How difficult is interstellar travel? I’m a huge fan of space travel both real and imagined, and have followed the voyages of the Starship Enterprise since its earliest manifestations. But warp engines aren’t real, and cheating the universe’s speed limit of the speed of light requires physics of the most speculative sort. What would it take, for real, to send a human to the nearest exoplanet, Proxima Centauri b, 4.22 light years away?
This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.
https://cdn.eso.org/images/screen/eso1629a.jpg
Let’s keep the physics real while giving ourselves every advantage that we can. We’ll start off by making this a solo one-way journey. One person requires less in the way of life support to keep them alive. Getting there is hard enough! Getting back would be at least twice as hard.
The fully loaded Space Shuttle Orbiter had a mass a little shy of 150 U.S. tons, much of which was payload not designed to support the crew. Let’s be generous to our brave astronaut and provide them with a 300 ton craft. They will have a greenhouse on board that will recycle carbon dioxide, help supplement oxygen, and supply fresh food. There will be perfect recycling of water and waste. Life support, let’s assume, will not be an issue. We will have adequate shielding so that the effects of cosmic radiation will be minimized to the extent possible.
And let’s not subject our crew to the deleterious effects of prolonged weightlessness. We’ll get them there as fast as possible, accelerating to the halfway point, then decelerating to arrive at our destination and stop without zooming by. Accelerating at 1g all the way, we’ll experience normal weight.
This will get us to a maximum velocity of nearly 95% c (95% of the speed of light) at the halfway point. At those velocities, relativistic effects are significant. While our trip takes a little less than six years for Mission Control on Earth, our intrepid space voyager experiences the passage of only a little more than three and a half years. Save the Oreos for the halfway flip over and arrival ceremonies.
What would it take? If we assume 100% efficient fuel that converts all its mass into the equivalent energy, our 300 ton spacecraft would have to carry more than 11,000 tons of fuel. And traveling at those incredible speeds means that shielding better be really good, not only to protect against cosmic radiation that will arrive from head on with greater force. A dust speck at these speeds can wreak devastation. Remember that a 15 gram bullet does no damage if dropped on your foot. But fired from a gun at 250 meters per second? Quite a different story.
Sending three men on a two week long voyage to our nearest celestial neighbor more than fifty years ago stretched our technology to the limit, and we haven’t repeated the feat since. Interplanetary travel is likely a couple of decades away. Interstellar travel by humans will remain in the realm of science fiction for any foreseeable future.
You can play with your own real physics based trips at this handy site.