skunk-works-digest Thursday, December 4 1997 Volume 06 : Number 093 Index of this digest by subject: *************************************************** U-1 Re: Rolling an SR-71 (was Re: U-1) Re: U-1 Re: Rolling an SR-71 (was Re: U-1) subscribe New Scientist on Stealth Re: New Scientist on Stealth Re: Rolling an SR-71 (was Re: U-1) Re: Rolling an SR-71 (was Re: U-1) *************************************************** ---------------------------------------------------------------------- Date: Wed, 3 Dec 1997 08:03:09 -0500 From: Tom Robison Subject: U-1 Was watching the Wings episode last night entitled "Spyplanes", and updated version of an earlier release. Two questions came to mind... We are all familiar with the U-2, but this designation leads one to wonder, was there ever a U-1, and if so, what was is used for? They stated that the U-2's primary camera was a 105mm. I assume this means the size of the film, corner to corner. What is the focal length of the lens? Is the shutter speed and f-stop fixed, automatic, or variable by the pilot? It also ocurred to me that I've never seen an SR-71 do a roll. Is it capable of such? Or is it that such frivolity is "unseemly" in the eyes of the Air Force? Tom Tom Robison, tcrobi@most.fw.hac.com Airborne Communications Systems, Hughes Defense Communications, 1010 Production Rd. Fort Wayne, IN 46808 (219)-429-5589 Any opinions expressed herein are mine alone, and do not reflect the views or opinions of Hughes Defense Communications, Hughes Aircraft Corp., Hughes Electronics Corp., General Motors Corp., Raytheon Corp., God, or my wife. ------------------------------ Date: Wed, 03 Dec 97 10:15:23 EST From: keller@eos.ncsu.edu Subject: Re: Rolling an SR-71 (was Re: U-1) Tom Robison wrote (in part): [stuff about U-2 snipped] >It also ocurred to me that I've never seen an SR-71 do a roll. Is it >capable of such? Or is it that such frivolity is "unseemly" in the eyes of >the Air Force? Although my copy of the SR-71 dash-1 is at home and I'm at work right now, I do quite specifically recall that the dash-1 does say that flying aerobatic maneuvers with the SR-71 is prohibited. - --Paul ------------------------------ Date: Wed, 3 Dec 1997 14:41:33 -0500 (EST) From: Kathryn & Andreas Gehrs-Pahl Subject: Re: U-1 Tom Robison asked (besides other things): >We are all familiar with the U-2, but this designation leads one to >wonder, was there ever a U-1, and if so, what was is used for? The still-used U-Series (U = Utility) started in 1952 as a US Army (and USAF) designation series with the U-1 for the US Army, followed by the U-2 for the USAF, but comprised mainly re-designated models. In 1962, the series replaced the former USAAF (and later US Army and USAF) L-Series (L = Liaison, introduced 1942), as well as the USN (and USMC) U-Series (U = Utility, introduced 1955). Some aircraft were re-designated from the USAAF (and later US Army and USAF) C-Series (C = Cargo, introduced 1925), and the US Army A-Series (A = Amphibian, introduced 1948). Several of the U-aircraft are used for reconnaissance, surveillance and intelligence gathering, including all or at least some versions of the U-2, RU-8, RU-9, HU-16, RU-21 and HU-25, and specifically SAR (Search And Rescue) missions, like the HU-16 and HU-25. Some were specifically designed for the COIN (Counter-Insurgency) role, like the AU-22, AU-23 and AU-24, while the QU-22 was a target drone. The rest are mainly used for light cargo and passenger transport, liaison duties, training and other utility purposes. The U-Series includes the following designations: ================================================= * U-1 Otter = DeHavilland Canada DHC.3 Otter (previous designations: C-137, UC) * U-2 'Dragon Lady' = Lockheed (Skunk Works) (later also TR-1, ER-2) * U-3 'Blue Canoe' = Cessna Model 310 (previous designations: L-27) * U-4 'Aero Commander' = Rockwell (Aero Design & Eng.) Model 520/560/680 (previous designations: L-26 -- USAF versions) * U-5 Twin Courier = Helio Model H.500 (only 2) * U-6 Beaver = DeHavilland Canada DHC.2 Beaver (previous designations: L-20, maybe also U2C) * U-7 Super Cub = Piper PA.18-135 Super Cub (previous designations: L-21, also L-18) * U-8 Seminole = Beechcraft