belle@skipper.dfrf.nasa.gov (Steve Belle) (05/09/89)
Just watched the orbiter Atlantis touch down. Runway 22 was used again (this is the only concrete runway at Edwards). The decision of which runway to use was delayed until the last moment because of cross winds. Scattered clouds in the area made visual sighting of the orbiter difficult until about a minute after the double sonic boom. Another perfect landing!
todd@ivucsb.UUCP (Todd Day) (05/09/89)
In article <272@skipper.dfrf.nasa.gov> belle@skipper.dfrf.nasa.gov (Steve Belle) writes:
~Just watched the orbiter Atlantis touch down. Runway 22 was
~used again (this is the only concrete runway at Edwards).
I went all the way out to Edwards, and had a lot of fun waiting for
and watching the shuttle land. However, I was disappointed that the
crowd does not get to be closer to the actual landing site. We could
barely see it when it landed, although the view when it flew over us
was fantastic!
BTW, for those of you going to future launches, look for Avenue E
and 140th street. The signs blew over and we had a hard time finding
the viewing site.
--
-Todd Day-
ivucsb!todd@anise.acc.comphil@titan.rice.edu (William LeFebvre) (05/09/89)
In article <779@ivucsb.UUCP> todd@ivucsb.UUCP (Todd Day) writes: >I went all the way out to Edwards, and had a lot of fun waiting for >and watching the shuttle land. However, I was disappointed that the >crowd does not get to be closer to the actual landing site. We could >barely see it when it landed, although the view when it flew over us >was fantastic! I suspect that they had you positioned for a landing on runway 17 (that's certainly where the convoy was poised). The switch to 22 was made within 20 (15, even?) minutes of landing. Really unfortunate for those that made the trip. Take solace in the fact that the camera views that NASA Select provided weren't very good either...."There it is, coming down. It's almost ready to touch the pavement. Whoops, there's a building in the way. Oh I see it rolling again. Oh, now it just went behind that hanger,...", etc. William LeFebvre Department of Computer Science Rice University <phil@Rice.edu>
todd@ivucsb.UUCP (Todd Day) (05/10/89)
In article <3240@kalliope.rice.edu> phil@Rice.edu (William LeFebvre) writes: ~I suspect that they had you positioned for a landing on runway 17 (that's ~certainly where the convoy was poised). The switch to 22 was made within ~20 (15, even?) minutes of landing. I'm kinda curious about what runways are what, so I'm going to draw a crude map: +-----+ | | +-----+ | | | | | | +-----+ | | +-----+ | 22 | various buildings +-------+ strip ^ ^ --> N ^ ^ about half-a-mile ^ path of shuttle ^ ^ ^ ^ ^ ^ fence ^ --------------------------------------------------------------------------- X - where I was What I want to know is, where is runway 17? We saw no markings on the dry lake bed in front of us. Also, it looked like the fence was fairly permanent, so most landings must have the crowd at the same place. The radio claimed right before the landing that it was going to come in NE to SW, which would have given us a cherry view. -- -Todd Day- ivucsb!todd@anise.acc.com
shafer@drynix.dfrf.nasa.gov (05/11/89)
In article <3240@kalliope.rice.edu> phil@titan.rice.edu (William LeFebvre) writes: > In article <779@ivucsb.UUCP> todd@ivucsb.UUCP (Todd Day) writes: > >I went all the way out to Edwards, and had a lot of fun waiting for > >and watching the shuttle land. However, I was disappointed that the > >crowd does not get to be closer to the actual landing site. We could > >barely see it when it landed, although the view when it flew over us > >was fantastic! > I suspect that they had you positioned for a landing on runway 17 (that's > certainly where the convoy was poised). The switch to 22 was made within > 20 (15, even?) minutes of landing. Really unfortunate for those that made > the trip. Take solace in the fact that the camera views that NASA Select > provided weren't very good either...."There it is, coming down. It's > almost ready to touch the pavement. Whoops, there's a building in the > way. Oh I see it rolling again. Oh, now it just went behind that > hanger,...", etc. The Shuttle Public Viewing Area is always in the same place, far away. This is a hazardous event and they don't want people very close. The Shuttle is filled with dangerous stuff and the Air Force and NASA don't want to spray 400K bystanders with NO4 or hydrazine. We are not even allowed to stand out on the ramp when they tow the Shuttle to the MDD. I thought this was one of the least viewable landings. The high sun angle really made