Why astronauts are stuck on the ISS

It looks like two of Nasa’s most experienced astronauts - who have been stuck in space for over two months - won’t return to Earth until February 2025. “Sunny” Sunita Williams and “Butch” Barry Wilmore were only supposed to take part in an eight-day mission, but a problem with the Boeing Starliner spacecraft that took them to the International Space Station means they will remain in space until next year. With me to explain what’s going on and what will happen to the two astronauts is broadcaster Richard Hollingham from the Space Boffins podcast. And he’s the perfect person to ask because not only has he partied with one of the astronauts, he’s also just penned a piece for the BBC called What happens when astronauts get caught in space…

Richard - This is Boeing's Starliner, the rival to the Dragon Spacecraft. It's been much delayed. Its trial uncrewed flights were not wholly successful. This was its crewed flight, first crewed flight, to the International Space Station. And what they found was on approach to the Space Station, 5 of the 28 thrusters failed. They recovered the spacecraft fine, and docked successfully. They're on the Space Station. The question then is, are these thrusters going to fail again? So there have been tests ever since and, well, I think the best word to sum them up is inconclusive. So that's why they've made the decision to keep them there.

Chris - So this is a bit like having a car parked in the garage and you could jump in it, but you might break down on the motorway. And obviously when it's life and death like this, no one's willing to take that risk.

Richard - Yeah. So it's a little complex with the problem with the thrusters because they don't entirely understand what's happening. They've been running a load of tests in space, docked to the Space Station, and in space the thrusters seem to be absolutely fine. There seems to be no problem. The actual problem does appear to come down to a single component, a Teflon element within the thruster, which seems to be swelling and reducing how much propellant passes through the thruster. That seems to be the problem. But in NASA's words, they do not understand the physics of the problem. So it might have fixed itself, it might be fine, but they don't know why. And that's obviously a real worry.

Chris - Why can't they just come home? And, I mean I know I'm trivialising a bit, but what is the problem with sending something else up there to get them back? There are things going to resupply the International Space Station quite frequently, aren't there?

Richard - Yeah, I mean, they could even actually fit in the Dragon that's docked to the Space Station. They could fit two extra people into that Dragon spacecraft. They could actually bring them back now. And it's about the balance of risks, isn't it? So right now, the safest place to be is on the Space Station. If something catastrophic were to happen to the Space Station, a piece of space junk hit it, some sort of depressurisation event, a fire, all the awful things that could go wrong in space, they could come back straight away. And they'd either come back jammed into the Dragon Capsule, which is already docked to the Space Station, which is the SpaceX spacecraft. Or they could come back on Starliner because the risk suddenly shifts. So right now it's safer to stay on the Space Station. And given that these astronauts are so well-trained, the best option I think is to keep them on the Space Station, extend their mission, send a spacecraft up with just with two spare seats, and then they come back after a long duration mission, which is very usual on the Space Station, and they come back early in the new year.

Chris - I did hear that the one downside for the two astronauts is they didn't pack many pairs of pants. I'm being slightly facetious, but they didn't take extra clothes. And of course you don't. You don't do that when you go into space. Weight is everything. You don't take what you don't need. So they're kind of living in the same clothes a lot.

Richard - It's true. And also they had to actually take some of their personal possessions off Starliner to take in some spares for the plumbing system on the Space Station. So even on their eight day mission, they didn't have many personal possessions with them. So some have been sent up since, more will be sent up in supply missions and in the Dragon mission, which will now only carry two astronauts. There are going to be some difficult decisions made at NASA about which two astronauts get bumped off that mission. I wouldn't want to be in those meetings. So they are going to get some personal possessions. I imagine too, either in the Dragon Mission coming up or in a forthcoming supply mission, there are supply missions all the time. They'll also take up their presents for Christmas as well.

Chris - Have you interviewed or met the pair of them, having made hundreds of space programs and episodes of things like Space Boffins over the years. Have you had them on the program?

Richard - No. I've not interviewed Butch or Sunny, but I have been at a party with Sunny Williams. So I used to do the live launch commentaries for the European Space Agency when Soyuz flights launched with NASA astronauts or the European Space Agency astronauts to the International Space Stations. I was in Moscow mission control and she was one of the astronauts assigned there. So they always had astronauts there in the sort of support roles in Moscow. And so I was at a party with Sunny Williams. I can confirm she is lovely. Very chatty, great person. I mean, you know, the ideal companion on a space station.