The Naked Scientists

The Naked Scientists Forum

Author Topic: Are gravity shields conceivable as a means of propulsion in space?  (Read 2729 times)

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3822
  • Thanked: 19 times
    • View Profile
In Sci-Fi novels of the early twentieth centaury space ships were often propelled by moveable gravity shields.
Assuming that gravity is mediated by Gravitons a particle thought to be much lighter than Neutrinos  this does not seem to be a very practical idea .
Test have been made to see if any gravitational screening effects are seen during a Solar eclipse but any tiny effects noticed were probably due to atmospheric cooling when the light was cut off.
« Last Edit: 29/09/2013 09:45:49 by chris »


 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: Gravity sheilds
« Reply #1 on: 26/09/2013 21:00:00 »
I find it dubious. 
Typically the gravity is the sum of all the gravitational pulls.  So, with the moon between the earth and the sun, then earth is pulled by both the sun and the moon. 

And, of course, any effective gravitational shielding must be carried with the vessel.

Hmmm...
Perhaps one would find an exotic particle that is repelled by gravity, somewhat like diamagnetic elements are repelled by magnets.  Then, why not build the ship out of them unless they were "toxic" to humans. 

Of course, a particle that is repelled by gravity would be rarer than helium-3 on earth.

Some people speculated that antimatter might have a negative gravitational interaction, but all indications are that it behaves in gravity
 exactly like regular matter.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: Gravity sheilds
« Reply #2 on: 26/09/2013 21:31:53 »
I find it dubious. 
Typically the gravity is the sum of all the gravitational pulls.  So, with the moon between the earth and the sun, then earth is pulled by both the sun and the moon. 

And, of course, any effective gravitational shielding must be carried with the vessel.

Hmmm...
Perhaps one would find an exotic particle that is repelled by gravity, somewhat like diamagnetic elements are repelled by magnets.  Then, why not build the ship out of them unless they were "toxic" to humans. 

Of course, a particle that is repelled by gravity would be rarer than helium-3 on earth.

Some people speculated that antimatter might have a negative gravitational interaction, but all indications are that it behaves in gravity
 exactly like regular matter.
For gravitational shielding to exist there must, as you say, exist particles which are gravitationally repulsive. We don't know of any at the moment per se. However we do know of dark energy which is gravitationally repulsive made possible through the that constant (whose name I've temporarily forgotten).
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8667
  • Thanked: 42 times
    • View Profile
Re: Gravity sheilds
« Reply #3 on: 28/09/2013 16:58:25 »
Imagine I set up a heavy eccentric flywheel on a horizontal axle.
I put this hypothetical gravity shield under one side of the wheel.
That side becomes lighter. So it rises and the wheel starts to spin.
I couple that spinning wheel to a generator and I have a perpetual motion machine that continuously does work with no fuel.

Somehow, I doubt that the shield exists.
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3822
  • Thanked: 19 times
    • View Profile
Re: Gravity sheilds
« Reply #4 on: 28/09/2013 20:21:39 »
I understand that you need a light years thickness of Lead to stop Neutrinos gravitons are postulated to be vastly lighter making your gravitational screen rather impractical.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: Gravity sheilds
« Reply #5 on: 28/09/2013 21:08:28 »
The perpetual motion argument may not hold up as the scenario may not be significantly different than permanent magnets, and diamagnetic materials. 

So, if one had a substance that repelled matter, then it would also not allow the matter to easily approach it, and BC's eccentric shaft would still stop.

Or, perhaps you could consider buoyancy (on Earth) as being similar to antigravity, and we know that many materials are boyant on water, and a few including hydrogen and helium gas are boyant in our atmosphere.

What would be the meaning of boyancy in space?

While there would be significant benefits to a space ship to decrease the attraction to planets and stars, momentum, or the resistance to change of motion is a property of mass, and not gravity.
 

Online jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3925
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
If you heat the air in a balloon it rises. What if you heat the helium in a balloon. Of course your container is going to leak. Maybe faster due to increased pressure. What about super hot helium?
 

Online jeffreyH

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 3925
  • Thanked: 53 times
  • The graviton sucks
    • View Profile
Using a system against itself is the best answer. If we could control a graviton beam and set it to match the gravitational field at the surface of the earth we could direct it down from orbit. It would cancel gravity at ground level and induce a lift at higher altitudes. However this could also allow the atmosphere to escape like a release valve. This seems to be an indication that any true anti-gravitational device would be more useful as a weapon rather than a propulsion system. You could possibly suffocate suffocate enemies at a distance.
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums