Is Sunita Williams really ’stuck’ in space or is it a choice? NASA Starliner astronauts could return if...

Are NASA astronauts Sunita Williams and Butch Wilmore really "stuck" in space or is it their choice to spend more time in weightlessness than scheduled? Here's a deep dive into two factors that may explain the idea behind Starliner astronauts' extended stay in space.

1. Starliner could return 'if absolutely necessary'

First, Steve Stich, manager of NASA's Commercial Crew Program, said earlier this month, "Starliner is 'go' to return in an emergency." His statement came as NASA maintained that Starliner could still return astronauts to Earth if absolutely necessary.

But in what conditions would Sunita Williams and Butch Wilmore be brought back from space? The "absolutely necessary" situation will arise if the Starliner capsule must serve as an escape pod from the ISS in an emergency or if any of Starliner's perishable items – such as its solar panels - show signs of expiring earlier than planned, Reuters reported.

Wilmore said that on July 10, two astronauts tested a "Safe Haven procedure," sheltering inside Starliner in the event they needed to suddenly undock from the ISS. The test went well, he said.

Meanwhile, Sunita Williams explained one of the checks for Starliner involved practicing for safe haven "to make sure that we have all the emergency equipment laid out and we need to have to get into or spacecraft and use it as a safe haven – in case something happens to the space station," she said.

An official also spoke about how they will return to Earth if they were to do it today. On July 10, the official said that if they were to do the "undocking today", they would just perform a nominal undocking and return. He said that the propulsion system is highly redundant on each other. "So if there was an issue in any one of the thrusters, the redundance will take over and bring us safely home," he added.

2. Starliner is not the only option NASA has to bring back astronauts

If not Boeing's Starliner, NASA also has the fallback option to bring back the two astronauts quickly from space using a rival company’s spacecraft, SpaceX’s Dragon spacecraft, if there were a true emergency.

The Crew Dragon ferried four astronauts to the station in March and is able to fit more people in an emergency. But the use of Crew Dragon seems unlikely. SpaceX is Boeing's competitor.

However, NASA focuses on safely returning Williams and Wilmore to Earth, and the prime option is to return on Boeing’s Starliner capsule. 

On August 2, Boeing said in a statement that it “remains confident in the Starliner spacecraft and its ability to return safely with crew”.

So, why are Starliner astronauts overstaying in space?

Earlier this month, Wilmore said that human space flight is not easy in any regime and there have been multiple issues with every spacecraft that has ever been designed, and "that's the nature of what we do".

"The mantra you have heard that failure is not an option, that's why we are staying here now," he had said.

On their extended stay in space, Wilmore added the crew faced degradation in the thrusters. "And that's why we are staying because we are going to test it...We are going to get the data we need to help inform our decision so we make the right decision," he said.

Meanwhile, Sunita Williams explained why studies on Starliner were important. She said that the service module (SM), where the thrusters are situated, will detach from the capsule and burn up in the atmosphere. This would mean the end of being able to study how they react in space.

"We have practised a lot, and I have a real good feeling that the spacecraft will bring us back home...we are learning now to optimize our specific situation to make sure that we know everything about it [the spacecraft]...," Sunita Williams said on July 10, in her first interaction with media after Starliner launch.

NASA had earlier rescheduled the planned return three times, and now has no date set for it. As per a Reuters report, Starliner could stay docked at the ISS for up to 72 day while relying on various backup systems.

Why Starliner's return delayed: ‘Helium leaks, thruster anomalies’

Starliner, which was supposed to return around mid-June, has now been in space for over 50 days as the crew pursues fixes mid-mission. 

The team, in space and on ground, has been conducting thruster testing and working on a return flight readiness review to prepare for Starliner’s eventual undocking and landing.

Starliner launched on June 5 on Crew Flight Test (CFT), carrying Butch Wilmore and Suni Williams to the International Space Station (ISS) for a planned week-long stay. The spacecraft reached the ISS on June 6.

During the trip, Starliner experienced helium leaks and thruster anomalies – which delayed the spacecraft's return. The capsule has had five helium leaks, five maneuvering thrusters go dead and a propellant valve fail to close completely.

Starliner's propulsion system is part of the craft's "service module". The problems center on this system, which is needed to back the capsule away from the ISS and position it to dive through Earth's atmosphere, Ruters reported.

Many of Starliner's thrusters have overheated when fired, and the leaks of helium – used to pressurize the thrusters – appear to be connected to how frequently they are used, according to Stich.

What's situation now? '27 of 28 thrusters healthy, helium levels stable'

Boeing said on Saturday that tests were conducted and they confirmed that “27 of 28 RCS [reaction control system] thrusters” are healthy and back to full operational capability. 

“Starliner’s propulsion system also maintains redundancy and the helium levels remain stable. The data also supports root cause assessments for the helium and thruster issues and flight rationale for Starliner and its crew’s return to Earth,” Boeing informed.

On 1 August, NASA informed that teams are taking their time to analyse the results of recent docked hot-fire testing, finalise flight rationale for the spacecraft’s integrated propulsion system, and confirm system reliability ahead of Starliner’s return to Earth from the International Space Station.

What if Starliner thrusters malfunction on return mission?

It is important that thrusters perform nominally, and only then the Starliner will be able to undock and return safely. NASA and Starliner want to be absolutely sure before making the return journey and hope that "nothing else surprises" them during the trip.

So what if thrusters are damaged? In that case what would NASA do differently? Mark Nappi, who leads the Starliner efforts at Boeing, said they don't believe that they have damaged thrusters. But they want to "fill in blanks and run" tests to ensure everything's fine.

Adding to Nappi's reply, Steve Stich said there was only one thruster that was producing very low thrust "that we would disable for the rest of the flight, and that's going to be the plan for the...undocking right now. That would be B1 A3 thruster. We would not have that thruster available and with the OMAC system for de-burn, that should happen nominally..."

However, the two officials maintained that they full confidence in the thrusters.

The thrusters are needed to guide the Starliner spacecraft into position for reentry and also to slow the capsule to a proper speed before the service module separates. It is after this stage that the capsule takes that final plunge. To recap, the mission is delayed because at least one of 28 thrusters was malfunctioning.

NASA astronauts Sunita "Suni" Williams and Barry "Butch" Wilmore made history as the first people to fly aboard the Starliner spacecraft.