Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!uunet!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!quiche!mingmar From: mingmar@cs.mcgill.ca (Ming MAR) Newsgroups: sci.electronics Subject: Re: R.A.M. (was Re: Police Radar Frequency Info) Message-ID: <1991Jun24.055534.24442@cs.mcgill.ca> Date: 24 Jun 91 05:55:34 GMT References: <1991Jun18.005130.28440@cs.mcgill.ca> <2005@ole.UUCP> Sender: news@cs.mcgill.ca (Netnews Administrator) Organization: SOCS, McGill University, Montreal, Canada Lines: 174 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. -- 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.