Cheaper way to space!? A supergun.

Ian Stirling wrote:

George William Herbert wrote:
garfangle wrote:
(George William Herbert) wrote:
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".

My bad...though couldn't we develop some anti-G shield?
snip
There are things that can be done to increase human G-tolerance.
Lying flat gets you to 20+ transient Gs without serious problems,
snip
As others have pointed out, anything mechanical that you can
harden a lot (artillery shells take tens of thousands or 100,000 Gs)
snip
People... should ride gentler things.

If cryogenics is finally gotten working, then that incidentally solves
that problem, at least a bit.

'Cryonics,' not 'cryogenics.'
http://ask.yahoo.com/ask/20020718.html

And it's at least not forbidden by the current laws of physics that
we know, just lots and lots of apparently insoluble chemistry and biology
problems.

True, but....

I'd imagine a astronicle could cope with at least a thousand G.

Why?

There's already a signifigant problem with microcracking in the
bodies of suspended cryonics patients:

http://www.benbest.com/cryonics/cooling.html

http://keithlynch.net/cryonet/28/92.html

The hope is that nanothecnology or something similar can make the
repairs in the future, but one would prefer to minimize them to begin
with. Why also subject the body to accelerations that would encourage
this?

"garfangle" wrote in message
om...

My bad...though couldn't we develop some anti-G shield?

If we can do that, then we can dispense with the gun all together.

(of course all present theory makes it pretty clear that "blocking" gravity
is impossible.)


Ciao.

human body exposed to nearly 5,300 Gs for
a seventh of a second is "red goo on back wall of space capsule".
[...]
My bad...though couldn't we develop some anti-G shield?

IF we had that, we would not need the cannon!!!!

(garfangle) writes:

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?

Because conventional powder guns absolutely cannot accelerate a projectile
to even one-quarter the necessary velocity. Because even an exotic gun
that hypothethicall could reach such velocities, would be launching a
"capsule" containing an astronaut mass of bloody hamburger uniformly
smeared across the back wall and then cookked Very Well Done by
atmospheric friction.

Jules Verne seems to have actually understood this, which makes
Gerald Bull look even sillier. Though he at least didn't propose
manned gun launch.


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.

Except that Gerald Bull's design required *four* stages of external
boosters to go with the (tiny) payload, in order to reach orbit.
Designers who dispense with the cannon can do it with two rocket
stages, mostly by virtue of not having to design massively overweight
rockets tough enough to withstand cannon launch.


--
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John Schilling wrote:
(garfangle) writes:
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?

Because conventional powder guns absolutely cannot accelerate a projectile
to even one-quarter the necessary velocity.

That's not entirely true; there are conventional guns with
muzzle velocities around 3 km/s, which is 1/3 of the way there.

That's still 2/3 of the way not there, though.


-george william herbert

George William Herbert wrote:
John Schilling wrote:
(garfangle) writes:
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?

Because conventional powder guns absolutely cannot accelerate a projectile
to even one-quarter the necessary velocity.

That's not entirely true; there are conventional guns with
muzzle velocities around 3 km/s, which is 1/3 of the way there.

That's still 2/3 of the way not there, though.

Or 8/9ths, depending on how you do the numbers.

--
http://inquisitor.i.am/ | | Ian Stirling.
---------------------------+-------------------------+--------------------------
"I am the Emperor, and I want dumplings." - Austrian Emperor, Ferdinand I.

John Schilling wrote

Because conventional powder guns absolutely cannot accelerate a projectile
to even one-quarter the necessary velocity.

I'd have thought a Yank would know about guns.

Let's say for argument the necessary velocity is 8.5 km/s.

Bull got around 3.6 km/s at (S)HARP. There are a few 13,000 fps (~4km/s)
powder guns around today, and I've heard of plans for a 5km/s one, though I
doubt it could be called "conventional".

A slight variation is the two-stage gasgun, which can reach about 8 km/s. I
believe the first was built in 1957. LLNL built one in 1972 and is still
using it. It's powered by gunpowder.

Experimental railguns have already achieved 30,000+ fps, well over orbital
velocity, but the power supplies are very expensive.

