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Old October 25 2009, 07:33 AM   #1
drychlick
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if i shout a gun in orbit in a space ship

would a bullet act the same as a does on earth?
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Old October 25 2009, 08:28 AM   #2
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Re: if i shout a gun in orbit in a space ship

drychlick wrote: View Post
if I shout a gun in orbit in a space ship would a bullet act the same as a does on earth?
Depends how loud you shout at it.
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Old October 25 2009, 08:58 AM   #3
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Re: if i shout a gun in orbit in a space ship

drychlick wrote: View Post
would a bullet act the same as a does on earth?
Consider the forces applied to the bullet: forward velocity produced by the gun itself; backwards velocity caused by friction; the downward effect of gravity on recoil and the distance of the bullet's travel. Then consider how those forces and conditions can be different in your situation: inside a spaceship, in orbit around a planet such as Earth.

The forward velocity may not change as this is dependent on the gun type, which will be the same as on Earth, although as I'm not a gun expert, I'm not sure if the firing mechanism and the movement of ammo will be affected by gravity. The forward velocity is also affected by the velocity of the ship itself (it's in orbit but it's still moving very fast in both forward and downard directions ), as even in its ammo chamber doing nothing, the bullet is still travelling at the same velocity as the ship - indeed, as is everything else inside the ship, including you. Fired in anger, the bullet will therefore be travelling very fast in the forward direction due to the additional velocity generated by the energy transfer from chemical/potential to movement energy caused by the gun's firing mechanism - this forward velocity will still be the dominant force exerted upon it.

Consider the conditions inside the habitable areas of the space ship, if we're assuming that's where it's being fired. If atmospheric conditions are as close to Earth sea-level as possible, then the forward velocity is the same as on Earth for a given gun, affected by the same effects of friction as a bullet on Earth - still not enough to overcome the forward velocity produced by the firing. If it is fired outside the ship then it is subjected to the same high atmospheric/low orbital frictional forces (much less compared to Earth sea level) that any spaceship will be affected by in orbit around Earth or whatever other planet - not to mention the chance of it hitting micrometeorites, space junk, etc. which might have a small chance at significantly affecting the forward dominant velocity.

Of course, despite the forward velocity provided by the gun, remember that the bullet is falling to Earth at the same rate as the ship and everything else inside it, giving the effect of weightlessness. Once it tears a hole in your spaceship, decompressing the habitable cabins and killing everyone inside then in the long term, it is likely that the the bullet will fall to Earth in much the same way as other orbiting objects eventually do so without orbital corrective mechanisms. It would take some doing to produce a significant additional escape velocity from a handgun - if the gun was pointed at the Moon - to completely overcome Earth's gravitational force, even from the lowish Earth orbit most astronauts have become accustomed to.

If fired in true deep space - not in orbit, not inside any ship, without any gravitational pull from any solar systems and planets - then yes, the initial forward velocity burst and lack of frictional forces and gravitational influences means the bullet will travel forwards for a very, very long time.

Also remember that without a direct effect of an artificial gravitational field to provide a strong downward force to pull everything inside the ship towards the floor direction (including yourself, the gun, the ammo inside the gun and the individual components of the firing mechanism), that helps absorb the recoil of the gun under Earth gravitational conditions, you would also move in the opposite direction of the bullet to a much greater extent, in accordance with Newton's 3rd law of motion.



Hope that goes some way to answering the question.
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Last edited by Zion Ravescene; October 25 2009 at 09:34 AM.
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Old October 25 2009, 01:14 PM   #4
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Re: if i shoot a gun in orbit in a space ship

drychlick wrote: View Post
would a bullet act the same as a does on earth?
I'm not 100% certain a gun would work in a vacuum, but assuming you had a gun that would, the bullet would shoot off and keep going until it hit something (very unlikely) or got pulled into orbit by something.

There is no friction so the bullet would not eventually run out of puff as it does on Earth.
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Old October 25 2009, 03:09 PM   #5
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Re: if i shout a gun in orbit in a space ship

It depends how close to the Earth you were when you fired it, what direction you fired it, and other factors.