Twin Bonanza D50B/C50 (previous designations: L-23) * U-9 'Aero Commander' = Rockwell (Aero Design & Eng.) Model 520/560/680 (previous designations: L-26 -- US Army versions) * U-10 Super Courier = Helio Model H.295/H.395 (previous designations: L-28) * U-11 Aztec = Piper PA.23-250 Aztec (previous designations: UO) * U-12 (not used, skipped during 1962 re-designation) * U-13 (not used, skipped during 1962 re-designation) * U-14 (not used, skipped during 1962 re-designation) * U-15 (not used, skipped during 1962 re-designation) * U-16 Albatross = Grumman Model G-64/G-111/G-231/G-262 (previous designations: OA-16, A-16, XJR2F, PF, UF) * U-17 = Cessna Model 180/185 * U-18 Navion = Ryan (North American Model NA.154) Navion/Super Navion (previous designations: L-17, also L-22) * U-19 Sentinel = Stinson (Vultee-Stinson Model V76) (previous designations: O-62, L-5, OY) * U-20 = Cessna Model 195 (previous designations: LC-126) * U-21 King Air = Beechcraft Model 65-A90 King Air (also C-6, C-12, T-44, U-25) * U-22 = Beechcraft Bonanza 36, Model PD.1079/PD.249 * U-23 Pacemaker = Fairchild Hiller (Pilatus PC-6) Heli Porter (also V-12) * U-24 Stallion = Helio Model H.550A Stallion * U-25 Guardian = Dassault (Dassault-Breguet) Falcon 20 (originally: U-25 King Air = Beechcraft Super King Air 200, to C-12) * U-26 = Cessna Model 206 Turbo Super Skywagon (1 only ?) * U-27 = Cessna Caravan I - -- Andreas - --- --- Andreas & Kathryn Gehrs-Pahl E-Mail: schnars@ais.org 313 West Court St. #305 or: gpahl@acm.flint.umich.edu Flint, MI 48502-1239 Tel: (810) 238-8469 WWW URL: http://www.ais.org/~schnars/ - --- --- ------------------------------ Date: Wed, 03 Dec 1997 21:59:59 GMT From: georgek@netwrx1.com (George R. Kasica) Subject: Re: Rolling an SR-71 (was Re: U-1) On Wed, 03 Dec 97 10:15:23 EST, you wrote: > >Tom Robison wrote (in part): >[stuff about U-2 snipped] >>It also ocurred to me that I've never seen an SR-71 do a roll. Is it >>capable of such? Or is it that such frivolity is "unseemly" in the eyes of >>the Air Force? > >Although my copy of the SR-71 dash-1 is at home and I'm at work right >now, I do quite specifically recall that the dash-1 does say that >flying aerobatic maneuvers with the SR-71 is prohibited. > >--Paul Paul: I don't usually post, but I couldn't pass this up...does Prohibited mean the Air Force pilot is going to get written up, etc. if he does the roll, OR does it mean that BAD THINGS are going to happen to the aircraft... George ===[George R. Kasica]=== +1 414 541 8579 Skunk-Works ListOwner +1 800 816 2568 FAX http://www.netwrx1.com West Allis, WI USA georgek@netwrx1.com Digest Issues at: http://www.netwrx1.com/skunk-works ------------------------------ Date: Wed, 03 Dec 1997 21:51:48 -0800 From: G&G Subject: subscribe subscribe habu@airmail.net ------------------------------ Date: Thu, 04 Dec 1997 18:16:01 +1200 From: Brett Davidson Subject: New Scientist on Stealth The vanishing point =20 =F8=F8=F8=F8=F8=F8=F8=F8=F8=F8= =F8=20 When soldiers disappear before your very eyes and battleships hide at twenty paces,=20 the camouflager's art has reached its peak. Justin Mullins dons his cloak of invisibility LOOKING through radar eyes, the ground, sea and sky are= dark. Occasionally, however, bright beams sweep across the= landscape. For a spyplane high over enemy territory or a frigate delivering a special forces team to a distant shore and even for the team itself, the beams spell danger just as certainly as searchlights to aircraft in the Second World War.=20 The radar beams come from satellite, aircraft and= ground-based transmitters. For a split second, they light up most things they touch. Large, smooth objects such as buildings, vehicles and almost anything metal reflect radar well and light up like beacons. Trees and bushes are visible, though things made of plastic are= often invisible. Humans are dark, dreary figures decorated with bright belt buckles, zips and spectacle frames.=20 To get caught in the glare of a radar beam is to dice with death. But how do you hide? Camouflage designed to help people and machines blend into the visible background is of no use here. To vanish in the radar world requires different techniques altogether.