Re: SPACE: Lunar Warfare

Mark Grant (
Sun, 19 Jan 1997 18:42:45 +0000

On Sun, 19 Jan 1997, James Rogers wrote:

> Velocity is almost always better. 0.5mv^2...
> In the long run, it might just come down to energy efficiency.

However, when you're launching from the moon to the Earth that situation
changes dramatically. If you want energy efficiency then you want to
increase the *mass*, not the velocity. The energy boost you receive from
gravity is proportional to the mass, so the most efficient use of your
mass-driver is to launch a lot of rocks at the minimum velocity which will
get them to Earth, in order to increase the total mass and hence the total
energy boost. If you launch small rocks at >> escape velocity then you
gain very little from being higher up the gravity well; most of the impact
energy will be coming from your reactor rather than gravity. The whole
point of launching from the moon is that you want to use the gravitational
"free lunch".

Of course, terminal ballistics (e.g. atmospheric friction) will change the
most efficient velocity, but this would certainly be true for destroying
surface installations on another body with no atmosphere.


|Mark Grant M.A., U.L.C. EMAIL: |