Seems to me it would be cheaper to use compressed air cannons on the battlefield...if its possible.

This way an artillery crew could use one large compressor to operate several large cannons without the stress of deafening explosions.

We know its possible to hurl ten pound pumkins almost a mile using compressed air...

http://www.geocities.com/zbig10inch/

So why not artillery shells...which are vastly more aerodynamic!!!

Because Air cannons would probably cost more and would be more sophisticated. The cannons we use right now are ready for action at any given moment and are fairly simple, plus can be reloaded quickly. Plus has good reliability, a broken cannon would not be good fo you when your in a middle of a battle.

Because Air cannons would probably cost more and would be more sophisticated.
Yes, but the shells would be so much cheaper, having no propellent. All the weight could be used for the actual target explosive.

Seems to me it would be cheaper to use compressed air cannons on the battlefield...if its possible.

Portability. A compressor big enough to provide that kind of compression of air would be a damned big machine, not even counting the engine required to operate it.

I'm also pretty sure that the "explosive force" is not nearly so great as can be made with a shell full of powder. So not only is it difficult to maneuver, it's not as powerful.

Baron Max

Portability. A compressor big enough to provide that kind of compression of air would be a damned big machine, not even counting the engine required to operate it.

I'm also pretty sure that the "explosive force" is not nearly so great as can be made with a shell full of powder. So not only is it difficult to maneuver, it's not as powerful.
Aye, but we have compressors now that can manage up to 10,000 psi...and one compressor would serve several cannons.

The barrels might have to be longer, but a recoil mechanism wouldn't be neccessary.

the ability to easily relocate is very important.

We know its possible to hurl ten pound pumkins almost a mile using compressed air...

ten pounds at 0ne mile is a hell of a long way from a 500 pound artillery shell at 38 miles.

ten pounds at 0ne mile is a hell of a long way from a 500 pound artillery shell at 38 miles.
Thats a good point if your're considering self propelled shells...esp with a reload rate of three per minute!

without the stress of deafening explosions.
that deafening explosion is caused by air pressure. In the case of most cannons this pressure is caused by rapidly expanding gases, in the case of an air powered cannon... it will still be caused by the rapidly expanding gas.
Thus making an artillery shell air powered wont reduce noise.

Secondly, an air compressor requires energy which your going to have to store and transport, be it giant battery or fossil fuel generator or what, it doesnt matter.
Self propelled artillery shells store the energy in chemical form, and have the required amount of energy ready to go. Just load, arm, and fire.
A compressor would be much bigger, and require an equal amount of power. Unless it were nuclear powered, I doubt the fuel for the compressor would weight less than the chemical fuel powering todays shells.
What I mean is, if you took the weight of the 'gunpowder' on the shells, and the weight of eanough whatever fuel source you used for the compressor to fire the same amount of shell, the 'gunpowder' would weigh less.
Then the weight of the compressor and its generator would be an added setback.

Thus, todays self-propelled shells are compact, cheap, and easy to move around.

A compressor is big, expensive, hard to move, and could easily be destroyed. Imagine 1 armour peircing round incapacitating a whole artillery battery.

The barrels might have to be longer, but a recoil mechanism wouldn't be neccessary.
Why not? Are you familliar with Newton's laws? By conservation of momentum if I shoot a shell forward, something has to gain backward momentum...

EDIT: basicaly a compressed air cannon and a normal cannon work under the same principle: high pressure air rapidly expands forcing the projectile out of the barrel at high speed. The only difference is one uses a compressor to compress the air, the other makes use of an endothermic chemical reaction and Gay-Lussac's gas law.

-Andrew

You make some compelling points Andbna, however I would have thought that a compressed air release would be 'slightly' more gradual than a chemical explosion - hence the need for a longer barrel without an extending recoil mechanism.

You make some compelling points Andbna, however I would have thought that a compressed air release would be 'slightly' more gradual than a chemical explosion - hence the need for a longer barrel without an extending recoil mechanism.
I see, so more of a longer duration of a weaker force versus a short duration of a stronger force. It might work, though I would imagine they would still have some form of a recoil system in place. Also barrel friction becomes a factor, and then of course transportation again, if it's a long range gun the barrel will be pretty long already.

All in all I think the next weapon propulsion technology the military will adopt is going to be electromagnetic (rail) guns... though not for quite some time.
For recreaction however, compressed air seems to do quite a nice job on those pumpkins...

-Andrew

Yes, I believe the recoil mechanism on any barrel is simply there to make the instant of explosive gas expansion more gradual...so it doesnt simply blow up the barrel itself, or provide too much kick back.

Seems like a waste of energy.

Much of the energy of explosive chemical thrust is also wasted as heat.

The least wasteful kind of propulsion I imagine would the expansive force of super-cooled liquid nitrogen reverting to its gaseous state.

There actually is a type of gun that fires large ball bearings at an extremely rapid rate without explosives. It uses a motor to spin them around until they are flung out by centrifugal force.

Centrifugal weapon could deliver stealth firepower (http://www.newscientisttech.com/channel/tech/dn7365-centrifugal-weapon-could-deliver-stealth-firepower.html)