Thomas Pesquet will leave the ISS: how will his return to Earth unfold – bfmtv

This Monday evening, Thomas Pesquet and three astronauts will board a Crew Dragon capsule and begin a journey of more than 18 hours to find dry land.

French astronaut Thomas Pesquet completes his second mission to the International Space Station (ISS). On board the Crew Dragon shuttle, with the Japanese Akihiko Hoshide and the Americans Shane Kimbrough and Megan McArthur, he must undock from the ISS this Monday evening at 8:05 p.m., the departure initially scheduled for Sunday having been postponed due to bad conditions. meteorological.

Uncoupling from the ISS

Before their departure, the astronauts will do a sort of inventory of the ISS, “there is an inspection of the capsule which is made, in particular with the robotic arm on the outside which makes it possible to check everything”, explains at BFMTV François Forget, astrophysicist and CNRS research director. “We have already seen that they had taken out the costumes, they will also re-configure the station for the next crew,” also underlines Nathalie Tinjod, in charge of international relations at the European Space Agency (ESA).

Then, the astronauts will put themselves in the spacesuits, and their equipment will be checked, “and then at the same time on Earth we are preparing” for the return, explains François Forget.

Once in the Crew Dragon, “it all starts with undocking [‘désarrimage’ en français] the capsule will move away very slowly “, from the ISS, explains the astrophysicist.” As long as the capsule is close to the space station we stay at very low speed, that is to say a few centimeters per second, we put small pulses “, until you get” about ten kilometers below the station “.

The descent to Earth

Then begins the great descent to Earth. The capsule will begin “a series of orbit lowering maneuvers that align its trajectory with the desired landing location”, explains Space X. It is a gradual descent towards Earth while turning around, which takes the majority of the trip, or more than 16 hours.

During this trip, the astronauts will have a small handicap: they will not be able to use the toilets of the Dragon capsule, a leak problem having been discovered. “It is of course not optimal, but we are prepared to handle it,” said Megan McArthur on Friday.

Then the astronauts, arrived at the right level, “will cross the atmosphere with the heat shield forward”, explains on our antenna Olivier De Goursac, member of the astronomical society of France.

Entry into the atmosphere and landing

It is the last part of the trip which is the most difficult, “it is a critical phase”, explains the astronaut Patrick Baudry on our antenna. The shuttle “will enter the atmosphere at a very high speed, of the order of 27,000 km / h”, and “will brake in the very high layers of the atmosphere, which will release very, very high heat. This is something critical, they are in the middle of a fireball for a few minutes “.

Parachutes will be deployed, to “brake and stabilize the capsule, and then the brake parachutes will make it slow down to a speed compatible with the impact on the sea”, explains the astronaut, but “even if it is on the water, it’s still a shock “. From the opening of the parachutes to the landing, Space X counts 4 minutes on its time division.

“Technically, it is very, very well mastered”, assures Olivier De Goursac, even if the passengers will necessarily be moved. “When the parachutes open, if there really are extremely strong winds it can rock the ship.” “All these procedures Thomas Pesquet trained there before leaving with his crew. And the crew, when everything is going normally, doesn’t have much to do except undergo”, explains Patrick Baudry.

After its vertiginous descent, the Dragon capsule will be recovered from one of the possible arrival points, off Florida, by a SpaceX boat. It should “be a little smoother on the water,” said Thomas Pesquet. “Then what can happen is that things move a bit.” “We already have a little seasickness when we come back to land, so when we come back to sea it may be even worse, but we’ll see,” he added.

Rehabilitation once on Earth

Once recovered, the astronauts will be kept under observation for several weeks to help them recover. In the ISS, “they trained hard to be able to return to Earth in good conditions”, declares Patrick Baudry, but “once on the ground they will find gravity, and there it will be hard (…) he You have to train every day. But psychologically they are trained, they will hold out. “

The following rehabilitation “takes some time, some muscles are atrophied” after months in weightlessness, “others not”, declares Olivier De Goursac. “Some astronauts react more or less well, re-acclimatize quickly or not”. “The human body is not made for gravity, it is made to be on Earth,” he recalls.

“Thomas Pesquet will go from zero gravity to terrestrial gravity, it’s still difficult times, there is a rehabilitation that will be done gradually”, explains Michel Tognini, former astronaut, but “he will get back on his feet quickly”.

Salomé Vincendon with AFP BFMTV reporter