From: skunk-works-digest-owner@mail.orst.edu To: skunk-works-digest@mail.orst.edu Subject: Skunk Works Digest V5 #348 Reply-To: skunk-works-digest@mail.orst.edu Errors-To: skunk-works-digest-owner@mail.orst.edu Precedence: bulk Skunk Works Digest Tuesday, 11 July 1995 Volume 05 : Number 348 In this issue: Re: Speed of Sound Mach, TAS, et al. AEROSP-L Digest - 8 Jul 1995 to 10 Jul 1995 Skunkstock '95 -- Info offending address removed. Re: More on Ramjet (SR71) speed limitations X-15A-2 Mach 6 Imaging Resolution Test sr-71 mach SR-71, F-117, P-38 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: freeman@netcom.com (Jay Reynolds Freeman) Date: Mon, 10 Jul 1995 10:46:55 -0700 Subject: Re: Speed of Sound To first order, and then some, the speed of sound in the lower atmosphere of Earth depends on temperature and nothing else. It is proportional to the square root of temperature (measured above absolute zero). The speed of sound declines with altitude (usually) simply because it gets colder (usually) at higher altitude. In the old days they often made speed-record attempts in early jets flat on the deck on a hot day in summer, simply because under those conditions the speed of sound was high, and therefore the critical mach number for corresponded to a high actual speed. If I remember correctly, the exact relationship is speed of sound = square root of ( gamma * k * T / mu ), in which: gamma is 7/5 for atmospheric gases in the range of temperatures found where aircraft usually fly. (It changes if the diatomic molecules start to dissociate.) (This quantity has various names because it crops up in various contexts -- its most esoteric title is probably the "polytropic expansion exponent", though it also goes by various names containing the phrase "gas constant", which I won't list because there are far too many different kinds of "gas constant".) It is a pure number -- dimensionless. k is Boltzmann's constant, in units of energy per unit temperature, which is also units of mass times speed squared per unit temperature. T is temperature above absolute zero. mu is mean molecular mass, pretty constant in the lower atmosphere of Earth. Multiplying all out and taking the square root, we have units of speed, which is encouraging, but not positive proof that I have gotten it right. -- Jay Freeman, used physicist ------------------------------ From: (SSG, ANTHONY, MAA, 565) Date: Mon, 10 Jul 95 11:20:53 PDT Subject: Mach, TAS, et al. Somebody please clear this Mach issue up (it's probably clear to all of you). I maintain/repair instrument, autopilot, and inertial navigation systems on the last of the DOD RF-4C's. In the eight or so years I've been doing this, I've been under the impression that Mach is a function of airspeed and altitude (air pressure). A Mach indicator uses ram air pressure corrected for static pressure - there is no temp. correction except for what the temp. may do to affect the static pressure. Now, on the other hand, true air speed is ram air pressure corrected for altitude AND temp. Others I work with agree with this philosophy. Please show us the error of our ways as necessary. +---------------------------------+------------------------------------+ | | O | Anthony J.D. Midmore, SSgt, WG-12 \_____[|(.)|]_____/ | NV Air Nat'l Guard Avionics O ++ o ++ O | Reno, NV "Phamtoms Phorever" | (at least a couple of months) | +----------------------------------------------------------------------+ ------------------------------ From: Automatic digest processor (by way of kuryakin@arn.net (Illya Kuryakin)) Date: Mon, 10 Jul 1995 15:08:02 -0500 Subject: AEROSP-L Digest - 8 Jul 1995 to 10 Jul 1995 Forwarded from the NASM list: Date: Sun, 9 Jul 1995 15:56:33 -0400 From: "Mitchell Silvers aol.com" Subject: David W. Howe David W. Howe the first Pilot of a Jet VTOL at the Smithsonian, died on May 22,1995 of a massive stroke. He was also a World War 2 Flying Ace who was awarded the Distinguished Flying Cross, he flew P-51 Mustangs. It was also his idea which Larry Bell took to take wheels off helicopters and put on skids. His widow is Ann M. Howe, 3821 Draper Place, Erie PA. 16511. He served with three Air Forces the RCAF and RAF and the US 8Th Army Air Force. He was buried on June 8th at Arlington National Cemetery in Washington D.C.. He was also a member of The Society of Experimental Test Pilots out of California. Larry Bell nicknamed him the kid. He