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Gun fire in space


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Most accelerant chemicals for ammunition are now days in forms of fast and slow burning "Nitro Powders", and i would suspect that once the projectile/bullet is pressed into the cartridge case, most of the air would be pushed out at that stage, after ignition the bullet will accelerate down the barrel with no air in between the case and bullet, only that from its own chemical reaction.

So yes, i suspect it would fire!

Jeff.

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hhehe, cant you just tell when its been cloudy for a while......... we all get stir crazy.

My question, if I fire my rifle straight upwards, (and asssuming it has enough mv to reach that far) at what point would the round break free of the pull of gravity? You would need to know how fast it would have to leave the muzzle in order to reach space before gravity got the better of it.

BUT! As the effects of gravity will reduce as altitude increases, would the deceleration be uniform, or would it eventually start to slow down more slowly, thus makign it easier for the round to break free of gravity? I'd love to see a graphic on this :(

Peter, what rifle do you shoot? I have a Sako Finnfire Varmint .22LR and a CZ 452 American .17HMR. Also have a 12Ga and .410 up there. Mind you, since I started with the telescope, I hardly get to go out.

Cheers

TJ

.22 LR Anschutz 10 shot Semi Auto silenced 3-9x50 scope ...

.22 Hornet Brno Bolt Action 5 shot with Bipod and 3-12x60's ...

Mosberg ATP8 12G ( shot (8+1) ) Slugster with iron sights scope mounts..section 1 of course

Various "normal" 12G shotguns...

Used to have a 20G .22 Mag drilling which was interesting if you pulled the wrong trigger....

land cleared for .243 but no deer and wont let me have one for long range vermin destruction....

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.22 LR Anschutz 10 shot Semi Auto silenced 3-9x50 scope ...

.22 Hornet Brno Bolt Action 5 shot with Bipod and 3-12x60's ...

Mosberg ATP8 12G ( shot (8+1) ) Slugster with iron sights scope mounts..section 1 of course

Various "normal" 12G shotguns...

Used to have a 20G .22 Mag drilling which was interesting if you pulled the wrong trigger....

land cleared for .243 but no deer and wont let me have one for long range vermin destruction....

They wont let you have a .243 for charlie? Maybe because of the Hornet? And these days, there aren't many places without deer, even if they are just munties, and its still illegal to take those without >.243. You never see any?

Sometimes the officers involved are to blame. We had a really cool guy, shooter himself, who granted me an 'open' ticket after 12 months, but you get others who dont know one end of a gun from another.

I've always fancied a .17 Remy. 4000fps!

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lasers do have recoil. Each photon carries energy E=h*frequency and momentum p=h/wavelength or p=E/c. h is the famous Planck constant and c is the speed of light.

owowowowowoowww! My head hurts! Stop already. :(

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lasers do have recoil. Each photon carries energy E=h*frequency and momentum p=h/wavelength or p=E/c. h is the famous Planck constant and c is the speed of light.

Whoops, I stand corrected. Thank you for showing me the error of my ways.

What does it mean in real terms though? How much recoil would you get from firing a handheld laser, such as in Firefly?

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Super answers guys - oh and Themos, you beat me to it on the laser recoil!

I was going to mention that for solar sails (I'm sure given our demographic I needn't explain!) one of the propulsion methods was to use a laser to supplement the sunlight. In Robert Forwards SF book Dragonfly he proposes an interstellar solar sail vehicle propelled by Mercury orbiting/suspended lasers which were powered by solar collectors. For the controling space station he suggests one that is not in orbit around Mercury but rather suspended by a solar sail which is in equilibrium between Mercurys gravity and the propulsive force of the solar wind.

What fun!

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Of course! I completely forgot about the solar sails and 'topping' them up with lasers. I guess I was thinking more on the lines of lasers being fired from the USS Enterprise, where the recoil would have been negligable compared to the mass of the ship. Plus they'd have the engines on.

(Or are they photons on the Enterprise?)

This is turning out to be a damned interesting thread!

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The Enterprise is fitted with inertial dampers guys which cancel out recoil or other unwanted movements in any direction one would imagine they use them as breaks too and the weapons are phasers Photon Amplification by Stimulated Emission of Radiation and photon torpedo's not lasers

regards Pete aka trekkie anorak

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Surely an inertial damper would only work on all the constituent parts of the vehicle relative to each other, not as relating to its motion to the outside universe. Otherwise we are getting into the realms of inertialess drives like EE Doc Smith etc.

So surely the warp/impulse drives would act as breaking etc. If the ship were truely inertialess then the weapons fire would be sufficient to send the inertialess mass off in the other direction at extremely high velocity (Inertia = an objects resistance to acceleration).

Whereas if inertia were damped within the vehicle but not as relates to the outside universe then all accelerations would act on all molecules within that mass equally thus preventing the crew etc being reduced to strawberry jam (or other preserves as your preference...!)

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A further thought on the subsequent paths of bullet/gun after firing. Yes, Newton says they both go on forever if not acted on by an external force. But even in space we need to worry about escape velocities - I don't know what these are for the solar system, the galaxy, and the local cluster, but they'll all be greater than the speed of a bullet. So bullet and gun will both go into a big orbit around the Sun/galactic centre/local group centre of mass (or local supercluster centre....).

