I call BULLSHIT

[unixronin]

A centrifuge-based gun with no sound, no heat, no mechanical wear, no recoil even when firing .50-caliber projectiles at up to 8000fps at up to 120,000rpm cyclic, that cannot jam ...

Um, excuse me.  But.  This article was supposed to be published on April 1, right....?

Update:

phanatic, a poster on the guns thread, calculated the power requirements of this weapon from the specs claimed by the crank inventor and assuming perfect 100% efficiency.  Using those assumptions, he came up with a sustained power consumption of 100MW -- approximately 134,000 horsepower.

Noiseless?  Heatless?  Portable?  .... Yeah, RIGHT.

Comments

[radarrider.livejournal.com]

I can see how a centrifuge can be used to propel projectiles. This technology may very well be real, but the claims show the ignorance of those making them. I don't care how you throw stuff downrange, you will have recoil unless you throw something in the opposite direction with equal momentum. It's gonna generate some heat since TANSTAAFL. And there will be some friction in the bearings and feed mechanism.

An even bigger concern is accuracy. If you spin something around in a circle at high speed and release it, it will then travel in a straight line. There are two problems. The first is making sure you release the projectile at precisely the correct time. At the speeds they're talking about, milliseconds can make arcseconds, or even degrees, of difference in direction. The second is stabilizing the projectile in flight. Since it's a sphere, it will wobble unless it is spun due to its passage through air. If it is spun on the axis parallel to the direction of flight, it will fly straight. But how will the system impart that kind of spin? It would be easy to impart spin in a perpendicular axis but that would cause the round to curve in flight just like a baseball or golf ball does.

In short, I'll believe it when I see a working prototype.

[unixronin.livejournal.com]

Yup. In fact, a back-of-the-envelope estimate is enough to show that for the performance and dimensions claimed, projectile release is going to have to be timed with sub-microsecond precision to achieve accuracy competitive with a conventional rifle or LMG.

[koyote.livejournal.com]

okay, it's obviouse that the extreme claims are bogus, but let's look at what can be done with this.

let's start with 7.62 mm projectiles at 2500 fps (the pre production test) to eliminate the nuclear reactor. :)

to get 2500 fps, they have to be moving that fast in the 'fuge- so like a flywheel in a nice gas engine. No problem, really.

recoil? I'm going to refer to newton rather than TANSTAAFL, sorry- object in motion tend to stay in motion. Alrighty, all your "notfree lunch" is on the front end in the energy of accelerating the projectiles..... all of the acceleration occurs BEFORE "firing". Think terbuchet, not onager.

No, as for accuracy, you open the hole in the side of the 'fuge where yoou want it. done. thinking in simple mechanics instead of computerized high tech release gates is probably a good idea here. I'm not sure about spin, it's possible the pile o ball bearings in the spinning cylinder will get a predictable amount of spin going on. I'd have to get one of these put together to figure that out.


This isn't exactly revolutionary.netwonian engines have been around for a while- I think the sling is more than a few thousand years old :) (and it's possible to hit a bird on the wing with one...)

the rate of fire is where I'm losing it. I can see getting a few thousand bbs into the 'fuge and getting up to speed and then rotating your firing hole wherever you want. I'mnot sure how you are going to maintain a flow of projectiles from storage and 0 fps to outside edge of the 'fuge and 2500 fps. Again, it would be useful to have a low tech one built up. I've got a spare ac motor laying around.....

[koyote.livejournal.com]

excuse the typos. blackberry.

[unixronin.livejournal.com]

recoil? I'm going to refer to newton rather than TANSTAAFL, sorry- object in motion tend to stay in motion. Alrighty, all your "notfree lunch" is on the front end in the energy of accelerating the projectiles..... all of the acceleration occurs BEFORE "firing". Think terbuchet, not onager.

No, it doesn't work that way. OK, assume it's all spun up and foll of balls... everything is in dynamic balance. Now you open the firing gate, and balls start blying out. The moment the first ball leaves the wheel, there is an out-of-balance moment due to its opposite number.

Think of it this way: all the spinning balls are exerting force on the inner wall, all around. Open that wall at one point, and a "jet" of balls escapes. At that point, there is no force being exerted on that part of the wall. What else works this way? A rocket engine. You can call it recoil or you can call it thrust, but you can't evade conservation of momentum -- there WILL BE an equal and opposite reaction.

[koyote.livejournal.com]

okay, yes. releasing the kinetic energy pressed against the side of your centrifuge at one point is going to create a small imbalance opposite that point- but to maintain a rate of fire, you have to be adding another ball into the mix, which would alleviate that.

The force being removed isn't going to be enough to matter to a 28 pound weapon, for sure. certainly not pintle or roof mounted. Depending on how the mechanism works, the imbalance could be *before* release and thus accounted for in the design, static in point, or precessing. It's even possible (though I can't figure out how) to use the imbalance to feed the machine.

[unixronin.livejournal.com]

okay, yes. releasing the kinetic energy pressed against the side of your centrifuge at one point is going to create a small imbalance opposite that point- but to maintain a rate of fire, you have to be adding another ball into the mix, which would alleviate that.

No it won't, because the new ball you're adding isn't up to speed yet. So in addition to the reaction from the ball you've just released, there's the rotational drag of getting the new ball spun up.

The force being removed isn't going to be enough to matter to a 28 pound weapon, for sure.

From a single ball, you might not notice it. But it's still there. With a weapon firing as many as 2,000 balls per second, you most definitely will. Trust me on this, there WILL be a recoil force, and it won't be small. You can't just "account for" conservation of momentum through a clever design. The inventor is a crank, and his claims for this weapon are every bit as bogus, if perhaps slightly less obviously so, than those for every "perpetual motion machine" ever invented. There's ways to cheat recoil and not pass it on to the firer or mount point by ejecting a countermass (be it gas, as in a recoilless rifle (http://en.wikipedia.org/wiki/Recoilless_rifle), or plastic strips as in the Armbrust 300 (http://en.wikipedia.org/wiki/Armbrust)), but there's no way to construct a projectile weapon that does not produce any recoil forces in the first place that doesn't require obtaining an exemption from compliance with the physical laws of this Universe. Even the sling you mentioned earlier has recoil.

[koyote.livejournal.com]

I think that the frictionless and heatless comments aren't exactly intended to be cold-fusionesque. It's very tempting when critiquing a design to go voerboard on that. The projectiles won't be hot, the device won't flare up on an IR sensor like a rifle, it's relatively heatless, etc.

I mean, okay, let's talk about 1940s era recoilless rifles. Recoilless? Well, no, you couldn't actually balance a 75mm RR on a pin and fire it and expect it to stay. But it's an accepted and usefully descriptive term for "able to be shoulder fired rather than mounted in a tank"- and people don't argue it much.

[micheinnz.livejournal.com]

You know what they say -- if something looks too good to be true, it probably is.

[greyman.livejournal.com]

It's very simple, really, you open the gate diametrically opposite at the same instant. Bingo, no recoil.

Errr... might be a bit difficult to minimize "collateral damage" or whatever the current term is. "Point this end toward enemy, opposite end toward nearest officer".

[mazianni.livejournal.com]

This got picked up on boingboing too.

http://www.boingboing.net/2006/12/28/silent_but_deadly_dr.html

Lots of links to various comment threads debunking the DREAD.