interesting things i learned

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captneil19

New member
in talking with my friend who works for nasa ,he told me that they actually fired a rifle on the moon,he never said what caliber but he said the fps was 3,200 on earth.Check this out,on the moon they calculated it to be 160,000fps.He also said sound dont travel,theres no drag,an if you were to shoot it straight up when it hit ,it would make a small crater.Can you imagine that,can you imagine aiming at a target an pulling the trigger knowing the bullet is travelling that fast at the target,can you imagine what it will do to it ??

I also asked him how fast does a bullet have to be traveling to melt it.He said 6,000 fps.At 5,000 it starts tearing apart an pealing back ,at 6,000 total liquid
The most I have ever seen is 4,200 fps,an that was with a 22/250 30 grain has anyone seen better or more

I cant see no use in achieving that speed,but im sure there are some knuckle heads trying to get there.First of all the liquid wouldn't reach the target.
The faster the bullet reaches the target the faster you see you messed up lol
 
Check this out,on the moon they calculated it to be 160,000fps.
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That right there proves that it's complete nonsense.

The velocity of the bullet comes from the conversion of the chemical potential energy of the powder into kinetic energy.

The location of that conversion is completely irrelevant. A rifle that fired 3,200fps on earth would fire 3,200fps on the moon, with perhaps a slight difference given that there's no air to push out of the barrel. I assume that variable would be inconsequential, as in undetectable.

He's also full of it about bullet max speeds. Several folks have exceeded 5,000fps (.22-250AI and Middle-stead) and nothing spectacular happens to most bullets. My own handloads exceed 4,400fps.

Also, the escape velocity of the moon is about 7,900fps. Any bullet fired straight up at a speed higher than that would NEVER come back.
 
As far as I know, no one has ever fired a gun on the moon.

Hit a golf ball yes. Gun, no.

Regarding the velocity? Absolutely not.

Velocity is dictated by the expansion of gas while in the barrel. That happens at a set speed, which isn't affected by the lack of gravity. If a bullet leaves the barrel at 1,000 feet per second on earth, it's going to be very close to that velocity on the moon.

What WILL change, however, is the bullet's range, its trajectory, and its velocity over distance.

Because of the moon's much weaker gravity and the lack of atmosphere the bullet won't slow down nearly as quickly, nor will it "fall" to the surface of the moon nearly as quickly.

It's very possible that a bullet's range on the moon can be measured not just in feet or yards, but in tens of miles.
 
captneil19 said:
in talking with my friend who works for nasa
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I REALLY, REALLY hope that he works for NASA in something like the housekeeping department, because his technical knowledge is pretty much zero.

Several years ago I was involved with some rail gun tests where the projectile velocity was over 8,000 FPS. Never managed to melt anything. The gun was designed for a projectile velocity of about 20,000 FPS, don't know what they finally reached.

The Yugoslavians had a railgun that would deliver about 10,000 FPS back in the 1980's, 25 or 30 years ago.
 
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Capt,

Just for grins and giggles I just called a friend of mine and described your post to her.

Sorry to say, but she chuckled at your friend's assertions. She says your friend may work for NASA, but that there are a lot of people who work for NASA who don't know diddly about this sort of stuff.

My friend, however, literally DOES work for NASA, and in a position to know about stuff like this.

She has her doctorate in physics and is literally a rocket scientist working at NASA's Goddard Space Flight Center, working on unmanned satellites and the like.
 
"Several years ago I was involved with some rail gun tests where the projectile velocity was over 8,000 FPS. Never managed to melt anything. The gun was designed for a projectile velocity of about 20,000 FPS, don't know what they finally reached."

One of the guys I worked with at my current company was, while in the Navy, involved in investigating how to destroy rogue satellites that posed a danger of coming back to earth.

He was with the team that was investigating rail gun technology. They ended up getting a scrap satellite that had been built but for some reason never launched, and they fired roughly a 1 pound slug at it at 12,000 or so feet per section (IIRC), or something over 2 million foot pounds of energy.

The film he showed me was absolutely staggering. He said that from a 3 ton satellite, the largest piece they recovered was less than 100 pounds, and they found some pieces nearly a mile away from the test range.

Nearly everything they found was burned or scorched to some degree because of the plasma wash.

He had a big chunk of it mounted on a plaque on his wall, and you could actually see where the aluminum started to melt.
 
160,000fps is not going to happen, but I would expect some increase in velocity due to lack of air (gas) pressure on one side of the projectile in the barrel. Interesting fluids problem for someone with the time.
 
but I would expect some increase in velocity due to lack of air (gas) pressure on one side of the projectile in the barrel.
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Just for the heck of it, I figured the volume of a 24" .308 barrel (24" in front of bullet) and then how much air (in grains) would be in that barrel at Standard Temperature and Pressure. It comes to 0.566gr.

