‘Project Hail Mary’ Made Us Wonder How to Survive a Trip to Interstellar Space

Editor’s note: This story contains mild spoilers for Hail Mary Project.

I’ve long been perplexed by something in Andy Weir’s 2021 book Hail Mary Project: Why did two of the three fictional astronauts die during interstellar travel?

That could be because Weir put his travelers in an induced coma for four years, says Haig Aintablian, an emergency room physician and flight surgeon who directs UCLA’s space medicine program.

“How cool would it be if you fell asleep a few hours after launch and woke up as soon as you arrived on the planet or celestial body you were approaching? But, he said, “I don’t think keeping the human alive and in a comatose state is necessarily the best option.” »

After all, “the human body is not designed to just be a stagnant blob,” he says. Astronauts in a coma would risk developing fatal blood clots and debilitating muscle wasting from inaction. Infections from the tubes and devices needed to keep a person in a coma alive would also be risky.

So, I wondered: What other ways could people survive interstellar travel?

Frozen, Aintablian suggests. “The day you can freeze someone and thaw them, you will have solved the problem,” he says.

But the problem could be more than technological. No one knows if the human body can withstand the physiological rigors of freeze and thaw like wood frogs do. The human heart doesn’t function well below about 28° Celsius, explains integrative biologist Matthew Regan of the University of Montreal. Some people have survived larger drops in body temperature, but only temporary, he says, not the years it would take to travel to a distant star.

Maybe hibernating to the stars is the answer.

Some small mammals that hibernate, such as arctic ground squirrelscause their body temperature to drop below freezing during torpor, when the rodents’ metabolism slows significantly. “It’s 2 percent of what it usually is,” Regan says. “They’re just starting to build up. It’s like the pilot light levels are up.”

Hibernating bears conserve less energy, lowering their body temperature only a few degrees, to 31°C or 32°C (about 88° to 90° Fahrenheit). Torpid animals are sedentary but they do not develop blood clots and their muscles do not atrophy, unlike bedridden humans.

If humans could slow down our metabolism a bit like bears do, space travel would require fewer resources to keep the crew fed, healthy, and happy. Torpor could even help protect against ionizing radiation, a big problem for space travelers, Regan says.

But it probably wouldn’t be possible to repeat the whole trip. Every two weeks, gophers and other hibernators wake up, warm their bodies and move around. Nobody really knows why. This can promote muscle regeneration and help the brain stay healthy, says neurochemist Kelly Drew of the University of Alaska Fairbanks.

Humans may also need to wake up to keep their brains sharp and their muscles strong. And eat.

Indeed, it may not be a good idea to fatten up astronauts before the big trip, says hibernation biologist Hannah Carey of the University of Wisconsin-Madison. Bears that gain weight before hibernation develop high cholesterol levels; bears recover as their weight decreases, but in humans, this side effect could put astronauts at risk of heart disease.

Some captive ground squirrels in Carey’s lab quickly became roly-poly, but then died mysteriously during hibernation. “They still had a lot of body fat. So it’s not that they were lacking it,” Carey says. Maybe their hearts couldn’t handle the stress, she suggests.

Yet none of this explains why the astronauts died in Hail Mary Project. With the film adaptation scheduled to hit theaters in March, I asked Weir what happened. Their deaths were not a failure of human biology, he said. “It was a technological failure. I mean, being in a coma for four years is a dangerous proposition at the best of times. So a small technological failure can lead to catastrophic results. Which it did in this case.”