From: rat@erg.sri.com (Ray Trent)
Newsgroups: rec.autos.driving
Subject: Re: Covert radar gun under development.
Keywords: auto,radar
Date: 16 Apr 92 19:43:48 GMT
Reply-To: rat@erg.sri.com (Ray Trent)
Organization: SRI International, Menlo Park, CA

In the referenced article, (Jason K. Schechner) writes:
>	New Corevettes do indeed have fiberglass bodies, but there is

Have they ever made a Corvette that didn't have a fiberglass body?

>still a lot of metal in the thing:  The engine (enough metal for ya?) for
>one!  But the things that the radar sees are the grille, the headlights, 
>and any metal trim. 

True enough. Nevertheless, anyone that has looked carefully at a
Corvette almost has to come to the conclusion that the designers
considered making it at least somewhat stealthy. The glass body is not
the end of it.

For one thing, unlike most cars, there is a space in front where one
could put a RAM blanket that would obscure the grill and engine
without affecting engine performance (the air intake is on the
bottom). Strangely, if one looks at the composition of the "energy
absorbing pad" that is installed in the front bumper for collision
force dissipation, one tends to find it interestingly coincidental
that the material has high-impedence electrical conductive properties
(and its thickness is suspiciously close to optimal for absorbing
radar). No, I don't really believe this was intentional. But it`s
amusing. 

For another thing, the headlights (when in non-operating mode) on
Corvettes since at least '84 point towards the back of the car, not
the front. And as far as I've been able to determine, they have no
significant metal trim.

For another thing, almost all of the metal parts in the car (except
the grill and engine), including the semi-vertical frame pieces are
oriented so as to provide a scattering profile away from an incoming
radar signal (police radars are *not* military radars...you don't
really need to lower the cross section all that much to screw them up
enough to argue convincingly that there is a reasonable doubt as to
your speed...as though the Consitution really protected you from the
mobile revenue collectors...).

For another thing, when they added UV reflective coating to the
windshield, the engineers insisted on leaving a 3 inch square
unobstructed in front of the rear view mirror (ostensably for "garage
door openers") because the coating significantly decreased the
sensitivity of radar detectors mounted in that location. Not enough to
*actually* make garage door openers stop working, of course...just
enough to reduce the range of a radar detector quite a lot.

And, of course, the front cross section of the Vette is quite small
compared to all but the smallest sports type cars. And most of the
cross section is close to the ground, which tends to scatter quite a
bit (I haven't thought enough about it to say whether this helps or
not, though). 

Anyway...a Vette still shows up quite nicely on radar. It might not be
as difficult to make it somewhat stealthy as you seem to think,
however.

On the other hand, do you remember that joke about the 2 guys and a
bear (oddly appropriate, don't you think :-). You don't have to be so
stealthy as to be invisible, you only have to outrun the guy next to
you...

And it would be harder to make a Vette stealthy from the rear, because
the gas tank is right there in plain view and there ain't all that
much room to screw with.
-- 
"When you're down, it's a long way up
 When you're up, it's a long way down
 It's all the same thing
 And it's no new tale to tell"                      ../ray\..
Newsgroups: rec.autos.driving,rec.autos