=20 The problem of invisibility is even more difficult in the world of thermal imaging. Radar has a wavelength of several centimetres or more, while thermal imaging uses wavelengths between 8 and= 14 micrometres. In this spectrum, hot humans, engines and= exhaust gases glow brightly, while metallic objects often appear dark. Hiding from thermal imagers is more difficult than evading radar since the camouflage must match the temperature patterns of the surroundings.=20 Then there is short wavelength infrared and, of course, the visible spectrum to worry about. Throw in ultrasensitive listening devices and the emerging techniques of millimetre-wave imaging and it is clear just how difficult it is to hide on the battlefield.= =20 With so many different spying eyes, the arts of camouflage, concealment and deception have never been more demanding.= As if hiding in each part of the spectrum were not difficult= enough, today's artisans of invisibility must hide their charges in all these spectra at once. So military scientists are amassing an impressive collection of new materials, devices and simulators in an effort to tackle the problem--inflatable decoys that look like tanks, artificial fogs in which ships or soldiers can hide, and virtual worlds that depict a battlefield in any region of the spectrum.=20 The deadly game of hide-and-seek in the radar spectrum began with a vengeance in the 1960s when the CIA wanted to protect its= U-2 spyplanes from missiles that homed in on radar reflections. The first attempts to camouflage the aircraft involved trying to cancel out the incoming radio waves by broadcasting out-of-phase signals at the same frequency. But in the early 1960s, several U-2s using these devices were shot down over Russia and China. The= aircraft's designers, from the famous Lockheed Skunk Works in= Palmdale, California, concluded that the missiles simply homed in on= the out-of-phase signal.=20 Today, stealth aircraft and stealth ships rely on different principles. =20 The first trick is to stop the incoming radio waves reflecting back to the radar receiver. "Imagine standing in a darkened room= with a torch and trying to spot a mirror," says Brian Spilman, a weapons engineer at the British shipbuilders Vosper Thorneycroft.= "The mirror will only reflect the light back to you if it's perpendicular to the beam." To stop this happening, many stealthy designs have strangely angled facets, says Spilman, who is well versed in this black art. Earlier this year, Vosper Thorneycroft unveiled= Sea Wraith II, a stealth ship designed by a team under Spilman.= =20 Snookered by design=20 Another way to minimise reflections is to avoid right angles between a craft's surfaces. Concave dihedrals, where two flat surfaces meet at right angles, and trihedrals, where three perpendicular= flat surfaces meet at a corner, redirect radio waves back to their source over a wide range of angles. "It's like aiming the cue ball into the corner of a snooker table. The ball will come straight back to you over quite a range of angles," says Spilman. This aversion to right angles is what produces the strange shapes of Sea Wraith and the US Air Force's F-117A stealth fighter.=20 The third essential ingredient for stealth is radar-absorbing paint, which works like a myriad of badly performing radio aerials. The rapidly changing electric field of a radio wave can excite the motion of electrons in a thin strip or wire of a conductor--this is the principle behind an aerial. In a conductor, the electrons flow freely and reradiate the signal. But in a poor conductor, such as a carbon fibre, the material's electrical resistance converts the electrons' energy into heat. A similar "damping" effect takes place= with magnetic materials known as ferrites which turn the= magnetic component of radio waves into heat. Either way, the radio= waves are absorbed.=20 Radar-absorbing paint is a gloopy coating containing millions of these damping fibres, which end up randomly oriented in all directions. The fibres work best if they are about a quarter of a wavelength long, and by choosing different fibre lengths, the paint can even be tuned to absorb specific wavelengths. Since military radar has a wavelength in the centimetre range, the coating is much thicker than most paints.