Low Gravity and Recoil

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ThePenguinKnight

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What would me the difference in recoil between, say, firing a 12ga shotgun in the earth's surface vs firing the same shotgun on the surface of the moon? Would felt recoil (ignoring the obvious issue of spacesuits providing a recoil buffer :p) be the same, or more?

Random question, I know, but I am a curious fellow with only a passing understanding of physics. Thanks in advance :)
 
Actually I wonder if it wouldn't feel different since gravity is a key factor in helping the man resist the recoil of the gun. So the recoil might be the same but what you actually feel could be very different in terms of literally being blown off your feet. :what:

On an unrelated note, would smokeless powder burn as well in an environment without oxygen? Or would it fail to burn completely and render a gun useless?
 
Perceived recoil...probably the same. Actual recoil I am sure would be higher. Actual user reaction to recoil will be drastically different.

There is no atmosphere on the moon, so the projectile will come out at a higher velocity (for every action their is an equal but opposite reaction) since the projectile comes out slightly faster, the weapon will recoil slightly faster. There is also less air resistance keeping the weapon from recoiling, or you from moving backwards. Although at the same time, having no atmosphere would likely decrease the chamber pressure on firing.

With no athmosphere and lower gravity there are also fewer outside forces to counteract inertia after firing, so the gun and you behind it will move farther back, and retain your velocities for longer.
 
I believe perceived recoil would be slightly greater in a low gravity environment due to reduce gravity pulling "down" on the firearm at arm's length.
 
If you're driving your car at the speed of light and turn on the headlights, can you see them in front of the car?
 
Wait now, You didnt just download the new zombie maps for Black Ops did you? :D
 
Shooting something while in orbit is the same as shooting something while in freefall. Do you think shooting a 12-gauge shotgun noticeably affect your velocity if you shot if while jumping out of an aircraft?


200px-Newton_Cannon.svg.png
 
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youngda9 said:
If you're driving your car at the speed of light and turn on the headlights, can you see them in front of the car?
Click to expand...

If you're in a car moving a lightspeed, everything behind you is redshifted far below the visible region, so you see nothing. Everything ahead of you in blueshifted 'way up beyond cosmic ray energy, so you're instantly incinerated.

That's why Star Trek didn't use a Buick. :)
 
Oh gosh. Another physics bash. I feel like the doc, who after telling the wife that the husband died of a large myocardial infarct, walked out past them in the waiting room and heard her say he died of a massive intestinal fart.

Now that this engineer has done his lamenting at the basic failures of high school science programs, down to brass tacks.

1. Gunpowder has its own oxidizer, so it should fire in a vacuum. You probably wouldn't need hearing protection, as the sound waves would only carry through your body.

2. Air not being in the barrel would not appreciably affect jack in terms of force balancing.

3. Muzzle rise would be interesting. One of the reasons that a gun rises up so much is that you are holding against it, and thus are predisposed to lift it when the pressure is reduced. I'd say, since inertia is the same, but you are applying less force to hold it up, muzzle flip might be less, or pretty close to the same.

4. Recoil will be the same, as regards to the gun hitting you. But, you will be less set up to deal with it, as you will have less traction. Traction, the frictional force keeping you from peeling out and falling on your can, is related to the qualities of the surface, and the gravitational force. Reduce the gravity and you have less capability to keep your footing. However, a proper shooting stance would help a lot, as you'll just rock back, not slip.

Short version: not much difference.
 
AK103K said:
Wait now, You didnt just download the new zombie maps for Black Ops did you? :D
Click to expand...
... No comment :neener:

As far as the physics of it go, what y'all have been saying is pretty much as I figured. I just had a thought and figured I would see if I missed anything. Plus it's fun seeing random topics on here :p

First one on the moon colony needs to resurrect this thread with a YouTube video :D
 
"Where's the KA-BOOM? there was supposed to be an Earth-shattering KA-BOOM!"
Click to expand...

Nice.:D

I always wanted to be an astronaut firing a FA rifle at the Earth with steel core ammo to see what sort of 'meteor' shower would result.
 
Kliegl said:
2. Air not being in the barrel would not appreciably affect jack in terms of force balancing.
Click to expand...

Care to explain why not?

As I state earlier, the chamber pressure may be slightly lower, but the projectile's velocity will likely be higher. Obviously its mass is a constant and the mass of the firearm is constant as well. So the only thing that can change is the velocity. If the velocity of the projectile goes up, the velocity of the firearm traveling in the opposite direction will go up as well.

Do you have any argument as to why you doubt that the velocity of the projectile will not increase without air pressure holding it back?

There are plenty of times where experts expected one thing to happen and when they run the experiment, what they expected to happen did not.

