A few weeks ago we discussed the desirability of embryo space colonization as mean for establishing interstellar space travel. In that post we argued such program would not have any purpose for this and the next few generations, and its only reasonable aim is to ensure the continuation of our species in the event that human life in our Solar System would become impossible.
Another popular suggestion for interstellar travel, and possibly colonization, is the use of so-called sleeper ships. In such ship the passengers are kept in suspended animation, a kind of artificial hibernation. Suspended animation should be distinguished from cryonics, the supposed science of freezing human corpses in the hope that future generations will be able to revive them. Though both concepts are often confused, the primary difference between those two are that in the former process the body’s metabolism is slowed down, but not terminated. In the latter process there’s no whatsoever metabolism present.
There are several technological issues with sleeper ships which has to be resolved before such ship could be launched. With the current state of affairs humans and other animals can be held into suspended animation for several hours or in some cases even days. Since interstellar space travel might take several decades to several thousands years, huge improvements in this field of science need to be made.
A related issue is that slowing down one’s metabolism might extend one’s life, but not necessarily long enough to arrive at the desired destination. And further even a suspended animated body still requires life support, which needs to last for many hundreds of years because repairs are not possible during the trip.
By travelling at relativistic speeds, one could take advantage of time dilation, the phenomenon that time will run slower if you are travelling faster. An interstellar journey might look from the perspective of an Earth bound observer a 1,000 years, but (depending on the actual speed) might be only a few decades for the passengers. This has clear benefits for the designers of the ship’s life support system, they only have to make sure their product will last for several decades instead of a 1,000 years.
Like embryo space colonization one should ask what purpose sending sleeper ships to distant star systems would serve, assuming the technical issues can be solved. Since an interstellar mission might take several centuries from our terrestrial perspective, current generations and those following immediately after us may not receive any benefit from such mission. And possibly humanity might not even exists in this part of the universe by then.
Therefore the main reason for the use of sleeper ships is for the sake of the passengers, as they are the only ones who will live long enough to witness the completion of the journey. But as a formal objective of public policy of interstellar space colonization, does not make much sense, unless we use it to transport all of humanity to an interstellar destination, or at least of all humans who are willing to emigrate to such destination.
Of course groups of selfish people might decide that they want to board a sleeper ship, maybe are these the same people as preppers, who will do anything to survive upcoming disasters. But these people shouldn’t count on public funding for their emigration plans. However, these are also the people for who sleeper ships are actually a solution.
Sleeper ships are currently not feasible, and offer also no clear benefits for the majority of currently living humans. The colonization of our own Solar System is feasible within a few decades from now, and can produce benefits for those who will remain on Earth. As a method of interstellar space colonization it’s only of interest for a small number of people.