=20 Detection is only one part of a radar's job. It also has to identify what it detects. However good the design and however efficient the absorbing paint, an aircraft or ship will always reflect some energy back to the radar receiver. In many cases, even this tiny signature can be enough for a military radar to identify the type of ship or aircraft it has caught in its beam.=20 So Sea Wraith employs a little deception. The ship has a mast that it raises in peace time, fitted with various dihedral and trihedral shapes. These strongly reflect radar signals, masking the ship's real signature. "Should anyone try to measure the signature in= peace time, they'd get a false reading," says Spilman. During a war, the mast would be lowered and the radar signature changed.=20 Sea Wraith is also camouflaged in the thermal part of the spectrum, to defend against heat-seeking missiles. A ship's thermal signature comes mainly from the engine exhaust, which heats up the funnels. To minimise this effect, Sea Wraith passes its exhaust= through seawater before expelling it. This cools the exhaust from more than 300 C to ambient temperature. "All that comes out of our funnel are cool gases," says Spilman.=20 But even this measure is not enough to fool the latest generation of anti-ship missiles. These home in on their target using thermal video images. An onboard computer can recognise a specific class of ship even if the angle of view changes. "These missiles are= almost impossible to distract with flares, which look nothing like ships to high-resolution imagers," says Spilman. The only way to protect the ship is to hide it entirely--and this is exactly what Spilman and his team have done.=20 Sudden mist=20 Sea Wraith has a cloaking device that hides the whole ship= from sensors in the visible and infrared regions. The vehicle will be fitted with thousands of tiny nozzles that spray atomised water into the air, enveloping the ship in a giant cloud of fine water droplets. This absorbs both short and long wavelength infrared as well as visible light, but allows the ship's radar to work normally.=20 A similar but more ambitious method for vanishing has been called for by US military chiefs. A few years ago, Western= generals believed they had a significant advantage when fighting at night because they had night vision sights. These imagers see by starlight, which is at its most intense in the short wavelength= infrared spectrum, between 0=B74 and 1 micrometres.=20 But today, armies all over the world have night vision sights, which the Americans say has significantly reduced their advantage. Now they want to regain it. The US still has a significant lead in the technology of thermal imagers, which work in the long wavelength infrared region and can also produce good images at night. So the military chiefs have turned to the Defense Advanced= Research Projects Agency, a military research organisation based in Arlington, Virginia, to devise a way to blind night vision sights while allowing thermal imagers to operate.=20 DARPA's answer is Magic Vision, a smoke intended to block visible and short wavelength infrared but remain= transparent to longer wavelengths. It's still in the early stages of development and DARPA is reluctant to discuss it. But they have a tough task ahead of them. The smoke itself will have to absorb or scatter radiation selectively in the visible and short wavelength infrared. The smoke generator will need to be lightweight--one person should be able to carry it together with, say, 19 litres of fuel. And this will have to generate enough smoke to quickly engulf a small group of soldiers. The smoke must also hang around as long as possible.= Perhaps most difficult of all, DARPA wants to make the smoke= nontoxic and environmentally friendly.=20 In the absence of a smokescreen, military designers must fall back on more conventional forms of camouflage. For this, they need to know what their equipment--whether a tank or a= uniform--looks like in every spectral region, so that they can make it blend in with its surroundings in that spectrum. These images will change depending on whether it's night or day, summer or winter= and whether the equipment is being used in rural or urban= terrain. Carting the equipment around to different places for= testing is expensive and time-consuming, so researchers at Britain's Defence Clothing and Textile Agency (DCTA) in Colchester are= pioneering another option.