From: skunk-works-digest-owner@mail.orst.edu To: skunk-works-digest@mail.orst.edu Subject: Skunk Works Digest V5 #527 Reply-To: skunk-works-digest@mail.orst.edu Errors-To: skunk-works-digest-owner@mail.orst.edu Precedence: bulk Skunk Works Digest Thursday, 30 November 1995 Volume 05 : Number 527 In this issue: Re: Swedish pulse detonation wave engines Re: Swedish pulse detonation wave engines ignition... Aurora Re: Swedish pulse detonation wave engines SR-71 and Aurora Re: Hypersonic speed -MOSTLY- evades shooting down ! Ramjet Efficiency/Design Considerations Re: Mac(h)rihanish Re: Hypersonic speed -MOSTLY- evades shooting down ! Re: Hypersonic speed -MOSTLY- evades shooting down ! Re: Ramjet Efficiency/Design Considerations See the end of the digest for information on subscribing to the skunk-works or skunk-works-digest mailing lists and on how to retrieve back issues. ---------------------------------------------------------------------- From: Kauto Huopio Date: Wed, 29 Nov 1995 13:14:32 +0200 (EET) Subject: Re: Swedish pulse detonation wave engines On Tue, 28 Nov 1995, Steve Schaper wrote: > How would this compare in cost efficiency to rocket engines for boosters? A > shuttle with say, 800 hz PDWs might be interesting. Hmm, an engine with 800 detonations per second? Sounds like ear-cracker. - --Kauto *********************** Kauto Huopio (Kauto.Huopio@lut.fi) ****************** *Mail: Kauto Huopio, Laserkatu 3 CD 363, FIN-53850 Lappeenranta, Finland * *Tel : +358-53-4126573 (I am NOT at home very often..) * ***************************************************************************** ------------------------------ From: Charles_E._Smith.wbst200@xerox.com Date: Wed, 29 Nov 1995 04:19:05 PST Subject: Re: Swedish pulse detonation wave engines Not very well. Airbreathers don`t perform too well above 100K feet! Also, they suffer from the same thermodynamic limitations as turbojets at low and mid altitudes. Using lasers to supply energy to the reactants doesn`t sound too efficient. What powers the laser. Wouldn`t power generation for the laser have to be included in the total cycle efficiency for the engine? Seems like a spark plug would work a lot better! Chuck ------------------------------ From: "I am the NRA." Date: Wed, 29 Nov 95 08:23:17 PST Subject: ignition... >Using lasers to supply energy The energy supplied is small. Initiaton energy only. Like a spark plug. The reactant(s) supplied the output energy. >to the reactants doesn`t sound too efficient. Lasers come in all sizes. All that is needed is initiation energy. >What powers the laser. Wouldn`t power generation for the laser have to be >included in the total cycle efficiency for the engine? Sure. Same thing that powers a spark plug/igniter >Seems like a spark plug would work a lot better! Spark plug exposed to "detonation" [1] does not last long. If geometry requires it to be "in center" of fuel/reactant mass, popping two or more laser beams in may well be better than one physical THING subsject to damage. [1] Are we talking honset-to-pete _detonation_ in these engines? Or just "fast combustion"? ============================================================= By Defintition, a hypersonic, atmospheric craft is not stealthy. IR search & track looking up sees a hot thing against cold space. Looking down, it sees a hot thing against (realtively) cool surface. Hypersonics (by definition) lack loiter time. Hypersonics start running into difficulties 'seeing' thru the hot gasses around them... regards dwp ------------------------------ From: Patrick Wiggins Date: Wed, 29 Nov 1995 11:53:12 -0700 (MST) Subject: Aurora Ok, I've been lurking out here for months. Guess it's about time I screw up the nerve to make a contribution... :-) Have there been any Aurora sightings *lately* (in the last year or so)? I've been reading Aviation Leek for years now and I don't recall any mention of any sort of Aurora sightings for well over a year. And, to the best of my knowledge, there don't appear to have been any *recent* sightings mentioned here either. Opinions, please? Thank you, Patrick :-) Patrick Wiggins, Hansen Planetarium, SLC, UT email: patrick.wiggins@k12.uen.gen.ut.us ------------------------------ From: larry@ichips.intel.com Date: Wed, 29 Nov 1995 11:12:09 -0800 Subject: Re: Swedish pulse detonation wave engines Urban_Fredriksson writes: >FOA, the Swedish defence research establishemen, is >developing pulse detonation wave (PDW) engines. ... > >Studies has been underway since 1993, the first test rig >was run in the spring of 1994 and was publicly shown during >a