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2006-11-06 Science & Technology

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Posted by 3dc 2006-11-06 20:55|| || Front Page|| [6 views since 2007-05-07] Top

#1 The Phalanx and the "Gatling" gun to which this refers are not two different systems. The latter is apparently the Vulcan 20mm cannon, developed by GE in the late '40s and used in many many applications since. It has been the standard gun of US fighter aircraft since the late 50s. It really does operate on the Civil War era Gatling principle, with 6 rotating barrels, but the resemblance ends there.
It is a component of Phalanx, which is an integrated system incorporating the mount and a very accurate and highly automated fire control system.

I used the tracked Vulcan system in Vietnam. This was the Vulcan gun mounted on an M-113 APC chassis, with a rather rudimentary range-only radar to assist the gunner in tracking. It was intended as an air defense weapon but was devastatingly effective against ground targets.
The Phalanx system is enormously more sophisticated but it uses basically the same gun.
The British have a similar system, Goalkeeper, but this uses the GAU-8 30mm cannon developed for the A-10.

To some extent, what matters here is not the gun itself but the fire control system, which must be autonomous and extremely fast-reacting. Some naval planners believe that a larger gun firing proximity fused ammunition would be more effective.
The latest 57mm Bofors naval gun, for instance, fires up to 160 6 pound explosive shells per minute. This will fill the air with splinters, any one of which can do fatal damage to an oncoming missile. This is heavier than the Phalanx, but not by a tremendous amount, and it is still manageable for ground applications.

Posted by Atomic Conspiracy 2006-11-06 21:37|| 2006-11-06 21:37|| Front Page Top

#2 AC, I trust that the fire control systems are designed to "lead" their target as opposed to shooting directly at it. This is like photographing a moving target whereby you aim slightly in front of its trajectory so that it is in-frame once the shutter activates. In the same vein, I would assume that these fire control systems aim to have the incoming projectile fly into the outgoing fire so that the missile intercepts the bullets as opposed to the other way around. Is this so?

SIDEBAR: I asked a friend of mine who was a Huey door gunner in Viet Nam whether the pilot had to make course corrections to account for weight loss, due to ejected lead and brass, once the minigun started firing. He confirmed this in no uncertain terms.

Posted by Zenster">Zenster 2006-11-06 22:15|| 2006-11-06 22:15|| Front Page Top

#3 Zenster, I would think the thrust from the firing gun is more of an issue than the brass/weight loss. I was told at AUSA a few weeks ago that the 7.62mm Dillon minigun put out more than 300lbs of thrust.

Posted by Remoteman 2006-11-06 22:28|| 2006-11-06 22:28|| Front Page Top

#4 Zenster:

Incoming usually has little or no bearing change.
An exception would be an artillery or mortar shell on the way up in the first half of its trajectory.
Still, the fire control stuff has been able to calculate lead for decades.

Posted by Richard Aubrey">Richard Aubrey 2006-11-06 22:28|| 2006-11-06 22:28|| Front Page Top

#5 I was told at AUSA a few weeks ago that the 7.62mm Dillon minigun put out more than 300lbs of thrust.

Cool! I envision an automotive propulsion system that deters tailgaters!!!

Posted by Zenster">Zenster 2006-11-06 22:41|| 2006-11-06 22:41|| Front Page Top

#6 Zenster
Even a fairly primitive system like the tracked Vulcan could calculate lead angles automatically. It did this by sensing rate change from the optical sight and combining this with range, the latter provided by the boresighted radar dish.
The optical sight was not automatically offset but the system provided an offset aim point. This was to allow the gunner to compensate for very slight errors in the system or to vary the aim point for a maneuvering, not just moving, target. These errors could result from atmospheric conditions or such things as barrel wear. Some systems compensate for these automatically but in those days it was easier just to do it by eye, with the gunner's own judgment interacting with the automatic system.
The Vulcan system was very accurate, especially with 50 rounds per second coming out of it, but it lacked all-weather and night capability, and didn't have just a lot of range.

Posted by Atomic Conspiracy 2006-11-06 22:47|| 2006-11-06 22:47|| Front Page Top

#7 "In the same vein, I would assume that these fire control systems aim to have the incoming projectile fly into the outgoing fire so that the missile intercepts the bullets as opposed to the other way around. Is this so?"

Oops, forgot to answer your question. Actually, it is a combination of both, the system arranges for them to meet at a point common to both flight paths. This has been done automatically since the 1940s.
In some ways a missile is an easier target than a manned aircraft since most missiles do not take evasive action. The few that are capable of evasive action do not do so actively (that is, in direct response to defensive fire). Piloted aircraft can of course evade actively though it is not easy and is highly range-dependent.
The scenes in Top Gun of fighters dodging tracer streams were not fiction. It can be done, but not without a pilot, at least not yet.
Contrary to popular impressions, many missiles are no faster than airplanes.
For ballistic projectiles like Hezbollah's unguided rockets, the velocity is higher but not by as much as might be thought; and the flightpath is completely predictable even though it is not a straight line.
The missile's real advantage is its small size, especially when seen head-on.

Posted by Atomic Conspiracy 2006-11-06 23:05|| 2006-11-06 23:05|| Front Page Top

#8 A problem I see with a land based Phalanx system is collateral damage from expended shells.Sea based systems expended shells fall harmlessly in the ocean.Laser type system may be better.

Posted by Flomoter Ulolush5791 2006-11-06 23:27|| 2006-11-06 23:27|| Front Page Top

#9 In some ways a missile is an easier target than a manned aircraft since most missiles do not take evasive action. The few that are capable of evasive action do not do so actively (that is, in direct response to defensive fire).

I had heard that cruise missiles have the ability for evasive maneuvers. I must assume that this amounts to selecting an alternate flight plan once defensive fire is encountered, as opposed to actually maintaining the same course whilst evading incoming fire.

I was well aware of "leading" fire control (almighty thanks to Harold S. Black, inventor of the negative feedback loop), but just wondered if it attempted direct intercept or the "fly-through" model I proposed. With the proverbial hail of lead the Phalanx system puts out, it can toss up an impenetrable screen of fire.

Another question: It would seem desirable to vary ever so slightly the outgoing trajectory of the system's fire so as to create a swath instead of a projectile stream. Are there some sort of "rockers" that gently sway the system, or is this naturally accomplished through flight variations induced by subtle barrel mis-alignment, ballasting, atmospheric turbulence or bullet tumble?

Finally, is there any way to integrate the "Metal Storm" technology to this current arrangement? I know it would take a major redesign to swap barrels instead of bullets, but the enhanced fire rate would be tremendous. More than anything, its delightful to see a mature technology like this continue to live on well past its anticipated date. (Much like the hard disk drive, which has outlived all expectations by massive orders of magnitude.)

PS: Thank you for the replies, AC and all.

Posted by Zenster">Zenster 2006-11-06 23:39|| 2006-11-06 23:39|| Front Page Top

23:55 twobyfour
23:39 Zenster
23:30 elbud
23:27 Flomoter Ulolush5791
23:07 bunyip
23:05 Atomic Conspiracy
23:04 Barbara Skolaut
22:59 Barbara Skolaut
22:56 Barbara Skolaut
22:47 Seafarious
22:47 Atomic Conspiracy
22:41 Zenster
22:38 Zenster
22:34 Zenster
22:28 Zenster
22:28 Richard Aubrey
22:28 Remoteman
22:25 Zenster
22:21 anon
22:21 Alaska Paul
22:15 Zenster
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22:00 trailing wife