it hard to follow the aircraft around the HAC. I picked it up overhead and then lost it. The clouds were perfectly placed to make it difficult! I finally picked it up on final, about half-way across the lakebed. I even had the aid of being able to watch the tracking TM antenna, since I was on the roof at Dryden. (This antenna was pointing at the Shuttle from about the coastline to touchdown.) I infinitely prefer the early landings, with the low sun angle. By the way, did those of you who were at the landing notice that you could hear the Shuttle really well? It's usually very hard to hear. -- M F Shafer NASA Ames-Dryden Flight Research Facility shafer@elxsi.dfrf.nasa.gov or shafer@drynix.dfrf.nasa.gov NASA management doesn't know what I'm doing and I don't know what they're doing, and everybody's happy this way.
paulc@hp-lsd.HP.COM (Paul Carroll) (05/14/89)
< / hp-lsd:sci.space.shuttle / shafer@drynix.dfrf.nasa.gov / < < By the way, did those of you who were at the landing notice that you could < hear the Shuttle really well? It's usually very hard to hear. I presume you mean the 2 sonic booms? They were rather loud, but seemed normal given all other sonic booms I've heard. (Lucky and didn't even know it :-) By the way, can anyone inform me as to why there are 2 sonic booms, and not just one, from the shuttle? Is this due to deceleration from Mach 5 such that the wave from Mach 5 and one from Mach 1 (or so) arrive at the ground at the same time? Just wondering, but there didn't seem to be any direction for the booms. They just seemed to occur together. As far as how the landing went, it was rather confusing to see the shuttle turning in the East and coming in overhead. I still expected a crosswind landing and couldn't figure out how the shuttle was going to make it's final lefthand turn (which it didn't, after all). Still, it looked real good going by almost directly overhead. Also, given there were only some 30,000 people at the landing, it must be a real bear when a few 100,000 people show up. I sat in the traffic jam for about 1.5 hours :-( Boy, did it get warm. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + Paul Carroll "Dear Lord, please break the laws + HP Logic Systems Division of the universe for my convenience." + hplabs!hp-lsd!paulc - Emo Phillips ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
shafer@drynix.dfrf.nasa.gov (05/16/89)
In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: > I presume you mean the 2 sonic booms? They were rather loud, > but seemed normal given all other sonic booms I've heard. > (Lucky and didn't even know it :-) No, you can hear the airframe noise. It sounds like a transport, throttled back to idle. You're hearing the drag, as it were. Maybe the crowd was too loud where you were. > By the way, can anyone inform me as to why there are 2 sonic > booms, and not just one, from the shuttle? One from the nose, one from the wingtips/tail. You can hear a double boom with any aircraft if the conditions are right. If the aircraft is flying really low and fast in the medium altitude supersonic corridor here at Edwards you'll hear a double boom, but it's not usually as nice as the Shuttle boom. When the smaller aircraft is higher or slower the booms run together and you hear one longer boom, without the high frequency component. > As far as how the landing went, it was rather confusing to see > the shuttle turning in the East and coming in overhead. I > still expected a crosswind landing and couldn't figure out > how the shuttle was going to make it's final lefthand turn > (which it didn't, after all). Still, it looked real good going > by almost directly overhead. This is the HAC or heading alignment circle. This lets the pilot line up on the runway and make the actual reentry path slightly less critical. For example, they changed the runway after the de-orbit burn, using the HAC. > Also, given there were only some 30,000 people at the landing, > it must be a real bear when a few 100,000 people show up. > I sat in the traffic jam for about 1.5 hours :-( Boy, did it > get warm. I don't think there were even 30,000 people--the TV shots from the helicopter showed a small group. You're right about the traffic, though. You can get passes to be over by Dryden for the non-classified landings. I posted this a while ago and I'll post it again as the next mission is imminent. -- M F Shafer NASA Ames-Dryden Flight Research Facility shafer@elxsi.dfrf.nasa.gov or shafer@drynix.dfrf.nasa.gov NASA management doesn't know what I'm doing and I don't know what they're doing, and everybody's happy this way.