Yes, a bullet ought to fire iin space as modern ammunition is self-oxidized.
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Old October 25 2009, 04:00 PM   #6
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Re: if i shoot a gun in orbit in a space ship

USS KG5 wrote: View Post
There is no friction so the bullet would not eventually run out of puff as it does on Earth.
The paths of bullets on Earth is affected more by gravity than friction. Everything falls at the same rate, and as the Mythbusters demonstrated a couple of weeks ago, a bullet fired horizontally from a gun will take exactly the same amount of time to reach the ground as a bullet that's simply dropped from the same height. Same with a bullet fired upward -- it's gravity, not friction, that's doing the primary work of slowing it down (and then speeding it up again once it begins its descent). This is another thing the Mythbusters covered; in the unlikely event that a bullet is falling straight down, then air friction would balance out gravity once it reached terminal velocity, so it wouldn't fall any faster, but it would still be falling. And in the more common scenario, it would be following an arc and its aerodynamic shape would minimize air friction, meaning it would descend faster than terminal velocity (which is why it's so dangerous and illegal to fire bullets into the air -- you could kill someone miles away).

So in every case, air friction is not a significant factor in the trajectories of bullets. Assuming they don't hit anything else, gravity will always bring them to the ground well before air friction could affect their horizontal velocity by any significant degree.
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Old October 25 2009, 04:12 PM   #7
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Re: if i shout a gun in orbit in a space ship

Chaos Descending wrote: View Post
It depends how close to the Earth you were when you fired it, what direction you fired it, and other factors.

Yes, a bullet ought to fire iin space as modern ammunition is self-oxidized.
The other factor would be how the weapon and ammo reacts to the extreme cold
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Old October 25 2009, 04:18 PM   #8
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Re: if i shout a gun in orbit in a space ship

clint g wrote: View Post
Chaos Descending wrote: View Post
It depends how close to the Earth you were when you fired it, what direction you fired it, and other factors.

Yes, a bullet ought to fire iin space as modern ammunition is self-oxidized.
The other factor would be how the weapon and ammo reacts to the extreme cold
The cold of vacuum isn't as bad as the cold is atmosphere, unless you leave the gun and ammo out for it to freeze. If you had just left a spacecraft with it's room temperature atmosphee and started firing, you'd instead find you're having problems with overheating, since there's no air for the heat being generated to conduct to.
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Old October 25 2009, 05:17 PM   #9
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Re: if i shout a gun in orbit in a space ship

^That's right. The "cold of space" is a myth. Vacuum is a superb insulator. If you're in space and you're in darkness -- say, in the Earth's shadow or in interstellar space -- then you'll gradually radiate away your heat, but much more slowly than you would in air or water where there's a material substance to conduct or convect heat away. But if you're in direct sunlight, as you would be most of the time that you're in Earth's orbit, then you'd be heated up even faster than you would be on the surface -- again because there's no atmosphere to intercept or carry away a portion of the heat energy of sunlight. And given that a body orbiting the Earth is only going to be in darkness for less than half of the time -- way less than half if the orbit is large -- you'd have more to worry about from overheating than freezing.
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Old October 26 2009, 11:19 AM   #10
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Re: if i shoot a gun in orbit in a space ship

Christopher wrote: View Post
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There is no friction so the bullet would not eventually run out of puff as it does on Earth.
The paths of bullets on Earth is affected more by gravity than friction. Everything falls at the same rate, and as the Mythbusters demonstrated a couple of weeks ago, a bullet fired horizontally from a gun will take exactly the same amount of time to reach the ground as a bullet that's simply dropped from the same height.
Yeah I know gravity on Earth will affect the bullet before friction - but the OP was not exactly clear about whether his space ship is in open space or in LEO, or variations thereof. If in LEO I doubt a normal handgun would provide enough velocity to send the bullet out into open space, so gravity would again be the deciding factor?
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Old October 26 2009, 02:24 PM   #11
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Re: if i shoot a gun in orbit in a space ship

LEO orbital velocity is normally around 7,800 m/s. A handgun's muzzle velocity would be only a few hundred m/s, a few percent of that. So if you were in LEO in open space and fired a bullet, you'd just send it into a slightly different, more eccentric orbital path than your own. You wouldn't be able to decelerate it enough to cause it to fall to Earth or accelerate it enough to break orbit.
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Old October 26 2009, 03:09 PM   #12
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Re: if i shoot a gun in orbit in a space ship

