From: skunk-works-digest-owner@mail.orst.edu To: skunk-works-digest@mail.orst.edu Subject: Skunk Works Digest V5 #578 Reply-To: skunk-works-digest@mail.orst.edu Errors-To: skunk-works-digest-owner@mail.orst.edu Precedence: bulk Skunk Works Digest Thursday, 21 December 1995 Volume 05 : Number 578 In this issue: Mail failure Re: MDC and GD win A-12 law suit Re: Waverider [NASP] Hodefoneaminit Hodefoneaminit Stealth Santa's Sleigh & Reindeer 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: POSTMASTER@RPSPO4.ATTATLMFG.AtlantaGA.ATTGIS.COM Date: Thu, 21 Dec 95 07:31:00 PST Subject: Mail failure [005] Mail retry count exceeded sending to: ATTATLMFG /RPSPO2 - ------------------------------------------------------------------------------ Return-Path: <@attatl.AtlantaGA.NCR.COM:skunk-works-digest@gaia.ucs.orst.edu> Received: from attatl.AtlantaGA.NCR.COM by attatl.AtlantaGA.ATTGIS.COM id <30D95D9F@attatl.AtlantaGA.ATTGIS.COM>; Thu, 21 Dec 95 05:14:07 PST From gaia.ucs.orst.edu!skunk-works-digest Thu Dec 21 05:07 EST 1995 remote from attatl Received: by attatl.AtlantaGA.NCR.COM; 21 Dec 95 05:07:49 EST Received: from ncrgw1.UUCP (ncrgw1@localhost) by ncrhub5.attgis.com (8.7.3/8.7.3) with UUCP id FAA18922 for rpspo2.atlantaga.attgis.com!cfoster; Thu, 21 Dec 1995 05:02:37 -0500 (EST) Received: by ncrgw1.ATTGIS.COM; 21 Dec 95 04:59:35 EST Received: (from daemon@localhost) by gaia.ucs.orst.edu (8.7.3/8.7.3) id AAA10894 for skunk-works-digest-outgoing; Thu, 21 Dec 1995 00:06:02 -0800 (PST) Received: (from majordom@localhost) by gaia.ucs.orst.edu (8.7.3/8.7.3) id AAA10887 for skunk-works-digest-send@mail.orst.edu; Thu, 21 Dec 1995 00:06:01 -0800 (PST) Date: Thu, 21 Dec 1995 00:06:01 -0800 (PST) Message-Id: <199512210806.AAA10887@gaia.ucs.orst.edu> From: skunk-works-digest-owner@gaia.ucs.orst.edu To: skunk-works-digest@gaia.ucs.orst.edu Subject: Skunk Works Digest V5 #577 Reply-To: skunk-works-digest@gaia.ucs.orst.edu Sender: skunk-works-digest-owner@gaia.ucs.orst.edu Precedence: bulk Skunk Works Digest Thursday, 21 December 1995 Volume 05 : Number 577 In this issue: Waveriders revisited. Satellite Observations Waverider, Whatever Happened to the Satellite Observations - [Corrected Copy] MDC and GD win A-12 law suit Latest Av Week ! 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: Charles_E._Smith.wbst200@xerox.com Date: Wed, 20 Dec 1995 04:10:21 PST Subject: Waveriders revisited. Funny the topic came up when it did. I was going over some flying wing resources sent to me by a friend and one of the magazines had a great article about the B70. I love the B70 because I remember my dad taking me to Wight-Pat as a yoot to go see it. It was soooo cool, and I somewhere have pictures of me as a young guy sitting on the tires- I`ll have to find them. Be neat for the office. I was remembering studying compression lift principles and - - -BOOM- it hit me. Almost all new fighter designs use compression lift. The principle of compression lift uses the shock wave(s) from the fuselage to compress the air below the wing. The B70 shows this well. Notice the foward fuselage is symmetrical(ish) and above the wing, whereas the rear part of the fuse- is detached-from the front, and is located beneath the wing. Notice the similarity to the the B70 basic planform when you look at the side-view of the F15, or Mig 29. Also, the F16 shows a similar structure. The LE sweep is chosen to enclose the in the shock cone at the design point Mach number. Pretty cool, huh? I won`t go into all the boring details, but you should get the basic picture. Hope this sheds a little light on the subject. Chuck - ------------------------------ From: "Terry Colvin" Date: Tue, 19 Dec 95 16:35:31 EST Subject: Satellite Observations Forwarded interview with Jacques Vallee, astrophysicist: Terry W. Colvin Fort Huachuca (Cochise County), Arizona USA "No editor ever likes the way a story tastes unless he pees in it first." -Mark Twain - ------------------------------ From: "Terry Colvin" Date: Wed, 20 Dec 95 07:05:51 EST Subject: Waverider, Whatever Happened to the Forwarded from the Space Tech list: Date: 17 Dec 1995 22:08:04 GMT From: "August,james,a " Subject: Whatever happened to the Waverider? Michael Lammers wrote: >At design conditions, the lateral edges of a waverider