Re: go interceptors!

From: Mike Lorrey (
Date: Sat Jul 21 2001 - 07:32:40 MDT

John Clark wrote:
> James Rogers <> Wrote:
> >these days balloon decoys primarily serve to generate an illusion for optical sensors.
> And Radar sensors, the balloon's would certainly have an aluminum coating.
> > The reason spherical decoys work is that from many aspects, the cone shaped
> > warhead looks essentially identical to the spherical decoy to the optical
> > sensor. Therefore, a sphere always takes on a theoretically valid profile
> > of a real warhead, thereby serving its purpose.
> Let me see if I understand this, from certain very specific directions a cone
> can look like a sphere so really a sphere is more like a cone than a cone is
> like a cone. You know, that really does sound like something a military man
> would say, like the Vietnamese war general who said "We destroyed the
> village to save it".

Sorry, John, you aren't thinking microgravitationally. A cone balloon in
free fall will without guidance not remain oriented toward reentry, and
thus will yaw to orient orthogonal to its direction, and continue
spinning. This is detectable versus the guided orientation of the IRVs,
which do not drift. If you deploy a balloon, it will always have the
same cross section view to you no matter how much it spins and drifts.

The problem is that a) a balloon will have a different radar sig than
cones, and b) a balloon will have a different mass, and therefore will
follow a different trajectory than the much heavier IRV. For this
reason, the best 'decoy' is another IRV. You might as well put a bomb in

> >A real warhead has a stable aspect with respect to its trajectory. With a
> >cone-shaped decoy, a sensor can detect any rotation of the decoy that is
> >inconsistent with a real warhead
> If that bothers you then put the real warhead in a round balloon then you
> won't know if it's spinning or not, it would greatly dilute the infrared signature too.
> Do this and I'll withdraw my objection to round decoys, in fact I'd insist on them.

Unfortunately, the round object is a poor reentry vehicle. It slows down
to subsonic too easily, the cone is designed to reenter and hit the
target at a high supersonic velocity, reducing airtime. If it goes
subsonic, then the IRV can be intercepted much easier with simple
machine guns.

> > In any case, the decoy was largely irrelevant to the test.
> Ain't that the truth.

What it shows is that decoys are irrelevant as a FUD strategy.

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