If we could get far enough away from galaxies as to make their influence negligible we would still have to contend with Hubble expansion. Contrary to what Newton said, moving objects in an expanding universe all slow down to zero speed with respect to the overall expansion - space effectively stretches so as to negate their speed. The end result is a bullet and gun which are both "stationary" relative to the background radiation (i.e. they each see a constant background temperature all round), yet are receding from each other at an enormous velocity (i.e. each sees the other as red-shifted).

Andrew

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there was a book about 20 years ago called war in 2080 and it concluded that the biggest problem with firing a gun n space was the effect of the sudden rise in temperature of a mechanism that had cooled down in a near vacuum, sooner or later it will jam or shatter which could cause problems for whoever is holding it and anyone in the shrapnel's path. you could find yourself finding out what happens when you fire a gun and you're in a vacuum as well as the gun :shock:

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So i suppose if you fire a gun in orbit, it may eventually be a pain in the a*** :(

Jeff.

there's a short story somewhere (think ts caled the dueling machine or somthing like that) where two men are on a small moon and resort to throwing rocks at each other, the winner's tactic is to conentrate on avoiding his opponent's rocks till one of them completes an orbit and hits his assailent in the back :thumbright:

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Most accelerant chemicals for ammunition are now days in forms of fast and slow burning "Nitro Powders", and i would suspect that once the projectile/bullet is pressed into the cartridge case, most of the air would be pushed out at that stage, after ignition the bullet will accelerate down the barrel with no air in between the case and bullet, only that from its own chemical reaction.

There is such an excess of propellant gases compared to the amount needed that air in or not in the barrel at the time of firing would make no significant difference.

I am interested in what happens to the bullet if you fire it in the direction you are already going. I suspect it would enter an elliptical orbit with a higher apogee than yours, but would intersect your orbit at one or more points. As the speed of the bullet wouldn't add much to your own orbital velocity, the difference wouldn't be much.

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  • 2 weeks later...

If you were free-floating when you fired it (assuming it would fire), would there be a backlash kick that would send you flying off in the opposite direction?

Newtons third law, for every action there is an equal and opposite reaction, so the force that propells the bullet forward would also act in the opposite direction back towards the person firing the gun. You would accelerate backward slower than the bullet would accellerate forward, because accelleration = Force/Mass, greater the mass, the slower you accellerate when a force is applied.

Please correct me if i'm wrong.

This thread is really interesting, I've learnt heaps of stuff already. :)

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managed to find the book i was on about

its called

"war in 2080" by David langford,

i've no idea if it's available as my copy was printed in 1981 but if you can find it it's quite a good read, especially his comments on death rays and how when the high teck soldier staggers onto the battlefield, weighed down by his beam weapon and protective gear, prepared to reek death and destruction on anyone who comes within 100yds, only for the dispicable enemy to pick him off with an old fashioned rifle from a safe distance.

EDIT : it is available used, there's a modern review of it which points out the areas were time / developments have overtaken it and the mistakes withoin it, but overall it's still pretty good

review here

http://sciencefictionfantasy.blogspot.com/2007/11/review-war-in-2080-by-david-langford.html

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Just doing some mental gymnastics here. Suppose a rifle bullet weighs half an ounce, and I weigh 9600 half-ounces in my spacesuit. If the bullet leaves the barrel at a velocity of 600 m/s, I would be kicked backwards at a leisurely pace of 6.25 cm/s, a velocity which could easily be absorbed by any large object such as a space station, large rock, fat friend, etc. The bullet would not lose velocity as there is no air to slow it down, so it would arrive with the same lethal force at any distance to which I could reliably aim.

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Here's another twist. :) Let's say there's a line of identical mass astronauts, free-floating with 6" of room between each of them. The first one fires the gun and is pushed back, causing them to bump into the next one. How long will it be until the movement is absorbed (not sure if that's the right word) by the bodies of the astronauts? I suppose it would depend on their individual mass, right?

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Here's another twist. :) Let's say there's a line of identical mass astronauts, free-floating with 6" of room between each of them. The first one fires the gun and is pushed back, causing them to bump into the next one. How long will it be until the movement is absorbed (not sure if that's the right word) by the bodies of the astronauts? I suppose it would depend on their individual mass, right?

Don't think i'd like to be in that scenario :p:laugh:

Jeff.

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Well, if I am an average sized astronaut, and hit the guy behind me, we will continue together at 3.125 cm/s. When we contact the next two astronauts, our speed will be reduced to 1.56 cm/s. Another four astonauts, 0.78 cm/s, another 8 astronauts, we are down to 3.6 mm/s. We need 16 more astronauts to get the speed down to 1.8 mm/s, at which point we are stopped for all intents and purposes, although we can involve an infinite number of astronauts before reaching a value of zero.

I should like to point out that no astronauts were hurt as a result of this experiment.

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..at which point we are stopped for all intents and purposes, although we can involve an infinite number of astronauts before reaching a value of zero.

Ok.. thanks, WH!! :thumbright:

I should like to point out that no astronauts were hurt as a result of this experiment.

:laughing3: :laughing3:

Caught me totally off guard with that one. :)

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  • 3 weeks later...

It depends if the astronaut collisions were elastic or in-elastic. Are they bumping helmets :oops: or squidgy bits? :shock:

This thread reminds me of a uni exam question: If you fire a bullet (of mass X) into a block of wood (mass y) suspended (by a light inextensible string, length z), how far will the block swing back?

Thus linking pendulums to laws of motion... :scratch:

mjcp

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