will ride >on a captured shock wave. Waveriders often have lower drag, higher >lift, or higher lift/drag ratios than conventional shapes at >hypersonic speeds. I guess the key point here is that they only >have this performance at very high velocities. >From what I understand, the real problem with waveriders is the problem >with a lot of high-performance hypersonic designs -- the darn thing >has got to fly at subsonic velocities at some point to land. Generating >lift at subsonic and supersonic speeds is quite different, and only more >complicated when you are riding shock waves. I believe that most of >the work being done now is to investigate the low-speed aerodynamic >characteristics of wave riders, hence the tests at Ames. From my understanding a waverider shape takes advantage of the leading edge attached shock to act as an endplate, which prevents the high pressure below the wing from leaking into the low pressure above it. This effectively lowers the induced drag which gives a higher L/D ratio. To visualize a simple waverider shape imagine a shock cone (which will be more pointy i.e. larger height to base ratio for higher mach numbers). Now pick a design mach number and using that cone geometry and the desired angle of attack (small) you can get an idea as to what your waverider planform looks like. The problem is that you must keep the rest of the vehicle inside the shock cone or you will suffer high drag and high heat loads (and make more shock waves). You end up with sort of a flattened, curvy shape which has low drag but also low volume. A lack of volume ends up being the big problem with a waverider SSTO. We have low drag, but we can't fit in enough fuel to make orbit (so far). The waverider is a good shape for a cruise vehicle however, since the shape is optimized for a rather narrow range of mach, as are cruise vehicles like missiles or airliners. For more and better info try John D. Anderson's book on Hypersonic Aero or check the NASA RECON database on the web. Jim August UTA/NASA Center for Hypersonics - ------------------------------ From: "Terry Colvin" Date: Wed, 20 Dec 95 08:02:31 EST Subject: Satellite Observations - [Corrected Copy] Forwarded interview with Jacques Vallee, astrophysicist: SATELLITES There are many more satellites in low Earth orbit than in geostationary orbit. Any evening or morning, you can see several satellites to the naked eye. MIR comes across at about mag 0. This is as bright as the brightest stars. In the UK, some newspapers used to publish the times of satellite passages in their weather section (!). I used to work at the University of Aston, Earth Satellite Research Unit where these predictions for the press were prepared weekly. Our work was in observing selected satellites with a large camera (huge in fact; 610mm f/1 to those who have an interchangeable lens camera), calculating their orbits and monitoring changes to their orbits due to changes in upper-atmosphere winds and density and also determining the harmonics in the Earth's gravity field (shape to put it simply, but not wholly accurately). Note that most satellites move from west to east (prograde) and in the evening usually move into the Earth's shadow before reaching the eastern horizon. In the morning, they tend to come out of shadow and move towards the east. Satellites in retrograde orbits move from east to west, although most retrograde satellites are only just retrograde (inclination of orbit to the equator of just over 90 degrees) so tend to move more north-south or south- north. A low satellite (say 150-200km height) will cross the sky in a few minutes, but most of this arc is accomplished in about one minute when it is highest in the sky. Satellites with large flat surfaces (like solar panels) can produce substantial glints and it is not uncommon for such glints to reach mag -4 (similar to Venus). There are a few reports of some satellites glinting to even brighter than this, enough to cast shadows. In general, a satellite is brightest when in the opposite side of the sky from the Sun (east in the evening and west in morning) and when close to being in eclipse. During transition into shadow, a satellite can appear quite red if it is bright enough to activate the colour receptors in the eye. Note that