The two astronauts testing Boeing’s new Starliner spacecraft were supposed to start their way back to Earth on Wednesday evening, but instead they will remain at the International Space Station (ISS).
The ship’s return to Earth had already been delayed due to problems with some thrusters and leaks of helium gas that pushes fuel into the propulsion system.
NASA is conducting a thorough investigation into the technical issues before making a decision on whether to retrieve the astronauts.
Suni Williams and Butch Wilmore aren’t in danger, but what went wrong with the spacecraft and what does it mean for their journey home?
Starliner launched on June 5, despite a small helium gas leak. Helium is used to push propellant into the propulsion systems used for maneuvers in space and to slow down to reenter the Earth’s atmosphere.
The leak was extremely small and the engineers believed it would not affect the mission and therefore continued with the launch.
But four more helium leaks occurred during the mission and five of the 28 thrusters failed during the approach to the space station, four of which were restarted.
The mission was expected to last eight days, but the return date was postponed as engineers investigated the problems.
Subsequently, on June 18, NASA announced that Starliner would begin its journey home at 10 p.m. EST on Wednesday, June 26 (3 a.m. Thursday, June 27 BST).
NASA had previously stated in a blog post that the leaks did not pose a safety risk to the astronauts because: “Only seven hours of free flight time are required to conduct a normal end-of-mission mission, and Starliner currently has sufficient helium in its tanks . to support 70 hours of free flight activity after undocking.”
But just a few days later, after high-level meetings, NASA concluded that the planned return should be “adjusted” to a July date. No additional information was provided as to why the decision was changed.
NASA stated that flight engineers wanted to study the spacecraft to figure out the fractures before it reenters Earth’s atmosphere. That’s because the crew capsule will parachute to the ground, but Starliner’s faulty lower ‘service module’ will burn up on re-entry, meaning information will be lost about what went wrong.
The space agency emphasized that the astronauts were not stranded and that Starliner was certified to return to Earth in the event of an emergency on the ISS.
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, head of Rocket Engineering, a British company specialising in rocket propulsion systems, says he understands why the launch took place, but says it would have been better to get to the bottom of the cause of the leak and fix it.
“The risk is that we try to get things too perfect, that it takes too long and that it becomes too expensive, with the result that public and political support disappears,” he said.
“But what I think is that maybe they didn’t think enough about the exacerbation of the leak after launch. This is something that NASA and Boeing probably should have done.”
That would have been extremely expensive because it required removing the rocket from the launch pad and removing the propulsion system from the spacecraft.
Another problem for NASA’s assessment is why these issues were not identified in either of Starliner’s two previous unmanned flight tests, according to Dr Simeon Barber, a space scientist at the Open University.
“The issues we have seen in recent weeks are not of the kind we expected at this stage of the Starliner development program,” he said.
“The whole point of this was to test what it would mean if astronauts got involved in piloting the spacecraft in terms of performance. Instead, we seem to be dealing with more fundamental issues that should have already been resolved.”
Finally, for NASA there is the crucial issue of identifying the underlying cause of the helium leaks and thruster problems. Until they do, any analyzes of the risks of the astronauts’ safe return and any contingency plans will be incomplete, Dr. Barber said.
“Unless the cause is understood, they must make a return judgment based on incomplete information. Without fully understanding the cause of a failure, you cannot say with certainty that you do not have a systemic problem that affects not only the primary propulsion system, but also the backups.”
As a last resort, NASA and Boeing could send their astronauts back to SpaceX’s Dragon capsule, which would be extremely embarrassing for Boeing. But according to Dr. Baker, we are not in that area yet.
“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 problem other than it needs to be analyzed and resolved before the next crewed flight.”