Electric Politics | A Small Brainstorm

U.S. Navy railgun test 2008 So there I was the other night with insomnia, considering what ammunition for a rail gun of the future might look like. And it occurred to me, projectiles that move fast for great distances through the atmosphere must encounter friction drag in a similar way to that experienced by submarines, whales, or competitive swimmers. Why is it, then, that bullet casings, artillery shells, and even rocket cones are smooth? So here's an idea that may have some practical (though deadly) applications — my cursory searches of Google and the U.S. Patent and Trademark Office's database suggest it's an unknown idea that hasn't been patented: if any EP reader wants to spend a few hundred bucks trying to patent it, go right ahead, and if you later make millions licensing it to the military I'd appreciate a large donation.

For a while now scientists have realized that friction drag in water can be reduced by making surfaces microscopically knobby and irregular. The same principle holds for the latest submarine coatings, knobby whale flippers, and the new super competition swim skins (most recently used at the Beijing Olympics). Having a small degree of turbulence at the interface between an object moving through water and the water itself helps create a laminar flow, reducing drag. The principle has been tried in aircraft as well, and from my quick review through Google evidently will reduce drag by about 5-10%. The problem with adding a coating to an aircraft wing, however, appears to be that the costs of cleaning it exceed the benefits. The point being, nevertheless, that moving an object at high speeds through the atmosphere creates a very similar set of problems to that of moving more slowly through water.

I would suppose that the costs of trying to machine small dimples and/or stipples on an ordinary bullet casing could well exceed any benefits from increased accuracy or speed. That would be true, certainly, for ammunition used in a typical fire fight. But not necessarily true for longer range targets — if dimples/stipples on a bullet casing improved accuracy by a few inches at one hundred yards it might indeed be very useful. Or by a few feet for tank or artillery shells at longer ranges.

If you have too much time on your hands and feel like plunking down several hundred bucks to apply for a patent, go for it! And if I'm right and the idea hasn't yet been patented I'd guess that you could find a bullet manufacturer somewhere willing to develop some test prototypes on spec for the military market. It's an unknown whether the cost/benefit for any found efficiency would be worth it, but if it were this is a potentially valuable idea.

I'd start the patent process myself but I don't have enough time to write the patent application up properly and I have some ethical reservations about making money from military technology.

Or I just may be full of crap. For all I know there are lots of engineering reasons why the principle of modulated turbulence to improve laminar flow doesn't apply to bullets, shells, and so forth. Hard to say...

Comments

Golf balls are the practical application. With stuff that go supersonic and or beyond stratospheric, it probably will not make a difference.

Posted by: YY | October 28, 2008 11:10 PM

Bizarrely enough, I was just thinking on this the other day but in relation to slower moving objects such as cars and trucks where the dimples may provide a reduction in drag to produce a reduction in fuel consumption. Maybe on just the leading edges would be enough. A new automotive styling trend for the hybrid driving hypermilers.

I am not an aeronautical engineer but I recall that above supersonic, the shock wave that extends from the tip of the bullet, missile, or artillery shell may alter most or all of the rules of aerodynamics and render the dimples effectively useless.

An interesting analogy is the Russian "supersonic" rocket powered torpedo Shkval (the one suspected of sinking the Kursk) that emits a jet of compressed air from its tip to create a cocoon of bubbles around itself, called supercavitation, to effectively eliminate the drag from water and increase its speed by up to 200 knots. This process is also used in US anti-mine artillery shells to penetrate 50 to 100 feet into the water to detonate mines. The tip of the shell has a specially shaped indentation to trap some air when it hits the water and release these bubbles for the trip from the surface to the mine.

Unfortunately using air to reduce the drag of air doesn't help. Perhaps some other material such as a gas plasma might be effective ...

[Thanks, Andy — I know you're an excellent engineer. And, btw, I was considering an image of the Shkval for this item!]

Posted by: Andy Schiltz | November 4, 2008 10:04 PM

Name

Email Address

URL

Remember personal info?