Christopher wrote: View Post
LEO orbital velocity is normally around 7,800 m/s. A handgun's muzzle velocity would be only a few hundred m/s, a few percent of that. So if you were in LEO in open space and fired a bullet, you'd just send it into a slightly different, more eccentric orbital path than your own. You wouldn't be able to decelerate it enough to cause it to fall to Earth or accelerate it enough to break orbit.
Remember, the force is applied two ways. You aren't anchored to the Earth so the recoil force will alter your orbit as well.

I had that in mind as a science-fiction story. Someone is stranded in a bad orbit, but happens to have an old handgun and a supply of ammunition. How much it could alter your orbit depends on how much ammo and time you have.
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Old October 26 2009, 04:32 PM   #13
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Re: if i shoot a gun in orbit in a space ship

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Remember, the force is applied two ways. You aren't anchored to the Earth so the recoil force will alter your orbit as well.
Of course I remember something as elementary as Newton's Third Law. However, I also remember Newton's Second Law, F = ma. The mass of a typical bullet is maybe around 10 grams. The mass of a typical person in a spacesuit might be somewhere around 100 kilograms. Therefore, the acceleration imparted to the person shooting the gun is going to be about 1/10000 the acceleration imparted to the bullet, so its effect would be trivial in comparison. It would introduce a slight perturbation in your orbit, but nothing significant enough to be worth mentioning.

I had that in mind as a science-fiction story. Someone is stranded in a bad orbit, but happens to have an old handgun and a supply of ammunition. How much it could alter your orbit depends on how much ammo and time you have.
You couldn't alter it by very much in any case. Going by the figures above, and assuming that the ratio of final velocities is proportional to the ratio of accelerations, firing one bullet might impart a delta-vee of a few cm/s. So if you have, say, 20 rounds, you might be able to change your velocity by around half a meter per second or so. So if you were drifting away from your spaceship at a relatively slow rate, then maybe it could make a difference -- though you'd have to understand orbital mechanics well enough to know the right direction to fire in, since it's counterintuitive. But if you're talking about making a substantial change in your orbit, that's not in the cards.
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Old October 26 2009, 04:58 PM   #14
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Re: if i shoot a gun in orbit in a space ship

cold on earth ruins bullets because of condensation of water in the air could occur in the powder that is if the bullets aren't sealed properly. In space that is not a problem. Bullets would work better in space than in Antarctica....
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Old October 27 2009, 02:54 AM   #15
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Re: if i shoot a gun in orbit in a space ship

Christopher wrote: View Post
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Remember, the force is applied two ways. You aren't anchored to the Earth so the recoil force will alter your orbit as well.
Of course I remember something as elementary as Newton's Third Law. However, I also remember Newton's Second Law, F = ma. The mass of a typical bullet is maybe around 10 grams. The mass of a typical person in a spacesuit might be somewhere around 100 kilograms. Therefore, the acceleration imparted to the person shooting the gun is going to be about 1/10000 the acceleration imparted to the bullet, so its effect would be trivial in comparison. It would introduce a slight perturbation in your orbit, but nothing significant enough to be worth mentioning.

I had that in mind as a science-fiction story. Someone is stranded in a bad orbit, but happens to have an old handgun and a supply of ammunition. How much it could alter your orbit depends on how much ammo and time you have.
You couldn't alter it by very much in any case. Going by the figures above, and assuming that the ratio of final velocities is proportional to the ratio of accelerations, firing one bullet might impart a delta-vee of a few cm/s. So if you have, say, 20 rounds, you might be able to change your velocity by around half a meter per second or so. So if you were drifting away from your spaceship at a relatively slow rate, then maybe it could make a difference -- though you'd have to understand orbital mechanics well enough to know the right direction to fire in, since it's counterintuitive. But if you're talking about making a substantial change in your orbit, that's not in the cards.
Oh no, it would have to be one of those situations where you just needed a small change in your delta-v to avoid a high speed collision of some sort.
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