A lot of things are falling into place for NASA's inevitable moonshot to Mars. (Mars-shot?) However, one of the original challenges remains one of the more elusive ones: How do you get the astronauts to live on a spaceship for six months without going crazy? You put them to sleep, that's how.
For the past decade or so, scientists have been exploring various ways to get astronauts to hibernate on the way to Mars. This is like falling asleep in the backseat on your way to grandma's, but times a thousand. A long sleep like that has its complications, though. For one, you have to keep the astronauts fed and hydrated while they're out. You also have to figure out a way to keep the astronauts' muscles from atrophying and prevent bone loss from the extended stay in a zero gravity environment. (Check out this interactive graphic from NASA to find out the other effects of space exploration on astronauts' bodies.)
The benefits of the hibernation approach, meanwhile, are undeniable. The astronauts would still need sustenance and supplies but not nearly as much as they'd need if they were awake the whole time. Another benefit comes from radiation shielding. Since the astronauts can all be contained in a small area, there'd be no need to outfit the entire spacecraft with radiation shielding. Finally, there are plenty of psychological benefits to letting astronauts sleep through the impossibly long trip rather that post up with a Kindle or whatever it is astronauts do while bored in space.
It's very clear how putting the astronauts in a state of hibernation would benefit the voyage. What's less clear, however, is how to actually do it. Scientists have a few ideas.
One of NASA's favorite ideas involves inducing a state of therapeutic hypothermia. In other words, they want to drop the astronauts' body temperatures so that they consume less energy. Space.com spoke to John Bradford who's been working on the hibernation problem about the benefits, and Bradford explained that for every single degree the body temperature drops, its metabolic rate drops 5 to 7 percent. Researchers hope to get a 10 degree drop which would mean a 50 to 70 perent reduction in metabolic rate.
"We're not freezing anybody," said Bradford. "It's not cryopreservation; it's closer to hibernation. So they're still breathing, and they still need sustenance." It's called a hypothermic torpor. Ideally, the coma would be induced by letting the spaceship cool down in the freezing cold of space bringing the astronauts' body temperatures down, too. Meanwhile, the astronauts would still need life support. They would be hooked up to breathing machines and get food delivered through an IV.
It all sounds fairly uncomfortable, but it's entirely possible. The current record for keeping a human in an induced hypothermic torpor is ten days. NASA would have to boost that to six to nine months, the amount of time required for the trip to Mars, or plan for the astronauts to wake up and go back to sleep several times during the trip.
A few years ago, when scientists were first exploring the possibility of hibernation in space, they focused on a number of drugs that could induce the sleeping state. One is known as DADLE (short for D-Ala, D-Leu-enkephalin), and it's had great results in the lab. Scientists put ground squirrels to sleep using the opiate-like drug during the summer months, for instance, and saw no adverse side effects when the squirrels woke back up.
Using such a drug on humans is more complicated, since the human body is more complicated, but scientists remain optimistic since DADLE resembles the chemicals found in hibernating animals like bears. "The molecule DADLE is similar to others we have in the human brain and resembles one of the hibernation triggering proteins in hibernators," said Prof. Marco Biggiogera a few years ago on behalf of the European Space Agency. "It can reduce the energy required by cells, whether isolated in cultures, or present in other animals or organisms."
Obviously, none of these hibernation techniques is without risk. Even in a state of reduced hibernation, there's a good chance that the astronauts could experience some bone loss and muscle atrophy. One way that researchers are looking to solve that would be a 2001: A Space Odyssey kind of centrifuge that would spin slowly, creating a small gravitational force. If it spins too slowly, it won't have the desired effect. This is tough. If it spins too fast, it'll make the astronauts sick. Imagine waking up from a six-month-long sleep covered in six-month-old vomit. Not ideal.
However scientists decide to do it, though, it's looking more and more like the hibernation method is the way to go. Without hibernation, current technology would only allow four to six people to travel to Mars in a long-range spacecraft. However, if they could be squeezed into a small room, there could be as many as 10 to 20 hibernating astronauts. The only thing to watch out for would be stray asteroids or pesky engine trouble. Because millions of miles away from Earth, a ship-full of astronauts asleep at the wheel has the potential to be very dangerous thing. [Space.com, Nature, NASA, The Guardian, Twitter / @bethbeck]