One option that NASA engineers considered was to add “active heating” elements to the shoes to provide more warmth. Shoe radiators come with a trade-off, Pfister says. “If you’re actively heating, you need to draw energy from somewhere.” This means that batteries and cables can add weight to the shoes and the overall load carried by the astronauts.
With astronauts set to explore the lunar surface for extended periods of time, and possibly build a permanent lunar base on future missions, even small amounts of extra volume can make movement less efficient. Engineers will have to make sure the shoes fit as snugly as possible, but they face another challenge their Apollo counterparts didn’t — the range of astronauts’ body sizes. It will see Artemis the first woman to set foot on the moon. This means that a wider range of shoe sizes may have been required compared to the Apollo missions, where all the astronauts were male and were Almost all the same height, age and weight.
“We’re looking at ways we can work with individuals to get a shoe that’s a perfect fit for them,” says Pfister, who spends many hours walking around in model shoes and suits to test how they feel. But rather than having several custom sizes made, the shoes will come in specific sizes that can then be adjusted using padding inserts and external tensioning mechanisms.
“The AxEMU lunar boot will be more comfortable and portable than the ones used during the Apollo missions,” Ralston adds.
Astronauts will also spend a significant amount of time before starting training with their boots on to make sure they perform as expected on the Moon. “They’ll train and train in these shoes, and they’ll try different options, until they get the perfect fit,” Pfister says. “Breaking moon shoes is just as important as breaking new ones.”
And for those who like an extra bit of comfort, there are always lower-tech solutions. “Personally, I wear two socks on each foot — I feel better over six hours,” Pfister says.
