Scientific/Stupid Question

Ok, I'm just wondering.
A gun's firing relies on the explosion of a cartridge/bullet/rocket fire Right?
How can this be possible in space, there is no oxygen for the gun powder to burn.
Ok, so mars has some atmosphere, but very little.
Just a reality check, unless you can explain to me how firearms can work in very little or no atmosphere.

The gun will fire , gunpowder contains Oxygen, the only problem is in space the projectile will leave the gun at x-mph while you are propelled in other direction at y-mph :)

You didn't seem to have a problem with all of the gun's functionality underwater in Q3A.

Bullet's aren't jammed full of gunpowder there's also some air inside to ensure ignition.

fodders said:

The gun will fire , gunpowder contains Oxygen, the only problem is in space the projectile will leave the gun at x-mph while you are propelled in other direction at y-mph :)

OOOhhhhh, thanx physics boy

Well considering that nothing burns in Mars' atmosphere because its pure CO2, the explosion wouldn't happen unless there was some sort of supply of oxygen. When it _does_ go off, there would be a hell of a recoil cause Mars has like half our gravity. As for fodders down there, gunpowder does not have oxygen in it. Gases will only dissolve in certain solids. That is, unless, if your gunpowder is this foamy shit.

elyuca said:

OOOhhhhh, thanx physics boy

Yeah, that law of physics has only been known for 300 years, physics boy must be a real science nerd.

it just works ok!
leave me alone!

If you are asking about how the guns fired in the bases of Doom1 - obviously the buildings have been pressurized and oxygenized or else humans couldn't have worked there in the first place. So they made it like earth atmosphere. Or maybe the UAC changed the whole planet structure, or built an air shield above the bases.

deadnail said:

You didn't seem to have a problem with all of the gun's functionality underwater in Q3A.

Bullet's aren't jammed full of gunpowder there's also some air inside to ensure ignition.

Hmmm. Are bullets usually perfectly airtight though? If they are not, then the primer would have no way to spark.

Perhaps it could be a shotgun fueled by oxygen much the same way a flamethrower is fueled by gas. Hmmm...that could be a new Doom 3 weapon...oxygen powered shotgun...joy!

OK, not to many physics graduates on this board today eh ;) ?

Bullets/rockets/grenades etc all have a cself contained propellent. Simple example is gunpowder. Contains Sulphur/carbon/Potassium nitrate. The nitrate group breaks down to release oxygen (which as you point out, is lacking in space)
which is then oxidized in the following burn/explosion. This is how rockets in space work though typically they take along liquid oxygen to burn with the liquid hydrogen.
So....if you fire you 10 mm G20 on the surface of mars, what will you notice? Nothing!! You may 'feel' a little more recoil due to the fact that the you are not anchored so well to the surface due to low gravity and the bullet will exit the gun at a slightly higer velocity because there is no air in the barrel to resist the bullet. Also the report would sound somewhat different due to the nature of the thin air.

Is that OK...or do you want more detail?

Errrmm isn't that what I said in 1st reply, minus all the waffle?
And as he said "in space" there is no gravity and the vacuum would ensure no sound
".. Also the report would sound somewhat different due to the nature of the thin air.
"

Psyonisis said:

As for fodders down there, gunpowder does not have oxygen in it. Gases will only dissolve in certain solids.

"gunpowder. Contains Sulphur/carbon/Potassium nitrate. The nitrate group breaks down to release oxygen ....which is then oxidized in the following burn/explosion"

Psyonisis said:

Well considering that nothing burns in Mars' atmosphere because its pure CO2, the explosion wouldn't happen unless there was some sort of supply of oxygen. When it _does_ go off, there would be a hell of a recoil cause Mars has like half our gravity. As for fodders down there, gunpowder does not have oxygen in it. Gases will only dissolve in certain solids. That is, unless, if your gunpowder is this foamy shit.

Errrmmm, actually you will find that recoil is completely independent of the gravitational field. Eg interstella space or at the surface of the sun, recoil is the same. This is due to a basic law called 'conservation of linear momentum'. You may 'feel' like the recoil is a little higher due to the fact that you weight less on the surface of mars, ie, you are not anchored as well as you are on earth. And like the other dude (fodders) said, gunpowder has its own oxygen. Same thing goes for the bullet primer (more or less).

Also, some guns which strong chamber/barrels can shoot underwater. Certain Glocks can.

fodders said:

"gunpowder. Contains Sulphur/carbon/Potassium nitrate. The nitrate group breaks down to release oxygen ....which is then oxidized in the following burn/explosion"

If I remember correctly the recipie is 1 part sulphur, 1 part carbon, six parts potassium nitrate. Best results when you "corn" it. That is you grind up the ingredients into as fine a powder as possible, mix with water into a thick paste, then let it dry.

Kaboom........ :)

Don't try this a home kids. Really, it's dangerous. You may not live to regret it.

Correct me if I'm wrong, but doesn't the first ep. of Doom take place on a MOON of Mars? Phobos? Then it would be a different story. And the second and third eps. are in Hell, with the second one being on a moon (Deimos) teleported to Hell. Anyway, the first episode is the only one really in question, and it's pretty logical that the humans would treat the atmosphere, though it would take years, so they could live there. By the way, I love these post here on this topic! They're very interesting!

stphrz said:

Don't try this a home kids. Really, it's dangerous. You may not live to regret it.

