After decades of heavy and cumbersome suits, astronauts are getting an upgrade.

No one ever donned a space suit because it was comfy. Quite the opposite—space suits can be terribly uncomfortable because of the layers and layers of material and technological systems that protect astronauts from the cold vacuum of space and the pressure of ascent and descent through the atmosphere. But as both NASA and private companies probe further into the solar system, ergonomic design for astronauts—including their suits—will become all the more important.

In 2014, NASA contracted Boeing to build a new spacecraft to ferry astronauts to the International Space Station. The Starliner, which replaces the retired space shuttle, will begin launching in 2018, carrying between four and seven astronauts into space. With the new spacecraft comes a new space suit, from a design team led by former space shuttle commander Chris Ferguson and Shane Jacobs, design manager at the David Clark Company, which manufactures suits for aerospace crews.

Their new suit isn’t just safe—it’s likely the most comfortable ever designed.

That’s due to a variety of factors. Because this space suit is specifically meant for the short space flight between Earth and the International Space Station (a couple of days maximum), it doesn’t have to protect astronauts from the biting vacuum of open space. Instead, it’s designed as a fail-safe in case the spacecraft’s pressure wall malfunctions or there’s some kind of leak in the cabin environment.

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In general, a space suit can either be stiff enough to operate at higher pressures (but inhibiting to an astronaut trying to perform tasks) or more comfortable (but less protective). According to Justin Kerr, the spacecraft manager for NASA’s commercial crew program who has worked at the agency for 25 years this month, this is the central tension in space suit design. The ideal suit strikes a balance, says Kerr, who helps set requirements for the safety and design of the agency’s commercial partners, Boeing and SpaceX.

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In order to find that balance, the new Starliner suit features lighter, more flexible fabrics—it only weighs 20 pounds, about 10 pounds lighter than its space shuttle equivalent—and zipper systems at the waist to make sitting and standing more comfortable. Previous suits used metal rings at the joint areas in order to ensure a tight seal, but the Starliner suit minimizes the number of these rings wherever possible, since they can cause serious discomfort and even bruising during ascent and return. Instead of using a ring to connect the helmet to the rest of the suit, the Starliner helmet is actually incorporated into the body, with only a zipper for sealing.

Even the boots are a far cry from the clunky, lace-up boots of previous space suits. They’re much easier to put on and almost look like running shoes, which makes sense, since they were developed in partnership with Reebok. The gloves are 21st-century appropriate: They’re compatible with tablet touch screens, which feature in the Starliner’s design.

It takes between 10 to 15 minutes for an astronaut to don one of the suits, which is fast compared to the heavier, more cumbersome suits of the past. This speed isn’t just for convenience—it’s practical, because the suits need to be put on quickly in case of an emergency in-flight.

The suit is composed of two main layers. The inner layer is made ofGore-Tex fabric, which allows water vapor through but keeps air out, acting almost like a balloon. The outer layer is made of super strongNomex material, which is lightweight and fire retardant—it’s the same stuff used in firefighters’ uniforms.

“There’s a lot of science and engineering in it, but there’s a bit of art in it,” says Kerr. The stitching on the suit and the layering of fabric is somewhat of an art, he explains. You can’t engineer with fabric the way you can with metal, so only testing can reveal whether the suit will withstand the necessary pressure.

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During testing, the suits undergo double and triple the amount of pressure they’re expected to face in space, multiple times over. Once the suit is deemed safe in terms of pressure, then comes the mobility test, where the crew sits in their seats and completes a slew of tasks that reveals how easy it is to work in the suit. “It’s tiring to do a task like turning a wrench, or a dial, when you’re wearing a fully pressurized suit,” Kerr says. “It takes real effort over and over again. It’s like squeezing one of those hand exerciser things or a firm squeezy ball—do that about a thousand times.”

With NASA and SpaceX’s eyes turned toward Mars, innovation in space suit design and other aspects of astronaut comfort will be a necessary part of getting there. Kerr believes that the Starliner suit is a step in the right direction. “This suit isn’t designed for Mars, but features in there are taking steps [forward],” he says. If you’re sending a manned mission to the red planet, the crew will be spending plenty of time on its surface, performing tasks like collecting samples. The same tension between safety and mobility will apply—the less a crew member has to work against the suit, the longer they’ll be able to work in the field.

While the Starliner suit isn’t meant for Mars, perhaps it’s the grandfather to the one that will walk there one day.