rjnoe@riccb.UUCP (Roger J. Noe) (12/05/85)
> Why are there two sonic booms from the shuttle?
It's because there are two "sonic cones" formed by the shuttle. (There is
very likely a more scientific term for this, but I don't know what it is.)
With most supersonic aircraft, a cone-shaped shock wave expands from the
nose of the craft outward. Where and when this cone intersects the surface
of the Earth determines who hears the sonic boom. This cone usually expands
at a wide enough angle to engulf the rest of the aircraft. But the shuttle
has a pretty unusual shape. I think the vertical stabilizer (tail) rises
above the cone-shaped shock wave formed by the nose. This causes the tail
to slam into the surrounding air the same way the nose does, and a second
shock wave, also shaped like a cone, forms at the edge of the tail. This
is the explanation I have heard, anyway. I don't think the two sonic booms
are from the top and bottom points of the "N-signature" of the shock wave
formed at the nose, or else every supersonic aircraft would exhibit this
phenomenon. I used to hear F-4's go over my house many years ago, and I never
remember hearing a double sonic boom, although sometimes two or more Phantoms
would be in formation and each would have its own sonic boom. Could someone
elaborate on this, please? At least let me know if this is all accurate.
Thanks.
--
Roger Noe ihnp4!riccb!rjnoemsc@saber.UUCP (Mark Callow) (12/07/85)
> > Why are there two sonic booms from the shuttle? > > It's because there are two "sonic cones" formed by the shuttle. (There is > ..... > explanation about how it's due to the shuttle's "strange" shape > deleted for brevity. Concorde also makes a double sonic boom. -- From the TARDIS of Mark Callow msc@saber.uucp, sun!saber!msc@decwrl.dec.com ...{ihnp4,sun}!saber!msc "Boards are long and hard and made of wood"
tcculpep@uok.UUCP (12/09/85)
I remember reading in one of my physics classes that there are always two shock cones, one from the nose and one from the back (but not the tail). Normally you don't hear both of them because at low mach speeds (relatively) the time delay between shocks is so short they seem like only one. However, the shuttle is moving so fast that there is a noticable delay, until of course it has slowed to the slower speeds. taylor culpepper uokvax!uok!tcculpep univ. of oklahoma solar-shmolar, we be usin' fusion.
skip@ubvax.UUCP (Skip Addison Jr) (12/12/85)
In article <600@riccb.UUCP> rjnoe@riccb.UUCP (Roger J. Noe) writes: >> Why are there two sonic booms from the shuttle? > >It's because there are two "sonic cones" formed by the shuttle. (There is >very likely a more scientific term for this, but I don't know what it is.) >With most supersonic aircraft, a cone-shaped shock wave expands from the >nose of the craft outward. Where and when this cone intersects the surface >of the Earth determines who hears the sonic boom. This cone usually expands >at a wide enough angle to engulf the rest of the aircraft. But the shuttle >has a pretty unusual shape. I think the vertical stabilizer (tail) rises >above the cone-shaped shock wave formed by the nose. This causes the tail >to slam into the surrounding air the same way the nose does, and a second >shock wave, also shaped like a cone, forms at the edge of the tail. This >is the explanation I have heard, anyway. I don't think the two sonic booms > ... >-- > Roger Noe ihnp4!riccb!rjnoe Sonic booms are created by major displacements of air or air rushing in to fill a void. A sonic boom is generated by the tail of the shuttle as a result of the drastic change in the shuttle cross-section there. As the shuttle moves it leaves behind a void which the surrounding air fills. In fact, every exterior part of a super-sonic aircraft creates its own little "boom" (shock-wave), but the only noticeable ones are usually generated by the sudden intrusion of the nose and sudden abscense of the tail. A more streamlined aircraft has less of a boom. Notice the two wakes left by some boats at high speeds. Same principles. -- Skip Addison {amdcad, amd, cae780}!ubvax!skip
