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Spudguns in space

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Ragnarok » Sun Nov 22, 2009 6:17 pm

jackssmirkingrevenge wrote:Would it really need that much rocket power?

If you could stop it, relative to the Earth, it would drop purely from gravity. Bear in mind, at the ISS' orbit, gravity is still 90% of what it is on earth. It's only because anything in orbit is in free fall* that things appear weightless.

(*And only because of its sideways velocity does that freefall cause it to miss the earth - same basic principle as escape velocity, differentiated only by altitude)

Stop it orbiting, and without that "centrifugal force", it'd drop. Although it must be noted, the ISS does 7.7 km/s. That's quite a lot of "stopping it orbiting".

How about one huge fin then, could also serve as a shield, with a visor cut out :)

Consider where that heat is being radiated TO. You've got your soldier behind a large flat fin that's trying to lose 10 kW of heat in his direction - not good.

In practical terms, the best option is to create a firearm that'll survive high temperatures, and which uses the aforementioned water cooling (hey, it's what NASA uses for spacesuits).

Alternatively, just be prepared to deal with very short barrel lives.

Either way, as combat in a vacuum is not going to happen in the near future (and to be frank, would probably be short lived, given the fact that a mere glancing hit on a vacuum suit would prove fatal to the user), the matter is not of particular importance.
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Unread postAuthor: D_Hall » Mon Nov 23, 2009 12:49 am

jackssmirkingrevenge wrote:Why's that, considering the point of the Navy's current railgun development is a pure kinetic weapon. The concept of "smart spears" - guided metal rods without explosive - dropped from high altitude bombers has also been floated around, at least by those at the Skunk Works:


two words: nuclear weapons

say the Russians detect a massive launch of ICBMs We're just launching kinetic rounds against some hard targets in Iran. How do you convince the Russians that it isn't a nuke strike against them?

That, my friend, is a very dangerous game to play.

One that isn't much of a problem for rail guns or bombers.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 23, 2009 5:57 am

D_Hall wrote:two words: nuclear weapons


That's three words according to Dennis Leary:D

Fair point, though really you can fit a nuclear warhead to pretty much anything these days.

Alternatively, just be prepared to deal with very short barrel lives


You wouldn't need rifling though really, with no air resistance. Unless I've missed something, an unrifled projectile should show no tendency to tumble end over end, and of course fins would be useless.
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Unread postAuthor: POLAND_SPUD » Mon Nov 23, 2009 6:54 am

You wouldn't need rifling though really, with no air resistance
lol that's a fair point

also becasue there is no air resistance the guns wouldn't have to be as powerful
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 23, 2009 7:01 am

POLAND_SPUD wrote:also becasue there is no air resistance the guns wouldn't have to be as powerful


tsk tsk, that kind of thinking will keep you off any US consulting body on space warfare. Silly efficienct mad Europeans! MOAR POWER!!!!!!!

:D :D :D
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Unread postAuthor: Ragnarok » Mon Nov 23, 2009 8:28 am

jackssmirkingrevenge wrote:You wouldn't need rifling though really, with no air resistance. Unless I've missed something, an unrifled projectile should show no tendency to tumble end over end, and of course fins would be useless.

Yes, a fair enough point, but the discussion was about using terrestrial firearms in space. The point was originally sparked by Firefly - I'm sure fans will recognise the episode (D_Hall particularly so).

So really, the design was looking for something that could work both in or out of vacuum (perhaps in a similar way to how the Russian ASM-DT can be used on land or in water).

And rifling or not, a barrel still needs to maintain physical integrity.

So really, the design was looking for something that could work both in or out of vacuum.
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Unread postAuthor: D_Hall » Mon Nov 23, 2009 8:50 am

jackssmirkingrevenge wrote:Fair point, though really you can fit a nuclear warhead to pretty much anything these days.

only if you are interested in treaty violations.
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 23, 2009 10:53 am

Ragnarok wrote:So really, the design was looking for something that could work both in or out of vacuum (perhaps in a similar way to how the Russian ASM-DT can be used on land or in water).


Now that you mention it, the ASM-DT sounds like the perfect space weapon :)

only if you are interested in treaty violations.


Or do your design work somewhere within the Axis of Evil ;)
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Unread postAuthor: CpTn_lAw » Mon Nov 23, 2009 3:13 pm

Good ol' BP cannon :D And you get a free trip in the opposite direction :P
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Unread postAuthor: jimmy101 » Mon Nov 23, 2009 3:51 pm

Didn't a recent firefight in Afghanistan have problems with melting barrels of M16s?

If a real combat firefight can melt the barrel in air then in space the same firing scenario would make the barrel a molten pool after a lot fewer rounds were fired.

In addition, the breach would probably fail pretty early on. No cool air being circulated with each cartridge.

Further further more, a cartridge might not fit in the breech. What's the coefficient of thermal expansion for brass versus steel? Would the cartridge be too big or too small when the cartridge and the gun are at -200C or at +130C?

A year or so ago there was a blurb in PopSci about firing a rifle on the moon. Amazingly (or not depending on your point of view :) ) the academic they got to answer the querstion got things wrong. Like the affect of recoil. Recoil on the moon would be basically identical to that on earth. Indeed, it would probably be less noticable to the shooter since the shooter would be ~100 pounds more massive on the moon due to his spacesuit.
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Unread postAuthor: D_Hall » Mon Nov 23, 2009 5:37 pm

jackssmirkingrevenge wrote:Or do your design work somewhere within the Axis of Evil ;)

Except that they're signatories to the same treaties (well, I guess that depends upon your definition of "Axis of Evil.").
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Unread postAuthor: jackssmirkingrevenge » Mon Nov 23, 2009 7:45 pm

jimmy101 wrote:Didn't a recent firefight in Afghanistan have problems with melting barrels of M16s?


Unfounded, apparently.
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Unread postAuthor: Brian the brain » Tue Nov 24, 2009 1:20 pm

Ermmm....

How about just using a diver's speargun?
No airresistance means unlimited range so....


That would solve all pressure issues.

( yes a crossbow too, but that's unwieldy)
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Unread postAuthor: psycix » Tue Nov 24, 2009 2:40 pm

Mechanical seems like a very good way to store energy in space. Independent of the atmosphere, not generating a lot of heat.

On top of that, mechanical launch systems can be charged by electrical motors, for which the energy comes from solar panels (or nuclear).
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Unread postAuthor: jimmy101 » Tue Nov 24, 2009 3:39 pm

jackssmirkingrevenge wrote:
jimmy101 wrote:Didn't a recent firefight in Afghanistan have problems with melting barrels of M16s?


Unfounded, apparently.

Really?
Despite the military's insistence that they do, a small but vocal number of troops in Afghanistan and Iraq has complained that the standard-issue M4 rifles need too much maintenance and jam at the worst possible times.

A week ago, eight U.S. troops were killed at a base near Kamdesh, a town near Wanat. There's no immediate evidence of weapons failures at Kamdesh, but the circumstances were eerily similar to the Wanat battle: insurgents stormed an isolated stronghold manned by American forces stretched thin by the demands of war.

Army Col. Wayne Shanks, a military spokesman in Afghanistan, said a review of the battle at Kamdesh is under way. "It is too early to make any assumptions regarding what did or didn't work correctly," he said.
I would say it is unclear if there was a problem or not.

It must be said though that the M16 (and it derivatives) has had it's detractors since it was first used in Vietnam more than 40 years ago.
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