conference in the USA (the first PDW engine publicly >shown). Yes, I heard of this last year in fact through the US PDE community. The US community was very excited about it. In fact, SAIC in the US, was working with the Swedish researcher I believe. SAIC has some great CFD tools for PDE design. >Several types of fuels are to be tested: Acetylene, >hydrogen, ethane and others. There are some interesting 'others' that aren't being discussed. They wouldn't even tell me what they were. >One goal is to be able to use a laser to initiate the >detonation, so it can start without any previous combustion >sequence. > >A laser can be focused very precisely, which is good not >only to avoid combustion, but also to start the detonation >sequence in different places, and thus use the different >forces to guide the vehicle. Very interesting idea - the laser induced detonation at predetermined locations. The laser detonation is not a new idea. In fact, some US aircraft engines are going to laser induced ignition. >It is possible not only to use internal thrust chambers, >where the detonation wave is started from the rear of the >chamber by the ignition circuit, but also external >detonation waves, Yes. Using them in this manner for base drag reduction in the transonic regime has also been proposed. > This is where a >laser comes in handy, as it can start the detonation to the >rear of the engine in a predetermined spot. As I said above, this is a nice touch! Steve Schaper writes: >How would this compare in cost efficiency to rocket engines for boosters? A >shuttle with say, 800 hz PDWs might be interesting. Indeed! Remember that PDEs are very new engines and there's a lot that hasn't been done yet, but the PDE community has recognized that the PDE may be a very practical zero to orbital velocity engine cycle. It would use airbreathing up to a certain Mach No. and then switch to internal oxidizer in rocket mode, but the same PDE combustion cycle would run throughout. Since there are no moving parts, or very few moving parts, and weight and reliability are thereby enhanced over rockets, PDEs may represent the most practical orbital/high speed cycle. But they are too new to answer these questions yet. Since they're also so simple, they may represent the first practical jet engine cycle that I know of for Experimental private aircraft. Also the PDE thruster belt has been thought of. As far as vibration is concerned, the PDE community believes auto engine technology can help here. Larry ------------------------------ From: malsmith@cafe.net (Mallory Smith) Date: Wed, 29 Nov 1995 11:57:08 -0800 Subject: SR-71 and Aurora Dear PR person: As an old Naval Aviator I have had a lifelong interest in aircraft. Do you have a mailing list and if so does it have an Internet address? I am interested in finding out what I can about the Aurora aircraft referred to in Frederick Forsyth's book (Page 181 in the soft cover) the Fist of God. The Skunk Works seems the logical place to look. I'd be pleased to hear from you. Mallory Smith, USNR,retired, 572368 ------------------------------ From: larry@ichips.intel.com Date: Wed, 29 Nov 1995 12:06:12 -0800 Subject: Re: Hypersonic speed -MOSTLY- evades shooting down ! Brett Davidson writes: >>> A hypersonic vehicle would be virtually immune to interception because >>> even if it was tracked and a fast enough missile launched, ... Michael Stockton wrote: >> Little bit of the old US U-2 thinking here Brett and look what happened >> to Gary Powers.I appreciate the U-2 was subsonic however your same >> philosophy was applied but with this time with regard to altitude. >The U-2 was known to be vulnerable in 1960- "Oxcart" was well under way >then. Altitude presents the problem of range, but very high speed presents >a much more complicated challenge. Yes, many good points Brett, in fact, per "The Oxcart History", an operations analysis was done to determine the if the advantages in altitude, speed, and ECM that OXCART would have over U-2, would be adequate for the time. Indeed they have been haven't they! Michael Stockton wrote: >> A laser beam or particle beam will have no problem with hypersonic speeds! Brett Davidson writes: >Indeed, but nobody has any systems deployed, or is likely to for quite some >time. No practical laser or particle beam weapon has been demonstrated- ... Yes, I agree. But I'd like to explore this some more in another area. I don't know the answers yet, but here is the direction of thought: Remember that the highest speed hypersonic vehicles (the faster the better I guess) will have