What does it take to get to space? Skill, courage, and a men’s size medium

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

EVA capabilities blossomed during the era of NASA’s space shuttle. Astronauts rode robotic arms, floated tetherless through the void using jetpacks to steer, corralled satellites by hand, and built the International Space Station (ISS). They’ve done it all while wearing spacesuits based on the design first developed for the Apollo missions in the 1960s.

Each suit is a human-shaped spacecraft, featuring a backpack that houses a primary life support system; a layered, pressurized outer garment to protect astronauts from the space environment; and a “long john” undergarment that circulates chilled water via tubes over the body to stop the astronauts getting too hot inside their suit.

When designing these “next-gen” spacesuits in 1974, NASA opted for a modular “tuxedo” approach, in which the various components (upper torso, lower torso, helmet, arms, and gloves) could be mixed and matched to fit individual astronauts. The suits came in five sizes, from extra small to extra large, and were based primarily on male body shapes — females were not eligible for NASA’s astronaut program until 1978.

Fast-forward 47 years and Kimbrough and Pesquet were wearing those exact same spacesuits while working on the ISS, despite the fact the suits were only designed to last 15 years.

These days, NASA’s spacesuits are less like bespoke tailoring and more like remainder stock at an outlet mall; of the 18 suits originally made by the next-gen program, only four full suits remain. Four were lost in the Challenger and Columbia disasters, and others came to the end of their working lives and weren’t replaced.

This means that to be selected for an ISS spacewalk, an astronaut must fit one of the two remaining available sizes: men’s medium, or men’s large. The first all-female EVA, planned for March 2019, had to be postponed because only one medium-sized suit was available. Another medium suit was eventually cobbled together from spares, and astronauts Christina Koch and Jessica Meir successfully performed their groundbreaking spacewalk on October 18, 2019.