Mass Drivers and Cheap Space Access: Limits

From: Robert J. Bradbury (
Date: Mon Apr 17 2000 - 01:08:00 MDT

>From this URL:
we have:
> Scientists Drs. Henry Kolm and Peter Mangeau at Massachusetts Institute
> of Technology believe that it would be possible to accelerate a one tonne
> projectile to a speed of 12.3 kilometers per second in a time of only
> one-and-a half a second. This would be achieved on a ramped track, built
> on the side of a mountain, and nearly eight kilometers long. The energy
> required to operate the launch would be 76 billion Joules or, in power terms,
> 50 billion Watts.
> Costs of the proposal, which are discussed in the article, suggest that
> either a direct electromagnetic space launcher, or a hybrid
> first-stage-electromagnetic, record-stage-conventional-rocket system
> could deliver payloads into space at costs very competitive with
> conventional rocketry.
> One of the features of the incredibly short launch time (one-and-a-half
> second of acceleration, with emergence from the atmosphere less than a
> second later) is the enormous force to which any cosmonauts would be
> exposed. These are calculated to be as much as one thousand times the
> force of gravity. Currently, the limit for human endurance is a force
> about fifteen times that of gravity.

It goes on to discuss how you could engineer methods to allow humans
to tolerate higher G forces.

Using the figures quoted above, and the converter at:
and figuring a electricity cost of $0.10/kWh that works out
to about $2000 to launch me and a 1 tonne-~70kg "pod" into orbit.
You amortize the cost of the launch rail over a number of years
and millions of trips and it shouldn't drive the costs up much

Hmmm, 8 km, thats about 5 miles (sorry!), anyone have a good feel
for what the relative costs per mile are for light rail, TGV
or Maglev? It shouldn't be much more expensive than that.
Maybe $10million per mile? So at $50 million in construction
costs, that works out to around $0.16/U.S. person. Chump change
by any measure.


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