shafer@drynix.dfrf.nasa.gov (05/16/89)
Please excuse the clutter in the group, but my mail bounced. Todd, Send your address and I'll send you a map of the lakebed. The Public Viewing Area is _always_ in the same place--they don't move it if they change runways. -- M F Shafer NASA Ames-Dryden Flight Research Facility shafer@elxsi.dfrf.nasa.gov or shafer@drynix.dfrf.nasa.gov NASA management doesn't know what I'm doing and I don't know what they're doing, and everybody's happy this way.
hollombe@ttidca.TTI.COM (The Polymath) (05/18/89)
In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: }By the way, can anyone inform me as to why there are 2 sonic }booms, and not just one, from the shuttle? ... One from the Shuttle, one from the chase plane. -- The Polymath (aka: Jerry Hollombe, hollombe@ttidca.tti.com) Illegitimati Nil Citicorp(+)TTI Carborundum 3100 Ocean Park Blvd. (213) 452-9191, x2483 Santa Monica, CA 90405 {csun|philabs|psivax}!ttidca!hollombe
hhd0@GTE.COM (Horace Dediu) (05/18/89)
In article <4453@ttidca.TTI.COM>, hollombe@ttidca.TTI.COM (The Polymath) writes: > In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: > > }By the way, can anyone inform me as to why there are 2 sonic > }booms, and not just one, from the shuttle? ... > > One from the Shuttle, one from the chase plane. > No. The booms come from two different shock waves generated by the shuttle. At supersonic speeds the shuttle looks like: . . . . . <- shock wave 1 . <- shock wave 2 . (in 3-space, these . . are cones) --. . / | . / | . / | . _______________________/-----|__ . / USA : / | /-- ---| < \__| ------------------------------------- . . . . . . . . . . . yay! . . o . . -|- . .BOOM / \ .BOOM _____________________________________________________ (observer) on ground (Not to scale). There are many shock waves, but these are the biggest. The nose, and the bumps in the fuselage at the back which cover the engines cause the two shock waves. -- Horace Dediu GTE Laboratories (671) 466-4111 40 Sylvan Road UUCP: ...!harvard!bunny!hhd0 Waltham, MA 02254 Internet: hhd0@gte.com or hhd0%gte.com@relay.cs.net
shafer@drynix.dfrf.nasa.gov (05/18/89)
In article <4453@ttidca.TTI.COM> hollombe@ttidca.TTI.COM (The Polymath) writes: > In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: > }By the way, can anyone inform me as to why there are 2 sonic > }booms, and not just one, from the shuttle? ... > One from the Shuttle, one from the chase plane. There are no chase planes, since the Shuttle is "operational." I don't think the chases were supersonic anyway. I've loaned my SETP proceedings with the paper about chasing the Shuttle. When it comes back, I'll let you know. One boom is from the nose, one is from the wings. -- M F Shafer NASA Ames-Dryden Flight Research Facility shafer@elxsi.dfrf.nasa.gov or shafer@drynix.dfrf.nasa.gov NASA management doesn't know what I'm doing and I don't know what they're doing, and everybody's happy this way.
