SpaceX Cargo Mission Suffered Other Anomalies

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Doug Messier
on November 14, 2012, at 4:30 pm
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SpaceX’s recent cargo mission to the International Space Station experienced more problems than just an engine failure on the Falcon 9 booster. The problems included equipment shutting down due to a lack of radiation hardened components and a malfunctioning freezer carrying valuable experimental samples back to Earth for analysis.
ISS Program Manager Mike Suffredini briefed the NASA Advisory Council’s Human Exploration and Operations Committee on Wednesday, Marcia Smith reports. The anomalies on the first commercial cargo mission included:

  • One of three flight computers failed while Dragon was docked at ISS due to a suspected radiation hit. The computer was restarted but could not re-synchronize with the other two units. The computer was restarted but was not resynchronized with the other two units. SpaceX says that NASA felt it was not necessary to continue the mission.
  • One of three GPS units, the Propulsion and Trunk computers and Ethernet switch also experienced suspected radiation hits, but they were recovered during a power cycle.
  • All three coolant pumps failed after splashdown in the Pacific Ocean.
  • Glacier freezer was at -65 degrees Centigrade (C) instead of the planned -95 degrees C when it was opened three hours after splashdown, causing some samples to exceed temperature limits.
  • Problems occurred with one of the Dragon’s Draco thrusters.

Suffredini said SpaceX is still looking for the cause of a sudden drop in pressure that caused one of the Falcon 9′s Merlin engines to fail. NASA is participating in the investigation.

SpaceX’s next cargo mission to ISS is set for March 2013. A delay is possible depending upon the outcome of the investigation into the engine failure.

 

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  • warshawski

    Quite a few issues for SpaceX to work through, it is a concern there were so many issues but also a vindication of the design redundancy that Dragon completed the mission. The real test is to see what action is taken to address the problems encountered. For short duration cargo missions the radiation hardening of computers/GPS can probably be lived with but for longer duration or crew missions a fix is needed. The post landing cooling pump failure is a concern as all 3 went down at the same time, as it was at landing that may be a common cause.
    I hope SpaceX come up with causes soon and provide provide short term mitigation to get the next mision off the ground but still work on long term design solutions to eliminate the problems for the crew version.
    This is one reason why the incremental approach of cargo then crew with lots of test flights is a good idea as the bugs can be found and sorted before people are put at risk.

  • jamesh

    I suppose it’s better to get lots of little things to go wrong like this in one mission – it means they fix a LOT of stuff before for the next one. Nothing here, except the engine out, looks to be a real PITA to fix.

  • Spaceman13

    The flight computer issue could be a real pain. Not so much the fact that it reset, but the fact that it was not able to synchronize with the others.

  • http://Innerspace.net Stewart Money

    It may be a small difference, but in the report at spacepolicyonline.com, Mike Suffredini states that the flight computer B was “not resynched” as opposed to “could not be re-synched” after it was successfully re-booted. Either way it is still an issue.

  • Jim Hillhouse

    I’m more than a bit concerned that Dragon is doing ProxOps at ISS with only two working computers. Undocking offers plenty of opportunities for problems. For example, with only two computers, what is done if, simplistically putting it, one says, “Go backwards” and the other says, “Go forward”? This could be really bad.

    This isn’t the first time NASA has had issues with SpaceX’s choice of electronics, but those were supposedly dealt with before Dragon was docking with ISS.

    More fundamentally, why is Dragon even allowed near ISS by NASA with improperly shielded electronics and non-radhardened flight computers? What if these problems had occured before docking with ISS?

  • http://www.parabolicarc.com Doug Messier

    Stewart:

    You are right. I misinterpreted the original report. SpaceX is saying that it could have been resynchronized with the other computers but that NASA did not feel it was necessary to safely continue the mission.

  • Scott

    Do you guys really think NASA would haphazardly allow Dragon anywhere near ISS if it weren’t absolutely, beyond question, in a safe state of operation?

    Dragon is designed to be radiation tolerant. The system as a whole is extremely robust and can handle the effects of radiation (resets of individual components, etc). Not re-syncing the reset flight computer was a choice, made because it was not necessary to remain in a safe, robust state.

    Here is a fantastic, in-depth explanation and response from John Muratore, former chief engineer and flight director for the Space Shuttle, and now Director of Mission Assurance at SpaceX:

    http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog%3A04ce340e-4b63-4d23-9695-d49ab661f385&plckPostId=Blog%3A04ce340e-4b63-4d23-9695-d49ab661f385Post%3Aa8b87703-93f9-4cdf-885f-9429605e14df