something that no other aircraft type or missile (not warhead) has, namely it's designed for a very high heat load environment to begin with. What I'm talking about can be understood when one considers the fact that the thermal level that the Apollo command capsules encountered in reentry to earth (Mach 32.5 at 56 km alt.) was almost twice the heat levels of the surface of the sun (11,600 K versus ~6000 K on the sun's surface)! So, if one pushes hypersonic reconnaissance thermal load technology to the highest levels possible, that MAY enable a natural immunity from lasers to be obtained. This also begs the question of how can the plasma sheath surrounding a hypersonic vehicle be configured to help protect from laser penetration. The laser needs to be of a certain wavelength to penetrate the atmosphere anyway. Can the plasma sheath (again no other aircraft type has a plasma sheath) be configured to defeat such frequencies? Would the above problems for the laser, plus the speed of the hypersonic vehicle (again the faster the better), also require that the power for the ground based laser be so high that it is not even practical to build? The only hope for the laser side may be from a space based laser which has access to great power levels, but again there are still problems for the space based laser. Many of these problems came up during Reagan's Star Wars program. Larry ------------------------------ From: "joseph.r.sleator" Date: 30 Nov 95 10:37:49 Subject: Ramjet Efficiency/Design Considerations G'day skunkers Drawing on the copious ramjet experience on this list, does anyone know if ramjet engines can function efficiently at subsonic speeds? I'm thinking about using these on the blade tips of a helicopter. This was tried at Aberdeen Proving Grounds by the army about 30 years ago, but I don't know how successful they were. Apparently the design sucked lots of fuel. My design is basically a straight stainless pipe with an annular propane combuster in about the middle. It has a teardrop shaped diffuser at the front. (round on the front, pointy on the back. The widest part of the diffuser is coincident with the inlet lip (it's subsonic, ya see) I've already got a _limited_ amount of thrust from a wooden self-consuming ramjet with a similar shape. My other question is regarding nozzle diameter/shape. I'm assuming that I'd use the same surface area at the nozzle that I have at the inlet. _Reality check please._ I have some squeezing/flaring tools so making it smaller should be no problem. My intuition tells me that I should do something more elaborate with the nozzle. Is a simple smooth constriction good for low altitude subsonic use? Should I flare it out again? S'pose if it worked too well fuel control would be a problem. If the design accelerated the blades too much the efficiency would simply drop off as tips approach M1. Diagram: (set your font to courier or other monospaced font) /^\ / \ |=| |=|----- Inlet surface areas same as outlet. | \ / | | \ / | | /%\==|==----- Propane comes in here | /ooo\ | |/ooooo\|----- Perforated stainless diffuser. |ooooooo| | | | |---|----- Piezo spark device \ V / \ /------ Simple constriction for nozzle You start it up by spinning the rotor blades (the ramjet is at the end) and triggering the piezo spark generator (from a cig. lighter) and then you turn on the propane (pop...hiss...swocka swocka swocka swocka) Then you put on the music. Music? Yeah, I use Wagner... ;-) Seriously, though any comments would be greatly appreciated. Hopefully if I flounder around with this enough, Chuck will post his ramjet design paper on his W^3 site. Chuck, good photo of you, by the way. What are you holding? Chuck, can it really be this simple, or am I way off? Cheers, Thanks in Advance, Joe Sleator Sydney, Australia ------------------------------ From: albert.dobyns@mwbbs.com (ALBERT DOBYNS) Date: Tue, 28 Nov 95 22:26:00 -0500 Subject: Re: Mac(h)rihanish K&AG> Date: Tue, 28 Nov 1995 08:29:01 -0500 (EST) > From: Kathryn & Andreas Gehrs-Pahl > Subject: Mac(h)rihanish ......deleting some very interesting reading to keep this short.. K&AG> Sometimes a rumor is just a rumor. :) Your statement above is certainly true, but if it wasn't for rumors, lots of writers would be out of work! :) At one time I was absolutely convinced that a high-speed SR-71 replacement recon craft of some sort did exist. Everyone else called it Aurora including me. But after all the magazine articles, newspaper stories, and a few books came out, it seemed like the rumor generator (whatever that might be) ran dry. As of