On Tue, 8 May 2001 [EMAIL PROTECTED] wrote:
> Someone please stop me. I'm so weak. I can't resist.
> The radar cross section of a car dead-on is actually much less than its
> geometric cross section for lots of reasons. Here's a fun one from the
> past - a howitzer projectile has roughly the same radar cross section as
> a bumblebee.
A car's head-on cross section is a direct function of it's radiator cross
section and the reflectivity of same. It's not perfect but it's good
enough. A Vet for example has a radiator that is not vertical, it's angled
back toward the firewall. As a result the reflected beam goes straight up
for all intents and purposes. If you want to defeat the reflectivity of a
car you've got to defeat the radiator.
As to shell's from guns, ogive's are pretty stealthy. Comparing a shell to
an automobile is apple-orange in this context.
> A corner reflector has a very high reflectivity but its effective area
> varies as cosA. If you're off-axis it appears smaller but it still
> reflects directly back to the source.
It also reflects the beam at an offset.
> A flat plat should be a pretty simple diffraction problem but for the
> case where the dimensions of the plate are much larger than the
> wavelength ( true for many areas of a car but not all ) the plate is
> like a mirror.
> There's a corner reflector up on the moon that has been used to reflect
> laser signals.
Which are 3-4 MILES across...
Apples and oranges.
> Funny this topic keeps coming up - we were drawing sketches of stealth
> cars with absorbers, reflectors and thin metallic films on the
> windshield years before rumors of the 117 were out. The basic ideas are
> really old. Maybe one major accomplishment was making the damn thing
> fly.
windshield bounces upward, it's angled the wrong way to get a good
reflection for a gun, side windows and rear window, reflections from
within the cab, etc...
> Something sounds wrong here. I'm no radar guy ( I have written code that
> sorts targets ) but I would guess that a doppler radar has two
> measurements to make :
>
> 1) location of reflected signals. In which case Sandy's corner reflector
> will make the Yacht stand out nicely - a good thing for the recreational
> boater, not so nice if you're smuggling.
Except it's a weak signal to start with and it's being reflected 1/r^2 as
well. Which means at long distances, when it would really be useful, it's
got a well attenuated beam that is further attenuated on reflection. As
Sandy get's closer the reflected signal gets strong, but you're gonna have
to be right on top of the radar detector to be effective. A tad too late.
Almost all passive systems are good only if you're real close, directly
contrary to the goals, mask your signal while you're way out...
> What the hell "burn through" is I have no idea except that it sounds
> like it has something to do with large collections of neurons that have
> long been unsuccessfully attempting to act in concert finally producing
> a coherent thought.
"Burn through" is a EW term, in the detection context it means to keep
boosting your signal until you can 'burn through' any jamming. In the
usual context it means the aircraft increases transmitter output until
the jamming signal can be differentiated from the desired signal and a
'lock' obtained. Shortly afterwards it's 'Falcon away'.
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The solution lies in the heart of humankind.
Chris Lawson
The Armadillo Group ,::////;::-. James Choate
Austin, Tx /:'///// ``::>/|/ [EMAIL PROTECTED]
www.ssz.com .', |||| `/( e\ 512-451-7087
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