Official recounts space station's spin

After a newly attached Russian compartment suddenly fired its thrusters Thursday, NASA said on Twitter that the station tipped by 45 degrees.

Actually, it was much more than 45 degrees.

In an interview, Zebulon Scoville, who was in charge at NASA's mission control center in Houston during the tumbling incident, described how the International Space Station spun 1½ revolutions -- about 540 degrees -- before coming to a stop upside down. The space station then did a 180-degree forward flip to get back to its original orientation.

The seven astronauts aboard were never in danger, Scoville said, and the situation did not spiral out of control. Still, in seven years as a NASA flight director, this was the first time that Scoville had declared a "spacecraft emergency."

Scoville was not even scheduled to work Thursday. Another flight director, Gregory Whitney, led the operations on NASA's side during the docking of the 23-ton Russian module named Nauka.

But Scoville had led earlier preparations for Nauka's arrival, and he was curious. "So I decided to put on a tie and just go and watch it from the viewing gallery behind the control room," he said. "And I was there with Holly Ridings, who's the chief flight director, and Reid Wiseman, the chief of the astronaut office."

After the docking, Whitney had some meetings to attend, so Ridings asked Scoville to take over the second half of Whitney's shift. "And I'm like, 'I'd be happy to. The docking -- the hard part -- is over. Let me go get a handover from him,'" Scoville said. "And so kind of impromptu, I went in and took the shift from him. He unplugged, I plugged in, and I turned around, and the caution warning board lit up."

It was 11:34 a.m. in Houston.

"We had two messages -- just two lines of code -- saying that something was wrong," Scoville said.

The messages said the space station had lost "attitude control" -- that is, it had begun to tip. Usually, four large, heavy gyroscopes spinning at 6,000 revolutions per minute keep the space station steady, but some force appeared to be overpowering them.

"And so at first I was like, 'Oh, is this a false indication?'" Scoville said. "And then I looked up at the video monitors and saw all the ice and thruster firings. This is no kidding. A real event. So let's get to it. You get about half a breath of 'Oh, geez, what now?' and then you kind of push that down and just work the problem."

Nauka's thrusters had started firing, trying to pull away from a space station it was securely docked to.

To make matters worse, there was no way to turn them off.

Scoville's counterparts at the mission control in Russia told him that Nauka was configured so it could receive commands directly only from a ground station in Russia. The next pass over Russia was 70 minutes away.

The new Russian module is docked on the underside of the space station. When Nauka tried to move, it pulled down the rear of the space station, and the front pitched upward. "It's exactly like doing a back flip," Scoville said.

Although the Russians had no way to regain control over Nauka, they could turn on thrusters on other parts of the space station.

The crew fired the thrusters on another Russian module, Zvezda, to counteract those of Nauka. When it appeared that might not be enough to stop the spinning, the thrusters on a docked Russian Progress cargo spacecraft pitched in as well.

After about 15 minutes, Nauka's thrusters petered out. Scoville said he did not know why, although reports said the module had used up its propellant. The mission controllers could then more easily bring the station to a halt. "After doing that back flip 1½ times around, it stopped and then went back the other way," Scoville said.

An hour had passed; everything was back to normal. Mission controllers told the astronauts to take the rest of the day off and relax. Scoville said training exercises had prepared them well on what to do when the space station tips over.

A statement Friday from Roscosmos, the Russian space agency, said there was a software glitch on Nauka and that as a result, "a direct command was given to fire the module's engines."

Preliminary analysis indicates that the space station remains in good shape.

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