now, I have no way of knowing if there ever existed the Aurora commonly described as flying at Mach 5+. All I ever read at one time made it sound like it existed and it wouldn't be long before it was made public...much like the F-117. But Aurora never appeared. But during the last 5+ years, some magazine article authors made a bit of money giving us the "evidence" that there is such a plane. A few books have been written about it as well. And Testors has probably made a tidy sum of money on their SR-75 and that other model. I've read that they made a lot of money on their F-19 model (which I still have sitting in its box, unassembled, collecting dust). Speculation can be fun sometimes. Most of the time it's probably not very productive. And once you're done and you're back into the real world, if no solid proof has been produced then it's still speculation. So as you have already pointed out: sometimes a rumor is just a rumor. But rumors seem to take an incredibly long time to die. People are still investigating the crash of a UFO at Roswell, NM. They write books, make movies, speculate over and over. And this is an incident that supposedly happened 48 years ago! Yet the rumors persist. Will the Aurora rumor continue until it's as old as the Roswell rumor? I don't think so......but I'm just speculating of course. <-said with a dash of sarcasm). In the meantime I still haven't finished reading all of Jay Miller's Skunk Works books. I did find 2 pages that have something that I wonder if anyone else has noticed. On page 120 is a photo that at first glance looks like an A-12 with 4 tail fins!! It isn't obvious at first (or it wasn't for me) that there are 2 A-12s parked side by side. The photograph was taken at the right angle so the main gears lined up. The nosewheel of the 2nd plane appears to be hidden by something. The two planes' shadows are visible but I didn't notice that when I looked at the picture for the first time. Looks can be deceiving. The second thing is what I think is an error in photo caption on page 147 (top photo). The first-flight date listed doesn't agree with the date listed on page 200. - -Al- - --- þ SLMR 2.1a þ SR-71: Your tax dollars at work...............at Mach 3! ------------------------------ From: Brett Davidson Date: Thu, 30 Nov 1995 15:06:42 +1300 (NZDT) Subject: Re: Hypersonic speed -MOSTLY- evades shooting down ! On Wed, 29 Nov 1995 larry@ichips.intel.com wrote: > Brett Davidson writes: >then. Altitude presents the problem of range, but very high speed presents > >a much more complicated challenge. > Remember that the highest speed hypersonic vehicles (the faster the better > I guess) will have something that no other aircraft type or missile (not > warhead) has, namely it's designed for a very high heat load environment > to begin with. What I'm talking about can be understood when one considers > the fact that the thermal level that the Apollo command capsules encountered > in reentry to earth (Mach 32.5 at 56 km alt.) was almost twice the heat > levels of the surface of the sun (11,600 K versus ~6000 K on the sun's > surface)! Wow! Moving into pure guesswork here, I think that the thermal load on an ablative heat shield is temporarily MUCH greater than is likely to be the case for a vehicle cruising (for however long) at, say Mach 6 The design problem may be easier in that the temperature may be well under 1000 K (?), but maybe more difficult in that it lasts longer- an hour or three instead of a few minutes. Also, the Apollo heat shields were ablative- they eroded, thus carrying heat away. From what I remember, the Apollo capsules decelerated at something like 10 G, while the space shuttles decelerate at a much lower rate -2-3 G (?) and use reuseable non-ablative tiles. Does anyone have any figures for these cases? > So, if one pushes hypersonic reconnaissance thermal load technology to the > highest levels possible, that MAY enable a natural immunity from lasers to > be obtained. The solution I hear most often for hypersonic vehicles is to circulate the cryonic fuel under the skin on its way to the engines. Lasers actually have relatively wide beams - a couple of metres or more - and work by increasing the thermodynamic load on the target beyond its structural limits. This can take several seconds, and maybe an active cooling system can dispose of those extra kilojoules falling on the skin as fast as they arrive. It would depenend on how great a margin of safety is originally designed into the system. Hmmm, interesting. Is there anyone who can elaborate without having to kill