shafer@drynix.dfrf.nasa.gov (05/19/89)
In article <4453@ttidca.TTI.COM> hollombe@ttidca.TTI.COM (The Polymath) writes: > In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: > }By the way, can anyone inform me as to why there are 2 sonic > }booms, and not just one, from the shuttle? ... > One from the Shuttle, one from the chase plane. There are no chase planes, since the Shuttle is "operational." I don't think the chases were supersonic anyway. I've loaned my SETP proceedings with the paper about chasing the Shuttle. When it comes back, I'll let you know. One boom is from the nose, one is from the wings. You may have already seen this, but our system got weird and I think this didn't make it. -- M F Shafer NASA Ames-Dryden Flight Research Facility shafer@elxsi.dfrf.nasa.gov or shafer@drynix.dfrf.nasa.gov NASA management doesn't know what I'm doing and I don't know what they're doing, and everybody's happy this way.
colwell@mfci.UUCP (Robert Colwell) (05/19/89)
In article <SHAFER.89May18154504@drynix.dfrf.nasa.gov> shafer@drynix.dfrf.nasa.gov writes: >In article <4453@ttidca.TTI.COM> hollombe@ttidca.TTI.COM (The Polymath) writes: > >> In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: >> }By the way, can anyone inform me as to why there are 2 sonic >> }booms, and not just one, from the shuttle? ... > >> One from the Shuttle, one from the chase plane. > >One boom is from the nose, one is from the wings. There's something I don't understand about this explanation. Even if one boom (shock wavefront) were emanating from the very tip of the nose, and the other from the very rearmost part of the craft, that would only separate the wavefronts by the length of the craft, which is approx. 120 ft. If the craft is travelling at, say, 300 mi/hr, then the time difference between the first wave and the second (as perceived by a stationary observer on the ground) would be 300 mi 5260 ft 120 ft ------ x ------- = -------- hr mi N hr Solving that for N in seconds, I get 0.27 seconds. My impression was that the booms were obviously separated in time. I'd expect that people might have a hard time distinguishing booms that were only 0.27 seconds apart. I read an explanation once that said the second boom was just the first boom reflected off an upper atmosphere layer. When the craft is going faster than a certain speed, the angle at which the primary boom leaves the nose is such that a significant portion of it can reflect directly back down, and the additional path length accounts for the time delay between booms. Supposedly there's some critical angle (hence critical speed) that allows the second boom. Bob Colwell ..!uunet!mfci!colwell Multiflow Computer or colwell@multiflow.com 175 N. Main St. Branford, CT 06405 203-488-6090
jlc@atux01.UUCP (J. Collymore) (05/19/89)
In article <4453@ttidca.TTI.COM>, hollombe@ttidca.TTI.COM (The Polymath) writes: > In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: > > }By the way, can anyone inform me as to why there are 2 sonic > }booms, and not just one, from the shuttle? ... > One sonic boom is caused by the nose of the shuttle piercing the sound barrier and the second sonic boom is caused by the THE SHUTTLES TAIL FIN also piercing the sound barrier! Jim Collymore
kluksdah@enuxha.eas.asu.edu (Norman C. Kluksdahl) (05/20/89)
In article <4453@ttidca.TTI.COM>, hollombe@ttidca.TTI.COM (The Polymath) writes: > In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: > > }By the way, can anyone inform me as to why there are 2 sonic > }booms, and not just one, from the shuttle? ... > > One from the Shuttle, one from the chase plane. > I was at the latest landing at Edwards, and there were NO chase planes. So your theory goes down (not with flames, but fading slowly into the mists....) Two sonic booms originate from different parts of the orbiter itself. The first is from the nose, and the second is from aft parts of the orbiter, such as wings and tail. The faster the orbiter is flying, the more closely spaced the sonic booms are--eventually they are indistinguishable. There has been (as usual) much discussion of this double boom phenomena here recently. All I will add is that, since the early 1960's when I lived in Sheridan Wyoming, I hadn't heard a sonic boom (we used to hear them ALL the time back then). The landing at Edwards brought back a few memories, and was almost overwhelming. ********************************************************************** Norman Kluksdahl Arizona State University ..ncar!noao!asuvax!enuxha!kluksdah alternate: kluksdah@enuxc1.eas.asu.edu standard disclaimer implied
jim@aob.aob.mn.org (Jim Anderson) (05/21/89)
In article <9090001@hp-lsd.HP.COM> paulc@hp-lsd.HP.COM (Paul Carroll) writes: >By the way, can anyone inform me as to why there are 2 sonic >booms, and not just one, from the shuttle? ... How far apart are these double booms?? -- Jim Anderson (612) 636-2869 Anderson O'Brien, Inc New mail:jim@aob.mn.org 2575 N. Fairview Ave. Old mail:{rutgers,gatech,amdahl}!bungia!aob!jim St. Paul, MN 55113 "Fireball... Let me see... How did that go?"
