DiscourseJuly 22, 2021 15:17:55 IST
Astronauts Shane Kimbrough and Thomas Pesquet successfully completed almost seven hours of EVA (extravehicular activity) to install solar panels on the International Space Station. What is needed to hand over a spacesuit and embark on such a technical and dangerous mission? Surprisingly, one of the most important criteria (in addition to the years of astronaut training) is body size.
EVA capabilities flourished during the NASA space shuttle era. Astronauts rode robotic weapons, floated impoverished through emptiness using jet kits to steer, etched satellites by hand, and built the International Space Station (ISS). They have done everything in their use of space suits based on a model developed in the 1960s for Apollo missions.
Each suit is a human-shaped spacecraft with a backpack with primary life support; layered, pressurized outerwear to protect astronauts from the space environment; and a “long john” underwear that circulates chilled water through pipes over the body to prevent astronauts from heating up in their costumes.
When designing these next-generation spacesuits in 1974, NASA opted for a modular tuxedo approach in which different components (upper body, lower body, helmet, arms, and gloves) can be mixed and adapted to fit individual astronauts. The costumes came in five sizes, from particularly small to very large, and were based primarily on male body shapes — women were not eligible for NASA’s astronaut program until 1978.
Fast forward 47 years, and Kimbrough and Pesquet wore exactly the same space suits when working on the ISS, despite the fact that the suits were only designed to last 15 years.
Today, NASA’s space suits are less than customized and more than the remaining stock in an outlet mall; of the 18 suits originally made by the next generation program, only four are full suits. Four were lost in the Challenger and Columbia disasters, and others ended their working lives and were not replaced.
This means that an astronaut is selected for ISS spacewalk to fit one of the two remaining sizes: men’s medium or men’s large. The first female EVA, scheduled for March 2019, had to be postponed because only one mid-size suit was available. The second middle suit was eventually mated to one of the spare parts, and astronauts Christina Koch and Jessica Meir successfully completed a groundbreaking space walk on October 18, 2019.
Most EVAs are performed in pairs, and air traffic controllers carefully choreograph the activities of each astronaut in a timely manner to minimize idle time and perform tasks as efficiently as possible.
Each EVA participant receives up to ten hours of training per hour of EVA time in a 12-meter-deep pool where astronauts practice all aspects of their space walks using life-size patterns of ISS components.
During the actual EVA, field operations instructors closely monitor the astronauts ’progress, and the astronauts can communicate with the ground administration, their EVA buddy, and the ISS crew as needed.
Space is a harsh environment. The space suit provides protection against radiation, extreme temperatures (between -270 ℃ and + 120 ℃) and small debris. EVAs are designed for low-risk episodes to track known objects to prevent them from colliding with space junk.
Astronauts must also take steps to avoid decompression sickness or “bends.” Just like a submarine that rises too fast from a deep dive, an astronaut who moves too fast from a pressurized space station to a lower pressure inside a spacesuit can suffer from painful and potentially deadly nitrogen bubbles that form in the bloodstream. Prior to EVA, astronauts “camp” overnight at the ISS airlock under reduced pressure to help adapt before putting on their spacesuits.
No one has died during the EVA, but there have been close calls. The first space walk by Soviet cosmonaut Alexei Leonov in 1965 ended in disaster, when the expansion of the suit in the vacuum of space almost prevented him from getting back into the Voskhod capsule.
And on July 16, 2013, Luca Parmitano entered the history books with the first two: the first Italian to complete a space walk, and the first near drowning in space. One week before EVA, one of the water suit’s water pipes had leaked. But this information was not provided in the chain of command, and the EVA was authorized by the supervisors of the operation to begin.
Within an hour, Luca’s helmet had almost two gallons of water, leaving him struggling to breathe. Luca was unable to see from her visor or communicate with her colleagues, but said she used her strap to navigate back to safety lock safety.
No doubt he and other astronauts want to hand over NASA’s new space suits, the “Exploration Extravehicular Mobility Unit (xEMU),” currently being developed for the Artemis program, NASA’s long-awaited return to the Moon.
Hopefully, Artemis Moonwalkers will have more options on top of their costumes, which means astronauts can be selected for missions because they have the right items without having to be the right size as well.
Steven Moore, Professor / Vice Dean Research, University of Technology, CQUniversity Australia