The pressure is assumed to be 14.7psi.

Considering that a .30 caliber bullet is going to weight 150 grains or more and the cartridge is generating 55-65,000 psi, the presence or absence of 1/2gr of air and 14 psi is completely irrelevant.
 
You have it wrong, the bullet reached 186,235 fps and broke the time barrier. It went back in time and killed Kennedy. A second shot went back and killed the Archduke Ferdinand.

What a joke.
 
1/2gr of air and 14 psi is completely irrelevant.
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My mistake, I didn't make myself very clear. The problem isn't a closed system. This is a compressible flow calculation, not a simple mass displacement.
 
Yes, but the bullet only "cares" because it has to move that fluid out of the way.

Worst case scenario is if that fluid is incompressible (or essentially a solid), that the bullet has to push out of the way.

I don't believe that there's any significant difference in the results no matter how complicated we make the math.

Truthfully, it's going to be ridiculously complex (impossible, practically speaking) to get a "real" answer but I think it should be pretty obvious that we don't need a "real" answer.
 
I would also tend to think that, firing a gun on the moon would present another minor problem in physics: That of handling the recoil.
 
No, because recoil is a function of momentum, which does not change on the moon. It's related to mass, not weight. It'd be a problem out in space, where you have nothing to brace yourself against to stop the spinning but as long as your feet are on the ground it shouldn't matter.
 
I've actually disintegrated bullets right here on Earth.
A friend gave ma a box of 178? gr Hornady ammo specifically designed for 30-30. I loaded up a few in a .308 & they just left scattered debris & smudges on the target at 25 yards.
I think it was velocity & twist rate exceeding design specs though, not anything extra terrestrial.

Maybe your friend worked for the "North Hill Association for Speleological Advancment"?

They "borrowed" the NASA initials back n the 70's for a caving club so they could wear kewl shoulder patches:D
 
Velocity is dictated by the expansion of gas while in the barrel. That happens at a set speed, which isn't affected by the lack of gravity. If a bullet leaves the barrel at 1,000 feet per second on earth, it's going to be very close to that velocity on the moon.

What WILL change, however, is the bullet's range, its trajectory, and its velocity over distance.
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I disagree, to a degree.

Lack of gravity is not an accurate statement, there is gravity on the moon, there is a lack of atmosphere though. So you are firing in a vacuum.

How can you think the lack of atmosphere has no effect when you consider the effect of firing a rifle while submerged in water? We know that the pressure can be so great that the weapon can fail catastrophically. So the atmosphere does have an effect.

Now I am not saying that the guy's stories hold water. I am just calling you on this because, well, it's wrong. The environment is part of the conditions involved in the experiment.
 
Now I am not saying that the guy's stories hold water. I am just calling you on this because, well, it's wrong. The environment is part of the conditions involved in the experiment.
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The environment effects things AFTER the bullet leaves the barrel.

Yes, the water slows the bullets muzzle speed too but it is 800 times more dense than air and you notice that the gun still works normally. Even 800 times more "atmosphere" in the barrel doesn't make a tremendous change. The difference between atmospheric pressure on earth and NO atmosphere is essentially zero.

The bullet on the moon would exit the barrel at virtually the same speed as it would on earth. The differences are that the gravity is lower and it would not lose any speed (for all intents and purposes) until it hit something.
 
"Lack of gravity is not an accurate statement, there is gravity on the moon"

Lack of the same level of gravity as on earth. Still doesn't matter, though. If there were no gravity on the moon at all it still wouldn't affect the gun during firing. Should have been more precise.


"How can you think the lack of atmosphere has no effect when you consider the effect of firing a rifle while submerged in water? We know that the pressure can be so great that the weapon can fail catastrophically. So the atmosphere does have an effect."

Water is almost totally incompressible, and dozens if not hundreds of times denser and more resistant to things moving through it (drag) than atmosphere.

You're really attempting to compare apples to oranges in this case because no one is talking about firing a gun under water on the moon. You are, in fact, the first person to mention water.

Firearms have been fired in vacuum chambers, and the effects on the firing cycle (ignition to bullet leaving the barrel) itself are almost nil and generally can't be discerned from the normal variations that you get in muzzle velocity during normal firing in an earth atmosphere.

The effects on the bullet once it leaves the barrel and travels through a vacuum are far more significant.

My statement is correct as it pertains to the actual subject at hand.

I'm sure if we replaced the gaseous atmosphere with one of solid concrete there would be a different series of effects, as well, but again, those don't pertain to the conversation at hand.
 
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