Why are astronauts still in space?

The two astronauts testing Boeing’s new Starliner spacecraft were supposed to begin returning to Earth on Wednesday night, but instead they will stay aboard the International Space Station (ISS).

The shuttle’s return to Earth had already been delayed due to problems with some of its thrusters and leaks of the helium gas that propels the fuel in the propulsion system.

Nasa is conducting a high-level review of technical problems before deciding when to bring its astronauts home.

Suni Williams and Butch Wilmore are not in danger, but what has gone wrong with the spaceship and what does this mean for their journey home?

Starliner was launched on June 5, despite a small leak of helium gas. Helium is used to propel the propellant in the propulsion systems used for maneuvering in space and to slow down to rent the Earth’s atmosphere.

The leak was extremely small and the engineers believed it would not affect the mission and so proceeded with the launch.

But four more helium leaks developed during the mission, and five of its 28 maneuvering thrusters were cut off on 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 issues.

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 had previously stated in a blog post that the leaks posed no safety risk to the astronauts because: “Only seven hours of free flight time are required to perform a normal mission completion, and Starliner currently has enough helium in its tanks. his. to support 70 hours of free flight activity after download.”

But just days later, after high-level meetings, NASA concluded that the planned return should be “adjusted” to a date in July. No additional information was provided as to why the decision was changed.

NASA stated that flight engineers wanted to study the spacecraft to get to the bottom of the mistakes before it re-entered Earth’s atmosphere. That’s because as the crew capsule parachutes back to Earth, the Starliner’s faulty lower ‘service module’ will burn up after re-entry, meaning the loss of some information about what went wrong.

The space agency emphasized that the astronauts were not stranded and that the Starliner was 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 regardless of 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 have understood the cause of the leak and repair it. .

“There is a danger of trying to make things too perfect and it ends 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 given enough consideration to the worsening of the leak after launch. That’s something NASA and Boeing probably should have done.”

This would have been prohibitively expensive, as it would have involved removing the rocket from the launch pad and extracting the propulsion system from the spacecraft.

Another issue for NASA’s review is why these issues were not identified in either of Starliner’s two previous unmanned flight tests, according to Dr Simeon Barber, who is a space scientist at the Open University.

“The problems we’ve seen in recent weeks are not what we would have anticipated at this stage of the Starliner development program,” he says.

“The whole point of this was to test what putting 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 leaks and propellant problems. Until they do, all risk analyzes of a safe astronaut return and any contingency plans will be incomplete, according to Dr Barber.

“If the root cause is not understood, they have to make a return judgment based on incomplete information. If you don’t fully understand the cause of any failure, then you can’t say for sure that you don’t have a systemic problem that will affect not only the primary propulsion system, but also the spares.”

As a last resort, NASA and Boeing could return their astronauts to SpaceXs Dragon capsule, which would be extremely embarrassing for Boeing. But we’re not in that territory yet, according to Dr Baker.

“With the 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 crew’s next flight.”