From: Mike Lorrey (mlorrey@datamann.com)
Date: Tue Jul 24 2001 - 12:45:54 MDT
Eugene Leitl wrote:
>
> On Sat, 21 Jul 2001, Mike Lorrey wrote:
>
> > Sorry, John, you aren't thinking microgravitationally. A cone balloon
> > in free fall will without guidance not remain oriented toward reentry,
>
> If we need orientation, we can use microthrusters to orient the warhead
> shortly before reentry. No need to spin anything, no funny signature.
>
> > 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.
>
> So we package the warhead into identical aluminized baloon as the decoys.
> Radar signature 100% the same.
No. A conical shape will deflect a much greater amount of radar energy
when it is coming from head on than from the side, while a balloon will
have the exact same radar signature during the entire trajectory. Thus,
the sig of the warhead will increase in strength as its angle of
incidence to the radar signal increases, and decoys will be filtered out
as that occurs.
>
> > 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
>
> Of course, you engineer the decoys and the warhead envelope to resemble
> each other as closely as possible.
That is my point.
>
> > follow a different trajectory than the much heavier IRV. For this
>
> Not in vacuum. As soon as you see drag, it's too late to intercept,
> anyway. Then, baloons are useless, admittedly. But they have served their
> purpose, already.
No, the ephemerides of a heavy warhead versus a light decoy will show
themselves by midcourse. A Missile doesn't follow a circular orbit, it
is elliptical, and thus mass differences will show the greatest effect
at the apogee point in the trajectory, long before it hits air.
The only way to mask this inherent disadvantage of a decoy until as late
as possible is to delay deployment of warheads and decoys until after
apogee and shortly before reentry. This increases the vulnerability of
all warheads on the bus to being interdicted by a single laser pulse
(those that blow up will damage their fellows, and induce unrecoverable
spin/yaw/roll rates to the bus and its payload. Releasing the unstable
warheads from such a situation simply guarantees their debris as they
burn up will be dispersed over a wider area...
>
> > reason, the best 'decoy' is another IRV. You might as well put a bomb
> > in it.
>
> I thought the warheads were MIRVed already? Let's say 5% the real Mc Coy,
> 95% decoys?
Again: What is the point of using decoys? A really effective decoy will
have all the same characteristics of a real IRV with a real warhead in
it. Especially if nukes are as cheap as John claims they are, there is
no economical reason why you should waste a good IRV with no warhead:
put a nuke in the damn thing.
And: warheads are not MIRV'd, missiles are. A MIRV'd missile has
multiple warheads, each in its own IRV, all on a bus in the nose,
generally arranged in in circular clusters of either 3,5,7, or 10
warheads, depending on the missile. A fully armed missile can't carry
more mass than it's designed to throw in warheads without giving away
that it's carrying more mass in its trajectory, so you need to remove a
real warhead to put in one or more decoys, so you are cutting in on the
effectiveness of your missile immediately the first time you decide to
even use decoys. Then you are dealing with a 'minefield' type problem:
radars / IR devices can track x + d 'warheads' separating from the MIRV
bus, therefore, the system knows that of the total bogies, where d are
the number of decoys and x is the number of warheads, and where x + n
equals the actual carrying capacity of the bus. n * M(x) = d * M(d),
i.e. how many decoys mass as much as one warhead (as well as how many
can take up one warhead slot on the bus.
It follows that the most effective decoy will occur when M(x) = M(d),
and therefore, since they are of equal mass, one must assess the
strategic value of that mass. An actual warhead has far more effective
utilization efficiency of that mass than a mere decoy.
>
> > Unfortunately, the round object is a poor reentry vehicle. It slows
>
> You don't have to be spherical at/during reentry, you only have to be
> spherical during the ballistic arc outside of the atmosphere.
SO what if you put a round envelope around a conical IRV? It's the mass
that counts.
This isn't really difficult to understand: its why sabots are so
effective as projectiles.
>
> > 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.
> >
> > What it shows is that decoys are irrelevant as a FUD strategy.
>
> I think I'm giving up now.
This was dealing with John's inane notion of having all IRV be
spherical.
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