The US army has reportedly tested a battlefield 2.5kps "electromagnetic gun"
intended for tanks, but I don't know how that works. Another "e-m gun" was
developed (or at least funded) as part of the SDI project, to shoot down
sats and incoming warheads, but again I know no details.


Various types of gasgun using eg hydrogen as the working fluid can also
reach orbital velocity plus, at least in theory.

I designed one about 30 years ago, to launch 2-ton blocks of ice. Almost
everyone I spoke to then laughed at the idea, though I've seen it suggested
again since.


Because even an exotic gun
that hypothethicall could reach such velocities, would be launching a
"capsule" containing an astronaut mass of bloody hamburger uniformly
smeared across the back wall

For people you need about 300km of barrel length, at about 10g max. The only
really suitable place to build one is in Ecuador. Which is unfortunately
subject to earthquakes and volcanoes.

Exiting from the gun barrel is a bit of a hard problem, you change very
quickly from +10g to -(lots of) g's. Atmospheric heating isn't actually that
much of a problem, though aerodynamic forces are. As are noise and other
environmental considerations!



Guns may also be useful for getting the first few kps and a bit of altitude,
though that is a bit problematic as far as cost/benefit goes. They are
initially expensive, and the high acceleration and aerodynamic forces mean
that the second-stage projectiles need to be strongly built and thus heavy.
Alternatively the gun must be long, and even more expensive.

The military potential is also a problem, but that's a problem in any space
effort. The US Govt., and especially the US military, does not want anyone
(else?) in space.


--
Peter Fairbrother

Peter Fairbrother wrote in message ...
John Schilling wrote

Because conventional powder guns absolutely cannot accelerate a
projectile to even one-quarter the necessary velocity.

I'd have thought a Yank would know about guns.

Let's say for argument the necessary velocity is 8.5 km/s.

Bull got around 3.6 km/s at (S)HARP.


The maximum muzzle velocity of the 1960's era HARP gun never exceeded
2 km/s.

SHARP (the large, Lawrence Livermore gas gun built in the mid 90's)
got to 3 km/s, but the projectile only massed a few kilograms.

The engineering of building a larger light gas gun (larger than SHARP)
is *extremely* challenging. The 40 ton breech block of SHARP was the
largest forging of high-cobalt, high-nickel steel ever attempted.


There are a few 13,000 fps (~4km/s)
powder guns around today, and I've heard of plans for a 5km/s one


Reference, please. You can prove on gasdynamics grounds that a powder
gun can *never* exceed 3 km/s muzzle velocity.


A slight variation is the two-stage gasgun, which can reach about 8 km/s. I
believe the first was built in 1957. LLNL built one in 1972 and is still
using it. It's powered by gunpowder.


Two-stage gas guns have demonstrated velocities of 10 km/s, but with
projectiles only massing a few grams. See my comment above regarding
scaling of gas guns.


Experimental railguns have already achieved 30,000+ fps, well over orbital
velocity,


References, please. I am not aware of any railguns exceeding 6 km/s.
--
Andrew J. Higgins Mechanical Engineering Dept.
Assistant Professor McGill University
Shock Wave Physics Group Montreal, Quebec CANADA
http://www.mcgill.ca/mecheng/staff/academic/higgins/

Andrew Higgins wrote:
[...]
The engineering of building a larger light gas gun (larger than SHARP)
is *extremely* challenging. The 40 ton breech block of SHARP was the
largest forging of high-cobalt, high-nickel steel ever attempted.

It seems likely, to me, that EDM would replace forging for
larger structures.

There are a few 13,000 fps (~4km/s)
powder guns around today, and I've heard of plans for a 5km/s one

Reference, please. You can prove on gasdynamics grounds that a powder
gun can *never* exceed 3 km/s muzzle velocity.

I think that's not true with a travelling charge;
but nobody has made reliable travelling charge guns.

I'm not familiar with 4 km/s conventional guns either,
though, and would like to see a reference.


-george william herbert

George William Herbert wrote:

I think that's not true with a travelling charge;
but nobody has made reliable travelling charge guns.

Has anyone mentioned ram accelerators in this thread?

Paul