Mass driver for commodity supplies

--- In spacesettlers@yahoogroups.com, Dave Handwerk wrote:
>
> Hi Chris,
>
> I think there are studies going on right now. But
> testing can be fairly easily done in a vacuum
> centrifuge. Most of the item you mention below could
> probably make the high "Gee" trip, except that the
> plastic film you speak of may receive a permanent
> crease in it. Softer items, like plastics, circuit
> boards, mechanisms, and so forth can be "hardened", by
> encasing them in water then freezing to very cold
> temperatures. Or in a similar but less corrosive agent
> than water.
> ...
> Another idea that would allow the electromotive launch system (EMLS)
to be used for a much more general use, would be to build the tube so
that it floats in the deep equatorial ocean. That way the launch tube
could be aimed to insert the spacecraft into any inclination and at
any elevation angle. Thus by adjusting the launch speed, any altitude
(apogee). By building in a small apogee "kick" motor, virtually any
orbit, or beyond, would be attainable....

Dave,

It's interesting that you should mention freezing the water and
embedding other items in the frozen payload for stabilization against
high "G" forces. I was thinking along the same lines myself but I
didn't want to over-complicate my first post on the subject. I hadn't
thought about using a submerged launch tube but the idea is
intriguing. It would permit launching over unpopulated areas, which
would be not only desirable but required I think.

One of the problems I foresee with an EMLS is the need for some
sort of heat shielding skin for the payload. If it leaves the launch
tube at anything approaching orbital velocity (17,500 mph, Mach 23)
the frictional heating and aerodynamic drag in the atmosphere would be
tremendous. Although a largely water payload frozen to cryogenic
temperatures (eg liquid nitrogen, -196 C)would help to stabilize the
projectile against aerodynamic stress loads and help to minimize heat
build-up, I'm not sure that alone will do the job. Any thoughts on this?

Of course the initial velocity of the projectile can be less that
orbital velocity if an apogee kick motor is used. In this regard the
nitrous oxide/rubber motor Burt Rutan used comes to mind. Any thoughts
on this?

There is also the question of optimal projectile size. Can an
object the size of an Atlas rocket be launched or would it more likely
be the closer to the size of a Sparrow missile?

I read the item about the "gas station in space". In fact, I believe
there's an article at Space.com about a company already proposing to
provide this service using water and other materials from the moon.
That's ok for the distant future but it doesn't help much right now.

Chris