Early this morning, the crew of a commercial space mission opened the hatch of their Crew Dragon capsule as they orbited 435 miles above Earth.
Half the Polaris Dawn crew, SpaceX astronaut Sarah Gillis and billionaire CEO Jared Isaacman, successfully pulled themselves out through the hatch and became the first private crew to perform a spacewalk. The other half, SpaceX astronauts Scott Poteet and Anna Mennon, were strapped into their seats inside the Crew Dragon, but they were still be exposed to most of the risks that come with a spacewalk. This may be the riskiest mission a commercial space crew has ever undertaken — but that’s not because they’re not space agency astronauts.
Part of the risk of tonight’s spacewalk comes from the fact that Polaris Dawn is a test flight for a new spacesuit design, and test flights carry a risk of something going wrong — as Starliner commander Butch Wilmore pointed out last month.
But most of the risk is that the whole Crew Dragon cabin was depressurized and open to the vacuum of space. That means that if something goes wrong, Isaacman and Gillis won’t be able to scramble into an airlock that can refill in a matter of minutes — and it means the whole crew will be impacted.
“You’re throwing away all the safety of your vehicle,” said Isaacman during an August 19 press converence. “It now comes down to your suit; it becomes your spaceship.”
These are big risks — testing a new spacesuit design while your whole ship is open to space — but they’re not new. The crews of the Gemini missions faced them more than 50 years ago and paved the way for all the spacewalks that have happened since. Here's a look back.
“Throwing Away All the Safety of Your Vehicle”
The Gemini spacecraft didn’t come with airlocks, so on all 9 Gemini missions, spacewalks meant opening the hatch and exposing the whole cabin — and both astronauts — to the vacuum of space. Both astronauts had to suit up, and the mission commander sat strapped into his seat, doing pretty much the same things Poteet and Mennon did during the Polaris Dawn spacewalk: keeping an eye on oxygen lines and tethers, taking pictures of the astronaut floating around outside, and hoping nothing goes wrong.
Shut the Door Behind You!
One problem with using your whole spaceship as an airlock is that your life depends — more than usual — on the main hatch closing properly once everyone is back on board. Gemini IV astronauts McDivitt and White nearly faced certain death when their hatch failed to latch after White’s spacewalk in June 1966.
When the hatch refused to seal, McDivitt had to negotiate with a stuck spring in the latching mechanism. It wasn’t an obvious problem, and without a vacuum-chamber test on the ground — and a lot of time spent taking apart the mechanism afterward — McDivitt might not have been able to fix it. He and White would then have faced a grim choice: suffocate in orbit in when their suits ran out of oxygen, or burn up during re-entry thanks to the open door in their capsule.
Early pressure suits, like the ones the Gemini crews wore, tended to puff outward like big person-shaped balloons, thanks to the pressure being so much greater inside the suit than outside. That made it very difficult for astronauts to move — and being able to move is sort of important when you’re trying to clamber around the outside of a spacecraft, using hand tools and operating valves. On the Gemini IX mission in June 1966, Cernan reported that his spacesuit became so stiff that it was excruciatingly painful to move, and a stuggle to even breathe.
In March 1965, Soviet cosmonaut Alexei Leonov became the first to discover this problem, but it continued to plague Gemini crews. The spacesuits NASA and European Space Agency astronauts use aboard the International Space Station today aren’t inflated to such high pressure, and they’re easier to maneuver, but still cumbersome. Artemis crews will wear more streamlined spacesuits with more movable joints. And Polaris Dawn’s spacewalk will test SpaceX’s new EVA suits, which are also supposed to be more flexible than the current models.
The Great Success Of Gemini IV, June 1965
Sometimes, testing new equipment goes really well. Ed White, during the first spacewalk by a U.S. astronaut, loved the experience and his handy “zip gun,” more formally known as a Handheld Maneuvering Unit: a gun that fired bursts of oxygen as thrust to help White move and steer. White made 3 laps back and forth to the end of his 25-foot tether before the gun ran out of air, and then he had to pull himself along the tether — but was still having so much fun that he didn’t want to come back inside.
The Near-Fatal Gemini IX, June 1966
A spacesuit doesn’t only have to keep the astronaut protected from vacuum and supplied with breathable air. It’s got to control the astronaut’s temperature – and usually overheating is the biggest problem, as Cernan found out. His June 1966 spacewalk was supposed to be a test of the Astronaut Maneuvering Unit: a backpack with a small rocket on the back. It turned into a grueling near-death experience for Cernan.
In the dim light of an in-orbit sunset, he worked his way around the outside of the Gemini capsule — struggling to find usable handholds — where the folded-up AMU was stowed. After unpacking and unfolding the AMU, connecting his oxygen line, and switching on a bunch of valves, Cernan still had to maneuver himself (in his stiff, ballooned spacesuit) into the backpack and strap in.
But his suit had no real cooling system, and every movement Cernan made was encumbered by his pressure suit, which was beginning to squeeze him painfully. By the time he had managed to struggle painfully into the rocket backpack, Cernan was weak with heat exhaustion, his sweat was fogging up the inside of his helmet, and his heart was racing at a dangerous 180 beats per minute. Stafford cancelled the AMU test and ordered Cernan back inside — and he almost didn’t make it.
Similar problems befell Gemini XI pilot Rick Gordon, six months and three Gemini missions later.
What Did We Learn From This? A Lot, Actually
Cernan and Gordon’s painful, harrowing experiences did exactly what they were meant to do: teach NASA how to make spacewalks safer and more practical for the astronauts that came after them. That meant more handholds on the outside of spacecraft, for one thing — a design element that would have save Cernan a lot of strain and sweat. It also meant training astronauts in a 6.2 million gallon swimming pool, using neutral buoyancy to simulate microgravity. Astronauts can get a feel for moving around in their bulky suits and practice their spacewalks on underwater mock-ups of spacecraft.
The first astronaut to train for a spacewalk in the pool was Gemini XII pilot Buzz Aldrin, later known as the first man to pee on the Moon. (History does not record whether he also peed in the pool.)
What Happens Now?
Thanks to the Gemini missions, and all the spacewalks since, we know more about spacesuits, the physiology of being in space, and spacecraft design. We have better spacesuits and better communications gear. But the crew of Polaris Dawn will still face the same dangers the Gemini crews faced before any of Isaacman’s crew was even born, and they’re doing it for similar reasons.
