Between five and seven million years ago, the first human ancestors appeared when some apelike animals in the Afar Triangle, East Africa, started walking on two legs. From there, they started expanding and exploring. They moved to other continents, populating what is now Europe, Asia and America. Some of them built boats and sailed tremendous distances to islands they didn’t know existed. Today, knowing (almost) everything about Earth, we are looking at space. More than 50 years ago we set foot on the Moon. Now, our next goal is Mars. After that, we might move on to other planets in our solar system. We may explore further into the Milky Way. Perhaps, we will eventually travel to other galaxies.
Why we (might) need cryogenic sleep
A big problem connected to space travel is speed and distance. Since planets are so far away from each other, it may take years, even centuries, to get there. Let’s consider interstellar space travel within our solar system. According to NASA, on average and with the current technologies, it would take us about 7 months to get to Mars, when it’s placed at a distance of 480 million km from Earth along its orbit. We would need around 6 years to get to Jupiter and 9.5 years to get to Pluto. If you have ever gotten bored on a long-haul flight, imagine spending years waiting inside a spacecraft.
Imagine now how long it would take if we decided to travel between galaxies. If we wanted to go, for example, to the Andromeda Galaxy, the closest large spiral galaxy. We would need to cover a distance of 2.537 million light years that is about 22.833.000.000 million km. If we compare this number with the seven months needed to land on Mars, we can see that it would take about 28 million years to reach the Andromeda Galaxy. This figure is not exact but it can give us an idea of how much time we would need for intergalactic travels. Since no human can live that long and our consciousness is still perishable, how can we solve this problem?
Many sci-fi movies, such as 001: Space Odyssey, Interstellar or Passengers, have already shown us one possible option: induced cryogenic sleep, also known as suspended animation — incorrectly! To be exact, “cryogenic sleep” implies very low temperatures, whereas “suspended animation” is usually achieved by a reduction of only a few degrees. However, in the media the terms are usually being used interchangeably.
Cryogenic sleep: pros and cons
Cryogenic sleep can be seen as a sort of artificially-induced human hibernation. In nature, there are several animals that can reduce their metabolism by reducing the temperature of their bodies. In this state they can go on for months with limited food and water. To give an example, ground squirrels spend 8 month in a hibernation state called torpor, during which their heart rate, metabolism, and body temperature are incredibly low. After these months, their body warms up and they “come back to life” without any damage. While humans can’t naturally decide to hibernate themselves, it might be technically possible. Several researchers are currently studying how to put humans into something similar to cryosleep. From a medical point of view, this could help treat diseases such as heart disease, diabetes and Alzheimer.
But what are the pros of cryogenic sleep for space travel?
- First of all, astronauts would be able to travel for months without noticing it. Mental health is indeed a problem when having to spend so much time locked inside a very small space with other individuals.
- Additionally, they would need way less food and water. By carrying less cargo, the ship would use less fuel.
- The cryosleep chambers could protect astronauts more efficiently from harmful cosmic radiation. While on Earth, its atmosphere and magnetic shield protect us. In space, astronauts are exposed to radiation.
- The chambers could have an artificial Earth-like gravitational force that would keep astronauts’ bodies in shape. In fact, because of the lack of gravity, astronauts have to fight against muscle atrophy or bone degeneration by exercising on average two hours per day. The technology necessary to produce artificial gravity in a space as wide as a spacecraft would be extremely complex and expensive. On the other hand, cryosleep chambers are small in size and studies are underway to make gravity possible inside them.
- Finally, cryosleep (compared to cryopreservation) can be reverted relatively easily, by simply bringing the body back to its normal temperature, without damage to the body.
What are the cons instead?
- The first one is that this technique hasn’t been successfully perfected yet.
- Secondly, hibernation doesn’t completely stop aging. The metabolic reduction achieved through the use of low temperatures slows down the aging process. With advanced technology, aging could be significantly slowed down, maybe even for centuries. Yet, cryosleep alone will unfortunately not allow us to travel to the Andromeda Galaxy.
Cryopreservation for space travel
If we want to eventually reach extragalactic planets, cryopreservation may be the solution we are looking for. Cryopreservation is a procedure the body undergoes after legal death that allows it to be preserved for as long as it’s needed through the use of very low temperatures (-196 °C). In fact, through vitrification, all biological processes stop. The astronauts could be preserved even up to 28.000 years, without virtually any change or degradation.
Clearly, it will be necessary to develop the technology necessary for revival before even considering how cryopreservation can be applied to space exploration. In any case, we still have a lot to explore in our own galaxy.
Current cryosleep research
Are there actually any researches trying to achieve cryosleep for space travel? The answer is yes. Engineers and scientists at the aerospace company SpaceWork Enterprises are working on a project called Torpor Inducing Transfer Habitat For Human Stasis To Mars for NASA.
The idea is to use a medical practice called Therapeutic Hypothermia (TH) that is commonly applied for traumatic injuries. The metabolic rate is decreased significantly by cooling the body down by only 5 to 7 degrees Celsiaus. In fact, the metabolic rate decreases by 5% to 7% per 1 C decrease in core body temperature.
Astronauts will go through several two-week cycles of suspended animations. During these days, they will receive intravenous feeding and their waste will be removed through catheters.
Considering what is already being developed for cryogenic sleep, this technology being used in space flight might not be so far away. Certainly, there are still many problems to be solved. Space travel presents many difficulties. For some of them, we still haven’t found a solution. But if we look back to the past, even sailing presented a number of difficulties when the technology available to us was still in its infancy.
At Tomorrow, we are excited to have a chance to witness the future developments of aerospace technology. Revival technology would allow us to save lives and give our members a chance to live an extended life. Who knows if cryopreservation will really be used for intergalactic travel in the future!