Can a Gravitational 'Gun' Accelerate Objects?

[LAP3141]

Hello,

Special arrangements of charged material can be used to accelerate charged objects or particles, e.g. a cathode ray tube.

I am just wondering if it would be somehow possible, in principle if not in practice, to accelerate objects with gravitational force using special arrangements of matter. I am thinking of some sort of gravitational "gun."

Usually the gravitational force pulls objects together, but could there be some special arrangement of matter where an object can be accelerated without colliding or going into an orbit?

Actually, I don't believe that it would be possible but maybe I am just not imagining the right arrangement or distribution of matter.

The technique of the gravitational "slingshot" can be used to accelerate spacecraft but I am thinking of something else where an object, initially at rest, would be attracted by an arrangement of matter, also at rest, and accelerated to some final velocity and then just travel away independently.

 

[.Scott]

If all mass is at rest, and stays that way, then the gravitational field will not change. A particle which starts at rest within that system will start to fall but will not exist the gun. At best, it will find some "orbit" that it will follow - at every point maintaining the same total for kinetic and potential energy. At worse, it will hit part of the gun.

 

[jbriggs444]

If all mass is at rest, and stays that way, then the gravitational field will not change. A particle which starts at rest within that system will start to fall but will not exist the gun. At best, it will find some "orbit" that it will follow - at every point maintaining the same total for kinetic and potential energy. At worse, it will hit part of the gun.

If one had a pair of orbiting massive bodies and injected a test object, it could be ejected with increased velocity -- a gravitational slingshot. Hopelessly impractical for a hand-held pistol, of course.

 

[.Scott]

If one had a pair of orbiting massive bodies and injected a test object, it could be ejected with increased velocity -- a gravitational slingshot. Hopelessly impractical for a hand-held pistol, of course.

The OP mentioned that is his last paragraph - and prohibited it.

 

[LAP3141]

At best, it will find some "orbit" that it will follow - at every point maintaining the same total for kinetic and potential energy.

Consider an annulus (ring) of matter and a particle located on the central axis of the annulus but some distance away from the plane of the annulus.

Initially the particle will "fall" toward and then through the annulus, with maximum velocity as it passes through the annulus plane. The particle should oscillate between both sides of the annulus.

But as the particle moves through the plane of the annulus, if we then rapidly split and move each half of the annulus away from the central axis, the particle will travel a greater distance outward along the axis. Could we ever separate the halves of the annulus far enough (not infinity) so that an "escape" is possible?

 

[Drakkith]

But as the particle moves through the plane of the annulus, if we then rapidly split and move each half of the annulus away from the central axis, the particle will travel a greater distance outward along the axis. Could we ever separate the halves of the annulus far enough (not infinity) so that an "escape" is possible?

Certainly. You could attach rockets to the annulus and push it backwards, away from the accelerated object, or even radially outwards, but it's far more practical to attach the rockets to the object instead. That way you get the advantage of having the rockets and their fuel accelerated along with the object, which provides a large efficiency advantage for the rockets. You also don't have to move your giant annulus.

Note that the annulus will be attracted towards the object as well, so you'll have to either counter this motion somehow, or allow for this motion in your design and implementation.

 

[Khashishi]

How is this different from dropping something? If you drop a cannonball from the top of a tower, is this not a "gravity gun" firing the ball down?

 

[sweet springs]

In aerospace engineering and planet orbital mechanics, gravity assist or swing by is dealt with as gravitational slingshot.
That maneuver is used for changing moving direction of space crafts and also accelerating or decelerating space crafts applying it for moving planet forward or backward. Best.

 

[davenn]

In aerospace engineering and planet orbital mechanics, gravity assist or swing by is dealt with as gravitational slingshot.
That maneuver is used for changing moving direction of space crafts and also accelerating or decelerating space crafts applying it for moving planet forward or backward. Best.

that has already been mentioned way back in the OP and dismissed

 

[russ_watters]

https://en.wikipedia.org/wiki/Trebuchet

 

[DrStupid]

https://en.wikipedia.org/wiki/Trebuchet

The OP asked for acceleration of objects with gravitational force. In case of the Trebuchet gravity provides the energy but the projectile is accelerated by electromagnetic forces.