The Difficult Options for Interstellar Spaceflight – Part II

By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University

This is the second article in a two-part series about humans and interstellar spaceflight.

In the first article, we discussed the enormous challenges of human interstellar spaceflight and how they might be overcome with better and faster spacecraft propulsion technology. In this second article, we’ll look at the two other ways we might achieve interstellar space travel.

A second option would be for medical and biological science to extend human lifespans for the purposes of accommodating the enormous interstellar trip durations using current spacecraft capabilities. This option would forego the pursuit of speed, and instead focus on improving human longevity in order to survive the trips at lower speeds.

Imagine, for example, that we’re able to achieve about five percent light speed within the next few decades, as predicted in part I of this article. Again, this would make for a 100-year trip to Alpha Centauri. Some humans already live beyond 100 today, so surviving the trip is at least possible.

Medical Researchers Believe It Won’t Take Much to Push the Average over the 100-Year Mark

Many leading medical researchers today believe that it won’t take much to push the average lifespan beyond the 100-year mark, perhaps even as far as the 200- or 300-year limits. Experimental work today in gene editing, stem cell therapy, nanomedicine, and artificial life support is aimed at slowing the aging process and reducing life-threatening diseases.

For example, some scientists are experimenting with ways to regulate metabolism so that cellular regeneration occurs at a much slower rate, thus slowing subject organisms’ “biological clocks.” One way to do this is by lowering body temperature. Some researchers are experimenting with the feasibility of freezing living organisms and re-animating them at a later point after thawing; some frogs are actually able to do this naturally already, so it is, in theory, possible.

A few key researchers even believe that cryonics could slow or stop the aging process altogether. Freezing during voyages would have the added benefit of hibernation for passengers, so they need not be awake and aware for the entirety of a 100-year trip. (Talk about “Are we there yet?”)

The Possibility of Replacing Most or All Human Body Organs with Synthetic Substitutes

Other researchers are looking at the possibility of replacing most or all human body organs with synthetic substitutes that are far more reliable and not susceptible to disease. Imagine that you could “download” your consciousness into an android robot which is impervious to biological threats, and which can be repaired with replacement parts as needed, just like parts on a car.

If humans remain organic, aerobic organisms — that is to say, life that requires oxygen, food and water, moderate temperatures, and other key conditions to survive — then interstellar spacecraft would still need to consider life-support requirements for century-long voyages. However, if the synthetic engineering (i.e. “cyborg”) route can be realized, then we might not be dependent on all of these extra systems and components — such as artificial gravity, food production, climate control, waste management, and others. That would make for much simpler spacecraft designs.

Like the cryonics prospect, such synthetic avenues might also allow for some type of hibernation during the voyage so that space travelers need not be conscious for the entire trip. However, it should be noted that such evolutions in medical science, if possible at all, are probably more than a few decades away.

It’s also worth reiterating that a 100-year trip is the estimated time required — at five percent light speed — to reach the nearest star to our Sun. To travel to the furthest reaches of our galaxy at that same speed, we’d be looking at trips that are as much as 25,000 times longer. As such, even if we managed to achieve immortality through biological or synthetic means, such trips might be awful wastes of our time and not worth the effort.

The Third Option Would Be to Accept the Constraints of Speed and Mortality

The third and final option would be to accept the constraints of speed and mortality as we find them, and instead design interstellar missions to support multi-generational crews. This is perhaps the easiest avenue for the human race right now, but it is not without its own challenges.

First, a large enough crew to make such a journey would need a gene pool diverse enough to avoid the genetic abnormalities of incestual procreation. If we were to make the trip to Alpha Centauri today, using technologies with speed capabilities such as those of the New Horizons probe, then again, we would be looking at an approximately 78,000-year trip.

Assuming an average generational lifespan of 80 years, this would require nearly 1,000 generations before the trip would be completed. This means a large crew.

We would also need to be selective in crew screening to ensure that male and female passengers are fertile enough to procreate. Sterility and infertility could bring a tragic end to such a mission. Similarly, we would likely want to screen out any inheritable genes for major debilitating illnesses, so that the probabilities of genetic disabilities or diseases are minimized; naturally, we would need all crew members to be as able-bodied and able-minded as possible.

We would also absolutely need a source of artificial gravity for the trip, most likely through centrifugal force achieved by rotation. We know from the longest stays of astronauts aboard the International Space Station — which have only been a few hundred days at most — that microgravity has significant degenerative effects on the body, including bone mass deterioration and muscle atrophy. And we can only speculate about other much more long-term harm on body systems like the cardiovascular and digestive functions.

So, passengers on space voyages lasting their entire lives would absolutely need gravity approximating 1G to allow for healthy living and optimal longevity. In addition, all of the other factors necessary to life on Earth would need to be incorporated on such a ship. They would include light and darkness for circadian rhythm, food and water for sustenance and body maintenance, temperature control, breathable air, and a robust social environment to support healthy minds. There’s also that pesky issue of having to deal with lethal cosmic radiation in deep space.

It’s likely that if we ever accomplish interstellar travel, it will be through some hybrid of these three options. Technology will continue to improve, and with it spacecraft will inevitably get faster, which will shorten trip durations. Medical science will also advance, so humans will continue to push up the average lifespan, and perhaps even find ways to eventually suspend aging and death.

And some trips may be so far and so long that multiple generations will be needed to accomplish them anyway. Although none of these options is easy, I suspect that if we keep pursuing them success is simply a matter of determination, ingenuity, and patience.

About the Author

Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.