phil@titan.rice.edu (William LeFebvre) (05/22/89)
In article <862@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes: >... >Solving that for N in seconds, I get 0.27 seconds. My impression was that >the booms were obviously separated in time. I'd expect that people might >have a hard time distinguishing booms that were only 0.27 seconds apart. I'd expect that you're wrong. That's a quarter of a second, which is most certainly distinguishable (or for you computer types: 250 milliseconds). Being a former percussionist (you know, one of those guys that plays drums), I remember routinely playing notes on a snare drum that are a quarter of a second apart (four notes per second). Believe me, the notes were quite distinguishable. Or don't believe me. But if you don't believe me, do the following experiment: tap the countertop once a second (use your watch to time them). Double the rate, then double it again. Quite distinguishable. And in fact, about the same rate that the shuttle's booms are heard at. William LeFebvre Department of Computer Science Rice University <phil@Rice.edu>
colwell@mfci.UUCP (Robert Colwell) (05/23/89)
In article <3305@kalliope.rice.edu> phil@Rice.edu (William LeFebvre) writes: >In article <862@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes: >>... >>Solving that for N in seconds, I get 0.27 seconds. My impression was that >>the booms were obviously separated in time. I'd expect that people might >>have a hard time distinguishing booms that were only 0.27 seconds apart. > >I'd expect that you're wrong. That's a quarter of a second, which is most >certainly distinguishable (or for you computer types: 250 milliseconds). >Being a former percussionist (you know, one of those guys that plays >drums), I remember routinely playing notes on a snare drum that are a >quarter of a second apart (four notes per second). Believe me, the notes >were quite distinguishable. Or don't believe me. But if you don't >believe me, do the following experiment: tap the countertop once a second >(use your watch to time them). Double the rate, then double it again. >Quite distinguishable. And in fact, about the same rate that the >shuttle's booms are heard at. If the craft were really travelling at 300mph, there wouldn't *be* any sonic booms. It has to be travelling at over twice that speed to even generate the booms. So the arrival time difference between the booms (if they exist) from the front and back of the craft would actually be at most 1/10 of a second. If the front/back explanation is right, (and I don't dispute that one can hear sonic events separated in time by 1/10th of a second, I just wonder if the attack portion of the boom's sonic envelope is sufficiently sharp that a second one 0.1 seconds later would be obviously distinguishable) then why don't all supersonic aircraft generate this same phenomenon? I was under the impression that the craft had to be sufficiently fast to have this occur, and that it happened with the shuttle because it was going umpteen zillion mph at the time, much faster than normal aircraft can achieve. (Ok, the front/back explanation would hold up better with longer aircraft; is the shuttle one of the longest supersonic aircraft? I would have imagined a B-1 to be much longer). Bob Colwell ..!uunet!mfci!colwell Multiflow Computer or colwell@multiflow.com 175 N. Main St. Branford, CT 06405 203-488-6090
shafer@drynix.dfrf.nasa.gov (05/23/89)
