Are We Reaching the End of Spacewalks?

  • In Science
  • 2019-05-21 14:39:00Z
  • By Popular Mechanics

From Popular Mechanics

It's June 3, 1965 and astronaut Ed White, in orbit over Hawaii, emerges from a space capsule to become the first American to conduct a extravehicular activity, or EVA. Connected with a single tether providing power and communication lines, he maneuvers using an oxygen gun for propulsion, takes in the view, and poses for pictures.

"I feel like a million dollars," White says.

These days EVAs are not done for the photos, they are part of the maintenance and operation of the International Space Station. They are planned to the minute, and astronauts seldom have time for a selfie (or joyriding with jet-guns).

"We've been so fortunate that we haven't had a major accident, but statistically, doing an EVA is just as dangerous as launching and reentry," says Garrett Reisman, former NASA astronaut with a nearly 7-hour spacewalk on his resume now a professor at USC.

EVAs are hard, dangerous, and time consuming. It makes sense that today's space engineers would want alternatives as they design the next generation of space exploration hardware, but there is a reluctance to leave orbital spacesuits behind.

"It comes back down to design decisions that you make when you are in the very early stages of designing your space station," Reisman says. "How are you going to cope with failures? Are you going to design things for very high reliability, or do you design so that when things break you just replace them? If you're going to do that, do you put those things on the inside or the outside?"

The easiest way to limit the number of spacewalks is to put things that need maintenance inside a space station. But future space stations will be smaller than the sprawling ISS and that strategy may not be possible. For example, NASA's Lunar Gateway plans are much smaller than the ISS-around 2,000 cubic feet of habitable volume compared to the relatively roomy 13,696 cubic feet.

Instead, the Gateway has a sharp focus on automation; the station will only be crewed part of the time but the designers are pledging it will operate on its own-fulltime. That might give exterior-mounted robotic arms the advantage over the gloved hands of a spacewalker. But NASA appears to be planning for some orbital spacewalks, with requirements that the lunar space station's short-range communications and airlock can accommodate "astronaut EVAs."

Bill Pratt, Lockheed Martin's NextSTEP Habitat Program Manager, says that their proposed Gateway design includes a separate EVA module "so you don't have to depressurize the entire Gateway any time you do a spacewalk."

But it also seems like the real heavy lifting will be done by machines.

"We've designed our proposed Gateway elements so that robotic components, such as the Canadarm and autonomous docking systems, can handle the in-space assembly and operations without requiring EVAs," Pratt says.

So in the future, EVAs could become an emergency measure rather than typical maintenance. "There will always be some situations that we can't anticipate," Pratt says, " a human being is uniquely qualified to address unforeseen challenges and solve problems in real time

As a real-world example, Reisman relates his experience during an EVA on STS-132. He and Steve Bowen had to install a new Ku-band antenna on the top of the International Space Station. The assembly went routinely, with Reisman perched on the end of a robotic arm serving as an orbital cherry picker, but when it came time to connect the power and data cables, they didn't fit.

"We tried really hard to push the thing together. We're yanking on that thing and shoving with all of our might," he says. "Inside they could feel the space station shaking because we were pushing so hard."

The solution came with the impending sunrise by putting the male connector in the shade with the female connector in the sun. "We used thermal expansion," says Reisman. "When metal gets hot, it expands, and when it gets cold, it contracts. I waited for a few minutes, and then I took the connector...and I put it in right in place."

Apart for our irreplaceable ability to problem solve, there's a much more straightforward solution for making spacewalks safer. "We can make a better suit," Reisman says.

Today ISS astronauts are stuck with suits for the Space Shuttle program. Back then, EVAs were not a priority, says Pablo De Leon, the director of the University of North Dakota's Space Suit Laboratory. In fact, they were only developed as emergency equipment.

"The space shuttle is like, basically a delivery cargo, and you don't abandon a truck in the middle of where you are doing something," he says. "They just developed the shuttle space suit as a contingency case there was a failure on the electric motors that close the doors, an astronaut was supposed to go outside and crank them closed for reentry."

No partner on ISS developed a separate space suit for the station, so the ones available today are basically same suit that's been used for 30 years. "We've gotten good at working around it, and we've developed all kind of tools and equipment to compensate for the restrictions that the suit places on you," Reisman says.

The best hope for a new generation of orbital EVA suits may come from the private space industry, who are designing their own spacecraft, space stations, and equipment. "NASA is giving way more freedom to the contractors and to the companies that they ever did in the past," De Leon says. "NASA is just kind of leaving the companies to design whatever is best for their projects."

That freedom may lead to the long-awaited arrival of new EVA suits. New materials, especially composites and fabrics, can shave weight and extend an astronaut's range of movement. The suit can be built to operate at the same pressure as the space station, removing the threat of the bends and the resultant need to acclimatize hours before a spacewalk.

"If we can make a better suit...then human EVA capability will vastly improve," Reisman says.

Never use a robot to do an astronaut's job.

This article appeared in the June 2019 issue of Popular Mechanics. You can subscribe here.

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