Alternatives to centripetal force and constant acceleration to simulate Earth-like gravity

Question

This is follow-up to @Erik's answer to the question Is artificial gravity feasible in manned long-term space exploration? I'm curious, whether there's any alternative methods to simulating effects of gravitational acceleration as felt on Earth (9.78 - 9.82 m/s²), if there's any ongoing research, or proposed methods of achieving this? Could, for example, dynamic principles of a gyroscope (i.e. powerball) be used to create equally distributed centripetal force on the whole inner spherical body of a space station? Could such rotation on all three axis be sustained with inertia?

I don't want to limit my question to artificial-gravity only, but would also like to know of possible ways to actually create long-term sustainable gravitational fields, be it directly by producing gravitons, or by other ways of producing gravitational effects of a large mass body with small mass bodies, if this is at all feasible (quantum mechanical black holes maybe?), and how far are we from seeing any of such systems demonstrated either on paper and/or actual model-scale systems?

I am not interested in infeasible far-out / fictional ideas, but actual scientific research in this area and pragmatics of proposed (if any?) alternative methods.

Answer 1

Wikipedia has a good page on the subject of artificial gravity, highlighting many (very interesting) possibilities.

• Rotation
• Linear acceleration
• Mass
• Magnetism
• Gravity generator/gravitomagnetism

Rotation is exactly what you would expect. The spacecraft is a big rotating cylinder, just like in physics textbooks.

Linear acceleration, however, is a very interesting idea:

Any spacecraft could, in theory, continuously accelerate in a straight line, forcing objects inside the spacecraft in the opposite direction of the direction of acceleration.

Note, however, that you need to keep accelerating. As soon as you need to slow down, your gravity goes away. Therefore, this would probably be best for very long-range voyages.

The idea of using Mass for gravity basically involves installing an ultra-high density mass in the spacecraft to attract objects toward it, simulating gravity.

Magnetism is another interesting one:

A similar effect to gravity has been created through diamagnetism. It requires magnets with extremely powerful magnetic fields. Such devices have been made that were able to levitate at most a small mouse and thus produced a 1 g field to cancel the Earth's; yet it required a magnet and system that weighed thousands of kilograms, was kept superconductive with expensive cryogenics, and required 6 megawatts of power.

^{Using this technique to levitate a frog.}

Gravity generator/gravitomagnetism is highly theoretical, and probably won't work anytime soon:

In science fiction, artificial gravity (or cancellation of gravity) or "paragravity" is sometimes present in spacecraft that are neither rotating nor accelerating. At present, there is no confirmed technique that can simulate gravity other than actual mass or acceleration.

Answer 2

There is already an accepted answer but I think there are some points worth making.

If you have rocket engines capable of thrusting at 1 G for as long as necessary, then linear acceleration kills two birds with one stone, being also the fastest comfortable way to get to your destination. You accelerate until the midpoint of your journey, and then decelerate (just acceleration with a different direction vector) the rest of the way. Only once you reach your destination does it become wasteful to keep thrusting. This is not uncommon in science fiction that tries to be scientifically accurate. Arthur C. Clarke's Imperial Earth and the more recent Expanse series by James S. A. Corey are set in futures where this is the normal way to get around the solar system.

This could only be done with something like fusion or pulsed nuclear rockets.

Paramagnetism is an unlikely candidate. No matter how much you improved it, it would still involve an immensely strong magnetic field. Those have neurological effects and are also inconvenient since you can't have any ferrous matter in the spacecraft.

As for a "gravity generator", you have to realize that we know what gravity comes from and it's pretty much just mass (or stress-energy which in practice is mostly mass). In other words, it's not just that we don't have evidence that it's possible; we do have evidence that it's not possible. To be fair, evidence is not proof and we can't know what will or won't be discovered in the future. But there is no reason to think every technical problem must have a solution, and this really looks like a thing the universe may not permit.