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Q: Hard Sci-fi Gravity Manipulation ( No Answer,   1 Comment )
Subject: Hard Sci-fi Gravity Manipulation
Category: Science > Astronomy
Asked by: caelarch-ga
List Price: $10.00
Posted: 27 Feb 2006 21:35 PST
Expires: 29 Mar 2006 21:35 PST
Question ID: 701744
I'm working on a hard sci-fi RPG and can't wrap my tired brain around
this question.  I want to design a gravity manipulation system, that
does the following things while breaking as few known scientific laws
as possible. 1) Provide for Counter-Gravity, i.e. make matter within a
defined area or attached to a generator less effected by gravity- i.e.
weigh less without changing its mass.  2) Provide Inertial Dampening-
i.e. ensure that all points in a vessel or other field are accelerated
simultanously, so that a ship can maneuver without danger at mulitples
of g without endangering the crew. 3) Provide reactionless 'thrust'.
4) Provide artificial gravity, on ships as well as increase or
decrease gravity on a planet, moon or astroid for teraforming.

My main questions are these.  How much power must a generator consume
in order to accomplish goal 1 without creating the possibility of a
perpetual motion machine.  How much power, in Watts would be necessary
given various levels of efficiency (say 50%, 80% and 100%) to
accelerate 1 metric ton at 1 g via effect 3 (again, the goal is to
avoid violating conservation of mass/energy).  How much power, in
Watts to create forces within a vessel to counter acceleration due to
ship's maneuving or even impact from objects/weapons?  Any idea as to
some reasonable value for the amount of power needed for effect 4. 
Note, I am employing lots of Handwavium in the function of these
devices, I just want to make sure a clever player doesn't ask why use
Fusion, when a Agrav "waterwheel" could provide infinite energy. A
formula and explanation are much more useful than just simple answers.
There is no answer at this time.

Subject: Re: Hard Sci-fi Gravity Manipulation
From: marcusl-ga on 03 Apr 2006 16:38 PDT
Lots of handwaving indeed!

1) "i.e. weigh less without changing its mass."  -- well, you can't.
either make it farther removed from the source of gravitation or
remove some mass, F = Gmm/r^2 as you're aware, not many variables =) 
but not too hard to program to fake it I'm sure.

2) "ensure that all points in a vessel or other field are accelerated
simultanously"   for this, check out things under the heading of
"rigid body motion". regardless of how complex the motion of your ship
is; translation and rotation.  translation is the motion of the center
of mass of your object and everything will have the same value
wherever it is.  rotation is in relation to the center of mass.  the
wikipedia article is more complicated than you need in terms of

velocity of B respect to A =  w X r(b/a)
where X is a vector cross product, w is angular velocity, r(b/a) is
the location of b with respect to a.

a(b/a) = alpha X r(b/a) + w X v(b/a)      
where a(b/a) is acceleration of b with respect to a, alpha is angular acceleration.

3) Provide reactionless 'thrust'.  "reactionless" not possible. proper
equation would be the force necessary is obviously f=ma, that force
times the distance will give you the work done, divide by time for a

4) "artificial gravity" you can have on ships by rotating them. the
angular velocty squared times the radius will give you the outward
acceleration. get that equal to g and you're set.  as for planets and
such, just need more mass.

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