🚀 go-pugleaf

In article <2005@ole.UUCP> ssave@ole.UUCP (Shailendra Save) writes:
>   Stealth does use a RAM for *reducing* detection by radar. 

No argument from me.

In article <2005@ole.UUCP> ssave@ole.UUCP (Shailendra Save) writes:
>From article <1991Jun18.005130.28440@cs.mcgill.ca>, by mingmar@cs.mcgill.ca (Ming MAR):
>> Do you have any idea how Radar Absorbing Materials
>> work?
 
I had posted a follow-up article asking the originator of this
thread (Bill Dorsey) to explain how radar absorbing materials
work.  I didn't get a response.
 
I later asked you but since you gave no explanation, I'll assume
you have no idea how radar absorbing materials work.  Thus far, I
haven't seen anyone in this newsgroup explain how it works.
 
Can anyone here explain how radar absorbing materials work?
 
>   the aerodynamics of the planes on the aircraft are such that no
>   radar is reflected back to the originator. 
 
Radar cross-section is reduced but not eliminated.  Generally
speaking, I'm not disagreeing -- merely quibbling.
 
>   it takes
>   only a windshield or a head-lamp lens to get an accurate enough 
>   reading of the vehicle speed.
 
Are you saying that the windshield glass reflects radar back to
the gun?
 
>   So let me ask you your question. Do you have any idea how Stealth
>   aerodynamics work? 
 
You started your article on that very topic, so... if I didn't
know before, I know now.
 
I'm not exactly sure what you mean by "stealth aerodynamics."  I
am an aerodynamicist.  I received my Master of Engineering from
the University of Toronto Institute for Aerospace Studies in
1977.  You tell me what you mean by "stealth aerodynamics" and
I'll tell you if I know anything about it.  That part of the
discussion can be conducted in sci.aeronautics.
 
Now, getting back on track, yes, I am aware of the technique of
redirecting reflections away from the illuminator.  What I don't
know is how Radar Absorbing Materials work.  (I have my own
ideas, but I'd like to know for sure.)
 
You said that you took a course in radar technology and said that
a stealthy car would look like a bumpy chameleon.  I assume you
mean the type of pyramids one finds in an anechoic chamber.  I
said that stealthy cars don't have to look like that and gave
aircraft as examples of non-bumpy vehicles.
 
I hadn't intended to answer your article, but then you posted
another one <2017@ole.UUCP> wherein you said:
 
>  If RAM worked 100%, like you contend they do, how come
>  Czechoslovakia has come out with a detection method which can
>  detect the Stealth aircraft at 250 miles?
 
I have never implicitely or explicitely contend that RAM reduces
radar cross-section to zero.  If that is the _only_ point you
wish to make, then fine, we are not in disagreement.
 
I haven't heard of any breakthroughs from Czechoslovakia.
Perhaps you could supply details?  A couple of people in this
newsgroup, Mike Hermann and Joel Lessenberry, suggested
Over-The-Horizon-Backscatter as a surveillance tool.  Tom
Edwards suggested Ultra Wide Bandwidth, presumably for target
acquisition.  Apparently, noone else has heard anything about
Czechoslovakia.
 
Last year, there were reports out of Saudi Arabia about radar
detection of F-117's.  For your edification, I include below my
translation of an article about it.  Remember, the article was
written before the F-117 was able to prove itself in the war.
 
From "L'Express International" 21 September 1990 (the Stealth
Fighter sighted issue):
 
On cover:  "Gulf:  The American invisible airplane detected by French
radar"
 
On page 19:
 
Exclusive
 
The radar that snared the stealth airplane
 
Nasty surprise for the Americans:  the Saudi Shahine system, contructed
by Thomson, detects the F-117A.  And obliges them to reconsider their
device.
 
The American stealth plane F-117A was spotted several times by the
French radar of the Shahine ground-to-air missile system in Saudi
Arabia.  This information, gathered last week from sources close to the
Saudi army, puts into question the American device deployed in that
country.  To shelter them from a possible detection by the Iraqis, the
commander of the U.S. Air Force has immediately transfered the bombers
of this type to a base in the southwest of the Saudi kingdom, next to
the Red Sea, near Yemen.
 
The F-117A, the latest in American technology, was designed "for
penetration in a high threat density environment and for attacking high
strategic value targets."  The unsuspected performance of the radar
which equipes the Shahine missile batteries, constructed by Thomson-CSF
for Saudi Arabia, were obtained during flights of the bomber near the
sites where the anti-air defense system is installed.  The pulse-Doppler
surveillance radar thus came to snare, several times, the invisible
plane at a distance of about 17 kilometers.  The computer was able to
integrate sufficiently the characteristics as to establish an actual
signature of the F-117A, this permits the system to recognize
immediately the target.  The probability of destruction of a target by
the Shahine is 90% with one missile and 99% in the case of a
simultaneous firing of two missiles.
 
The stealth plane, of which the principal characteristics are very
angular forms and a special radar signature reducing covering, is on the
other hand lacking in aerodynamic qualities and manageability.  Its
speed is no faster than "high subsonic," it peaks at 900 km/h.  Spotted
by radar, the F-117A has nothing but its jamming system and chaff to try
to escape the missiles.  Entered into service in October 1983, this
airplane has been put to the test on numerous radar systems.  With
success.  And even if its bombing capability, tested in the month of
December 1989 in Panama, was revealed as mediocre, the program was
considered a success.
 
It seems that, aside from the intrinsic capability of the Shahine, the
clean conditions in Saudi Arabia favored the spotting of the F-117A --
far horizon, heat and reverberation, diffusion of electromagnetic waves.
What ever the cause, its detection by radar, whatever the reason, puts
into question the very design of the aircraft -- its developement and
construction of 59 copies will cost a total of $6.5 billion.
 
It is a contract of $4 billion that Thomson-CSF, prime contractor --
with Giat (Groupement industriel des armements terrestres) and Matra --
signed in 1984 with Saudi Arabia for the delivery of an anti-air defense
system baptized Shahine, "Falcon Eye."  The Shahine, developed
exclusively for Riyad starting from Crotale missiles, today find
themselves on the front lines of defense of the Saudi kingdom.  This
position explains the discretion of Thomson-CSF concerning the
performance of its equipment.  The electronic systems division,
contacted by L'Express, refuses all comments.  "We wish to neither
confirm nor deny this performance.  Several Thomson employees are on
the other side with the French and foreign hostages, and we can't say
anything while they're in Iraq."  They add that the Saudi clients don't
like superfluous comments.
 
A certain number of Thomson-CSF employees are in Iraq, posted for the
maintenance of the radar system sold to Iraq and of its mobile version
installed on board Ilyushin aircraft.  Do the Iraqis also have the
means to detect the F-117A?  They are equiped with a French anti-air
system, the Roland, manufactured by Euromissile.  The Iraqis today
possess 14 AMX-30 tanks equiped with Roland and have at their disposal
133 Roland 1 and Roland 2 launch sites.  Their arsenal has grown to
2,780 missiles, whose performance is however inferior to that of the
Shahine.  Besides, in order for the Iraqi system to come to discover the
F-117A signature, the radar has to identify it several times.  It is
unlikely that the Americans will give them that opportunity.
 
Nevertheless, it is likely, sooner or later, that other radar will be
able to, like Shahine, identify the F-117A, constraining the expensive
stealthy bomber to a brief carreer.
 
 -- <by> Jean-Michel Caradec'h
 
And, for what it's worth, I remember reading in _Aviation_Week_
that an American anti-aircraft radar failed to lock-on an F-117
even after visual sighting.  Aviation Week also had an issue
concentrating on anti-stealth technology.