On Thu, 18 Sep 2003 04:24:06 GMT, Chad Irby wrote:
In article ,
(phil hunt) wrote:

On Wed, 17 Sep 2003 21:26:04 GMT, Chad Irby wrote:

Unless there's some exteme qualifiers, you have to assume it's a fairly
general average. With even moderately ambitious stealth, you can get a
good reduction in cross section across the board (even a 10% reduction
gives you several extra miles of "shoot first" at long ranges).

To be precise, 1 mile at 40 miles range.

What sort of formula are you using for this?

acquisition_range = k * rcs^0.25

where (k) is a constant. Basically it's the inverse-square law, both
from the radar to the target, then from the target back to the radar
again.

So for every 1% you increase the RCS, you increase acquisition range
by 0.25%

I don't consider 40 miles
"long" when we're looking at airborne missiles with ranges of over 100
miles. 40 miles is "medium." At 100 miles that's still a couple of
miles of extra time before acquiring,

2.5 miles

Consider the old-tech F-117. They fly it through some of the most
heavily-defended airspaces, *ever*,

Oh? Did Serbia and Iraq have modern AA systems? I think not.

The phrase you're looking for is "golden BB."

Never heard of it.

But with the number of
missiles around Baghdad in GWI and II, it easily qualifies.

Don't understand you.

And since
you're claiming that stealth isn't that important,

I don't recall ever making that claim -- perhaps you could vremind
me where I did.

we should have lost
them on a regular basis. We didn't.

How detectable is the F-117 (and F-22) using visual or IR sensors?

With pure visual, planes are pretty hard to find at anything like a safe
distance.

What do you mean by "safe distance"?

If you're in a plane, you're not going to be using image
magnification to find the other guy, unless you know right where he's
coming from in the first place.

I more had in mind an observer on the ground.

Even with that, you have camouflage for
the human optical frequencies,


and pure IR is not very useful for very
long ranges.

Why not? Is is more or less useful than visual? Does it make a
difference whether it is day or night? And what do you mean by "lonh
ranges"?

A quick BOTE calculation suggests that with clear air conditions, a
F-22 would in principle be detectable at 100 km with the sort of
digital equipment you can buy in a high street shop (a 10 m wide
object would produce an image 10 pixels across, assuming a 1000 mm
lens and a focal plane with 100 pixels/mm) though I'm sure in real
life conditions wouldn't be good enough to spot it in daylight.
Spotting the exhaust at night might be easier, especially for IR
sensors.

"Detecting" versus "acquiring and identifying," I'm afraid.

I don't think so. Once something hase been detected, finding its
exact position should be relatively easy. If we are using visual
sensors, we could have several point towards it and use parallax to
get the exact position. (Here I'm only considering using passive
sensors in an air defence system, since they are immune to
anti-radar missiles and anti-radar stealth. (Obviously they are not
immune to making the aircraft smaller, but there are practical
constraints to doing that).)

Once the position is got, the defenses can fire a missile to
intercept, using ground-controlled mid-course guidance, and active
radar (or IR) terminal homing.

Identifying is fairly easy. Either use IFF or the known positions of
friendly aircraft to know whether it's hostile. If you know it's
hostile, use the size of sensor returns to guess more or less what
it is (cruise missile/ small fighter/ big fighter/ AEW), though the
precise nature isn't very important, since in all cases the response
would be the same.

Narrowing
down the field of view enough to make visual ID makes for a lot less
coverage per sweep. If you know where the target is, it gets fairly
easy, but you have to look in the right direction first, and hope
there's no clouds or haze in the way.

Yes.

And if you can manage to "detect" a 10 pixel object, you still have to
figure out what the heck it is.

Why? You only have to detect whether it's hostile or not.

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