there are some groups of satellites that orbit in formation. One is the NOSS group (surveillance of shipping) that has four satellites in close formation. There are several such NOSS formations in orbit. I have seen these by chance on several occasions. If you want to go out and see satellites, there is an excellent Web page that allows you to predict satellite passes for your own site. Try it on http://chara.gsu.edu/sat.html A couple of months ago, there was the first part of a fascinating interview with Jacques Vallee which included how he became involved in UFO investigations. I include these sections again below followed by my comments. There is one thing I wish to make clear. I am commenting ONLY on Vallee's 1961 sighting. The mystery of the destruction of the data is not being considered at all in the following comments. > 50 GCAT: How did you first become interested in UFOs and paranormal >phenomena? > > Vallee: I started out wanting to do astronomy and I ruined essentially >a perfectly good career in science by becoming interested in computers. This >was in France in the early days of computing and the earliest days of >satellites and space exploration. So I took some of the earliest computer >courses at French universities. > > My first job was at Paris observatory, tracking satellites. And we >started tracking objects that were not satellites, were fairly elusive, and ********************************************************************** >so we decided that we would pay attention to those objects even though they >were not on the schedule of normal satellites. And one night we got eleven >data points on one of these objects--it was very bright. It was also >retrograde. This was at a time when there was no rocket powerful enough to ************************************************************** >launch a retrograde satellite, a satellite that goes around opposite to the ***************************** >rotation of the earth, where you obviously need to overcome the >earth's gravity going the other direction. You have to reach escape velocity >in the direction opposite the rotation of the earth, which takes a lot more >energy than the direct direction. And the man in charge of the project >confiscated the tape and erased it the next morning. > > So that's really what got me interested. Because up to then I thought, >Scientists don't seem to be interested in UFOs, astronomers don't report >anything unusual in the sky, so there probably isn't anything to it. >Effectively, I was in the same position that most scientists are in >today--you trust your colleagues, and because you don't see any >reports from credible, technical witnesses, you assume that there is >nothing. And there I was with a technical report--I don't know what it was. >It wasn't a flying saucer--it didn't land close to the observatory. But >still, it was a mystery. And instead of looking at the data and preserving >the data, we were destroying it. > > 50 GCAT: Why did he destroy it? > > Vallee: Just fear of ridicule. He thought that the Americans would >laugh at us, if we sent it--all of the data on satellites was being >concentrated in the U.S. And we were exchanging our data with international >bodies. And he just didn't want Paris observatory to look silly by reporting >some thing that he could not identify in the sky. > [This was in] 1961. Later I found out that other observatories had >made exactly the same observation, and that in fact American tracking >stations had photographed the same thing and could not identify it either. It >was a first magnitude object: it was as bright as [the star] Sirius. You >couldn't miss it. It didn't reappear in successive weeks. ************************************** > It's just a little anecdote, but to me that fact that we destroyed it >was more important than what we saw. And that reopened the whole question for >me: Are there things that scientists are observing and not talking about? And >then I started extending a small network of scientists, which is still >active, and found that there was a lot of data that was never published. In >fact, the best data has never been published. I think a great deal of the >misunderstanding about UFOs among scientists is that the scientists have >never had access to the best