Comments (You may use HTML tags for style)



Home FAQ Contact Archive EP Store EP Alerts © 2012 ElectricPolitics	A Small Brainstorm So there I was the other night with insomnia, considering what ammunition for a rail gun of the future might look like. And it occurred to me, projectiles that move fast for great distances through the atmosphere must encounter friction drag in a similar way to that experienced by submarines, whales, or competitive swimmers. Why is it, then, that bullet casings, artillery shells, and even rocket cones are smooth? So here's an idea that may have some practical (though deadly) applications — my cursory searches of Google and the U.S. Patent and Trademark Office's database suggest it's an unknown idea that hasn't been patented: if any EP reader wants to spend a few hundred bucks trying to patent it, go right ahead, and if you later make millions licensing it to the military I'd appreciate a large donation. For a while now scientists have realized that friction drag in water can be reduced by making surfaces microscopically knobby and irregular. The same principle holds for the latest submarine coatings, knobby whale flippers, and the new super competition swim skins (most recently used at the Beijing Olympics). Having a small degree of turbulence at the interface between an object moving through water and the water itself helps create a laminar flow, reducing drag. The principle has been tried in aircraft as well, and from my quick review through Google evidently will reduce drag by about 5-10%. The problem with adding a coating to an aircraft wing, however, appears to be that the costs of cleaning it exceed the benefits. The point being, nevertheless, that moving an object at high speeds through the atmosphere creates a very similar set of problems to that of moving more slowly through water. I would suppose that the costs of trying to machine small dimples and/or stipples on an ordinary bullet casing could well exceed any benefits from increased accuracy or speed. That would be true, certainly, for ammunition used in a typical fire fight. But not necessarily true for longer range targets — if dimples/stipples on a bullet casing improved accuracy by a few inches at one hundred yards it might indeed be very useful. Or by a few feet for tank or artillery shells at longer ranges. If you have too much time on your hands and feel like plunking down several hundred bucks to apply for a patent, go for it! And if I'm right and the idea hasn't yet been patented I'd guess that you could find a bullet manufacturer somewhere willing to develop some test prototypes on spec for the military market. It's an unknown whether the cost/benefit for any found efficiency would be worth it, but if it were this is a potentially valuable idea. I'd start the patent process myself but I don't have enough time to write the patent application up properly and I have some ethical reservations about making money from military technology. Or I just may be full of crap. For all I know there are lots of engineering reasons why the principle of modulated turbulence to improve laminar flow doesn't apply to bullets, shells, and so forth. Hard to say... Posted by George Kenney on October 28, 2008 4:37 PM « The World's Best Potato Chip \| Main \| ✘ EP for Obama ✘ » Share this post: Comments Golf balls are the practical application. With stuff that go supersonic and or beyond stratospheric, it probably will not make a difference. Posted by: YY \| October 28, 2008 11:10 PM Bizarrely enough, I was just thinking on this the other day but in relation to slower moving objects such as cars and trucks where the dimples may provide a reduction in drag to produce a reduction in fuel consumption. Maybe on just the leading edges would be enough. A new automotive styling trend for the hybrid driving hypermilers. I am not an aeronautical engineer but I recall that above supersonic, the shock wave that extends from the tip of the bullet, missile, or artillery shell may alter most or all of the rules of aerodynamics and render the dimples effectively useless. An interesting analogy is the Russian "supersonic" rocket powered torpedo Shkval (the one suspected of sinking the Kursk) that emits a jet of compressed air from its tip to create a cocoon of bubbles around itself, called supercavitation, to effectively eliminate the drag from water and increase its speed by up to 200 knots. This process is also used in US anti-mine artillery shells to penetrate 50 to 100 feet into the water to detonate mines. The tip of the shell has a specially shaped indentation to trap some air when it hits the water and release these bubbles for the trip from the surface to the mine. Unfortunately using air to reduce the drag of air doesn't help. Perhaps some other material such as a gas plasma might be effective ... [Thanks, Andy — I know you're an excellent engineer. And, btw, I was considering an image of the Shkval for this item!] Posted by: Andy Schiltz \| November 4, 2008 10:04 PM Leave a comment Name Email Address URL Remember personal info? Comments (You may use HTML tags for style)

A Small Brainstorm

Comments

Leave a comment