The Downside With Spinning Spacecraft

Whereas it might be superior for folks to have the ability to reside in area, a “weightless” surroundings poses some severe challenges. People operate greatest on Earth’s floor, the place they’re affected by a relentless gravitational pressure. With out it, there are well-known consequences of long-term publicity to microgravity, together with bone mass loss and muscle atrophy.

So if we need to reside in area, we’ll have to create a man-made gravity surroundings. We solely have one methodology for doing that: Construct a car that strikes with a relentless acceleration. The commonest idea is to create a spacecraft that spins. However that’s not fairly as straightforward because it sounds. Right here’s why.

Feeling Weight

First, let’s go over the fundamentals of gravity and what it means to really feel your weight.

Gravity is an attraction between objects which have mass. Since each your physique and the Earth have mass, there may be a lovely pressure that pulls you towards the Earth and retains you on the bottom. Regardless that this pressure is continually performing on you, you don’t really feel it, as a result of the Earth concurrently pulls on all elements of your physique, making the impact undetectable.

I do know what you’re pondering: “I am sitting right here on this chair, and I can completely really feel my weight.” Truly, what you’re feeling isn’t gravity. It’s the pressure of the chair (and the bottom) pushing up on you. We name this upward-pushing pressure your “obvious weight.”

We are able to get a superb really feel for the idea of obvious weight by taking a fast journey in an elevator. The elevator begins at relaxation. However if you push a button, it begins shifting upwards. Which means it should have an upward acceleration—no less than for a really brief period of time, till the elevator will get as much as its touring pace. Throughout this upward acceleration, you’re feeling a bit heavier. Then as soon as the elevator will get close to its programmed ground, it has to decelerate. Which means it accelerates within the downward route. Throughout this time, you’re feeling lighter.

However, in fact, your precise weight by no means fluctuated. Your actual weight is a measure of how a lot pressure gravity exerts in your physique, and it’s the results of the interplay between your mass (m) in addition to the mass of the Earth and your distance from its heart. On Earth, gravity exerts a pressure of 9.8 newtons per kilogram. (Mass and weight are various things, so on a planet with completely different gravity, your weight could be completely different, despite the fact that your mass could be the identical.)

Driving an elevator modifications none of those components. What it does change is your obvious weight. It is somewhat unusual, however this impact is tremendous helpful for a spacecraft.

Linear Acceleration

As an instance you’re in area the place there’s no gravity—and even in low Earth orbit, the place there may be microgravity, which is the identify we give to a “weightless” surroundings. What in case your spacecraft had an enormous elevator that consistently accelerated upwards? If the acceleration of the elevator had the identical worth because the gravitational discipline on the floor of the Earth, your weight would really feel precisely prefer it does now.

In fact, a spaceship with an infinite elevator is impractical. It will be simpler to simply make the entire car speed up. That will completely create synthetic gravity. The truth is, that is the first methodology used on ships within the science fiction sequence The Expanse.