The Difficult Options for Interstellar Spaceflight – Part I
By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the first article in a two-part series about humans and interstellar spaceflight.
Sustaining human life in outer space is a challenging undertaking. Despite about 200,000 years on the planet in our current, highly-evolved form, humans have only within the last 60 or so years figured out how to go into space without getting killed.
The process of getting to space itself is incredibly dangerous. Three astronauts died in 1967 when a fire broke out during a launch pad simulation. Also, the entire seven-member crew was lost aboard Space Shuttle Challenger in 1986 when one of the vehicle’s solid rocket boosters burned through its partitioned coupling and into the main fuel tank on ascent.
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Returning to earth is just as risky. In 2003, Space Shuttle Columbia disintegrated on re-entry after part of its heat shielding was lost and the air friction burned through the fuselage.
There Have Been No Recorded Casualties in Space
Miraculously, there haven’t been any recorded casualties in space itself, but that doesn’t mean there haven’t been any close calls. One need look no further than the harrowing story of Apollo 13 and the crew’s dance with death on their way back from the Moon after an oxygen tank explosion on their lunar lander.
At present, commercial space companies are for the first time attempting to go into space for the purposes of tourism and other ventures. But even after 60 plus years of human spaceflight, we still cannot guarantee the safety of astronauts. In 2014, one of the spaceships in Richard Branson’s burgeoning space tourism company Virgin Galactic broke up in mid-air and crashed in the Mojave Desert, killing both pilots.
Suffice it to say space is hard. Yet we’ve barely begun to scratch the surface of space exploration. Ninety-five percent of all astronauts who’ve ever flown haven’t ventured beyond low-Earth orbit.
A brave few have made their way as far as the Moon. No human in the history of our species has ever gone further. But we painfully know how much still lies beyond.
The Milky Way Is Estimated to Consist of at Least 100 Billion Stars
An entire solar system with potentially colonizable worlds such as Mars, Europa, and Titan awaits us. Our galaxy, the Milky Way, is estimated to consist of at least 100 billion stars. Early research from missions such as the Kepler and K2 missions suggests that more than half of those stars are probably orbited by one or more planets. Indeed, we have much to see and many places to go.
The nearest star to our own Sun in the Milky Way galaxy is Alpha Centauri. Light speed is about 670,000,000 mph, and Alpha Centauri is about 4.39 light years away. So at light speed, it would take 4.39 years to reach Alpha Centauri.
Current Technology Does Not Allow Spaceships to Come Anywhere Close to Light Speed
But our current technology does not allow spaceships to come anywhere close to light speed. As a point of comparison, one of the fastest spacecraft ever developed was the New Horizons probe launched in 2006 for a Pluto fly-by in the Kuiper belt. At 36,660 mph, it took New Horizons more than nine years to reach Pluto in the outer solar system.
If New Horizons were redirected toward Alpha Centauri, it would take the probe 78,000 (!) years to reach our closest neighboring star. And again, Alpha Centauri is our nearest neighbor. It’s right in our own galactic backyard, so to speak. The Milky Way is estimated to be some 100,000 light years in diameter, meaning it would take New Horizons almost two billion years to cross from one side to the other.
In order to make interstellar travel for humans a practical reality, there are only three options. The first would be to develop technology to greatly increase the speed of our spacecraft so that interstellar voyages could be completed safely within a human lifetime.
This idea likely holds some promise, though it has its limitations. Currently, new prototype propulsion technologies such as the ion engine and solar sails are being tested. It is thought that in a relatively short span of R&D time — say, within the next 10 to 20 years — we might have a working, reliable means of traveling through space at much, much faster speeds than we currently can go.
But speed is relative. These new technologies might allow us to achieve perhaps five percent of light speed. However, at such velocities it would still take a spaceship more than 100 years to reach Alpha Centauri, meaning everyone on board would be dead before the end of the trip. We’d need to go faster still. Much faster.
And faster speeds are theoretically possible, although Einstein demonstrated in his theories of relativity that as an object approaches light speed, its mass increases exponentially. Ergo, it gets harder and harder to accelerate, requiring more and more force the faster it goes.
Light speed itself is, in fact, unattainable for ordinary matter. An object traveling at light speed would have an infinitely large mass, which violates the known laws of physics. So although we might achieve some more significant fraction of light speed than five percent, these technologies are probably further off in terms of their time to actualization.
However, if we do accomplish, say, 50 percent light speed capability, then a trip to Alpha Centauri might be accomplished within a decade’s time. This is obviously much more manageable, although we would then need to wrestle with the complicated matters of sustaining human life in space for 10 years at a clip.
But an even more obscure caveat presents itself with traveling at a significant fraction of light speed. Einstein’s work in relativity also revealed that an effect known as time dilation occurs as a body accelerates. Essentially, the faster an object goes, the more time slows down for that object relative to stationary onlookers.
At the speeds we’re used to traveling in cars and planes — dozens or hundreds of miles per hour — time dilation is negligible. However, at a significant fraction of light speed, the effects of time dilation can be drastic.
Imagine making a 20-year roundtrip to Alpha Centauri at half-light speed. When you returned to Earth, you would find that more than a century has passed for everyone who stayed behind. Time dilation is not some kind of optical illusion; it is a real phenomenon and we as a species will need to wrestle with its consequences if we intend to undertake space travel at very high speeds.
In the second part of this article, we’ll look at the other two options for human interstellar space travel.
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.