data. This is me now again, Rob McNaught. I worked in optical satellite tracking for several years, operating a large camera in the UK and Australia. It seemed unlikely that I could have met and corresponded with so many satellite observers world wide and not have heard of this mystery, so I contacted a couple whom I new were very active. One, Russell Eberst, is I believe the most prolific amateur observer of artificial satellites and he responded thus: "As for Vallee's satellite, I imagine the retrograde object he mentions from 1961 was Samos [2] 1961 Alpha 1. It was 7metres long 1.5metres in diameter and may well have occasionally reached +1 magnitude, though I remember it more around +2.5 There is also a slight chance that if seen after 1961 October, it may have been Midas 4 1961 Alpha-Delta 1 which was launched that month into a high [3500km?] polar, slightly retrograde orbit and was classified by the U.S. for several months. It was rarely naked-eye visibility, though occasionally gave out brief, bright flashes which could catch the attention of anyone staring into the clear dark sky. The reason the team-leader destroyed the observations may have been to ensure the security of the orbit imposed by the U.S. authorities was not compromised. (bit of speculation there)." Vallee said "[they] started tracking objects that were not satellites, were ******************************************************* fairly elusive". This seems rather strange. If you don't have predictions for ************** an observed object, it does not mean that it is not a satellite. If you rely on NORAD, you wouldn't know about the large and very bright Keyhole photo-reconnaissance satellites because they don't publish their orbits. This also applies to NOSS, Lacrosses, Milstars etc. In addition, for every payload there are usually several other objects that make orbit; from the final stage and fairings to unintentional fragments. Not all of these were adequately tracked in the early days. Vallee said: "It didn't reappear in successive weeks." This makes no sense, as *************************************** without knowledge of the orbit, one cannot assume that an object would have visible passes for its non appearance to be an anomaly. Western Europe also has much cloud, so a pass could easily have been missed. It is also possible that the brightness was due to a very low perigee height (closest distance to the earth in its orbit) which is often the case for rocket bodies or fragments from launches which can decay within days of the launch. The object seen by Vallee could perhaps have been 1961 Sigma 2 (the nose-cap of Midas 3), which re-entered 13 days after launch. A satellite which shortly thereafter re-entred would certainly explain the subsequent non appearance. In addition, depending on the inclination, the node of the orbit precesses (like the wobble of a spinning top), taking a satellite through periods of visibility. Vallee said "This was at a time when there was no rocket powerful enough to ************************************************************** launch a retrograde satellite ...". This is simply wrong. Even in April 1959, ***************************** the tenth ever satellite launch, the US Discoverer 2 was launched into an 89.9 degree inclination orbit. Although not quite retrograde, the Thor Agena launch vehicle was clearly capable of reaching a (slightly) retrograde orbit. The earlier attempt at a US military polar orbiting photo-reconnaissance satellite, Discoverer 1, launched in Feb 1959, was not adequately tracked due to the satellite tumbling, but the inclination was about 89.7 degrees. The first retrograde satellite was another US military satellite, Samos 2, launched on 1961 Jan 31 with a 97.4 degree inclination. This was followed by Midas 3 on 1961 July 12 (91.2 degrees) and Midas 4 on 1961 Oct 21 (95.9 deg). The launch vehicles were Atlas Agena A (Samos 2) and Atlas Agena D (the Midas satellites). SAMOS = Satellite And Missile Observation System. MIDAS = MIssile Defence Alarm System Vallee said: "all of the data on satellites was being concentrated in the U.S." **************************************************************** This is also not quite true. The Soviet Union had their own international tracking program and in