When it comes to spacewalks, size matters


NASA astronaut Shane Kimbrough (left) and ESA astronaut Thomas Pesquet conduct a spacewalk outside the space station in June, using suits that are well over their lifespan initial life. (credit: NASA)


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On June 25, astronauts Shane Kimbrough and Thomas Pesquet successfully performed an almost seven-hour extravehicular activity or spacewalk (EVA) to install solar panels on the International Space Station, the latest in a series of three EVAs they performed in June. What does it take to don a spacesuit and venture into such a technical and dangerous mission? Surprisingly, one of the main criteria (besides the years of astronaut training) is body size.

EVA capabilities flourished in the days of NASA’s space shuttle. Astronauts mounted robotic arms, floated unattached in a vacuum using jetpacks to steer, circled satellites by hand, and built the International Space Station (ISS). They did it all by wearing spacesuits based on the design first developed for the Apollo missions in the 1960s.

These days, NASA spacesuits look less like tailored clothing and more like leftover inventory in a mall.

Each suit is a human-shaped spaceship, complete with a backpack that houses a primary life support system; a layered and pressurized outer garment to protect astronauts from the space environment; and a “long john” underwear that circulates chilled water through tubes over the body to prevent astronauts from getting too hot inside their suits.

When designing these “next generation” spacesuits in 1974, NASA opted for a modular “tuxedo” approach, in which the different components (upper torso, lower torso, helmet, arms and gloves) could be mixed. and matched to suit each astronaut. The suits were available in five sizes, from extra small to extra large, and were primarily based on male build. Women were not eligible for the NASA astronaut program until 1978.

Fast forward 47 years, and Kimbrough and Pesquet wore the exact same spacesuits when working on the ISS, despite the suits being only designed to last 15 years.

These days, NASA spacesuits look less like tailored clothing and more like leftover inventory in a mall. Of the 18 suits originally manufactured by the Next Generation program, only four complete suits remain. Four were lost in the Challenger and Columbia disasters, and others have reached the end of their working lives and have not been replaced.

This means that in order to be selected for a sortie in the ISS, an astronaut must match one of the two remaining available sizes: medium man or tall man. The first all-female EVA, scheduled for March 2019, had to be postponed as only one mid-size wetsuit was available. Another medium suit was finally cobbled together from spare parts, and astronauts Christina Koch and Jessica Meir successfully completed their groundbreaking spacewalk on October 18, 2019.

Most EVAs are performed in pairs, and flight controllers meticulously choreograph each astronaut’s activities well in advance, to minimize downtime and get tasks done as efficiently as possible.

Each EVA participant takes up to ten hours of training per hour of EVA time, in a 12-meter-deep pool in which astronauts practice every aspect of their spacewalk using life-size mock-ups of the components of the ISS.

During the actual EVA, ground mission controllers carefully monitor the progress of astronauts, and astronauts can communicate with ground control, their EVA buddy, and ISS teammates as needed.

Space is a hostile environment. The spacesuit provides protection against radiation, temperature extremes (ranging from -270 ° C to + 120 ° C) and small particles of debris. To guard against the risk of being hit by “space debris,” EVAs are scheduled for low-risk periods, based on tracking known objects.

Hopefully Artemis moonwalkers will have more options when they put on their suits, meaning astronauts can be selected for missions because they have what it takes, without also needing to be the right one. cut.

Astronauts also need to take steps to avoid decompression sickness, or “turns”. Much like a diver ascending too quickly from a deep dive, an astronaut moving too fast from the pressurized space station to the lower pressure inside their spacesuit may suffer from the formation of painful nitrogen bubbles. and potentially fatal in his bloodstream. Prior to an EVA, astronauts “camp” overnight in the ISS airlock at reduced pressure, to help acclimatize before donning their spacesuits.

No one died during an EVA, but there were a few close calls. Soviet cosmonaut Alexei Leonov’s very first spacewalk in 1965 almost ended in disaster when the expansion of his suit into the vacuum of space nearly prevented him from entering the Voskhod capsule. .

And on July 16, 2013, Luca Parmitano made history books with two firsts: the first Italian to perform a spacewalk and the first near-drowning in space. A week before his EVA, one of the water lines in his spacesuit had caused a leak. But that information was not passed down the chain of command, and mission controllers allowed his EVA to begin.

Within an hour, Luca had almost two liters of water in his helmet, leaving him struggling to breathe. Unable to see through his visor or communicate with colleagues, Luca said he used his tether to return to the safety of the airlock.

There is no doubt that he and other astronauts will want to don the new NASA “Exploration Extravehicular Mobility Unit (xEMU)” spacesuits currently in development for the Artemis program, NASA’s long-awaited return. on the moon.

Hopefully Artemis moonwalkers will have more options when they put on their wetsuits, which means astronauts can be selected for missions because they have what it takes, without also needing to be the right size. .


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