:) I remember son downloading hackers handbook when he was about12 and read how to make own explosives and was "off to the kitchen" to see if we had the stuff in :)We had to have a serious talk that day

fodders said:

"gunpowder. Contains Sulphur/carbon/Potassium nitrate. The nitrate group breaks down to release oxygen ....which is then oxidized in the following burn/explosion"

talking of gun powder.....
(kinda doom related)
in EVIL DEAD 3 (the army of darkness)
How dose ash make gunpower by looking in chemistry 101?
I've looked and it's just not in there!

This is because gunpowder doesn't "Burn" par-se.

Gunpowder endures a rapid decomposition from a solid material into a gaseous one. Since Gases all have the same density, but solid materials do not, when the solid materials are turned into gases they expand.

Gunpowder doesn't burn like a fire, it burns like a block of C4 (and C4 can blow up anywhere, even at the bottom of the ocean or in the depths of space - provided you run electricity through it).

There are two kinds of explosives:
Anaerobic (doesn't require air or any other material as a medium).
And Aerobic (requires air or some medium to combust in).

They both share in common that you need something to set them off (such as heat, electricity, percussion, etc.), but the difference is that one kind can detonate anywhere, and the other kind must have access to some other fuel to work.


Anaerobic Explosives:
C4, Dynamite, Primer Cord, gunpowder, titanium dust, etc. (and maybe if you're lucky - napalm)

Aerobic Explosives:
Gasoline, Alcohol, Grain-Dust (grain elevators have blown up over this!), wood (not really an explosive, but does burn).

The only reason why air is in the bullet casing is for storage purposes, and it does give the expanding gunpowder gas a head start (the volume is already filled, doesn't have to fill the volume of the casing before propelling bullet).

In space the gunpowder would actually fire BETTER thna on the ground becasue there is no air in the way that the bullet would have to push aside - gunpowder does not require oxygen to burn (actually it makes oxygen and a host of other gasses like methane and CO2).


If you fire a gun, here is what happens:
We will say the Total bullet energy of a certain cartridge is 2000 Joules (about as much as a 5.56 NATO round has).

Since the explosion of the gunpowder happens in all directions, and since it is contained by the barrel, it will expand forward and backward (which is two directions). Since it runs into something backwards it pushes on it. Thus 1/2 of the bullet energy goes into the bullet itself, and 1/2 half of the bullet energy goes into YOU (or whoever is holding the gun).

The reason why the gun doesnt hurt you like the bulelt hurts the target is because the bullet on average only weighs about 10 grams, but the gun may weigh upwards of 3000 grams so it goes backwards at you much much slower). In addition the stock or the handgrip has much larger area than the bullet does - which allows the enrgy to be spread over a wide area.

The bullet goes way faster than the gun because it weighs alot less, and it does damage to the target because it is shaped like a needle and has little surface area to stop it - it has alot of energy and the area it covers is quite small, which means that it doesn't have much material to punch through.

If you think of it, a bullet (generally speaking) actually has about the same energy as a 1lb rock that you or I could throw.

If you can punch something as hard as a gun stock hits you, you are giving off about as much energy as a bullet fired by that gun. Imagine having a long and thin spike in your hand like a gauntlet or something, and imagine how deep you could shove the thing if you punched with it your hardest - it would probably go farther into whatever you puched than a rifle bullet.
-----

I don't see how fires can happen on mars because oxygen is aobut nil (hint: explosives like gunpowder and C4 can explode anywhere).

"We will say the Total bullet energy of a certain cartridge is 2000 Joules (about as much as a 5.56 NATO round has).

Since the explosion of the gunpowder happens in all directions, and since it is contained by the barrel, it will expand forward and backward (which is two directions). Since it runs into something backwards it pushes on it. Thus 1/2 of the bullet energy goes into the bullet itself, and 1/2 half of the bullet energy goes into YOU (or whoever is holding the gun)."

This is good except for the energy part. If fact you recieve via the gun butt or handle the same change in momentum as the bullet that leaves the barrel. That is to say (assuming person and gun are still to start with) and we are dealing with magnitudes as momentum is a vector

M(p)xV(p) = M(b)xV(b). ....................................(1)

Where V is velocity, M mass and p and b assign to either the Bullet or the person.

So the Kinetic Energy of the bullet is

KE(b)= 0.5 x M(b)x V(b)^2 .......(KE equation)..............(2)

But what energy does the gun(and person) recieve approximately?

From Eq (1) we find the gun/person velocity

V(p)=( M(b) x V(b) )/M(p)...................................(3)

and so the KE of the person is

KE(p)=0.5 x M(p) x ( V(p) ) where V(p) is given above in (3)

This leads to

KE(p) = 0.5 x( M(b)^2 x V(b)^2 ) / M(p)......................(4)

So the ratio of the KE(p) to KE(b) is given by

KE(p):KE(b) = M(b):M(p)

SO, you can see that because generally M(b) << M(p) then in fact most of the Kinetic energy of the explosion is carried away by the bullet. This is a good(or bad depending on your firearms stance) thing otherwise our firearms would be less effective and we would recieve more kinetic energy to our body. This all comes about because of the squared dependence of Kinetic energy on velocity. If it was linear like momentum then we would recieve the same energy as the bullet.

Fin.

All the fancy-ass replies to this if edited and had geek ratio reduced by 300% would end up with my original reply......... "The gun will fire , gunpowder contains Oxygen, the only problem is in space the projectile will leave the gun at x-mph while you are propelled in other direction at y-mph" :)