The two astronauts testing Boeing’s new Starliner spacecraft were scheduled to begin returning to Earth on Wednesday evening, but will instead remain aboard the International Space Station (ISS).
The spacecraft’s return to Earth had already been delayed due to problems with some of the thrusters and a leak of helium gas, which pushes fuel into the propulsion system.
NASA is conducting a high-level review of technical issues before deciding when to return its astronauts home.
Sunny Williams and Butch Wilmore are out of danger, but what went wrong with the spaceship and what does that mean for their trip home?
The Starliner was launched on June 5, although there was a small leak of helium gas. Helium is used to propel propellant to the thruster systems used to maneuver in space and slow it down to re-enter Earth’s atmosphere.
The leak was extremely small and engineers believed it would not affect the mission, so they went ahead with the launch.
But four additional helium leaks developed during the mission, and five of its 28 thrusters failed during the approach to the space station, four of which were restarted.
The mission was supposed to last eight days, but the return date was pushed back as engineers investigated the problems.
Then on June 18, NASA announced that the Starliner would begin its journey home at 10:00 p.m. EST on Wednesday, June 26 (03:00 Thursday, June 27 BST).
NASA previously said in a blog post that the leaks did not pose a safety risk to astronauts because: “Only seven hours of free flight time are required to perform a normal end-of-mission mission, and Starliner currently has sufficient helium in its tanks to maintain 70 hours of free flight activity after disconnection.’
But just days later, after high-level meetings, NASA concluded that the planned return should be “adjusted” to a date in July. No further information was provided as to why the decision was changed.
NASA said on-board engineers wanted to study the spacecraft to get to the bottom of the bugs before it re-entered Earth’s atmosphere. That’s because while the crew capsule will parachute to earth, the Starliner’s faulty lower “service module” will burn up on re-entry, meaning a loss of information about what went wrong.
The space agency emphasized that the astronauts are not stranded and that the Starliner is certified to return to Earth in the event of an ISS emergency.
What happens next is subject to an “agency-level review” by NASA to decide what to do next.
The sequence of events raises questions about whether the launch should have gone ahead despite the leak.
Dr Adam Baker, who heads Rocket Engineering, a UK company specializing in rocket propulsion systems, says he understands why the launch happened but says it would have been better to get to the bottom of the cause for the leak to be repaired.
“There is a risk that we try to make things too perfect and end up taking too long and being too expensive, and as a result public and political support disappears,” he said.
“But what I feel is that they may not have considered the deterioration of the leak after launch enough.” This is something NASA and Boeing probably should have done.
This would be extremely expensive as it would involve removing the rocket from the launch pad and removing the propulsion system from the spacecraft.
Another question about the NASA review is why these problems were not identified in either of the two previous unmanned Starliner flight tests, according to Dr. Simeon Barber, who is a space scientist at the Open University.
“The problems we’ve seen over the last few weeks are not the kind we would expect at this stage in the Starliner development program,” he says.
“The whole point of it was to test what putting the astronauts in the control loop of the spacecraft would do in terms of performance. Instead, we seem to be dealing with much more fundamental issues that really should have been ironed out by now.
Finally, for NASA there is the critical issue of identifying the root cause of the helium leak and thruster problems. Until they do, any analysis of the risks to astronauts’ safe return and any contingency plans will be incomplete, according to Dr. Barber.
“Unless the root cause is understood, they have to make a return judgment based on incomplete information.” If you don’t fully understand the cause of a failure, then you can’t say for sure that you don’t have a systemic problem affecting not only the primary drive system, but also the backups.”
As a last resort, NASA and Boeing could return their astronauts to SpaceX’s Dragon capsule, which would be extremely inconvenient for Boeing. But we’re not in that territory yet, according to Dr. Baker.
“With new spacecraft, you have to expect the unexpected,” he says. “This is a completely expected bump in the road and I don’t think it’s a major concern, other than it needs to be analyzed and fixed before the next manned flight.”
