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. 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.
Each suit is a human-shaped spaceship, complete with a backpack that houses a main 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 tailored to individual astronauts. . The suits were available in five sizes, from very small to very 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 space suits when they worked 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 full 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 an ISS spacewalk, an astronaut must match one of the remaining two available sizes: medium-sized males or tall males. 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 closely 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 ℃ to + 120 ℃) 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.
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 can experience painful and potentially fatal nitrogen bubbles. forming 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 suits, meaning astronauts can be selected for missions because they have what it takes, without also needing to be the right one. cut.
Article by Steven Moore, Research Professor / Assistant Dean, School of Engineering and Technology, CQUniversity Australia
This article is republished from The Conversation under a Creative Commons license. Read the original article.