I am thinking about this scenario of throwing a satellite to Mars orbit with a high spin, Can we just throw that? one hypothesis can be that high-frequency spinning generates apparent gravity so it might have enough mass to follow mars’ orbit and reach it without using any energy but If anyone has his own expertise on this so it will be great!!

  • $\begingroup$ The answer to all questions like this is no. The basic conservation laws (energy, momentum...) can't be gotten around. We can spin something and make it lighter so that it's easier to launch. $\endgroup$ – uhoh Nov 21 '20 at 15:15
  • $\begingroup$ Can you explain it in more simple words by applying a mathematical approach as well? $\endgroup$ – Junaid Ihsan Nov 21 '20 at 15:26
  • $\begingroup$ You are saying that conservation laws can't be proved by doing this? $\endgroup$ – Junaid Ihsan Nov 21 '20 at 15:27
  • 1
    $\begingroup$ "high-frequency spinning generates apparent gravity" only for someone or something standing on the inside, in the rotating frame of the spacecraft, but that doesn't have any impact on the real gravitational forces from other bodies. "...and reach it without using any energy..." We can't change gravitational potential energy without using any energy. $\endgroup$ – uhoh Nov 21 '20 at 23:06
  • 1
    $\begingroup$ I am having a hard time understanding what this is saying but I am pretty sure that it's impossible. Spinning does not cause gravity. $\endgroup$ – ikrase Nov 22 '20 at 0:14

Your question isn't clear but I think I understand what you're after:

Put your satellite at the end of a rope, spin it around and release it when it's moving at the right velocity. There are a couple of problems with this:

  1. Unless your rope is exceedingly long you are going to subject your satellite to tremendous accelerations.

  2. Of what is your rope made? You're getting pretty close to the limits of material science by the time you have reasonable acceleration and throwing it to Mars.

Note that I am assuming your rope is already in orbit. Throwing it from the surface of the Earth introduces a bunch more problems:

  1. As michael_goulish points out, keeping your satellite from burning is decidedly non-trivial. This makes the Galileo probe that was dropped into Jupiter look easy by comparison--and half that probe was a heat shield.

  2. The acceleration it's going to take while being spun up is incredible--far, far beyond the hundreds of g's it will take as drag slows it in the lower atmosphere.

  3. I don't think we have anything we can build it out of but I'm not certain.

  4. And even if there is we currently do not know how to build something to survive the shockwaves that will be created by it's passage through the atmosphere while being spun up--the launcher will be destroyed.

As for a consolation prize: I have actually proposed a different form of spin launcher:

No rope, it's built around the lunar equator. There's no need for super strength because you can counter the forces by simply piling mass on top of the launcher and letting the moon's gravity keep it from flying apart. No brutal atmosphere effects, either. 5g in the launcher gives you an ejection velocity anywhere from sundiving to interstellar escape--obviously, if you don't need that radical a trajectory you can launch with less acceleration.

Megaengineering on a scale mankind has never done but all the basic technology already exists--you'll need some R&D to build linear motors and maglev systems for that environment but there's no reason to think it won't scale up.

  • $\begingroup$ Possibly worth mentioning that for a orbiting platform conservation of momentum still applies so any boost this way is not free, the launch platform will be slowed and need to expend fuel in some form to maintain orbit. $\endgroup$ – GremlinWranger Nov 22 '20 at 2:41
  • $\begingroup$ @GremlinWranger It needs to do something to maintain orbit but you can do it with something like an ion engine, or you can do it in reverse--put a catapult on the moon, toss rocks, let your spinner catch them and deorbit them. $\endgroup$ – Loren Pechtel Nov 22 '20 at 2:46
  • $\begingroup$ @LorenPechtel I am not considering any Physical attachment with my Sattelite, Assume that I spin my satellite without using any rope and throw it towards Mars orbit. Can it enter the orbit of Mars? $\endgroup$ – Junaid Ihsan Nov 22 '20 at 8:12
  • $\begingroup$ @JunaidIhsan I don't understand at all. If the satellite is simply spinning it's not going to go anywhere. The whole point of a spin launcher is to hold it in place building up speed until you let go--it lets you avoid taking your powerplant with you. (Or let it move out along a cable that's spinning at a fixed rate.) $\endgroup$ – Loren Pechtel Nov 22 '20 at 22:02
  • $\begingroup$ does letting it go from the correct height of an orbital elevator count? $\endgroup$ – user20636 Nov 23 '20 at 14:10

How about if we just try it for low Earth orbit at first? If we can't do that, we definitely can't get it to Mars. OK, orbital velocity for low Earth orbit is about 7 km/sec.
But if you are going to hurl something into orbit, it will have to start out with a lot more velocity than 7 km/sec, because it's going to lose a lot on the way up. So now you have a spacecraft shooting out of your spinlaunch facility doing maybe 9 or 10 km/sec right down here in the nice thick air. It will burn like a torch and make a beautiful bright streak up toward outer space. But not all the way up, I think.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.