don@umd5.UUCP (12/14/85)
> > I remember reading in one of my physics classes that there are always two > shock cones, one from the nose and one from the back (but not the tail). > Normally you don't hear both of them because at low mach speeds (relatively) > the time delay between shocks is so short they seem like only one. However, > the shuttle is moving so fast that there is a noticable delay, until of > course it has slowed to the slower speeds. > > taylor culpepper uokvax!uok!tcculpep > univ. of oklahoma > 'cuse me if I sound nit-picky to you, but one can't HEAR a sonic boom because by the very nature of the phenomena it is SUPERSONIC. One does sense the window-rattling abrupt changes in air pressure, however. If I'm not mistaken, the air pressure states go: ambient-low press.-ambient as the shockwave "cones" pass by. -- --==---==---==-- "What happened ?" "It seems the occipital area of my head impacted with the arm of the chair." "No, I mean, what happened to us ?" "That has yet to be surmised." ARPA: umd5!don@maryland.ARPA, don%umd5@umd2.ARPA BITNET: don%umd5@umd2 UUCP: ..!{ seismo!umcp-cs, ihnp4!rlgvax }!cvl!umd5!don
desj@brahms.BERKELEY.EDU (David DesJardins) (12/15/85)
In article <815@umd5.UUCP> don@umd5.UUCP writes: > > ... one can't HEAR a sonic boom >because by the very nature of the phenomena it is SUPERSONIC. > >One does sense the window-rattling abrupt changes in air pressure, however. >If I'm not mistaken, the air pressure states go: ambient-low press.-ambient >as the shockwave "cones" pass by. > I don't know what you think sound is, other than a variation in air pressure. The fact is that a sonic boom is produced by any object traveling at (or near) the speed of sound. It is (loosely speaking) the superposition of the sounds emitted by the object at different times, arriving at the observer at the same time. (Note that I am not claiming that this is completely accurate, but it is sufficiently so for this discussion.) Furthermore, in the absence of temperature changes pressure throughout a volume must be conserved, and so it is not possible for pressure to dip below ambient without also rising above ambient. Finally, I guarantee that I, and many other people, have HEARD sonic booms. -- David desJardins
arlan@inuxm.UUCP (A Andrews) (12/17/85)
> > > > I remember reading in one of my physics classes that there are always two > > shock cones, one from the nose and one from the back (but not the tail). > > Normally you don't hear both of them because at low mach speeds (relatively) > > the time delay between shocks is so short they seem like only one. However, > > the shuttle is moving so fast that there is a noticable delay, until of > > course it has slowed to the slower speeds. > > > > taylor culpepper uokvax!uok!tcculpep > > univ. of oklahoma > > > > 'cuse me if I sound nit-picky to you, but one can't HEAR a sonic boom > because by the very nature of the phenomena it is SUPERSONIC. > > One does sense the window-rattling abrupt changes in air pressure, however. > If I'm not mistaken, the air pressure states go: ambient-low press.-ambient > as the shockwave "cones" pass by. > > -- > --==---==---==-- > "What happened ?" > "It seems the occipital area of my head impacted with the arm of the chair." > "No, I mean, what happened to us ?" > "That has yet to be surmised." > > ARPA: umd5!don@maryland.ARPA, don%umd5@umd2.ARPA > BITNET: don%umd5@umd2 > UUCP: ..!{ seismo!umcp-cs, ihnp4!rlgvax }!cvl!umd5!don *** REPLACE THIS LINE WITH YOUR MESSAGE *** Unfortunately (?), the sonic boom itself is not supersonic; the phenomenon that causes the shock wave is supersonic. What you hear, you hear. What else is sound than perturbations that one can hear in the atmosphere? --enuf of fluid mechanics; less argyou uv mien verzuz mashines --arlan andrews
scw@ucla-cs.UUCP (12/24/85)