the UK, a civilian network operated initially out of the Royal Greenwich Observatory and later the Rutherford and Appleton Laboratory. This group collated accurate sightings, calculated orbits and issued predictions of satellite visibility. Following the termination of the US Moonwatch international network of satellite observers, it was very much the British who continued the tradition of visual observations. This message was sent to forteana-digest. Should the message be cross-posted, please copy any comments to rmn@aaocbn1.aao.gov.au I thank Tony Beresford for comments. References: "The R.A.E Table of Earth Satellites 1957-1982" D. G. King-Hele et al 1983 "The Encyclopedia of US Spacecraft" Bill Yenne, 1985 "Artificial Satellite Observing" Ed H. Miles, 1974 "Observing Earth Satellites" D. G. King-Hele, 1983 Cheers, Rob - ------------------------------ From: Kathryn & Andreas Gehrs-Pahl Date: Wed, 20 Dec 1995 15:07:05 -0500 (EST) Subject: MDC and GD win A-12 law suit General Dynamics Corp. (now Lockheed Fort Worth) and McDonnell Douglas Corp. have won their law suit against the Federal Government (specifically the Pentagon, represented by the US Navy), over the canceled A-12 Avenger II. Judge Robert H. Hodges Jr. of the U.S. Court of Federal Claims ruled, that he did not need to hear any more testimony, to find in favor of the companies. He decided that the contract was canceled "for the convenience of the government" and not "terminated for default", because the contractors did not conceal information from the Navy (as the USN argued), rather the government failed to provide the contractors with key data about stealth technology, that had already been developed. The court will rule on January 5, 1996, how much the USN has to pay to GD and MDC, which both sued for $1 billion each, even though it is expected that they will receive only about $350 million each. - - -- Andreas - - --- - --- Andreas & Kathryn Gehrs-Pahl E-Mail: schnars@ais.org 313 West Court St. #305 or: gpahl@raptor.csc.flint.umich.edu Flint, MI 48502-1239 Tel: (810) 238-8469 WWW URL: http://www.umcc.umich.edu/~schnars/ - - --- - --- - ------------------------------ From: BaDge Date: Wed, 20 Dec 1995 16:09:52 -0500 (EST) Subject: Latest Av Week ! Hi, The Dec 18th issue of AV Week has the year-end photo contest. Be sure and browse if not buy this issue at your local Barnes & Noble Bkstr., since they stock british mags. Several cool pix, including a knife-edge view of the F-117A, doing a wing-stand, distant topography in the background. If Andreas will pick his fav photo...(hint, hint) regards, ________ BaDge - ------------------------------ End of Skunk Works Digest V5 #577 ********************************* To subscribe to skunk-works-digest, send the command: subscribe skunk-works-digest in the body of a message to "majordomo@mail.orst.edu". 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 skunk-works-digest local-skunk-works@your.domain.net To unsubscribe, send mail to the same address, with the command: unsubscribe skunk-works-digest in the body. Administrative requests, problems, and other non-list mail can be sent to either "skunk-works-digest-owner@mail.orst.edu" or, if you don't like to type a lot, "prm@mail.orst.edu 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 anonymous FTP from mail.orst.edu, in /pub/skunk-works/digest/vNN.nMMM (where "NN" is the volume number, and "MMM" is the issue number). ------------------------------ From: Paul Adams Date: Thu, 21 Dec 1995 06:39:26 -0600 Subject: Re: MDC and GD win A-12 law suit More on this from the Wall Street Journal Web site : http://update.wsj.com/update/edit/frontpg.html Wednesday, December 20, 1995 U.S. Judge Rules General Dynamics, McDonnell Didn't Deceive Navy on Jet By ANDY PASZTOR Staff Reporter of The Wall Street Journal A federal judge, in a ruling that ultimately could cost the government more than $2 billion, rejected the Pentagon's claims that McDonnell Douglas Corp. and General Dynamics Corp. misled the military and thus should be held responsible for the cancellation of the A-12 attack jet. In a strongly worded decision, U.S. Claims Court Judge Robert Hodges wrote that the Pentagon suffered from an "utter failure of proof" in attempting to support its "central theory" that the