About sonic booms--you guys must live in the wrong neighborhood :-) Sonic booms are quite common here at Dryden, since we're right under the medium- altitude supersonic corridor. Come visit us, for the public tour, and you'll probably hear several. The overpressure and other characteristics of the shock are functions of the aircraft altitude, Mach, size, and weight. If the aircraft is very high, for example, the shock will have dissipated somewhat before it reaches the ground and the boom will be more like a rumble. The best booms are very sharp and distinct, with quite a bit of high-frequency content. These come from relatively low, fast, close aircraft. Double booms, like the Shuttle produces, aren't that uncommon. An F-4 can produce a very nice double boom--I've heard & seen them do it. There's a clue in that statement, that they were low enough and close enough that I could see them doing it. Any aerodynamics text will show you the shock waves coming off an aircraft. If you want to see pictures, look in Van Dyke's book, "An Album of Fluid Motion." He has a chapter of shock wave pictures and another of supersonic flow. This is an outstanding book, which everyone interested in aerodynamics should have. -- M F Shafer NASA Ames-Dryden Flight Research Facility shafer@elxsi.dfrf.nasa.gov or shafer@drynix.dfrf.nasa.gov NASA management doesn't know what I'm doing and I don't know what they're doing, and everybody's happy this way.
raveling@venera.isi.edu (Paul Raveling) (05/24/89)
In article <6949@bunny.GTE.COM> hhd0@GTE.COM (Horace Dediu) writes: >The booms come from two different shock waves generated by the shuttle. At >supersonic speeds the shuttle looks like: Approximately right, but there's a different aerodynamic reason. What I say next is subject to the disclaimer that it's been some years since I studied it, and my main aerodynamic interest was in sailplanes with a typical Vne of 135 knots. Both booms are caused by an abrupt pressure transition. This is easy to understand for the leading boom, but the transition causing the trailing boom is triggered by the fact that the shuttle no longer occupies the volume of airspace it just passed through. The trailing boom's shock wave forms at a different angle than the leading boom's shock wave because local airspeed is higher at that point than at the nose. This effect is visible in wind tunnel photographs of simpler forms, such as bullets, in supersonic flow. To update Mr. Dediu's drawing, this is roughly what I believe the Shuttle's case would look like: . . . . . <- shock wave 1 shock wave 2 ->. . (in 3-space, these . . are cones) --. . . / | . . / | . . / | . . _______________________/-----|__ . . / USA : / | . . /-- ---| . . < \__| . . ------------------------------------- . . . . . . . . . . . . yay! . . o . . -|- . . BOOM / \ .BOOM _____________________________________________________ (observer) on ground The time interval between the two booms is due to the different spreading angle; if the shuttle goes by at, say Mach 1.1 & 50K feet, the separation increases from the shuttle's length to a few hundred feet. Also note that these shock waves form ahead of and behind the object. An form with a relatively pointed nose, like an F-104, has a relatively large distance between its leading shock wave and the nose itself; this produces minimal drag due to feeding energy into the shock wave. A relatively blunt nose, such as the shuttles, will generate its shock wave much closer to, or even even on, the nose, and will produce much higher drag. >(Not to scale). There are many shock waves, but these are the biggest. The >nose, and the bumps in the fuselage at the back which cover the engines >cause the two shock waves. You bet. Shock wave structure, particularly on airfoils, can be pretty complex. The aerodynamicists from Lockheed who taught the class that I took mentioned that there are airfoils that can have local supersonic flow, initiating local shock waves, at airspeeds as low as .2 Mach. Needless to say, design of things such as airliner wings gets lots trickier as the intended speed gets into the normal transonic regime. ---------------- Paul Raveling Raveling@isi.edu
phil@titan.rice.edu (William LeFebvre) (05/24/89)
