and are scrambling to salvage the second Dragon Commercial Resupply Services mission to the International Space Station, after the unmanned cargo capsule encountered a thruster issue shortly after its March 1 liftoff that slowed the scheduled critical deployments of its solar arrays and rendezvous maneuvers.
This situation has forced at least a one-day delay in plans for a March 2 rendezvous and berthing of the Dragon capsule with the six-person orbiting science lab, according to Mike Suffredini,’s space station program manager.
The problem was identified by the Hawthorne, Calif.-based SpaceX control team as a temporary blockage or stuck valve in the helium pressurization for the Dragon’s orbital maneuvering and attitude control system. The difficulty was cleared in all four of the capsule’s thruster pods shortly after 3 p.m. EST. SpaceX was working to set up a perigee-raising maneuver to raise the low point of the initial 124 X 201-mi. (199 X 321-km) orbit by as much as 65 mi. to prevent the spacecraft from making an uncontrolled reentry into the atmosphere.
“Without raising perigee, [Dragon] would reenter within a day or two,” said Elon Musk, SpaceX CEO and chief engineer. “Once we do that burn, we have a lot of time to think about what we need to do next. We will do that burn soon.”
The Falcon 9/Dragon lifted off from Cape Canaveral at 10:10 a.m. EST as scheduled. The rocket and its payload settled into its preliminary orbit 10 min. later. The thruster issue prevented three of the four steering system pods from initializing. The control team finally extended Dragon’s power-generating solar panels at 11:49 a.m. EST, with commands issued from an Australian ground station, nearly 90 min. behind schedule.
The scheduled 25-day mission is the second by SpaceX under a $1.6 billion NASA cargo services contract awarded in late 2008. The first mission, successfully launched in October, followed a six-year, NASA-led Commercial Orbital Transportation Services (COTS) partnership. The COTS effort transitioned to commercial cargo operations following an initial Dragon visit to the station in May 2012.
NASA astronauts Kevin Ford and Tom Marshburn had been preparing to position themselves in the station’s U.S. segment Cupola observation deck, ready to reach out with the 58-ft.-long Canadian robot arm to grapple the supply vessel as soon as March 2.
The one-day delay will permit the NASA and SpaceX flight control teams to further assure themselves that at least three of the four thruster pods on Dragon are functioning with redundancy, Suffredini told a news briefing that followed several hours of troubleshooting. Three thrusters is the minimum required for the capsule to maneuver within reach of the station’s robot arm.
The capsule carries a cargo of slightly less than 2,300 lb. of U.S., European and Japanese research equipment and other internal and external supplies. At liftoff it was scheduled to remain berthed to the station’s U.S. segment Harmony module until March 25, when it was to de-orbit for a parachute descent into the Pacific Ocean off Baja California.
The Dragon mission dates are likely to be adjusted in response to the Day One difficulties. The schedule will be driven by plans for three of the station’s current crew—Ford, Oleg Novitsky and Evgeny Tarelkin—to depart for Earth in a Soyuz spacecraft in mid-March, Suffredini said.
William Gerstenmaier, NASA’s associate administrator for human exploration and operations, offered praise to SpaceX for its response to the problems.
“They were extremely professional through this whole activity,” said Gerstenmaier, who observed from the SpaceX Launch Control Center. “They did everything exactly right with the vehicle. The team in Hawthorne was awesome.”