I am not sure if these experiments have been run in a vacuum or not, but there are certainly videos of people running experiments in water. Since water pretty much simulates a more dense atmosphere from that on the surface of earth, it is nearly the opposite of running an experiment in a vacuum. What have we observed from people firing guns underwater?
 
Hmm, and here I though muzzle flip results from the torque of the accelerative force acting on the lever arm created when the grip is not coaxial to the barrel and action. Torque generated by a normal offhand stance, in a low enough gravity field, might not put the shooter on his butt, but on his head or even back on his feet after a back flip. In free fall, the shooter would spin freely in some complex manner derived from the torque applied and how his body flexes. I sense a homework problem here, perhaps a final question. :D
 
Yes, I will, and I will because it is the MAIN problem that novices in science and physics (no offense meant) face, and that is that, while they know what CAN affect something, they know not to what DEGREE it will affect it. The concept of significance is just utterly lost.

Sure, there's certainly some affect that the presence of air will have on the bullet in the barrel that wouldn't be there in a vacuum, but it is so very little that it would be hard to measure.

Atmospheric air is 14.7 psi. That's 14.7 psi air pressure in the barrel vs 60,000 psi of a decently loaded .308 behind the bullet. Now, remove the 14.7 psi of atmosphere, and you increased the pressure difference by 0.025% Your chamber pressure, on the other hand, won't change.

As for your comments about water....no. It has to do with density. Water is approximately some 775 times more dense than atmospheric air, so whatever you fire in it is going to have serious issues dealing with it. You cannot, in any meaningful way, draw any sort of analogy between shooting in water vs atmosphere, and atmosphere vs vacuum.

It's like saying, because I punch really slow underwater, I ought to be able to punch at LIGHTSPEED IN A VACUUM!!!! ::::insert mad air, er, VACUUM guitar solo:::: when there is statistically no difference between vacuum and atmosphere when comparing it to air and water.

I'm very much aware that sometimes experiments don't go correctly, but dismissing the statistically irrelevant usually is not problem; rather, it has to do with the statistically relevant. In other words, the caliber you choose will have thousands more times the effect of the sudden lack of atmosphere.

If that didn't compute, I must recommend remedial physics classes, sorry.

Chuck, good point, but it's actually the same thing. A force back towards the shooter acting on a moment arm going straight up from his shoulder does the exact same effect as a vertical force acting on the moment arm going straight out from his shoulder. It's like one of those multi handled lug wrenches...lifting UP on the right one does the same thing as pushing LEFT on the vertical one.
 
That is why I said perceived recoil would be the same...actual recoil would probably be higher. Meaning it wouldn't be high enough for the user to observe. Without experiments I don't think we would know for sure...it might be .00001% higher, or it might not be at all higher.
 
Lunar surface would add some trickier bits to the answer.
It's functionally a vacuum, but in a gravity well.
And that gravity well is only a sixth of Earth's.

So, if you and your suit dress out at 180# on Earth, you'll only tip the scales 20±# worth on the Moon. Which is complicated enough. But, your 12# SPAS only weighs 2#, while still having all its mass.

So, you could hold it one-handed. But, any misalignment in that one-hand hold, and the vectors will assert themselves around each of the applicable CG.

And, that's all before we get to the complexity of just how rigid a suit gets to be inflated to the 6-7psi used in vacuum conditions.
 
HOOfan_1 said:
Perceived recoil...probably the same. Actual recoil I am sure would be higher. Actual user reaction to recoil will be drastically different.

There is no atmosphere on the moon, so the projectile will come out at a higher velocity (for every action their is an equal but opposite reaction) since the projectile comes out slightly faster, the weapon will recoil slightly faster. There is also less air resistance keeping the weapon from recoiling, or you from moving backwards. Although at the same time, having no atmosphere would likely decrease the chamber pressure on firing.

With no athmosphere and lower gravity there are also fewer outside forces to counteract inertia after firing, so the gun and you behind it will move farther back, and retain your velocities for longer.
Click to expand...

This is sarcasm, right?
 
There is no atmosphere on the moon, so the projectile will come out at a higher velocity (for every action their is an equal but opposite reaction) since the projectile comes out slightly faster, the weapon will recoil slightly faster.
Click to expand...

Nah. The lack of atmosphere in the barrel ahead of the bullet might provide another 2-3 fps...but it wouldn't have an effect on recoil. The level of recoil isn't determined by the muzzle velocity. It's determined by the rate of acceleration and the force required to achieve that rate of acceleration.


Since the air plug in the barrel is absent, the force requirement would drop...making the actual recoil force...remember that equal/opposite thing...lower. Of course, you'd need an instrument that cost upward of a few million dollars to measure the difference...but that's about the long and the short of it.

Mass is mass. Friction is friction. Force forward is force backward. The lack of gravity and/or atmosphere doesn't change any of those things.
 
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