The International Space Station, over 900,000 pounds in mass and the size of a soccer field, is not designed to do backflips like an Olympic gymnast.
But when a newly connected Russian compartment suddenly fired its engines on Thursday, NASA announced on Twitter that the station had tilted 45 degrees. It was actually much more than 45 degrees.
“That got a little misreported,” said Zebulon Scoville, the flight director in charge of Thursday’s fall at NASA’s Mission Control Center in Houston.
In an interview, Mr. Scoville described the International Space Station spinning one and a half turns – about 540 degrees – before coming to an upside-down stop. The space station then rotated 180 degrees forward to return to its original orientation.
The seven astronauts on board were never in danger, said Mr Scoville, and the situation did not get out of hand. Still, this was the first time that Mr. Scoville had declared a “spacecraft emergency” in seven years as NASA flight director.
Mr Scoville wasn’t even supposed to work on Thursday. Another flight director, Gregory Whitney, oversaw operations on NASA’s side while docking the Russian 23-tonne module called Nauka – “science” in Russian.
But Mr. Scoville had made arrangements for Nauca’s arrival before, and he was curious. “So I decided to put on a tie and just watch it from the viewing gallery behind the control room,” he said. “And I was there with Holly Ridings, the flight director in charge, and Reid Wiseman, the head of the astronauts bureau.”
After docking, Mr. Whitney had to attend a few meetings, so Mrs. Ridings asked Mr. Scoville to take over the second half of Mr. Whitney’s shift. “And I say, ‘I would like to do that. Docking – the hard part – is over. Let me get a delivery from him, ‘”said Mr. Scoville. “And so spontaneously that I went in and took his shift off his shoulders. He pulled out the plug, I plugged it in and turned around, and the warning sign lit up. “
It was 11:34 a.m. Houston time.
“We had two messages – just two lines of code – that said something was wrong,” said Mr Scoville.
The news said the space station had lost “posture control” – that is, it had started to tip over. Usually four large, heavy gyroscopes spinning at 6,000 revolutions per minute keep the space station still, but some force seemed to overwhelm them.
“So at first I was like, ‘Oh, is that a misnomer?'” Said Mr. Scoville. “And then I looked at the video monitors and saw all the ice and engine ignitions. This is no joke. A real event. So let’s get to that. You get about half a breath of, ‘Oh my god, now what?’ and then somehow you push that down and just work on the problem. “
Naucasus engines had started to fire and were trying to move away from a space station to which it was securely docked.
Worse, there was no way to turn it off.
His colleagues at Mission Control in Russia told him that Nauka was configured to only receive commands directly from a ground station in Russia. The closest pass through 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 the back of the space station down, and the front leaned up. “It’s just like doing a backflip,” said Mr. Scoville.
The rotation speed reached a maximum of 0.56 degrees per second, said Mr. Scoville. That rotation isn’t nearly fast enough to create significant artificial gravity – he said the astronauts reported almost no noticeable changes in conditions within the station.
However, a spinning space station puts a strain on the structure, and the antennas no longer point where they’re supposed to. Mission controllers quickly informed the astronauts about what was happening and gave them instructions.
“We knew we had a limited time,” said Mr Scoville.
The declaration of a spacecraft emergency activated additional antennas in the United States that could communicate with the space station. Even so, the connection between the ground and space was lost twice, once for four minutes, the other time for seven minutes.
Orders from the ground stowed and locked the station’s solar systems. The astronauts made sure that the radiators that release heat from the station into space were closed.
Although the Russian air traffic controllers had no way of regaining control of Nauka, they were able to turn on engines in other parts of the space station.
Then the crew fired the engines of another Russian module, Zvezda, to counter those of Nauka. When it turned out that this might not be enough to stop the rotation, the engines of a docked Russian Progress cargo space probe also turned on.
After about 15 minutes, the Naucasus engines blew up. Mr Scoville said he did not know why, even though the module reportedly ran out of fuel. The mission pilots could then bring the station to a standstill more easily. “After doing that backflip a time and a half, he stopped and then went back the other way,” said Mr. Scoville.
An hour had passed; everything was back to normal. Mission leaders urged the astronauts to take the rest of the day off and relax. Mr. Scoville said training drills prepared them well for what to do if the space station falls over.
“Probably the intensity builds up a little,” he said, “but there’s a pervasive kind of composure that people don’t panic and just look at the data, find out what happened, and try to fix the problem from there to solve.”
In a statement by Roskosmos, the Russian space agency, on Friday it said that there had been a software error on Nauka and that as a result “a direct command was given to ignite the engines of the module”.
Preliminary analyzes show that the space station remains in good shape.
Despite the mishap and tension between NASA and Russia over the future of the International Space Station, Scoville said he had no doubts about the station’s operations.
“I have full confidence in the Russians,” he said. “You are a fantastic partnership with NASA and the entire International Space Station Program.”
At the end of his unplanned shift on Thursday, Mr Scoville made an exclamation of relief on Twitter.
Oleg Matsnev contributed to the coverage.