=20 The DCTA develops "add-on" camouflage for the Ministry of Defence. Its wares are used to hide everything from tanks= and soldiers to portable bridges and aircraft on the ground. In a small room on the second floor of the DCTA's Department of Camouflage, Concealment and Deception, mathematician Mark Rodgers is developing programs that can design camouflage in both the visible and thermal parts of the spectrum by simulating= the environment in which it will be used. "What I'd like to be able to do is to feed 250 pictures of terrain into a computer and have it come up with the best camouflage for that terrain," he says. Even in the visible spectrum this is not a simple task. A computer can easily work out the "average colour" in a scene, but this is of little use as camouflage because a block of average colour would stand= out clearly.=20 Instead, Rodgers has programmed his computer to count how= many patches of a chosen size appear in a given area, and to= measure their colours. It also counts how often different colours appear next to each other. The machine then generates a pattern that conforms to these numbers. The optimum size of the patches is also critical, a problem Rodgers is still wrestling with.=20 Things get even trickier in the thermal region. While= visible camouflage colours will look similar to their background regardless what time of day it is, the temperatures of these objects change constantly and at different rates throughout the day and= night. Modelling the temperature of a terrain at any time is plagued with difficulties because it depends on such a large number of variables--from the intensity of solar radiation and specific heat capacities of materials, to humidity and air temperature. Still, Rodgers is optimistic that advances in computing power will help. "Five years ago we couldn't have contemplated the things we= can do now," he says.=20 Beach ball decoy=20 The DCTA's computers are also simulating the battlefield as= it appears in the world of radar. The goal here is to develop decoys that convince radar operators that they have found tanks.= DCTA radar expert Tony Howard says that a tank reflects strongly from the front, where the barrel meets the turret, since this can be a right angle between two surfaces. It also reflects fairly strongly from the sides, where the wheels meet the side of the vehicle. The precise shape of decoys that mimic this pattern of reflections has not yet been finalised. But it could consist of an inflatable, metalised beach ball with dihedral shapes on both sides and a trihedral at the front. "The idea is that we'd develop decoy kits of simple shapes that could be set up quickly to mimic tanks and aircraft," says Howard.=20 More advanced radar decoys that mimic the signature of aircraft in flight are already being tested for the US Air Force. The Miniature Air Launched Decoy (MALD) is a scaled-down jet engine the= size of a coffee mug that can be fitted with aerodynamic= surfaces to mimic the radar signatures of much larger aircraft. The idea is that a number of MALDs would be carried over enemy territory by stealth planes, where they would be released and fly in formation for up to 30 minutes. The sudden appearance of a squadron overhead would force the enemy to light up their anti-aircraft radar systems which could then be targeted for destruction. Each= MALD is expendable and costs less than $30 000.=20 Of course, as modern camouflage systems get better, so too do the sensors used to see through them. In the near future, computers will routinely scan images of each battlefield location in every region of the spectrum, hunting for tell-tale signs of hidden= vehicles or soldiers.=20 Even America's stealth planes are not immune from this cat-and-mouse game. In the world of millimetre-waves,= aircraft stick out like sore thumbs, whether or not they have radar-absorbing paint. Millimetre-wave cameras are not yet widely available, but the writing is on the wall for today's= stealth technologies. Researchers such as Spilman, and Howard, are racing to find tomorrow's technologies. Lives may depend on their success.