It wasn’t quite Apollo 13 redux, but the emergency maneuvers to save SpaceX’s tumbling Dragon capsule minutes after its March 1 launch were terrifying nonetheless for space entrepreneur Elon Musk.
“We had this spacecraft just going through free drift in space, like just tumbling,” the SpaceX CEO recounted at the South by Southwest Interactive festival Saturday.
Musk recalled the minute-by-minute maneuvers the SpaceX team took to save the tumbling craft, which included borrowing a U.S. Air Force antenna array, hastily rewriting code and making the risky call to unfurl the solar panels before they froze.
The Dragon eventually docked with the International Space Station, the third flight by SpaceX to do so, and delivered its roughly 2,000-pound cargo of spare parts and plants. These were the minutes in between.
A successful launch, then Dragon spins out of control
The 10:10 a.m. launch of the Falcon 9 rocket from Cape Canaveral Air Force Station in Florida went off well, Musk told interviewer and former Wired Editor Chris Anderson, but problems began soon after spacecraft separation. The Dragon craft has four thruster pods, which help steer the ship in orbit, with a combined total of 18 engines and it was supposed to have enough redundancy that catastrophic failures would be avoidable.
“It can work with only two of the four thruster pods working,” said the laconic, South African-accented Musk. “Three weren’t working, which was a huge puzzle.”
The SpaceX controllers had a 2-kilobit connection to the craft that would go in and out as the antennas rotated – a connection roughly 28 times slower than a dial-up modem.
The first order of business, then, was to improve the bandwidth.
“So we asked the Air Force if we could have some of their long-range telemetry scanners,” Musk said. “We had this communication system we call Megaproxy. We had to the reroute the Megaproxy to go through the Air Force long-range dishes to blast the spaceship with enough intensity to upload new code to try to fix the problem.”
The team wrote code to try to “pressure slam” the three oxidizer tanks that weren’t working, he said. It was like giving the Dragon, the “equivalent of the Heimlich maneuver,” Musk said.
Freezing solar panels and a solution
But another problem was fast emerging.
The team didn’t want to unfurl the solar panels until two pods were active, but the temperature of the panels was dropping to absolute zero.
“It was dropping, dropping, dropping and we said okay… we better release the solar panels otherwise they could literally freeze in place,” Musk said.
The team ran simulations to see what would happen and they found that, like a spinning figure skater who extends her arms, unfurling the panels would slow down the rate of rotation.
With the craft tumbling at a slower rate, the SpaceX controllers were able to improve communications with the capsule. At about 3 p.m., Musk tweeted that the second pod was working and soon after the rest of the pods came online.
“That sounds terrifying,” offered Anderson.
The Dragon capsule is currently docked with the ISS and, “if all goes well,” will return to earth in a couple of weeks.
Top image: The Dragon capsule. Courtesy SpaceX