giant contractors concealed or withheld information about troubles afflicting the multibillion dollar A-12 project. "It is "manifestly clear," the judge ruled, that the government "cannot prove its case" that the companies were at fault in the development of the carrier-based, radar-evading Navy plane that was killed in 1991 for being grossly overbudget and behind schedule. As a result, the primary issue remaining in what is believed to be the costliest federal contracting dispute ever involves contractor claims that they are owed more than $2 billion. Judge Hodges is expected to rule on compensation and damages next year. A spokesman for McDonnell Douglas said the company was "very pleased with the ruling" and is looking forward to a decision on the remaining issue of how much the government owes the contractors. Spokesmen for the Navy couldn't be reached late Tuesday. The same judge decided last December that the government erred in the way it canceled the A-12 contract, but lawyers for the government countered that the ruling would provide a windfall for the contractors. Now, following a three-week trial, the contractors have strengthened their legal position and gained increased leverage to negotiate a possible settlement with the Pentagon. Estimates of potential settlements have ranged between $1 billion and $3 billion, depending on how much is allotted for how much the companies spent on development, various program-termination costs, legal fees and interest expenses. Originally conceived as a $52 billion program on the cutting edge of technology and a major symbol of President Ronald Reagan's defense buildup, the A-12 Avenger ended up as the largest weapons program ever cancelled by the Pentagon. Despite spending nearly $3 billion, the Navy didn't received a single, fully-assembled prototype of the plane. The cancellation also prompted a flurry of investigations, stirred up intense congressional scrutiny and broke new legal ground. The latest ruling, coming four years after the historic decision to pull the plug on the A-12, seems to finally gut the government's argument that the companies purposely kept Pentagon brass in the dark. "No credible evidence in the record permits us to infer any support whatsoever" for such claims, the judge ruled, adding that evidence of "concealment" by the contractors was "discredited on cross-examination." Copyright 1995 Dow Jones & Company, Inc. All Rights Reserved. Paul \ ___ / Paul Adams \ /___\ / paul@erc.msstate.edu ____________\___/__.__\___/____________ YF-22 \ \ / / \__/\___/\__/ ------------------------------ From: Brad Hitch Date: Thu, 21 Dec 1995 09:08:25 -0700 (MST) Subject: Re: Waverider [NASP] On Thu, 14 Dec 1995, Robin Bjorklund wrote: > > The Space Plane aerodynamics aren`t a challenge. Its the propulsion that > > makes the project unfeasible right now. The lastest research I`ve seen > > involves variable area combustion chambers. Yeah, right! And that assumes > > the flame impingent issues are resolved. > > I'm not sure I understand this problem fully. What problems are they (or > did they) have with flame impingement inside the engine? I doubt that it > was because of the high velocities inside the engine - as a simple bluff > body flameholder could be used to keep the flame where it should be. Or, > better yet, an aerodynamic flameholder could be used. Thus, the problem > with keeping the flame inside the combustor is not really that difficult > to solve. > > If you mean that the flame is impinging on the walls of the > combustor/nozzle/etc., why not just build in a secondary airflow dilution > zone into the impinged area. This helps to cool the walls of whatever > you want, to protect it from the heat of the flame. > > Thus, what exactly do you mean by "flame impingent issues?" Usually the combustor inlet air temperature is far above the fuel autoignition temperature and flameholders are not required. In fact, flameholders are difficult to make survive in this environment where coolant heat sink is always at a premium. The combustor design problems basically relate to high heat fluxes. A appreciation of this can be gained by a few simple calculations: Assume a Mach 10 scramjet (M0=10) you can compress fairly efficiently to Mach 5 (50% of M0), the temperature