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Re: O/T for you science buffs
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Posted by IT CAN BE DONE on November 09, 2003 at 10:17:16 from (12.222.30.13):
In Reply to: O/T for you science buffs posted by Jonathan on November 07, 2003 at 08:40:49:
The round can land at a speed equal to its muzzle velocity - and in real earth conditions. The trick is to use a different sort of gun, with a very slippery round, and get most of the return acceleration done before you hit dense atmosphere - and build the gun the same way you'd build a good tractor engine. A little background first: In posts below, I've run ballistics formulas and 32 ft./sec./sec. formulas in a spreadsheet and found the normal ballistics you get from www.remington.com give you 2500 to 3500 fps out of the muzzle with 2500 to 4000 ft. lbs. of "torque" on a 40 to 200 grain round that has .21 to .50 drag coefficient from a 24" barrel. It goes up a mile or two, gets to 0mph and falls at 32 ft./sec/sec. Usually the result is 200 to 300 fps when it hits. If you make goofy assumptions like no atmosphere but still 1G earth gravity and set drag coefficent to 0, you can get bullets flying up 20 or 30 miles - but they still land 100 or 200 fps short of 0 atmosphere muzzle velocity speed. If you go to the moon, they fly real well at .2G moon gravity, but you're bit on the backside as .2G = .2*32ft/sec/sec. You need more distance going up, or in other words, a more powerful gun. Then I remembered something I'd read about Gerald Bull and super guns, and realized it can be, and actually has been done. The method even has something to do with old tractors. Think of the bullet as a tractor piston, and the gun barrel as a tractor cylinder. The tractor has piston rings, but they're missing in the gun. Bull figured out a few things, one of them was adding piston rings to the gun. He took a device that sealed to the barrel and placed a round about 80% the size of the bore inside it. The device is formed in two parts, so it falls away after the round has left the muzzle, while the light sub caliber round keeps going. Guys who hunt with .50 cal black powder can find basically the same thing in their sabot rounds. Next trick was that with those "piston rings", the bullet doesn't need to be shaped to seal to the barrel. Heck with boattail rounds, he shaped his bullet to look something like a football. Instead of the .2 to .5 aerodynamic drag you're used to seeing in ballistics charts (or cars and trucks) this thing has a coefficient approaching .1. In other words it slips throught he air with the greatest of ease. Last trick was increasing torque. A longer stroke engine increases torque, right? Same trick with a long barrel gun. The same .44 caliber round has more punch when fired from a Remington rifle than it does from a Colt pistol. Reason is that you use more of the explosion energy to push the round, and less of it escapes at the muzzle. Enter Uncle Sam who's looking for a cheap way to get extra supplies up to astronauts. They hire Bull to design a super gun which would go up 100 miles then fire a small rocket to reach low orbit. They take two 16 inch naval guns, weld them together, and get a barrel about 100 feet long. Ship it to Arizona, and point it straight up. Insert the football shaped round they call a Martlett inside the piston rings or sabot, and pull the trigger. In Nov. 1966, they got a 185 lb Martlett to an altitude of 111 miles. It falls at least 90 miles at 32 ft/sec/sec before it encounters much atmosphere - and ends up hitting faster than when it left the barrel. Don't try this at home, as you're likely to end up demolishing your house. And don't be Gerald Bull, as he got assassinated for hiring out to a guy named Hussein. The point is something most tractor guys already suspect; you can do most anything with a bit more power.
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