In article <871@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes: >In article <3305@kalliope.rice.edu> phil@Rice.edu (William LeFebvre) writes: >>In article <862@m3.mfci.UUCP> colwell@mfci.UUCP (Robert Colwell) writes: >>>... >>>Solving that for N in seconds, I get 0.27 seconds. My impression was that >>>the booms were obviously separated in time. I'd expect that people might >>>have a hard time distinguishing booms that were only 0.27 seconds apart. >> >>I'd expect that you're wrong. That's a quarter of a second, which is most >>certainly distinguishable (or for you computer types: 250 milliseconds). > >If the craft were really travelling at 300mph, there wouldn't *be* any sonic >booms. Whoops. I guess I missed something. >is the shuttle one of the longest supersonic aircraft? In fact, I believe that it is. Not *the* longest, but probably one of the top five. Another possibility is that the shockwaves coming off the front and the tail are shaped differently. Isn't the shape determined by the shape of the object itself? Wouldn't the shape then determine the angle off the direction of the craft's forward travel? And wouldn't that in turn effect the amount of time the wave took to intersect with the earth? I don't know much about aerodynamics, so I'm just guessing. Also remember that the craft is rapidly decelerating. Isn't the shape of the wave also determined by the speed? Would that have anything to do with it? William LeFebvre Department of Computer Science Rice University <phil@Rice.edu>
hollombe@ttidca.TTI.COM (The Polymath) (05/26/89)
In article <8465@venera.isi.edu> raveling@venera.isi.edu (Paul Raveling) writes: } Also note that these shock waves form ahead of and behind the } object. An form with a relatively pointed nose, like an F-104, } has a relatively large distance between its leading shock wave } and the nose itself; this produces minimal drag due to feeding } energy into the shock wave. A relatively blunt nose, such as } the shuttles, will generate its shock wave much closer to, or even } even on, the nose, and will produce much higher drag. This is the opposite of what I was taught (and saw demonstrated). Shock waves tend to attach to a sharp leading edge and precede a blunt one. You can demonstrate the effect in water by observing the bow wave of a boat with a rounded bow in the water vs. one with a pointed bow. Don't flame if you haven't tried it. -- The Polymath (aka: Jerry Hollombe, hollombe@ttidca.tti.com) Illegitimati Nil Citicorp(+)TTI Carborundum 3100 Ocean Park Blvd. (213) 452-9191, x2483 Santa Monica, CA 90405 {csun|philabs|psivax}!ttidca!hollombe
raveling@venera.isi.edu (Paul Raveling) (06/01/89)
In article <4499@ttidca.TTI.COM> hollombe@ttidcb.tti.com (The Polymath) writes: >In article <8465@venera.isi.edu> raveling@venera.isi.edu (Paul Raveling) writes: >} Also note that these shock waves form ahead of and behind the >} object. An form with a relatively pointed nose, like an F-104, >} has a relatively large distance between its leading shock wave >} and the nose itself; this produces minimal drag due to feeding >} energy into the shock wave. A relatively blunt nose, such as >} the shuttles, will generate its shock wave much closer to, or even >} even on, the nose, and will produce much higher drag. > >This is the opposite of what I was taught (and saw demonstrated). I believe you're right. A blunt nose should logically produce a relatively larger zone of high pressure in which the flow goes subsonic between the shock wave and the nose. Pardon my rusty brain; give me a sailplane that's at least transonic & I'll start brushing up. >Shock waves tend to attach to a sharp leading edge and precede a blunt >one. You can demonstrate the effect in water by observing the bow wave of >a boat with a rounded bow in the water vs. one with a pointed bow. > >Don't flame if you haven't tried it. I used to own a boat with a pointed bow (a Soling) & agree completely in the context of displacement hulls. Planing hulls aren't germane to the analogy, but hydrofoils would make an interesting study. Does anyone know of research into hydrofoil section optimization? Now if only this worked on the freeway, where flow is viscous, even if not hypersonic, we could design and sell a lot of cars. ---------------- Paul Raveling Raveling@isi.edu