hardened parts. In the case of the flight computers, this change will bring with it a weight penalty and a decrease in processing power. Cost will be another factor in making the switch to radation-hardened equipment; it could be prohibitively expensive.
The Dragon didn’t leave its problems in orbit. One of the Draco thrusters rockets failed. All three coolant pumps failed after the capsule splashed down. The onboard GLACIER freezer lost power at splashdown, possibly due to water interacting with the external power units. Designed to return samples from the ISS at a controlled temperature of -139ºF, the samples were much warmer at -85ºF when the freezer was recovered and turned back on.
What this larger list of failure might mean for SpaceX’s future launches isn’t clear yet; a full assessment of the mission is still underway. But it could have a significant impact. Understandably, NASA wants to make sure anything that comes in the vicinity of the ISS won’t be a threat to the station. As Suffredini explains it, NASA doesn’t have the “go/no-go” authority over SpaceX launches but it is a very influential customer. SpaceX’s commercial resupply contract with NASA requires the company deliver a certain amount of cargo to the ISS over 12 (now 11) launches. But if NASA loses confidence in the company for any reason, it can opt to not put its cargo on the rocket. And without the major buyer’s payload, that rocket likely won’t fly.
For the time being things are still on track with SpaceX’s next launch scheduled for March of 2013. SpaceX hasn’t made any comments on the ongoing investigation. Musk said simply on Wednesday that it will likely be a number of weeks before the company releases the results of its investigation into the anomaly.Missions » ISS » COTS »