us afterwards? > This also begs the question of how can the plasma sheath surrounding a > hypersonic vehicle be configured to help protect from laser penetration. The > laser needs to be of a certain wavelength to penetrate the atmosphere anyway. > Can the plasma sheath (again no other aircraft type has a plasma sheath) be > configured to defeat such frequencies? I think the SWERVE tests proved that some frequencies could penetrate the sheath (AvLeak...um..damn, can't find it) for communications purposes and therefore weapons-level intensities may do so more easily at some frequencies than others too. The questions are whether it is a frequency that would have the desired effect soon enough could do so and whether the sheath is significant at the speed of the aircraft -say, Mach 6 instead of higher Mach numbers... The sheath itself would be quite slim from the front and sides- confined by the aircraft's conical shockwave. The combined effect of the opacity of the sheath, or at least its attenuation of a beam- and the active skin cooling would be quite effective perhaps. One interesting thing about this is that what is being proposed here is a de facto form of armorplate- something that no modern aircraft apart from the A-10 has! (?) > Would the above problems for the laser, plus the speed of the hypersonic > vehicle (again the faster the better), also require that the power for the > ground based laser be so high that it is not even practical to build? Still guessing, the role of the aircraft is perhaps an issue. A recon plane may fly at the low end of the hypersonic scale so that its own instruments aren't compromised by its own plasma, unless it slows to ~Mach 4 for its photo run and then accelerates up to Mach 6-7-whatever again. A strike aircraft might be a semi-ballistic Stuka spending most of its flight path at barely suborbital velocities and altitudes. Neither would be cheap or easy, of course. Lasers do spread out due to the impossiblity of perfect collimation and they also suffer atmospheric scattering and absorption which place limits on intra-atmospheric range that may be nearly absolute... increased power may mean fewer, or none built. The vital unacknowledged side of design (and strategy) is economics. > The only hope for the laser side may be from a space based laser which has > access to great power levels, but again there are still problems for the > space based laser. Many of these problems came up during Reagan's Star Wars > program. Now that's wher my idea for a space fighter comes in... :-) > Larry Very interesting --Brett ------------------------------ From: sschaper@mo.net (Steve Schaper) Date: Thu, 30 Nov 1995 00:43:59 -0600 Subject: Re: Hypersonic speed -MOSTLY- evades shooting down ! I was under the impression that weapons-grade lasers worked by explosively vaporizing a small amount of target surface, and pulsing at a rate designed to let the plasma cloud dissipate for the next burst to get through. The result is an explosive process that tears the target apart. ------------------------------ From: Wei-Jen Su Date: Thu, 30 Nov 1995 02:05:50 -0500 (EST) Subject: Re: Ramjet Efficiency/Design Considerations On 30 Nov 1995, joseph.r.sleator wrote: > G'day skunkers > > Drawing on the copious ramjet experience on this list, does anyone know if > ramjet > engines can function efficiently at subsonic speeds? I'm thinking about using Nope. Ramjet is not efficiently at subsonic speed. They did a lot of reserch about that and they didn't come up with a good solution yet. > these > on the blade tips of a helicopter. This was tried at Aberdeen Proving Grounds by The problem is if you put a engine on the blade tips of a helicopter, the stress on the blades will increase because there is a additional weight on the extreme (the worse case in centrifuga forces), plus the speed that will increase the stress. This will rip appart the blades. And how you going to control the direction of the trust??? Maybe this is important. I know that some idea was using trust on the tip of the blades but with the engine inside of the fuselage of the helicopter and the gas exhaust was driving throught a pipe inside of the blade. But, what I know, they never built it. May the Force be with you Su Wei-Jen E-mail: wsu02@barney.poly.edu ------------------------------ End of Skunk Works Digest V5 #527 ********************************* To subscribe to skunk-works-digest, send the command: subscribe skunk-works-digest in the body of a message to "majordomo@mail.orst.edu". 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