Space Travel and Artificial Gravity

One idea that can’t work, and one that would work if only…

Image credit: Science Photo Library

If there’s one iconic image nearly every sci-fi fan has imbued at some point, it’s the image of a huge rotating space station orbiting some suitably photogenic planet. For those sci-fi fans who understand that the “artificial gravity” of Star Trek, Star Wars, and countless other cowboys-in-space entertainments is totally impossible, the notion of using centrifugal force is their response to those who point out that the effects of prolonged microgravity on the human body are catastrophic.

When astronauts return from extended missions on the International Space Station, their muscles and bones are so deteriorated that they have to be carried because they’re incapable of walking, so weakened have they become — despite mandatory hours of daily exercise that is expressly designed to attempt to counter the deterioration. And so for sci-fi fans who are aware of the problem, artificial gravity is the solution. Artificial gravity, according to sci-fi fans, can be delivered by rotating whatever it is the humans are living in, so as to simulate the effects of the 9.8m/s² force acting on us as we wander around on our home planet. By constructing rotating space vessels we’ll be able to send people off into the furthest reaches of the galaxy — or at least to the nearest planet in our solar system — without them being too weak to crawl off their ship at the end of their voyage.

Except, alas, this idea is a non-starter. Setting aside the technical challenges and crippling costs of attempting to construct a large rotating space vessel, basic physics gets in the way.

Here on Earth we experience a constant force pulling us down toward the center of the planet. (Note: for the sake of simplicity I’m going to ignore the fact gravity isn’t actually a force but rather the result of mass creating a curvature of space-time.) Provided we’re not traveling at speed in an automobile, train, or aircraft, gravity is the only meaningful force operating on us and it pulls us in a constant direction: straight down, as per the illustration below. (NOTE: as the Earth rotates at approximately 1,600km per hour, there are centrifugal and inertial forces being generated but unless one is a sniper calculating the offset for a…