=20 From New Scientist, 06 December1997=20 ------------------------------ Date: Thu, 04 Dec 1997 11:28:02 GMT From: georgek@netwrx1.com (George R. Kasica) Subject: Re: New Scientist on Stealth On Thu, 04 Dec 1997 18:16:01 +1200, you wrote: > >The vanishing point > > Brett: FYI, posting an entire article from a magazine is most likely a copyright violation. In the future please refrain from doing this. Portions are generally OK however. ===[George R. Kasica]=== +1 414 541 8579 Skunk-Works ListOwner +1 800 816 2568 FAX http://www.netwrx1.com West Allis, WI USA georgek@netwrx1.com Digest Issues at: http://www.netwrx1.com/skunk-works ------------------------------ Date: Thu, 04 Dec 97 10:41:52 EST From: keller@eos.ncsu.edu Subject: Re: Rolling an SR-71 (was Re: U-1) George Kasica asked... >I don't usually post, but I couldn't pass this up...does Prohibited >mean the Air Force pilot is going to get written up, etc. if he does >the roll, OR does it mean that BAD THINGS are going to happen to the >aircraft... Never having served in the military, I'll leave the matter of administrative conquences due the SR-71 pilot who attempts any aerobatic maneuvers to someone else. I am curious about this question myself, though, so I would encourage someone else on the list to comment on it. As to consequences to the aircraft, if you look over the the operating limitations section of the dash-1, the prohibition on aerobatic maneuvers by the SR-71 is pretty much a case of stating the obvious. The dash-1 itself puts it about the best with its observation that while SR-71 can be operated over a remarkably wide range of mach number, this is achieved at the expense of severely limiting the flight envelope in terms of other parameters. This is particularly true of the angle of attack limits, g-limits and knots effective air speed (which is really a measure of dynamic pressure, correct?). While I suppose that it might be possible to barrel roll an SR-71 following the manner of Tex Johnston's famous barrel roll of the Boeing Dash-80 prototype, that might be all in terms of aerobatics which the SR-71 is capable of. I don't recall seeing anything in the dash-1 as to whether the SR-71 has fuel & engine lube oil systems capable of inverted flight (negative g's), but, given it's mission and the prohibition on aerobatics, I would rather think not. - --Paul Keller ------------------------------ Date: Thu, 4 Dec 97 8:36:03 GMT From: ahanley@usace.mil Subject: Re: Rolling an SR-71 (was Re: U-1) It might be worth pointing out that the SR-71 that is sitting at Blackird Airpark was retired because its limits were exceeded at an airshow and it was deemed at the time not worth the money to do the repairs (they were fat on SR-71s at the time). Even given USAF conservatism on how it flies its aircraft, the prohibition against aerobatics in the SR makes sense. Art Hanley Despite what you might want to Believe, none of any of the above Even remotely has anything to do With my employer. ------------------------------ End of skunk-works-digest V6 #93 ******************************** To subscribe to skunk-works-digest, send the command: subscribe in the body of a message to "skunk-works-digest-request@netwrx1.com". If you want to subscribe something other than the account the mail is coming from, such as a local redistribution list, then append that address to the "subscribe" command; for example, to subscribe "local-skunk-works": subscribe local-skunk-works@your.domain.net To unsubscribe, send mail to the same address, with the command: unsubscribe in the body. Administrative requests, problems, and other non-list mail can be sent to georgek@netwrx1.com. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace all instances of "skunk-works-digest" in the commands above with "skunk-works". Back issues are available for viewing by a www interface located at: http://www.netwrx1.com/skunk-works If you have any questions or problems please contact me at: georgek@netwrx1.com Thanks, George R. Kasica Listowner