In article <386@ubvax.UUCP> skip@ubvax.UUCP (Skip Addison) writes: >In article <600@riccb.UUCP> rjnoe@riccb.UUCP (Roger J. Noe) writes: >>> Why are there two sonic booms from the shuttle? >> >>It's because there are [...] anyway. I don't think the two sonic booms >> ... >>-- >> Roger Noe ihnp4!riccb!rjnoe > >Sonic booms are created by major displacements of air or air rushing in to >fill a void. A sonic boom is[...] and sudden abscense of the tail. A more >streamlined aircraft has less of a boom. > >Notice the two wakes left by some boats at high speeds. Same principles. Excuse me, right idea but wrong cause, The shock wave is formed when the air- flow velocity passes through the speed of sound. If you look at the upper surface of the wing of any aircraft flying near Mach 1 (Mach .6~~ < v <Mach 1.0) You'll see 2 'lines' running spanwise, these are 'shock waves' where the airflow over the wing transistions the speed of sound (increasing veloicity produces a stronger wave than decreasing veloicity so the forward 'line' will be much sharper and clearer that the trailing one. The 'lines' will appear to move forward and backwards on the wing as the airspeed and angle of attack change. They also move farther apart with increasing Mach number. At Mach 1 the will be at the leading and trailing edges. If the leading and trailing edges are far enough apart you'll hear 2 sonic 'booms' as the aircraft passes. Note that the primary sound energy is produced by the wings (or in the case of the space shuttle the whole aircraft (being all wing). Now the distance from the nose to the tail of the space shuttle is what? (150 feet??) so assuming (20000 feet & Standard Atm. and getting out my trusty pro-star. Mach 1 = 621 KTAS = 1048 FPS= ~.14 sec between the first boom and the second, but at 50000 Feet & SA Mach 5= 2743 KTAS = 4629 FPS = .03 seconds so it sounds like 1 (longer) boom). <scw>
ritter@spp1.UUCP (Phillip A. Ritter) (01/02/86)
In article <8173@ucla-cs.ARPA> scw@ucla-cs.UUCP (Stephen C. Woods) writes: >...Discussion of airflow dynamics deleted... Now the distance from the nose >to the tail of the space shuttle is what? (150 feet??) so assuming >(20000 feet & Standard Atm. and getting out my trusty pro-star. >Mach 1 = 621 KTAS = 1048 FPS= ~.14 sec between the first boom and the >second, but at 50000 Feet & SA Mach 5= 2743 KTAS = 4629 FPS = .03 seconds >so it sounds like 1 (longer) boom). > ><scw> The math may be perfect, but I have to disagree with the last statement. The shuttle sonic boom does NOT sound like one long boom. There are two DISTICT booms, easily detected by the human ear. This is from simple experiance - I have heard them several times as the shuttle passes almost directly overhead on its way into Edwards. Phil Ritter -- Phillip A. Ritter
steve@jplgodo.UUCP (Steve Schlaifer x3171 156/224) (01/02/86)
> In article <8173@ucla-cs.ARPA> scw@ucla-cs.UUCP (Stephen C. Woods) writes: > >...Discussion of airflow dynamics deleted... Now the distance from the nose > >to the tail of the space shuttle is what? (150 feet??) so assuming > >(20000 feet & Standard Atm. and getting out my trusty pro-star. > >Mach 1 = 621 KTAS = 1048 FPS= ~.14 sec between the first boom and the > >second, but at 50000 Feet & SA Mach 5= 2743 KTAS = 4629 FPS = .03 seconds > >so it sounds like 1 (longer) boom). > > > ><scw> > > The math may be perfect, but I have to disagree with the last statement. The > shuttle sonic boom does NOT sound like one long boom. There are two > DISTICT booms, easily detected by the human ear. This is from simple > experiance - I have heard them several times as the shuttle passes almost > directly overhead on its way into Edwards. > > Phil Ritter > -- > Phillip A. Ritter It has always seemed to me, in fact, that the booms were seperated by at least .5 seconds (although I have never actually timed them). The two booms are quite distinct. ...smeagol\ Steve Schlaifer >!jplgodo!steve Advance Projects Group, Jet Propulsion Labs ....group3/ 4800 Oak Grove Drive, M/S 156/204 Pasadena, California, 91109 +1 818 354 3171