best rifle for the moon
- Thread starter Ftom14cat
- Start date
Obviously the rounds are important, but I would be more concerned with the logistics of operating the weapon. Probably can't get your spacesuit covered finger inside the trigger guard on most guns. Can't bring a rifle to bear with that bulky helmet on. It would need to be a handgun of some kind without a trigger guard maybe.
hardworker
New member
Since it costs millions of dollars to launch every extra pound into space, I'm guessing a NAA 22 or ruger 380.
On the other hand, the inclusion of the minigun in Armageddon led to the sorts of space shenanigans no pistol could match.
On the other hand, the inclusion of the minigun in Armageddon led to the sorts of space shenanigans no pistol could match.
smoakingun
New member
ok, stop, there is no room here for for a pun that bad!
so im no math wiz..... but all this 1lb of pressure from atmosphere talk got me thinking.... wouldnt the amount of pressure on the round change drastically depending on the acceleration of the round down the barrel? i mean if we were talking constant velocity yes i see a constant value. but the speed of the round is not instantaneos... it starts at 0fps and leaves the barrel at say 3k fps. so if i remember my physics from college you need to be able to figure the acceleration of the round to find the force change between atmosphere and vacuum, as well as the static coefficients of friction from the barrel, and take into account the heat transfer to the barrel... yada yada... i really think achieving that 5k fps from black powder wouldnt be all that difficult. once you leave a gravity well wieght means nothing right? its all about mass... the mass of the mechanism doesnt change. but the mass of the atmosphere (or lack of it) inside the barrel does change. like i said, im no smart guy at all, just one who is now thinking to much at 4am when i should be asleep 
dang you TFL smarty pants!
dang you TFL smarty pants!Yeah and I think the 1lb is wrong also it would still be 14.7lbs it is a displacement of a column of air. The diameter of the column doesn't matter the static force always stays the same. If you took the barrel off of the gun and screwed a barometer to it. The pressure in the barrel will always read the same as the outside. The 14.7lbs of pressure will always have to be displaced before any movement can occur.
1lb of pressure is the pressure of what is exerted on the bullet surface outside the barrel. Inside the barrel the bullet is a piston and it will have to affect the entire pressure of the atmosphere.
1lb of pressure is the pressure of what is exerted on the bullet surface outside the barrel. Inside the barrel the bullet is a piston and it will have to affect the entire pressure of the atmosphere.
mapsjanhere
New member
The air in the barrel is absolutely negligible, it adds a quarter grain to the weight of the bullet.
That's 14.7 lbs per square inch. The frontal area of the bullet is quite a bit less than a square inch.... So, as a piston it only takes 1 lb of force to move a .308" piston against 14.7 lbs per square inch.
I come up with 0.55gr of air in the barrel, assuming a 30 caliber barrel 24" long at 60°F and 14.7psia. (Ignoring the volume taken up by the rifling, of course.) As the bullet accelerates down the barrel it does indeed compress the air in front of it, but I still hold that pressure to be negligible in comparison to the pressure behind the bullet. The pressure in front of the bullet is probably affected more by the propellant gasses that escape around it.
I come up with 0.55gr of air in the barrel, assuming a 30 caliber barrel 24" long at 60°F and 14.7psia. (Ignoring the volume taken up by the rifling, of course.) As the bullet accelerates down the barrel it does indeed compress the air in front of it, but I still hold that pressure to be negligible in comparison to the pressure behind the bullet. The pressure in front of the bullet is probably affected more by the propellant gasses that escape around it.
Brian Pfleuger
Moderator Emeritus
There is some force required to compress the air in the barrel as the bullet accelerates to supersonic speeds. The physics and equations of which are beyond me. Fluid dynamics, I suspect. Back in college I'm sure I wouldn't have had any trouble but that's back a few years.
This whole discussion is VASTLY simplified. There are numerous variables that we are completely ignoring, intentionally or otherwise. I can guarantee that the minuscule amount of air (and its pressure) absent from the barrel is entirely irrelevant given all those other variables that are completely ignored.
Temperatures on the moon can fluctuate from -245F to +225F, more or less.
What about the expansion/contraction of the barrel in super-hot or super-cold conditions of space? The difference between the expansion/contraction of the copper/lead bullet vs the steel barrel?
The performance of the primer or powder under those conditions?
Would normal springs even work at -245?
Anyway, the air in the barrel is irrelevant.
