shotguns in space

I can just see Abbott and Costello in space… Maybe a Star Trek walk-on…

Abbott: Lou, plot me a course to the 2nd planet of that binary system over there.
Costello: Why, Abbott? Who’s on the 2nd planet?
Abbott: No, Who is on the 1st planet, What’s on 2nd.
Costello: I don’t know…
Abbott: Oh, he’s on 3rd…
:rolleyes:

I think I saw that movie over Christmas vacation at my parent’s house, but I missed the falling bullet scene. I did see where Lou was crowned King of Venus…

Sorry for the nitpick but hardhead365, I believe you mean Tales of the gun instead of History of the Gun. It was the Magnificent Failures episode.

mangeorge wrote:

… but you’ll have a hell of a time cycling the pump-action to put the next shell in the chamber!

There are a few things to worry about here. In a vacuum, any oil or lube is going to evaporate pretty quickly. Sliding metal components in space are subject to a problem known as “vacuum welding” where they stick together. You’d probably get your first shot off, but after that I wouldn’t rely on an ordinary, unmodified shotgun working. You’d probably do better than a guy with an MG though!

It would be possible to design a shotgun specifically to work in a vacuum. Maybe a liberal application of a graphite or teflon based lube would fix an ordinary one as well.
The gyrojet was an interesting idea which was never widely adopted. The rocket would burn for the first 25 ft or so, meaning that if you shot someone at very close range it wouldn’t have enough velocity to do them much harm AND it could bounce off them and come back at you. Then when the rocket had burned out you had a very low density projectile (an empty metal tube) compared with a conventional bullet, so effectiveness would drop off rapidly with range. This didn’t matter so much for the pistol, but made a carbine or rifle pretty useless.
Baloo’s article indicates that the gyrojet was quite accurate, contrary to most other descriptions of it.

Sleepy Weasel:"A multi-stage hybrid would be a better option. Give it enough muzzle velocity for penetration as soon as it clears the barrel, and then the rocket motor let’s you penetrate harder targets at a greater distance."

Good idea, but you have to consider where the rocket exhaust is going. The gyrojet’s recoiless nature is due to the forward momentum of the rocket being countered by the backward momentum of the exhaust gases.

The gyrojet barrel was a simple tube with two rows of holes along it. If you put the equivalent of 25 ft of burn into the barrel length to get a decent muzzle velocity, you’re going to cook your hand. If you use a sealed tube and do the same thing, you’ve got a conventional gun with recoil and the gyrojet’s only good feature is lost.

The only way round it is to use a shoulder launch tube with the exhaust going out the back and the rocket burning out or switching to a very low burn rate before it flies out the front. Then you haven’t exactly got a pistol anymore!

Seeing as how we’re already hopelessly off-topic anyway, and there are some experts here, I’ve always wondered about something.
If a gun is mounted solidly, say in a massive concrete block, will some of the recoil energy be imparted to the projectile and increase it’s velocity?
I don’t think so, but physics isn’t my strong point.
I think the energy would be absorbed into the mass of the concrete block.
Peace,
mangeorge

Most will not cycle very well, though. GLOCKs are specifically designed to cycle underwater. All you have to do is buy the aqua kit. It has a heavier firing pin spring to move through the water and fluted spring cups to allow the water to flow over them.

…I would not recomend being IN the water when you fire it though. 'less you wanna piss blood or something.

Why? How does the vacuum do this? I am very curious. Even an unlibricated gun will work ok for a while (a decent one. not like a Jennings or something). What does the vacuum do to make the metal stick together?

mangeorge: Suggested thought experiment (or real experiment!) - take a big plastic bin, tip it on its side and duct tape it to a wheeled trolley. Get in it, crouch down in the bottom and see how far you can spring out by pushing against the bottom with your feet.

Try it again with the trolley braced against a wall so it can’t move backwards. D’you get any further? Same situation with a gun.

Simple physics, conservation of energy and conservation of momentum, tells us the projectile will have an increased velocity. If you have a free-floating gun (in space, say) the energy partitions between the projectile and the gun inversely according to their mass ratio. So if the gun weighs nine times as much as the projectile, then 90% of the energy ends up as KE in the projectile and 10% in the recoilling gun.
With the gun in a concrete block, you are effectively giving yourself a gun of infinite weight so all the K.E ends up in the projectile. However, with e.g. a 3kg rifle and a 10g bullet you already have 99.67% of the energy in the projectile, so you’re not going to get a big increase in velocity.

In the real world guns tend to have moving parts which recoil before the rest of the gun, the propellant gases make their own contribution to recoil, having the gun braced against your shoulder increases its effective mass and the simple physics becomes less useful!

Bear_Nenno: essentially, the question is why metals DON’T ordinarily stick together. The answer is surface oxidation and contamination - a permanent layer of crap on metal surfaces allows them to slide past each other. You can get metals to fuse by sliding them past each other under great pressure so the layer of crap is scraped off (friction welding. Also happens when a car engine seizes - the metal doesn’t actually get hot enough to melt.)

Under very high vacuum conditions, when metals slide past each other and scrape each other clean, no new oxide can form and the ultra-clean surfaces can stick to each other. This is a real weld, not a trivial bond. It has caused a lot of difficulty in moving parts on satellites - making a metal hinge which works properly in high vacuum is difficult.

A little detail is given here although it is called “cold welding”:

http://york-me.eng.hokudai.ac.jp/spacesystem/satellite/mission.htm

:o
mangeorge

A rocket gun isn’t going to protect you from the recoil, unless the rocket is designed to throw its exhaust away at an angle. Otherwise, the exhaust from the rocket will hit you and impart its momentum on your body. You’ll move in the opposite direction just as if you had fired a bullet out of a gun.

If some percentage of the exhaust misses you, you won’t accelerate as much. If the thing is designed to shoot the exhaust out the back in a cone that avoids you completely, then you’d feel no force.

The gyrojet is usually described as recoiless, although all this means is that the recoil is too small to notice. The question is, what proportion of the exhaust does hit you, and how do you perceive its force? That’s a tough question, since most of the rocket’s burn takes place outside the gun and you have the interaction with the atmosphere to consider. I agree that if you were firing it in orbit in a spacesuit, you will find it somewhat less “recoiless” than you thought.

Hadn’t thought about the exhaust angle, good point! The gyrojet had (four? 45[sup]o[/sup]?) vanes in its exhaust nozzle to deflect the exhaust and make the rocket spin, giving it gyroscopic stability and giving the gun its name. I guess that could give a conical exhaust?

Ben Franklin was right. Why use guns with their inherint physicial problems? A nice bow and arrow might work nicely. It will need some sort of modification to impart spin, as in a vacuum the fletching would be useless.

And the bow and arrow is still going to have a significant recoil. Perhaps more than the gun and bullet. Arrows are very heavy compared to a bullet. You just don’t feel the recoil of an arrow as much because the acceleration takes place over a very long time compared to the acceleration of the bullet.