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SpaceX, NASA scrutinize anomalies from cargo flight

BY STEPHEN CLARK

SPACEFLIGHT NOW

Posted: November 14, 2012



Engineers are combing through data from SpaceX's October cargo mission to the International Space Station, examining a rocket engine failure, electronics glitches from suspected radiation, and a power loss that could have imperiled precious medical samples returned from the outpost, NASA officials said Wednesday.

Dragon floats in the Pacific Ocean west of Baja California on Oct. 28 after splashdown. Credit: SpaceX



SpaceX's Dragon spacecraft successfully completed the commercial resupply flight, but the mission had to overcome several anomalies almost from the moment of its Oct. 7 launch. The mission's Falcon 9 booster suffered an engine failure moments after liftoff from Cape Canaveral, Fla., and investigators from SpaceX and NASA have found "no smoking gun" on the cause of the problem, according to Mike Suffredini, NASA's space station program manager. The rocket's computer detected a sudden loss in pressure in the combustion chamber of one of the first stage's Merlin 1C engines and commanded the engine to shut down 79 seconds after liftoff, according to SpaceX. The company formed a joint review team with NASA to find the cause of the engine failure, but despite going over an "enormous amount of data" in the last month, investigators have not determined the root cause of the engine problem, Suffredini said Wednesday in a meeting of the NASA Advisory Council's human exploration and operations subcommittee. Elon Musk, SpaceX's CEO and chief technology officer, said Wednesday it will "probably be several weeks" before the investigation releases any findings. According to Suffredini, who must sign off before NASA cargo is loaded aboard a SpaceX spacecraft, the suspect engine from the Oct. 7 launch underwent extensive testing before it flew. "It was never tested beyond any of its limits," Suffredini said. "It just spent a lot of time doing testing of different things before it actually flew, but it's not the only engine that's flown like that." Views of the launch 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 at the time of the engine failure. Footage showed what appeared to be debris falling away in the wake of the rocket, but SpaceX said the material was from an aerodynamic engine cover. The engine itself stayed intact, the company said. The Falcon 9 rocket continued into orbit, compensating for the lost engine by burning its other first stage engines and second stage longer. The mishap left the Falcon 9 with too little propellant to safely place its secondary payload - an Orbcomm communications satellite - in the correct orbit. The Orbcomm satellite was a prototype for a new generation of data communications satellites, but the craft fell from orbit less than a week after launch. Orbcomm declared the mission a total loss and filed an insurance claim.

Dragon grappled by the space station's robotic arm. Credit: NASA



The Dragon capsule reached the space station Oct. 10, making an automated rendezvous before astronauts snared the spacecraft with a robotic arm. The crew unloaded 882 pounds of supplies from Dragon's pressurized compartment and stowed nearly one ton of cargo back into the spacecraft for the trip back to Earth. While the ship was berthed with the space station, a suspected radiation hit took out one of Dragon's three flight computers, Suffredini said. Dragon's flight computers are not hardened to resist radiation, according to Suffredini, but the craft is designed to function with only two main computers operating at one time. Engineers believe radiation also shut down one of Dragon's three GPS navigation units, a propulsion computer and an ethernet switch during the flight. Controllers at SpaceX's headquarters in Hawthorne, Calif., recovered those systems to full operability, Suffredini said. Most spacecraft, including the station's European and Japanese resupply freighters, have radiation-hardened computers. But standard computers are less expensive and usually run faster, according to engineers. The Dragon capsule departed the space station and parachuted into the Pacific Ocean on Oct. 28. The craft carried refrigerated medical samples, including vials of blood and urine collected from astronauts, and other sensitive payloads for rapid shipment to laboratories. The biological samples were in cold bags and a GLACIER freezer, but the freezer may have lost power during splashdown, Suffredini said.

Dragon reached the Port of Los Angeles on Oct. 30. Credit: NASA



The capsule splashes down at a velocity of about 11 mph, dipping much of the spacecraft underwater before rebounding to the surface and floating. Engineers believe sea water leaked into electrical boxes, causing the freezer and three cabin coolant pumps to lose power. The GLACIER freezer was set at minus 139 degrees Fahrenheit. When SpaceX's recovery team opened the capsule, the freezer's temperature was minus 85 degrees, according to NASA. Scientists are studying the medical samples, which were returned to NASA's Johnson Space Center, said Josh Byerly, an agency spokesperson. "It wasn't a severe impact in terms of the temperature increase," said Byerly, who added the power snafu would not affect any contractual payments to SpaceX. According to Suffredini, although temperatures exceeded preset tolerances for some samples, researchers believe the temperature limits were conservative. "We're working our way through this, and we may limit the cold stowage coming home [on the next flight]," Suffredini said. Dragon is the only vehicle after the space shuttle's retirement capable of returning significant cargo from the space station to Earth. Two days after splashdown, the capsule arrived at a port near Los Angeles on a barge and was shipped to SpaceX's test site in McGregor, Texas, for safing and unloading. The October flight was the first of 12 SpaceX resupply missions to the space station. SpaceX has a $1.6 billion contract with NASA for commercial cargo services through 2016. SpaceX's next Dragon mission to the space station is now scheduled for launch March 1, about a six-week delay from a Jan. 18 target launch date publicized before the launch of the previous mission. Suffredini said the timing of SpaceX's next flight to the station was adjusted partly to accommodate a software update aboard the complex planned for early 2013.