#615 Is cryosleep possible?

Is cryosleep possible? In theory, yes, but not for the length of time needed to travel anywhere decent in space.

The idea behind cryosleep is to put astronauts into a state of suspended animation for the length of time it would take for them to reach wherever they are going. The advantages of this are that it will be far easier for the astronauts to spend long periods of time in a small spacecraft if they are not conscious and they won’t need to carry as many resources. If their metabolism can be slowed down, they won’t need as much food, water and oxygen as they would need if they were fully conscious.

The main problem with this is the sheer amount of time it would actually take to get anywhere in space. If we imagine that we have some kind of engine that can send a spaceship at 10% the speed of light, it will take about 40 hours for us to get to Neptune. Except, the most likely engine that could reach those speeds would be an ion drive, which would take several years to even get close to those speeds and the same again to slow down. However, ignoring things like that, we could travel the solar system fairly quickly. The problem comes if we want to go anywhere else. The nearest star is Alpha Centauri, which is 4.24 light years away. If we flew there with our 10%-the-speed-of-light spacecraft, we’d have two years to get to speed plus 40 years to get there and two years to slow down. And that’s the closest star. Space is enormous, and unless we can make spacecraft that travel much faster, they are just too far.

Let’s look at the 40 years to Alpha Centauri. Could we put an astronaut into cryosleep for 40 years? The goal would be to put humans into a state of hibernation, similar to that which bears go through every winter. Their metabolism and their heartbeat slows down to almost zero. How could this be done with a human? There are two theoretical ways, neither of which is currently possible. The first way is to chill the person’s body core down to 31 °C. The goal is to get the body cold enough temperature that is just above the point of hypothermia, which is hibernation. At this temperature, the heartbeat slows down and the metabolism almost stops. This is actually possible and is a process that is sometimes used in hospitals. If somebody is badly injured, the doctors can cool their body down to slow down the chemical reactions and give the doctors longer to perform surgery and treat the problem. Lowering a person’s body temperature can also lower the risks of brain damage. A person can last like this for up to three days.

The problem with this type of cryosleep is that it has never been tested for longer than three days and never on a healthy person. If it is possible to get a person into a state of hibernation, it will be incredibly difficult to wake them up. The shock may cause a heart attack or a stroke because the organs won’t yet be working properly, and the blood might not be circulating properly. Also, hibernating does not stop a person from aging. If a way of hibernating someone for 40 years is found, that person will still be forty years older when they arrive at Alpha Centauri.

The second type of cryosleep is completely freezing a person. There would be several ways of doing this. An astronaut could be flash frozen in a pod or coolant could be injected into their veins. They would have to be frozen in a way that doesn’t damage their cells or organs. If a living organism is frozen slowly, the water in the cells expands and ruptures the cell walls. They would have to be frozen in a way that doesn’t do this. Many food products are flash frozen these days, but there is no intention of trying to bring them back later. If a person could be frozen and then defrosted perfectly in the future, it would theoretically make cryosleep possible because a frozen person wouldn’t age. However, this is not possible with current technology. We do know how to free people. The cryonics industry has been freezing rich people for over 40 years. There are currently 250 people that have had their bodies frozen after death and are being kept in various cryogenics facilities. They have worked out how to freeze a body without damaging it, but they have no idea how to unfreeze it. Perhaps a way of doing this in the future will be discovered, but we cannot do it with current technology.

There is no way of knowing what technology will be available in the future and maybe it will be possible, but right now, cryosleep for long enough to reach the closest stars is not possible. And this is what I learned today.

Photo by Jacub Gomez: https://www.pexels.com/photo/photo-of-solar-system-1142950/

Sources

https://www.utdailybeacon.com/opinion/columns/ask-a-scientist-why-can-t-we-revive-a-cryogenically-frozen-person-will-it-ever/article_78b2d25e-45f0-11e9-a096-73accac20ed9.html

https://en.wikipedia.org/wiki/Cryonics

https://www.bbc.com/future/article/20150809-how-fast-could-humans-travel-safely-through-space