CAPE CANAVERAL, Fla. -- A scheduled rendezvous between the privately launched SpaceX Dragon cargo capsule and the International Space Station was postponed Friday when thruster pods on the capsule failed for several hours. But NASA and SpaceX officials expressed confidence the resupply mission would be completed.
After a flawless launch of the SpaceX Falcon 9 rocket from Cape Canaveral Air Force Station put the capsule in orbit Friday morning, ground control detected low pressure in oxidizer tanks for three of the Dragon's four thruster pods. The thrusters allow for precision manoeuvring of the spacecraft, and NASA requires at least three to be operating before the capsule approaches the space station.
But by late afternoon, SpaceX founder Elon Musk tweeted that all four thrusters were working. "Preparing to raise orbit. All systems green," he wrote.
Still, it was unclear when the Dragon capsule, carrying nearly 590 kilograms of supplies, would get permission to dock with the $100-billion station. Earlier, Musk had said he would be confident after an hour or two of test firings, but NASA officials were noncommittal.
Berthing opportunities with the space station come only about once a day and require a lengthy, careful dance between spacecraft, since both are flying at 27,360 km/h. Michael Suffredini, NASA's space station program manager, said a Sunday berthing was possible, but he was not ready to commit.
"We'll plan for the next opportunity," Suffredini said. But he added, "It is not our intention to waive safety requirements."
The exact cause of Friday's problem was unclear. Musk said his team's "preliminary guess" was that blockage, perhaps something frozen, formed in a line from a helium tank used to pressurize all four thruster oxidizing tanks. NASA officials concurred that seemed the likely cause.
"It was a little frightening there," Musk acknowledged. But he said the Falcon 9 rocket performed "super well" and praised SpaceX mission control in Hawthorne, Calif., for diagnosing and apparently fixing the problem.
None of Dragon's cargo is critical to life support on the station, though there are research packages to support 160 experiments, including 50 new ones. A NASA official said he does not expect any materials on board the Dragon to "go bad" if berthing is delayed a day or so, but he did not speculate on what would happen with a longer delay.
This was the second SpaceX flight to experience problems. Last October, one of the Falcon 9's engines cut off prematurely, though the capsule made it safely to the station. Hundreds of millions of dollars and NASA's long-term lower-Earth-orbit plans are dependent on the success of SpaceX, the only private company to successfully launch to the station and has a $1.2-billion contract for 12 supply flights.
-- Orlando Sentinel