Crew-12 Leaves the ISS: Dragon Freedom Undocking and Departure

NASA's SpaceX Crew-12 left the International Space Station at 8:05 a.m. EDT (7:05 a.m. Central) on October 7, when the Dragon Freedom spacecraft undocked while the station was traveling 262 statute miles over northern Cuba. On board were NASA astronauts Jessica Meir and Jack Hathaway, ESA astronaut Sophie Adenot and Roscosmos cosmonaut Andrey Fedyaev, who had spent 235 days aboard the station and were due to reach 237 days in space at splashdown.

The handover

Crew-13 had arrived on October 1 at 7:05 p.m. Eastern after a trip of about seven and a half hours. Its members are NASA astronauts Jessica Watkins and Luke Delaney, Canadian Space Agency astronaut Joshua Kutryk and Roscosmos cosmonaut Sergey Teteryatnikov. For almost a week the two crews overlapped while the newcomers learned to live and work on the station. Meir handed command of the station to Roscosmos' Pyotr Dubrov on the Sunday before departure, and Expedition 75 continued with Dubrov, NASA astronaut Oleg Novitsky, cosmonaut Anna Kikina and the Crew-13 members.

On departure day, Meir and Hathaway moved cold bags and polar freezers holding cold research samples into Dragon Freedom. The hatch between Dragon and the station closed at 6:05 a.m. Eastern, and the vestibule was then depressurized to vacuum. In a farewell message Meir thanked teams in Houston, at SpaceX and among the international partners, and singled out Richard Jones of the commercial crew office, who is departing NASA.

The undocking

Dragon's departure and deorbit are designed to be fully autonomous, so the crew took no action. Kutryk monitored from the cupola, and flight controllers in Houston and Hawthorne backed the crew up. The four crew members were suited, with visors down, for what the commentators called a dynamic event; the suits protect them in case of cabin depressurization and keep them cool.

• About 8:00 a.m. Eastern: the undock command was issued and the umbilicals retracted.
• Next four to five minutes: two sets of six hooks, 12 in all, opened. Once the second set was driving open, Dragon was committed to undock.
• 8:05 a.m.: "All hooks are opened. Separation confirmed."
• Departure burn zero: 16 seconds, sending Dragon up and around the station.
• Departure burn one: about 22 seconds, around 8:10 a.m. Eastern, followed by the go to doff suits.
• About 8:11 a.m.: Dragon exited the keep-out sphere.
• About 8:24 a.m. expected: exit from the approach ellipsoid, after which Dragon was on a safe free drift trajectory.

Unlike Soyuz, which relies on springs, Dragon undocks with two short firings of its Draco thrusters: the first breaks any stiction between the spacecraft and the docking port, and the second backs it slowly away.

The safety boundaries

The keep-out sphere is an invisible boundary with a 200-metre radius. Before a spacecraft enters it, the spacecraft must be configured so that it would not cross the boundary for at least four orbits, even if it lost all maneuvering. The approach ellipsoid measures 4 by 2 by 2 km. Vehicles outside it must be on a 24-hour safe free drift trajectory, meaning they would not enter it for at least 24 hours even after losing all maneuvering. While Dragon was inside, NASA and SpaceX ran integrated operations on a single "big loop" communications channel. Once it left the ellipsoid, SpaceX took over command and communication until splashdown.

The crew

• Jessica Meir, commander, has spent 442 days in space over two flights, the 10th most by a NASA astronaut. She did four spacewalks totaling 27 hours 38 minutes on this mission, and has seven spacewalks totaling 49 hours 22 minutes in her career, including the first all-female spacewalk with Christina Koch.
• Jack Hathaway, pilot, was completing his first spaceflight. He has more than 2,500 flight hours in 30 types of aircraft and has flown 39 combat missions.
• Sophie Adenot did three spacewalks totaling 19 hours 42 minutes on her first flight. Her 237 days are the seventh most by an ESA astronaut.
• Andrey Fedyaev, on his second mission after Crew-6, reaches 423 total days in space and is the first Russian cosmonaut to fly twice in Dragon.

Science and spacewalks

Crew-12 worked more than 1,000 hours on over 250 investigations. Veg-06 studied how spaceflight affects the relationship between plants and nitrogen-fixing microbes. IVGEN Mini is a compact system that makes saline from drinkable water, aimed at on-demand IV fluids; commercially available IV fluids have a shelf life of only about 16 months. During spacewalk 96 in August, the crew installed hardware to modify the station's 3B power channel in preparation for an ISS Roll Out Solar Array (iROSA). That iROSA is scheduled for delivery on SpaceX's 35th commercial resupply mission and will be the seventh.

The trip home

The flight was expected to last about 27.5 hours, taking Dragon through a phasing burn, trunk separation, closure of the nose cone, a deorbit burn and deployment of the drogue and main parachutes. Splashdown was targeted off the coast of California at 11:34 a.m. Eastern on October 8, with the crew to be picked up by a SpaceX recovery vessel. By then the crew will have completed 3,792 orbits and traveled more than 100 million statute miles.