## Lunar Mass Drivers Introduction

The lack of atmosphere on the moon gives us a tremendous advantage in
launching spacecraft -- we can accelerate the craft to orbital velocity
right on the surface of the planet. The subsequent reduction in the
amount of fuel required, and hence mass of the spacecraft, will be a key
element in the development of the moon as a space transportation node.

A very short mass driver would have huge acceleration for a short time.
A man-rated mass driver would be longer, but not significantly more
complex.

A man-rated mass driver, limited to 3 g's acceleration, designed to
escape from the Earth-Moon system starting at the surface of Luna would
be 63 miles (101 km) long.

To put that into perspective with respect to the visible surface of
Luna, that's roughly the width of Picard Crater, the large crater you
can see with a telescope in the southwestern part of Mare Crisium. (Or
roughly half the distance from Vik Olliver's place to the glow worm caves at
Waitomo, assuming one doesn't detour to too many wineries on the way.)

For an amusing comparison, a similar mass driver designed to escape the
Earth-Moon system from the surface of Terra would be 1,320 miles (2,124
km) long. But we wouldn't build a mass driver on the surface of Terra,
because as soon as the projectile hit Earth's atmosphere, it would
disappear in a puff of plasma at a theoretical temperature of more than
a million degrees.

### Details

In case you'd like to check my figures (which I whole-heartedly
encourage): I'm assuming a total delta V of 8,016 ft/sec (2,443 m/sec),
which is lunar escape velocity from the surface (7,776 ft/sec) plus the
additional escape velocity (240 ft/sec) required to escape Earth's
gravity at the mean distance of the moon.

### Formulas

Length of the mass driver S = V^{2} / ( 2 * a )

Escape velocity V = SQRT( 2 * Mu / R )

ASI W9700338r1.0.
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