Before Sunita Williams’ Splashdown, Moments Of Terror In Spacecraft

Arun Jain,

New Delhi:

A Dragon spacecraft bringing astronauts Sunita Williams and Butch Wilmore home after nine months in space splashed down off the coast of Florida at 5.57 pm (3.27 am IST). Shortly after, 59-year-old Williams and 62-year-old Bilmore were brought out of the spacecraft, smiling and waving, as the world cheered. NASA’s Nick Hague, and Roscosmos cosmonaut Aleksandr Gorbunov accompanied them on the 17-hour journey home.

But these moments of joy were preceded by hours during which the astronauts — and the world — had their fingers crossed. And the last leg was the most tricky when SpaceX’s Dragon spacecraft re-entered the atmosphere. At this point, the capsule is travelling at speeds going up to 28,800 kmph. The friction this creates takes the temperatures of its outer casing to about 1,600 degrees Celsius, with heat shields protecting the occupants inside. So, the cheers to celebrate Sunita Williams’ homecoming came only after the spacecraft turned a ball of fire entering the atmosphere and heading for a splash in the ocean.

What Protects The Astronauts

Docked at the International Space Station, the Dragon spacecraft is in a state of near-vacuum. Following a series of departure burns, it moved away from the station and began its journey home. As it enters Earth’s atmosphere, high friction is created, pushing the temperatures up significantly, as high as 1,600 degrees.

Dragon capsules use heat-resistant PICA material for the outer shell. Photo courtesy: NASA

Dragon capsules use heat-resistant PICA material for the outer shell. Photo courtesy: NASA

The SpaceX’s Dragon capsule is equipped with a heat-resistant casing of Phenolic-Impregnated Carbon Ablator of PICA. It was NASA that first used this lightweight material. Later, SpaceX got its Dragon capsule outfitted with PICA tiles for cargo and human movement to and from the International Space Station. The Dragon capsule that brought Williams and Bilmore home went from sparkling white to brownish by the time it splashed down, indicating how the outer shell burned as it entered the atmosphere, but ensured occupants’ safety.

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Manouevering The Splashdown

The Dragon spacecraft has a total of six parachutes — two drogue parachutes to stabilise it after it re-enters Earth’s atmosphere and four main parachutes to slow down the spacecraft before landing. Minutes before the splashdown, as the Dragon spacecraft approached the ocean, two main parachutes were deployed, stabilising and slowing down the capsule.

A minute later, four more parachutes opened, slowing down the capsule further. The target speed for the spacecraft at the time of splashdown is 16 miles per hour. This was achieved by slowing it down and positioning it over the ocean’s surface using the four parachutes. As the spacecraft splashed down, the next phase of work began. The first team that approached the spacecraft checked for gas leaks before opening the hatch and bringing the occupants out.

And Finally, The Cheers

The first to come out of the Dragon spacecraft was NASA’s Nick Hague, and moments later Aleksandr Gorbunov from Russian space agency Roscosmos emerged. The most awaited moment followed. Sunita Williams, whose eight-day mission to the International Space Station turned into a nine-month-long stay, came out, smiling and waving. The last to exit the spacecraft was Butch Wilmore.

Williams and Wilmore will undergo an extensive check-up following their 286-day stay in space. Bone and muscle deterioration, radiation exposure, and vision impairment are some risks space travellers face on their return to Earth after a prolonged stay in space.

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The lack of gravity causes significant, and sometimes irreversible, bone density loss. Muscles, usually activated by moving around on Earth, weaken because they no longer need to work as hard.


World