also tested the Bell X-14 and Bell Hydroskimmer. Mitchell Silvers Norcross GA. ------------------------------ From: Kathryn & Andreas Gehrs-Pahl Date: Mon, 10 Jul 1995 16:02:45 -0400 (EDT) Subject: Skunkstock '95 -- Info So far, ten people have said they would attend if possible, so it seems that Skunkstock '95 is really happening. That means we should give some information about where and when to meet. The "Wing And A Prayer" pilot's pub is located in Lancaster, between Rosamond (Edwards AFB) and Palmdale. The address is: Wing And A Prayer 44423 - 90th St. East Lancaster, CA 93535 (805) 946-2656 They are open from 11 a.m. - 9 p.m., and we will convene at 11 a.m. on Saturday, July 22. The pub is frequented by a lot of Edwards AFB and Palmdale pilots, but I don't know how many hang out there on weekends. The house specialty is their "World Famous Chili" and "Jalapeno Poppers". See you soon there (families are welcome too, btw!), - -- 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: Majordomo Admin Acct Date: Mon, 10 Jul 1995 14:10:18 -0700 Subject: offending address removed. /bin/nuked. Too busy closing on my house to pay attention to the list. Sorry for the delay. kean ------------------------------ From: larry@ichips.intel.com Date: Mon, 10 Jul 1995 14:24:25 -0700 Subject: Re: More on Ramjet (SR71) speed limitations In reply to Chuck Smith, larry@ichips.intel.com writes: >>A photo of the inlet spike retracted full back, that is, as the inlet spike >>is full back at max cruise. > >(snip snip...) > >>To help them a little here, 'that angle' you mention, is the angle that the >>cone shock off the inlet spike makes when the cone shock off the inlet >>spike tip meets the inlet cowl lip. At max cruise, that is where the inlet >>spike shock will be because that is the minimum drag configuration for the >>spike shock. Ted Gustafson replies: >If the purpose of the movable inlet spike at supersonic speeds is >simply to position the spike shock such that it intersects the lip of >the inlet cowl, then it seems that at max Mach number, the spike >would have to be at an extended--as opposed to fully >retracted--position relative to a less than Mmax condition. This >because the spike shock is more swept back with increasing Mach >number, and, therefore, the spike itself would have to be positioned >farther forward (relative to a lower Mach number condition) for the >spike shock to intersect the inlet cowl. I'm sure there must be >other considerations involved. Hmm, what am I missing here? Yes, if all the inlet spike had to do, was to form shock on lip, the inlet spike could be designed to remain fixed. But, as you suspect, the inlet spike retracting also does something else. The inlet spike also retracts to form a proper (minimum area) throat for the normal shock to reside in. There is some CONJECTURE (on my part), based on what I've seen of the internal geometry of the inlet, and what the shock trap does, and also aided by general supersonic inlet theory, that, due to the internal shapes of the inlet spike and cowl, that the inlet runs supercritical (the normal shock is swallowed) while the inlet spike is retracting, until the widest part of the inlet spike is seated in the shock trap, forming the throat. At that point the inlet runs critical, the lowest loss configuration. At least, from the standpoint of a propulsion nut such as myself, it looks like one heck of an interesting idea (after looking at the blackbird's internal inlet goemetry). >>Also, usually the theta-beta-Mach no. charts in compressible flow books are >>for 2-D wedges and not 3-D cones. It will be close but as we know, cones >>have another degree of freedom and the angles of shocks through cones are >>slightly different than for wedge generated shocks. There are charts >>available for cones if you want to be very precise. >Yes that's right. And to offer a further note, for a given Mach >number, the shock angle of a cone will be slightly less than that for >a 2-D wedge of the same half-angle. >To the students: If you can find one, an oldie but goodie you >should try to get is a copy of NACA 1135. Cool - Thanks! I have an old NACA book of compressible flow equations and shock curves at home. I'll have to check and see if it's that one! I found it at a used book store, and in fact, when I saw the nice quick reference list of equations as well as shock curves (especially the ones for cones), I