Bullet In Space

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Kind of a neat story about firing a gun in space, with an item about the effect of the expanding universe on a bullet.

http://news.yahoo.com/happen-shot-gun-s ... 10543.html

Hmm, A few glaring errors in that one.

Nope. You will only get a sphere if the gas is free to expand in all directions at the moment of explosion. If you fire a gun the gases leave the barrel at high speed in one direction. The resulting smoke trail is more likely to be a sort of sausage shape.

Huh? Fired from where? If you fired from earth orbit you would have to be extremely accurate to get anywhere near Jupiter. Of course you would also have to remember to fire at the point where Jupiter will be when the bullet reaches it roughly 60 - 100 years later.

Redacted

Last edited by nat4200 on 21 Apr 2012, 12:50 am, edited 1 time in total.

Actually, thinking about it, this would be pretty difficult. If you fire the gun in the same direction that you are orbiting the bullet will move up into a higher orbit than you. If you fire it in the opposite direction it will move into a lower orbit. If you fire at right angles the bullet will orbit in a different direction and I don't think it would ever cross your path but I have to admit I'm not sure of that one.

Here's a bit of a mind mangler. What happens if you fire straight down? I think it would just enter a lower orbit rather than hitting the earth.

A gun has been fired in space. The last cosmonaut to leave Salyut 3 fired the a 23 to 30mm gun that was affixed to the space station. Apparently other than a slight vibration, not much happened.

The idea of the expanding universe affecting the frequency of gas molecule/bullet collisions is interesting though. I wonder how true it is.

It would slow down and burn up in the atmosphere just like a tiny meteor.

That is the obvious answer however orbital mechanics can be really counter intuitive. You also need to keep in mind that the speed of a bullet (usually just under the speed of sound) is pretty low compared to orbital velocity (around 22 times the speed of sound or more).

I did some research on this and apparently the correct answer is that it would probably enter an elliptical orbit. Even weirder is that although you fired down, on average it will end up higher than you!

This link and this link explain more about orbits but you do need to wade through some maths.

I was thinking more like 20,000 mph. My bad.

My ancient computer cant get the site.

Pistol bullets maybe subsonic but a rifle bullet travels at half a mile a second ( about mach 2). Still nowhere near orbital velocity, much less escape velocity from the Earth.

The bullet from an infantryman's rifle and the projectlle fired by a two hundred ton fifty caliber sixteen inch naval gun from the Battleship Missouri that wieghs 2700 pounds (the wieght of a small car) have practically that same muzzle velocity of half of a mile a second.
The battleship guns are also rifled.

If the earth had no atmosphere both guns would have the same range of several dozen miles. But with the existing atmosphere the infantry bullet goes about one mile, and the naval gun has a range of 23 miles because the more massive projectile is less effected by drag from the atmosphere.

Forget about firing level for maximum range for a moment, but just shooting straight up.

Take the handheld rife, the naval gun, and a gun from a modern M-1 tank ( which fires kinetic energy projectiles at more than a whole mile a second). And aim each one straight up. Lets try it on the Moon.

The army rifle and the naval gun projectiles would both reach an altiitude of 30 miles if it were on an atmosphere free earth, but on the moon which has only one sixth the gravity ( and no really does have virtually no atmosphere) they would both reach 180 miles above the Moon's surface. The M1 shell would reach 360 miles about the surface fo the 2000 mile wide moon. Almost but not enough to escape the moon completely. Or atleast that would be my guess.