Crew-2 Heading Home with Crew-3 Still on the Ground

Weather permitting, four astronauts aboard the International Space Station will begin their return to Earth tomorrow even though their replacements are still on the ground. One American astronaut who is using Russia’s Soyuz spacecraft for transportation will remain on the space station, but the U.S. segment will be short staffed for at least a few days. [UPDATE, November 7: Crew-2’s return is delayed till Monday, November 8, due to high winds in the recovery area.)

If all goes according to plan, Crew-2 will undock from the ISS Sunday at 12:04 pm ET, an hour earlier than previously announced, and splashdown off the coast of Florida at 7:14 am ET Monday morning. Seven different splashdown locations are available on either the Atlantic or Gulf coasts. At the moment, a splashdown in the Gulf of Mexico seems most likely.

SpaceX’s spacecraft for ferrying people to and from Earth orbit are called Crew Dragon to differentiate them from the cargo version, Cargo Dragon. Each Crew Dragon mission is numbered in sequence, so Crew-2 is the second operational Crew Dragon mission.

Crew-2 has been on the ISS since April: NASA astronauts Shane Kimbrough and Megan McArthur,  Japan’s Akihiko Hoshide, and the European Space Agency’s (ESA’s) Thomas Pesquet.

At a media teleconference this afternoon, SpaceX Director of Dragon Mission Management Sarah Walker said the winds are forecast to be too high for this particular landing opportunity, however. They are monitoring the forecast and will make a final decision 6 hours before undocking.

An alternative is to wait until Monday. Orbital dynamics would make that a shorter return trip.  Undocking would be at 2:00 pm ET and landing just 8.5 hours later at 10:33 pm ET.

Once it undocks, three people will be left aboard the ISS — Russians Anton Shklaperov and Pyotr Dubrov and American Mark Vande Hei who are using Russian Soyuz spacecraft to get back and forth.

The plan was for Crew-2’s replacements to be on board ISS before they left. Crew-3 was supposed to launch on October 31 with a several day handover, but it has been postponed by a combination of weather conditions and what NASA terms a “minor medical issue” involving one of the crew members. Privacy rules prevent NASA from being more explicit and the affected astronaut has not chosen to share any information. By contrast, Vande Hei recently had to be replaced on a spacewalk for medical reasons and disclosed himself that the problem was a pinched nerve in his neck.

In any case, Crew-3 is now scheduled to launch no earlier than Wednesday and weather may delay that until Thursday or Friday. It is composed of three NASA astronauts — Raja Chari, Tom Marshburn, and Kayla Barron — and ESA astronaut Matthias Maurer. Which of them is experiencing the minor medical issue has not been disclosed, but NASA officials said today they expect it to be resolved before launch, whenever that is.

NASA does not assign backup crew members like Russia does. At today’s briefing, NASA ISS Program Manager Joel Mantalbano said if that a crew member experienced a major medical issue close to launch and had to be replaced, the agency would have to wait until someone else, perhaps an astronaut who already had flown a Crew Dragon, could be appropriately trained and had a spacesuit fitted.

Rather than trying to subsitute a replacement, NASA plans to deal with contingencies like that by arranging with Russia to routinely launch crew members from each other’s countries on a no-exchange-of-funds basis to ensure at least one American and one Russian is always aboard the ISS. NASA paid Russia to launch its astronauts to the ISS for many years and Russia has been reluctant to agree to this quid-pro-quo deal. Vande Hei’s trip was agreed to at the last minute through a U.S. company, Axiom. There is no comparable agreement for future flights though NASA hopes to have something in place for launches starting in the fall of 2022.

Vande Hei’s presence is fortuitous in this case, allowing NASA to bring Crew-2 back even though Crew-3 is still on the ground while maintaining a U.S. presence there. His mission was extended for an extra six months by a Russian decision to send two space tourists to the ISS to film scenes for a movie.

Crew Dragons have a certified on-orbit lifetime of 210 days, but SpaceX’s Walker and NASA Commercial Crew Deputy Program Manager Ven Fang said today that is a soft limit and they expect the spacecraft could stay in space longer. This specific spacecraft, Endeavour, will not reach the 210-day linit until November 19.  Asked why the rush to return Crew-2 if spacecraft lifetime is not the limitation, Fang simply said that historically weather conditions for splashdown worsen during the months of November and December.

If weather cooperates, Crew-2 will be back on Earth on Monday and Crew-3 will launch on Wednesday at 9:03 pm ET.