grabbed it! Larry ------------------------------ From: larry@ichips.intel.com Date: Mon, 10 Jul 1995 15:07:45 -0700 Subject: X-15A-2 Mach 6 Imaging Resolution Test I sat down with Milt Thompson's book on the X-15 program last night and read the chapter on the high speed X-15 flights. I don't know why I hadn't read at least this chapter before, being the nut I am about high speed, but this chapter really brought home how right the X-15 program was and how close we actually got to flying a manned aircraft with a fully operating scramjet (I guess you could honestly say however that what flew was partly operating!). In the airbreathing community, there was a lot of controversy about that Garrett scramjet, known as the HRE (Hypersonic Research Engine). One of the main complaints was that the engine was said to not be able to attain positive thrust due to excessive drag. Another complaint was that it wasn't designed by one of the then 'known' scramjet design communities (namely Marquardt, John's Hopkins APL, or GASL (General Applied Science Lab - Tony Ferri's outfit). But anyway, after Jack McKay's bad accident in X-15 number 2, when they elected to rebuilt it for high speed research and the scramjet tests (they actually lengthened the fuselage of the X-15 to add space for a LH2 tank to use as scramjet fuel), they really had their heads screwed on straight. Too bad the program never reached the fully operational stage for the scramjet. I recommend picking up Milt's book and reading it, it's quite good, especially that chapter if you're into high speed stuff! But, there was something in this chapter that should be of great interest to this list. Milt said, in this high speed X-15 chapter, that one of the experiments they flew (he indicated it was Pete Knight that actually flew it - Pete's 4th flight in the A-2, if I recall), was an imaging test flight at Mach 6! In other words, a flight to see what kind of image resolution one could get at Mach 6! There's no indication as to what the results were. There's that phrase Mach 6 again! Larry ------------------------------ From: "Frank Schiffel, Jr." Date: Mon, 10 Jul 95 18:48:56 CDT Subject: sr-71 mach Interesting, Mary. I was told by an operations/test pilot from Lockheed that the Max Mach on the SR-71 was 450 KEAS, that was the design point. About 3.2 M at 80,000 ft or so. Of course, this was before NASA had the SR-71 and it was after it was retired. I did hear that he had gotten to 600 KEAS onetime and really got chewed on for really exceeding the limits on the aircraft. Of course, I don't know what he was doing or at what altitude he had it at. I was told most of the operations were done at 3.1-3.2, 3.0 was used to go to the area of interest. Yes, Kelly did the chewing. regards, Frank ------------------------------ From: Wei-Jen Su Date: Tue, 11 Jul 1995 00:59:12 -0400 (EDT) Subject: SR-71, F-117, P-38 1) MS> The Machmeter only goes to 4, too. Mary, with all respect, the machmeter of the SR-71 goes to 6. I got pictures of the back and front seat of the SR-71. Some of those pictures you can get it in the internet which the site I forgot (sorry :) ). After dowload, you can use a zoom-in and see the limits of the machmeter. People in this mailing list has to take care of something that in Russia language call: "Maskirovka" Does anyone heard about the following stories? I don't know if it was true... 1) During Desert Storm, one of the F-117 was hit by a Iraqui missile loosing one of her V-tail. The pilot didn't know until he landed and he saw with his eyes because he didn't feel it any change (the cause is the highly sophisticate Fly-by-Wire system of the F-117). 2) The first sketch of the famous Lockheed P-38 was done in a bathroom tissue by the famous Kelly Johnson. If it is true, the invention of one of the best fighter of WWII was done in "the seat of thinking" :). How many books Ben Rich (one of his codename: Ben Over) has published to the general public? If I am understand, he only published "Skunk Works" bye Ben Rich and Leo Janos. I heard about some book name "Memories of Ben Rich". It is the same book? I appreciate to any that want and can answer these questions. Live Long and Prosper Su Wei-Jen ------------------------------ End of Skunk Works Digest V5 #348 ********************************* 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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