This whole discussion is VASTLY simplified. There are numerous variables that we are completely ignoring, intentionally or otherwise. I can guarantee that the minuscule amount of air (and its pressure) absent from the barrel is entirely irrelevant given all those other variables that are completely ignored.
Temperatures on the moon can fluctuate from -245F to +225F, more or less.
What about the expansion/contraction of the barrel in super-hot or super-cold conditions of space? The difference between the expansion/contraction of the copper/lead bullet vs the steel barrel?
The performance of the primer or powder under those conditions?
Would normal springs even work at -245?
Anyway, the air in the barrel is irrelevant.
Jim Watson had it right regarding the gunpowder on moon. Its deflagration.
wood + air (O2) = burning, combustion reaction takes place by heat transfer. It's the same reaction as gunpowder but between two different compounds.
Gunpowder (both black and smokeless) carries its own oxygen bound to the molecule as -O-NO2 moieties. This moiety when excited by heat transfer oxidises the carbon and hydrogen within the molecule.
High explosives are the same (smokeless powder will act as one) but instead of deflagration with the reaction at a flame front, detonation happens at a shock front and is much faster. The pressure wave excites the molecules into reforming into gaseous products with release if energy to propagate the reaction.
So with that said I believe the cartridges would need to be sealed to prevent gas (air) leakage into the vacuum, as the transfer of heat is influenced by the medium it acts through and within a cartridge the deflagration will act quite a bit different with no atmosphere and may give rise to duds.
Mleake1 is right about no added recoil, even less felt recoil. The downward force is less but horizontal the same, the mass and inertia governs the recoil not weight and gravity .
Chamber pressure will be lower as there is no atmosphere to push out of barrel though this eggect is minimal and may be countered by the lubrication effect of air (or lack thereof). Ballistic coefficient of the bullet is of no concern as well. So velocity retention is excellent, thus a big slow moving .44 or more would do the trick.
wood + air (O2) = burning, combustion reaction takes place by heat transfer. It's the same reaction as gunpowder but between two different compounds.
Gunpowder (both black and smokeless) carries its own oxygen bound to the molecule as -O-NO2 moieties. This moiety when excited by heat transfer oxidises the carbon and hydrogen within the molecule.
High explosives are the same (smokeless powder will act as one) but instead of deflagration with the reaction at a flame front, detonation happens at a shock front and is much faster. The pressure wave excites the molecules into reforming into gaseous products with release if energy to propagate the reaction.
So with that said I believe the cartridges would need to be sealed to prevent gas (air) leakage into the vacuum, as the transfer of heat is influenced by the medium it acts through and within a cartridge the deflagration will act quite a bit different with no atmosphere and may give rise to duds.
Mleake1 is right about no added recoil, even less felt recoil. The downward force is less but horizontal the same, the mass and inertia governs the recoil not weight and gravity .
Chamber pressure will be lower as there is no atmosphere to push out of barrel though this eggect is minimal and may be countered by the lubrication effect of air (or lack thereof). Ballistic coefficient of the bullet is of no concern as well. So velocity retention is excellent, thus a big slow moving .44 or more would do the trick.
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hardworker
New member
The problem with shooting guns in a no air atmosphere is the heat. There's no air to dissipate the heat from the gun, and solar radiation with no atmosphere to absorb it will make a gun get really hot as well.
The air in the bore is a barrel obstruction. In order to accelerate the bullet to 4000 fps, you also have to accelerate the air in the bore, or a large percentage of it, to 4000 fps.
It takes about 19 ft-lb of energy to accelerate .55 grains of air to 4000 fps so if you had a two ft long barrel, the average force on the front of the bullet would be about 9.5 pounds.
Still, insignificant.
Maybe someone with a high powered rifle, a chronogragh, a tank of helium, a place to shoot, and a lot of time on his hands could compare velocities of an air filled bore to the velocities of a helium filled bore. I bet the velocity difference would be far less than the normal shot to shot variations.
hardworker
New member
http://www.coolsciencefacts.com/2006/metal.html
Another problem. Guns are made of metal. Normally, metal has thin coating of oxidation on it. That keeps it from rusting. The oxygen in the atmosphere does it. In space, with no air, metal won't have that layer. And since the heat or cold would wreak havoc on lubrication, I'd bet you'd have a lot of metal-metal contact.
Another problem. Guns are made of metal. Normally, metal has thin coating of oxidation on it. That keeps it from rusting. The oxygen in the atmosphere does it. In space, with no air, metal won't have that layer. And since the heat or cold would wreak havoc on lubrication, I'd bet you'd have a lot of metal-metal contact.