Why can’t NASA send out a spacecraft and bring Sunita Williams back?

First, there is no urgency to bring them back immediately.

This is no Apollo 13 moment where the two astronauts are stranded miles above Earth in a damaged spaceship. Wilmore and Williams are safe on the International Space Station (ISS), a well-stocked, efficiently supplied, permanent ‘home’ for astronauts in space.

Second, the astronauts are not really “stuck” for unusually long.

The SpaceX spacecraft that will bring them back will lift off later this month, carrying members of NASA’s SpaceX Crew-9 mission to the ISS. The Dragon spacecraft can ferry up to seven astronauts, but NASA has so far used it for no more than four astronauts.

Wilmore and Williams will be on Dragon’s return flight, along with two other astronauts who are among those currently on the ISS.

However, Crew Dragon will not return immediately. As astronauts typically spend six months on the ISS (Scott Kelly spent a year in the station), the Dragon will return only after six months, with four astronauts on board. Wilmore and Williams are not really “stuck” in space.

Five spaceships are currently docked at the space station.

These are the SpaceX Dragon Endeavour (Crew-8 mission), the Northrop Grumman resupply ship, Soyuz MS-25 crew ship, and the Progress 88 and 89 resupply ships.

The Starliner crew ship was also docked to the ISS until last Friday.

The Soyuz MS-26 spacecraft will launch for the ISS on Wednesday (September 11) from the Baikonur Cosmodrome, a spaceport operated by Russia in Kazakhstan.

There are nine astronauts currently on board the ISS.

They include Wilmore and Williams. The others are: Oleg Kononenko (Commander), Nikolai Chub, Tracy Caldwell Dyson, Michael Barratt, Matthew Dominick, Jeanette Epps, and Alexander Grebenkin. Barratt, Dominick, Epps, and Grebenkin arrived at the ISS aboard SpaceX’s Dragon (Crew-8 mission) on March 5 this year.

These astronauts will be joined soon by NASA’s Don Pettit, and Russian cosmonauts Alexey Ovchinin and Ivan Vagner, who will be on board the Soyuz MS-26 spacecraft.

Besides the nine astronauts currently on the ISS, there are also three Chinese astronauts in space — Li Guangsu, Li Cong, and Ye Guangfu, members of the Shenzhou-18 mission — who are in China’s Tiangong space station.

The empty crew capsules can also function as ‘lifeboats’.

The crew capsules, which are docked to the space station, can become ‘lifeboats’ for the astronauts should they have to abandon the ISS, say, in the event of a deadly fire on board.

So, the docked Dragon capsule is the lifeboat of Barratt, Dominick, Epps, and Grebenkin. Similarly, the docked Soyuz MS-25 is the lifeboat of Kononenko, Chub, and Dyson. The Soyuz accommodates only three astronauts.

Till it left the space station, the Starliner was the lifeboat for Wilmore and Williams. Though NASA did not deem the Starliner capsule as being safe enough to bring the two astronauts back, it was understood that in case of a serious emergency on the ISS, the astronauts might have considered it safer to use it than remaining on the ISS.

Now that Starliner has returned to Earth, the SpaceX Dragon, which is scheduled to launch on September 24, will most likely be the escape vehicle for Wilmore and Williams in case of an emergency on the ISS.

The resupply ships docked to the ISS are cargo vehicles, and are not designed to carry astronauts.

NASA and the visiting astronauts are always prepared to deal with an emergency.

Whether it’s an aircraft, a rocket, or the space station, an emergency can strike at any time. On November 15, 2021, seven astronauts on the ISS scrambled into two docked spacecraft as the ISS passed perilously close to the debris field of a defunct satellite destroyed by Russia in an anti-missile test.

In his book Ask an Astronaut: My Guide to Life in Space (2017), the retired British European Space Agency (ESA) astronaut Tim Peake, who flew to the ISS in 2015 aboard a Soyuz spacecraft, described a serious fire on the Mir space station — which was operated by the USSR and then Russia from 1986 to 2001 — in 1997.

The fire, which was described by NASA astronaut Jerry Linenger as a “raging blowtorch”, was fanned by an oxygen canister that caught fire. The fire blocked the path to one of the Soyuz spacecraft, which the crew could use to evacuate, putting the astronauts’ lives at risk, Peake wrote. The astronauts were eventually able to extinguish the fire.

In An Astronaut’s Guide to Life on Earth (2013), former ISS commander Chris Hadfield described an encounter with a big rock that “just raced past us”.