Falcon Engine Shutdown, Freezer Glitch under Review

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CAPE CANAVERAL, Fla. — Space Exploration Technologies Corp.’s (SpaceX) first supply run to the international space station left behind a handful of technical issues to be worked out before the next flight, which is being retargeted from January to March.

Topping the list is the early shutdown of one of the Falcon 9’s main engines79 seconds after liftoff Oct. 7 from Cape Canaveral Air Force Station, Fla. The rocket’s other eight motors compensated for the loss, successfully delivering a Dragon cargo capsule into orbit to reach the station three days later.

The shutdown, however, forced SpaceX to honor a NASA stipulation that it skip a planned engine restart and deploy the Falcon 9’s secondary payload, an experimental Orbcomm communications satellite, into its intended orbit. Released instead into a lower-than-planned orbit, the satellite re-entered the atmosphere.

SpaceX and NASA also are looking into a Dragon flight computer shutdown believed to have been caused by a radiation hit. The capsule successfully departed the station with two of its three computers synchronized, in accordance with NASA flight rules, station program manager Mike Suffredini reported at a Nov. 14-15 meeting of the NASA Advisory Council’s Human Exploration and Operations Committee.

“SpaceX could have but did not resync the computer, which had automatically rebooted as designed. With two nominally performing computers, we still had redundancy as Dragon needs only one computer to fly. SpaceX offered to resync the computers, but NASA felt it unnecessary and provided the green light to depart the station,” SpaceX spokeswoman Katherine Nelson wrote in an email to SpaceNews.

Radiation hits also were suspected in the shutdown one of Dragon’s three GPS navigation units, a propulsion computer and an ethernet switch during the flight. All were quickly recovered, with no loss of function, SpaceX said.

Finally, a freezer carrying precious science samples from the station lost power when Dragon splashed down Oct. 28 in the Pacific Ocean.

Nelson said the power loss was likely due to water intrusion to the power management units, which are mounted outside the cabin and that the freezer was restarted.

“There was no water inside the cabin, as some have erroneously speculated,” she said.

“New waterproofing methods are being successfully tested on our avionics area for future flights,” Nelson added.