Centrifuge Weapons

Well, one of my friends passed me a link to the DREAD weapons system, a "revolutionary" system that obsoletes many firearms. It starts out with a great sales pitch.

The following article contains a link to the DREAD Weapon System Video. This is the first time this video has ever been shown to the public. The DREAD depicted in the video is a functional prototype that operates on a less-than-lethal mode. This prototype was dismantled for security purposes to protect the technology, after the making of this video. As of this posting, Defense Review (DefRev) is the ONLY publication in the WORLD that has any written materials or video footage, or any information whatsoever, for that matter, on this revolutionary new weapon system. You'll have to click on "Read More" (hypertext below) to view the complete article.

Oooo…. Sounds scary, doesn't it?

Imagine a gun with no recoil, no sound, no heat, no gunpowder, no visible firing signature (muzzle flash), and no stoppages or jams of any kind. Now imagine that this gun could fire .30 caliber and .50 caliber metal projectiles accurately at up to 8,000 fps (feet-per-second) with a variable/programmable cyclic rate of 30,000-120,000 rpm (rounds-per-minute), and enjoy a 360 degree field of fire. What if you could mount this weapon on any military Humvee (HMMWV), any helicopter/gunship, any armored personnel carrier (APC), and any other vehicle for which the technology were applicable?

It sound too good to be true, doesn't it? Well, although overall a pretty good idea the US Army Ordance Corps rejected it, and the rejection came during the Great War, also known as World War One. Of course, a decade prior to WW-I they rejected the electrically powered minigun, so their rejection doesn't say a whole lot about the utility of the idea. Their main complaint about the bearing flinger was that the diesel engine couldn't be manhandled through the trenches very easily. That earlier version flung half-inch ball bearings with a diesel powered centrifuge, and flung them in a wide horizontal arc in front of the weapon for maximum coverage against a line of advancing infantry. Now obviously you can easily adjust the muzzle velocity by varying the RPMs of the centrifuge, and sure enough you have no gunpowder and muzzle flash, as claimed for this centrifuge weapon.

One of the problems is accuracy, since the direction of travel of the ball prior to release is varying at the rotation rate of the centrifuge. If you had a one foot radius wheel flinging balls at 3141 feet per second, it would be spinning at 1000 revolutions per second (60,000 RPM). Putting that in terms a rifleman would be familiar with this means the aim of the ball is changing at a rate of 21.6 million arc-minutes per second. To release with 2.16 arc-minutes of accuracy the release has to be timed to a tenth of a microsecond. You can improve this by having the ball fly down a tube, but the ball itself is either going to be spinning with the rate of the centerfuge (again at 60,000 RPM) or rolling along the perimeter, in which case it's rapidly spinning in the other direction. Either way upon release the Magnus effect (the aerodynamic force on a rotating body that makes curve balls work) is going to be evident in the trajectory of the ball. However, this also means that the barrel can't be a really tight fit, so the ball has to roll down a smooth-bore tube, so accuracy is never going to be very high.

Another problem is the article's claims that such a weapon has no recoil. It even says it would work on satellites, magically flinging heavy high-velocity balls without upsetting the satellite's orbit. Boy is that crazy. Isn't it amazing that with a simple electric motor and a centrifuge someone thinks they can violate a law of physics so old that it predates Newton, holding that the momentum of a system can't just suddenly change, with some ball flung out without a corresponding an opposite motion of the flinger. As Christian Huygens and others observed, the mass times the velocity of particle A and the mass times the velocity of particle B is conserved as they react with each other in the absence of an external force. So let's take a realistic look at how this affects the centrifuge weapon.

You've got two balls rapidly spinning around their mutual center of mass, held together by some given force. You release the first ball as it's circular path aligns its instantaneous direction of travel with the intended target, so you eliminate the force keeping it bound to the other ball and let it fly. Now comes the nasty recoil part. The other ball is traveling in the exact opposite direction, and suddenly has no partner to keep the forces balanced. If your flinger was massless it would recoil with the same velocity as the ball you release, but in the exact opposite direction. Just take the mass times the velocity of the fired ball (its momentum) and divide by the mass of flinger and unfired balls to get the recoil velocity of the weapon.

The weapon still might be useful for defending vehicles, convoys, and fixed installations, but we've known about it for nearly a hundred years now, and you can read about the WW-I version of a ball bearing flinger in "Hatcher's Notebook", first printed in 1947. Go read the article, but remember that there might be a very useful weapon buried underneath it all.