of the stratosphere is about 400 R, the inlet static temperature ratio is T2 2 + (gam - 1) M0^2 - --- = ------------------ = 3.44 so T2=1376 R 400 2 + (gam - 1) M2^2 where gam is Cp/(Cp-R) for air (about 1.35 for an inlet), where Cp is the constant pressure specific heat for air, then down to Mach 3 in the inlet isolator to the combustor inlet (T3) T3 2 + (gam - 1) M3^2 - ---- = ------------------ = 2.09 so T3=2872 R (2400 F) 1376 2 + (gam - 1) M2^2 this is well beyond the temperature capability of any nickel or cobalt based superalloy, and this is the STATIC temperature (the temperature you would measure if you were traveling along with the air), NOT the stagnation temperature on the front of a flameholder. The stagnation temperature is astronomical and becomes difficult to calculate as the air begins to dissociate into atomic oxygen, etc. U3^2 The velocity at the combustor entrance is then M3^2 = -------- gam R T3 where R is the gas constant for air (1716 ft-lbf/slug-deg R) so U3 (the combustor entrance velocity) is 7740 ft/s (over a mile per second) Now add fuel to bring the combustor exit temperature (T4) up to 5500 R (T4), where dissociation of the combustion products will be underway and assume that you are flying at the altitude required to obtain a 2 atmosphere combustor pressure for good chemical reaction rates. The engine flow velocity will not change much with the heat addition. The combustor wall heat flux can be estimated from the Stanton number, which is a dimensionless heat transfer coefficient: h St = -------- rho U Cp where h is the heat transfer coefficient in the heat flux equation and rho is the gas density in the boundary layer Q" = h (Trec - Twall) [=] Btu/ft^2-s and Trec is the recovery temperature of the fluid in the boundary layer: Trec = T + 0.5 Pr^(1/3) U^2 / Cp where Pr is the Prandtl number for air (about 0.7). Assuming gam=1.25 for the burned gas, some algebra gives gam R 1.25 (1716) Cp = ------- = ----------- = 8580 ft-lbf/slug-deg R gam - 1 0.25 the recovery temperature in the boundary layer along the combustor wall is then Trec = 5500 + 0.5 (.7)^(1/3) 7740^2 / 8580 = 8600 degrees R (ouch!) Assume your combustor liner is made of a 3000 F capable ceramic material. The boundary layer gas density is approximately: 2 P4 2 (30 psia) (144 lbf/ft^2 per psi) rho = ----------------- = ---------------------------------- R (Trec + Twall) 1716 ft-lbf/slug-R (8600 + 3460 R) so rho = 4.2e-4 slug/ft^3 Finally, assume the Stanton number is about 0.002 (the "Universal" Stanton Number) the heat flux is then Q"= St rho U Cp (Trec - Twall) = .002 (4.2e-4) 7740 (8580) (8600 - 3460) Q"= 286700 ft-lbf/ft^2 per second or 368 Btu/ft^2 per second or 1.3 million Btu/ft^2 per hour !!! To put this into perspective, a home gas furnace may have a rating of 100,000 Btu/hr. This is like running 13 furnaces onto an area of 1 square foot, or, since the radiant heat flux from sunlight on Earth is about 0.1 W/cm^2 this heat flux is about 4000 "suns" !!!. This heat flux estimate is also assuming a flat boundary layer type flow. If something sticks out, like a flameholder or fuel injector, the local heat transfer coefficient and heat flux can be several times this value. To transfer this heat flux across the combustor wall material requires a temperature gradient which can easily introduce huge mechanical stresses in a poor conductor due to differential thermal expansion. This is why you may end up using copper rather than a nickel superalloy for the combustor liner. The flame impingement problem is where you inject fuel from the sidewall to avoid putting a fuel injection strut into the flow. The fuel jet acts like a solid blockage to the incoming air flow and creates a horseshoe shaped recirculation vortex at the root of the fuel jet which also entrains fuel. The result is an area of high heat transfer coefficient at near the burned gas stagnation temperature right upstream of the fuel injector. The heat flux here could easily be a factor of 20 or more above the heat flux calculated above. This is VERY hard to deal with. I hope that's not too much detail. Try out Heiser and Pratt's book "Hypersonic Airbreathing Propulsion" from AIAA. Brad Hitch TDA Research http://www.tda.com ------------------------------ From: Charles_E._Smith.wbst200@xerox.com Date: Thu, 21 Dec 1995 09:43:46 PST Subject: Hodefoneaminit ------------------------------ From: Charles_E._Smith.wbst200@xerox.com Date: Thu, 21 Dec 1995 10:03:08 PST Subject: Hodefoneaminit Brad Hitch writes in a well written letter ......... Now add fuel to bring the combustor exit temperature (T4) up to 5500 R (T4), where dissociation of the combustion products will be underway and assume that you are flying at the altitude required to obtain a 2 atmosphere combustor pressure for good chemical reaction rates. The engine flow velocity will not change much with the heat addition. I guess that statement throws me a little. I was under the assumption that the change in enthalpy would slow the flow. In my paper and model the the combustion chamber exit velocity is limited by thermal choking. (At Mach numbers higher than about 7, you really can`t enough heat to do any good, without the flow getting to Mach 1. The thing you kind of glossed over was Thrust = mdot (Uexit-Uintake). The whole idea is to get propulsion efficiency. You need to add as much heat as possible. But you get stuck with H2(l) since the adiabatic flame temperature of hydro-carbons dictates that the Ksp of the reaction will drive you away from stoichiometric. (You get CO and N02 and all kinds of nasties the "tree huggers" bitch about, along with a loss in thrust -instead of CO2 +H2O. For the real world, you start with the chemical reaction, develop the combustion chamber relationships, and then design the diffuser and nozzle to match the conditions. Try Oates` AIAA book. It gets into this. It doesn`t work just right fo hypersonics but graduate-type rocket scientists should be able to make the nessecary changes. Better yet, use his basics and re-derive. You`ll find the FA ratio that avoids choking is so lean you can`t get enough enthalpy gain. Also, just for grins you might want to check the area-ratio required to get from M10 at U1 to M5 at U2. You might end up with a pretty big intake! If you have screw around with H2(l) you might as well bring the oxygen along too. Now you have an engine that gives the same thrust at any Mach number, and can accelerate you for takeoff. (obviously, a M10 engine is useless for takeoff!) What I just desribed was -Rocket Motors. Other than keeping the flow expanded at the exit (which the aerospike and other designs claim to handle) you get the same thrust all the time. Problem is you get a big weight fraction for the T/O and cruise segments of the flight. Along the idea of area ratios, SCRAMjets are VERY design point sensitive. I don`t see any off-design application. So, you need a secondary propulsive source anyway(another engine with a different design point?) And you are absolutely right, the TOTAL temps are a barriers, to say the least. Better yet, look at the total pressures! Now you get feeling for what thermal AND aero stresses such an engine would have. About Anderson...... A brilliant visionary, a heckofalot smarter than me, but - he clings to Navier-Stokes in hypersonics. Be careful. Nice job, but we may have to agree to dissagree here. Chuck ------------------------------ From: David Windle Date: Thu, 21 Dec 1995 23:33:07 Subject: Stealth Santa's Sleigh & Reindeer I know classified data should not be transmitted on this group...but I received some information from a normally reliable source that a SAP involved LADC in a aero-genetic programme involving the subject of this message. It's all so clear now..that's why we can't see Santa and his sleigh or his reindeer. It seems that he landed at Palmdale, the Ranch and Wright-Pat to brief cleared personnel on the physics involved... I've really enjoyed our dicussions this last year and look forward to more of the same..Happy Christmas everyone. Best D ------------------------------ End of Skunk Works Digest V5 #578 ********************************* To subscribe to skunk-works-digest, send the command: subscribe skunk-works-digest in the body of a message to "majordomo@mail.orst.edu". 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 skunk-works-digest local-skunk-works@your.domain.net To unsubscribe, send mail to the same address, with the command: unsubscribe skunk-works-digest in the body. 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