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With a mass of more than 900,000 pounds and an area as large as a football field, the International Space Station was not designed to perform backflips like an Olympic gymnast.
But when a newly added Russian compartment abruptly fired its thrusters on Thursday, NASA said on Twitter The station is inclined at 45 degrees. In fact, it was much more than 45 degrees.
“This is a bit of a misreport,” said Zebulon Scoville, flight director for NASA’s mission control center in Houston, during Thursday’s rolling event.
In an interview, Mr. Scoville described how the International Space Station rotated one and a half revolutions – about 540 degrees – before turning upside down. The space station then made a 180-degree forward turn to return to its original orientation.
Mr. Scoville said the seven astronauts on board were never in danger and the situation was not getting out of control. Still, in seven years as NASA flight director, Mr. Scoville had declared a “spacecraft emergency” for the first time.
Mr. Scoville wasn’t even scheduled to work on Thursday. Another flight director, Gregory Whitney, led operations on NASA’s side during operations. Installation of the 23-ton Russian module named Nauka – “science” in Russian.
But Mr. Scoville had already led the preparations for the Nauka’s arrival, and he was curious. “So I decided to wear a tie and go watch it from the viewing gallery behind the control room,” he said. “And I was there with Holly Ridings, chief of flight, and Reid Wiseman, chief of the astronaut office.”
After the hookup, Mr. Whitney had some meetings to attend, so Mrs. Ridings asked Mr. Scoville to take over the second half of Mr. Whitney’s shift. “I’m like, ‘I’ll gladly do it. Placement – the hard part – done. Let me go and get a handover from him,'” said Mr. Scoville. “And it was so impromptu, I went in and got the shift from him. He unplugged it, plugged it in and turned around and the warning sign came on.”
It was 11:34 Houston time.
“We had two messages saying something was wrong – just two lines of code -” Mr. Scoville said.
The messages said the space station had lost “attitude control,” meaning it started tipping. Usually, four large, heavy gyros, spinning at 6,000 revolutions per minute, keep the space station steady, but some force seemed to overpower them.
Mr. Scoville said, “So at first ‘Oh, is that a false indication?’ I said,” he said. “Then I looked at the video monitors and saw all the ice and propellant shots. This is no joke. It’s a real thing. Let’s get to it. Half a breath of ‘Oh, God, what now?’ and then you kind of push it down and solve the problem.”
Nauka’s thrusters had begun firing, trying to get away from a space station where it was docked securely.
Worse still, there was no way to turn them off.
His colleagues in mission control in Russia told him that the Nauka was only configured to receive direct command from a ground station in Russia. The next crossing over Russia was 70 minutes away.
The new Russian module was placed on the underside of the space station. When Nauka tried to move, it pulled the back of the space station down and its front tilted upward. “It’s like doing an inversion,” said Mr. Scoville.
Mr. Scoville said the rotation speed reached a maximum of 0.56 degrees per second. This rotation isn’t fast enough to create significant artificial gravity—the astronauts reported almost no discernible change in conditions inside the station.
However, a rotating space station puts pressure on the structure and the antennas no longer point where they should be. Mission controllers quickly reported what was happening to the astronauts and gave them instructions.
“We knew we had a limited time,” said Mr. Scoville.
Additional antennas have been announced in the United States that can communicate with the space station in the event of a spacecraft emergency. But still, the connection between earth and space was broken twice, once for four minutes, the other for seven minutes.
Commands from the ground placed and locked the station’s solar power systems. The astronauts took care to lock the radiators that radiated heat from the station into space.
Although the Russian controllers had no way of regaining control over the Nauka, they could operate the thrusters on other parts of the space station.
The crew then fired the thrusters of another Russian module, Zvezda, to counter Nauka’s. When it became clear that this might not be enough to stop the spin, the thrusters of an anchored Russian Progress cargo spacecraft also stepped in.
After about 15 minutes, the Nauka’s thrusters went out. Mr. Scoville said he didn’t know why, although reports said the module was running out of propellant. Mission controllers could thus more easily stop the station. “After making this turnaround a time and a half, it stopped and then went back in the other direction,” said Mr. Scoville.
An hour had passed; everything was back to normal. Mission controllers told the astronauts to take the rest of the day off and relax. Mr. Scoville said the training exercises had prepared them well for what they would do if the space station overturned.
“It’s probably going to get a little bit more intense,” he said, “but there’s a pervasive composure of people who don’t panic and just look at the data, understand what’s going on, and try to work it out from there.”
A statement from Roscosmos on FridayThe Russian space agency said there was a software bug in Nauka, as a result of which “a direct command was given to ignite the module’s engines.”
Preliminary analysis shows the space station remains in good condition.
Despite the accident and Friction between NASA and Russia Regarding the future of the International Space Station, Mr. Scoville said he had no doubts about the station’s operations.
“I have full confidence in the Russians,” he said. “They are a wonderful partnership with NASA and the entire International Space Station program.”
At the end of his unplanned shift Thursday, Mr. Scoville left an exclamation of relief on Twitter.
Oleg Matsnev contributed to the reporting.
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