Back to Earth with a thump: Tim Peake prepares to bid farewell to the ISS

In astronaut circles, the return to Earth aboard the Soyuz capsule is described in a hundred ways, but a common thread runs through them. Even when all goes smoothly, the ride itself is never smooth. “It is physically extremely violent,” says Chris Hadfield, the retired Canadian astronaut. “We often describe it as 15 explosions followed by a car crash.”

It is with such thoughts in mind that Tim Peake will leave the International Space Station on Saturday morning after 186 days in orbit. At 4am UK time he and two others, Nasa’s Tim Kopra and Russian cosmonaut Yuri Malenchenko, will say farewell to their crewmates, clamber into the Soyuz, and close the hatch. Six hours later, they will hit the planet. With luck, not too hard.

Peake’s return to Earth will bring to a close an impressive first tour in orbit. The only Briton ever selected for the European Space Agency’s astronaut corps, the former helicopter test-pilot ran experiments, performed a challenging spacewalk, fixed a broken toilet, and berthed a visiting cargo vessel with the station’s robotic arm. “He’s done a magnificent job,” says Hadfield. “What a quality guy. He’s supremely capable.”

Not all of a modern astronaut’s work is technical. As the space station soared overhead at 17,500mph, Peake shared breathtaking photos with his 780,000 Twitter followers. He presented Adele with a Brit award, ran the London marathon on a treadmill, and read a bedtime story on CBeebies. Expect more once he is home.

Astronauts often have mixed feelings about the trip back to Earth. Last year, Samantha Cristoforetti broke the record for the longest single space flight by a woman, spending 199 days and 16 hours on the station. “You’ve been in orbit a long time and you are looking forward to seeing your family, but at the same time you realise you’ve spent time in an amazing and unique place and you don’t know if you’ll ever get a chance to go back,” she says. “You start missing the place before you even leave.”

The bulkiness of the spacesuits, and the equipment coming home, means that Peake, Kopra and Malenchenko are jammed tightly into the capsule. They must sit, cramped and uncomfortable, for nearly three hours before the press of a button releases a spring that gently pushes them away from the space station. Three minutes later, Soyuz will fire its thrusters to drift clear, and an hour after that, perform a de-orbit burn. Now the fun really starts: the Soyuz is falling to Earth.

The numbers, at least, are simple. When the Soyuz departs the space station, it must fall 250 vertical miles and decelerate from 17,500mph to a standstill in three and a half hours. Much of the speed is lost to the atmosphere. Having spent the past six months floating about, the crew will feel at least four times their weight on Earth as the atmosphere thickens and air resistance soars.

But before reentry, the Soyuz must shed two modules that are no longer needed. Explosive bolts fire and release the unwanted service and orbital modules, leaving only the bell-shaped descent module containing the crew. The firing of the bolts feels like someone is attacking the capsule with a sledgehammer.

As the descent capsule plunges into the atmosphere, G-force builds up on the crew. “It feels incredible. You are pushed far down into your seat. It feels like ten times your own body weight because your perception of weight is so completely off,” says Cristoforetti. The friction from the atmosphere chars the capsule and sears the heat shield at temperatures reaching 1600 Celsius. The air outside burns. “You are literally in a ball of fire,” she says.

The Soyuz capsule is programmed to reach a particular position at 30,000 feet where it automatically releases drogue chutes and then a full parachute. The crew must be ready to take over manual control at any second. Fully deployed, the parachute tugs hard on the capsule, and swings it around like a toy.

Down on the ground, the Russian search and rescue team will try and track the capsule as it falls. Once they have it in sight, they can radio the crew and keep them abreast of their altitude. Inside, the crew sink deep into their seats, which have risen up on shock absorbers. They stop talking, to avoid biting their tongues on impact. Seconds before touchdown, six retrorockets fire to slow the capsule further.

“He will be hurled about, shaken, spun, crushed, and snapped around like crazy when the parachutes open, and then he’ll crash into the Earth. And then, if it’s a windy day in Kazakhstan, the vehicle will roll end over end until it finally creaks to a stop,” says Hadfield of Peake’s return trip. “It’s an amazing ride home.”

The crew are due to land in southern Kazakhstan at 10.14am Saturday morning. They cannot climb out on their own, so will sit there, in a vessel charred, smoking, and most likely on its side, until helicopters arrive with the rescue team. After a swift round of medical checks, the crew will be flown to Karaganda, a nearby city, for a short ceremony and from there to their respective home agencies.

Peake will fly back to Cologne, home of the European Astronaut Centre, in the early hours of Sunday morning. There, at the Envihab facility, he will see his family in the flesh for the first time in six months, and spend the night in a proper bed. On top of tests to see how he adjusts to life back on Earth, a full programme of rehabilitation awaits, to rebuild the muscle and bone that astronauts lose in orbit.

“The one thing that really strikes you is your weight. I had this feeling that I was trying to balance a giant rock, which was my body, on two little toothpicks, which were my legs,” says Cristoforetti. But there are treats to coming home too, she says: the freshness of a salad, a decent shower, even if you do have to take it sitting down.

It will take some time for Peake to recover fully, says Hadfield. “It will take a few days for his head to clear, a few weeks to feel normal, a few months to be able to run properly, and a few years to grow his skeleton back.”