garfangle wrote:
(George William Herbert) wrote in message ...
garfangle wrote:
Instead of hauling their own fuel for propellent, which adds to its
weight, why not have manned craft launched from massive high-altitude
cannons? Why not further what the late-Gerald Bull envisioned (see
world.std.com/~jlr/doom/bull.htm) to build a supergun that could
launch projectiles large enough to be duplicated as manned capsules?
That way there would be little or no need for external boosters to be
hauled alongside the manned vehicle, greatly reducing the per pound
flight costs.
The gun could be large enough to shoot the craft into near-low earth
orbit and then small internal rockets could be used to get the craft
further into space. The craft could be sized such that it replicated
the apollo.
I imagine the dimensions would be at least 500 meters long, 30 meters
in diameter, and require an explosive shot of several tons of tnt.
Near-low earth orbit is 7,200 m/s disregarding atmospheric air
drag and circularization.
Assuming continuous accelleration:
V = a t
S = 1/2 a t^2
S = 500 = 1/2 a t^2
V = 7,200 = a t
[solve]
t = 0.1388... sec
a = 51,840 m/s/s ~= 5,290 Gs
The condition of the human body exposed to nearly 5,300 Gs for
a seventh of a second is "red goo on back wall of space capsule".
Try again.
My bad...though couldn't we develop some anti-G shield? 
I've wondered about using magnetic levitation for this.
It's by no means perfect, and the variation between body materials
will cause it to not work perfectly.
It might buy you a factor of 5?
Fit humans can naturally take about 25G for a minute (prone, immersed)
without significant harm. It's not very nice of course.
Coincidentally, this is enough to get to orbital speed.
Assuming that you can up this to 30G with better designed g-suits, and
that you can add another factor of 5 for magnetic levitation (there are
a number of problems that look like show-stoppers) then that's
still only 150G.
That's still a barrel length of around 30Km, with very optimistic
assumptions.
--
http://inquisitor.i.am/ | | Ian Stirling.
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If God hadn't intended us to eat animals,
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