lawrocket 3 #1 October 16, 2003 I've studied law, just not the laws of physics. A buddy and I were having a discussion to which we didn't know the answer. At what altitude can an object create a sonic boom? For example, when the space shuttle re-enters, at what altitude does the first sonic boom occur? I've never heard it when it passed over Cali to land in Florida. But it sure rattled my windows when it landed at Edwards... My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
QuickDraw 0 #2 October 16, 2003 I think it differs according to air pressure. -- Hope you don't die. -- I'm fucking winning Quote Share this post Link to post Share on other sites
CrazyIvan 0 #3 October 16, 2003 As far as I know is at ANY altitude, but, if it's too close to the ground it might throw the object off course.__________________________________________ Blue Skies and May the Force be with you. Quote Share this post Link to post Share on other sites
yardhippie 0 #4 October 16, 2003 to throw something else into the mix. Does it even make a sonic boom? Is sonic boom related to acceleration only? and... maybe the sonic boom does happen extremly high up and the air is too thin to carry the sound very far... just thinkin out loud... Goddam dirty hippies piss me off! ~GFD "What do I get for closing your rig?" ~ me "Anything you want." ~ female skydiver Mohoso Rodriguez #865 Quote Share this post Link to post Share on other sites
lawrocket 3 #5 October 16, 2003 Well, that's kind of my point. Does the sound just dissipate, or is there no sonic boom at 400,000 feet... My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
QuickDraw 0 #6 October 16, 2003 I suppose we should ask what sound waves are transmitted by. -- Hope you don't die. -- I'm fucking winning Quote Share this post Link to post Share on other sites
yardhippie 0 #7 October 16, 2003 im gonna go with there is NO sonic boom... but I need some background on the actual reason why a sonic boom occurs... Goddam dirty hippies piss me off! ~GFD "What do I get for closing your rig?" ~ me "Anything you want." ~ female skydiver Mohoso Rodriguez #865 Quote Share this post Link to post Share on other sites
QuickDraw 0 #8 October 16, 2003 I recall someone saying in a thread about Col. Joe Kittinger, that you have to travel faster to achieve the speed of sound at altitude. -- Hope you don't die. -- I'm fucking winning Quote Share this post Link to post Share on other sites
yardhippie 0 #9 October 16, 2003 this is cool hereGoddam dirty hippies piss me off! ~GFD "What do I get for closing your rig?" ~ me "Anything you want." ~ female skydiver Mohoso Rodriguez #865 Quote Share this post Link to post Share on other sites
yardhippie 0 #10 October 16, 2003 taking back my previous assumption... yes it makes a boom. I just heard it! Goddam dirty hippies piss me off! ~GFD "What do I get for closing your rig?" ~ me "Anything you want." ~ female skydiver Mohoso Rodriguez #865 Quote Share this post Link to post Share on other sites
lawrocket 3 #11 October 16, 2003 Ah, lad. We all know that sonic booms occur. The question is, my good man, at what altitude can a sonic boom first occur? It cannot occur in space, since it is a vacuum, and therefore no speed of sound. Cool pic (beware of Ivan. It's been posted here before, and he'll clicky you to it) My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
darkvapor 0 #12 October 16, 2003 Quotethat you have to travel faster to achieve the speed of sound at altitude. True. The speed equation can be expressed as 'speed of sound' = SQRT(yRT). Here, 'y' is actually gamma, a constant value (depends on medium, for air, about 1.4). R is a constant. T is temperature. Because temperature varies with altitude, so does the speed of sound. Quote Share this post Link to post Share on other sites
Beerlight 0 #13 October 16, 2003 Quote At what altitude can an object create a sonic boom? For example, when the space shuttle re-enters, at what altitude does the first sonic boom occur? I've never heard it when it passed over Cali to land in Florida. But it sure rattled my windows when it landed at Edwards... I know some people on here that are well versed in acceleration stats, but I'll throw my .02 in. Sonic booms can happen at sea level/ground level and go up I'm not sure how high. Most people in the U.S. do not hear sonic booms anymore due to the fact that it's prohibited below 30,000 feet. From that height, the sonic signature dissapates before reaching the surface...ie. your eardrums. I just went supersonic 2 weeks ago in an Air Force trainer, but we were at 39,000 feet and there was absolutely no sensation of exceeding Mach 1, just a little jump in airspeed indicator and the VVI had reverse sensing.... Hmmm...now I've run to long wif this! Oh, and the jet has to be pointing in your direction for you to hear it..... That's why you don't hear the Shuttle blow thru Mach in ascent, only on descent........cheers Quote Share this post Link to post Share on other sites
QuickDraw 0 #14 October 16, 2003 On this site the sonic boom is expected at 35000mtrs. http://www.legrandsaut.org/site_en/# Look on the image on the right. -- Hope you don't die. -- I'm fucking winning Quote Share this post Link to post Share on other sites
billvon 3,120 #15 October 16, 2003 >At what altitude can an object create a sonic boom? Any altitude at which there is atmosphere. The denser the atmosphere, the more energy there is in the shockwave, and the louder it seems to a listener on the ground. Also, the higher the altitude, the more distance the shock wave has to dissipate. >For example, when the space shuttle re-enters, at what altitude does >the first sonic boom occur? You'd have to define "sonic boom." A boom louder than X dB? Greater than X PSI overpressure? The ability to create a sonic boom begins as soon as the orbiter enters the atmosphere, but you wouldn't be able to hear it at that point due to the low amplitude of the boom. Some numbers from a NASA site: -------------------- Overpressures recorded on the ground during the landing of the orbiter Discovery on mission STS-26 Oct. 3, 1988 revealed that the intensity was 1.06 lb in the Santa Barbara area as Discovery crossed the coastline at a speed of Mach 4.37 at an altitude of 115,400 ft. Intensity rose to 1.15 lb in the Santa Clarita Valley area, 45 miles southwest of Edwards, as the vehicle's speed and altitude reduced. At Edwards, when Discovery was about 60,000 ft overhead just moments before the landing the overpressure was 1.25 lb. The highest reading during the landing approach over Southern California was 1.75 lb in the areas of Palmdale and Lancaster 20 to 30 miles southwest of Edwards. Typical overpressure of other aircraft types are: SR-71: 0.9 lb, speed of Mach 3, 80,000 ft Concorde SST: 1.94 lb, speed of Mach 2, 52,000 ft F-104: 0.8 lb, speed of Mach 1.93, 48,000 ft --------------------- The graph at the bottom of this page shows the trajectory and speed of an orbiter as it descends. FYI. Quote Share this post Link to post Share on other sites
QuickDraw 0 #16 October 16, 2003 QuoteSR-71: 0.9 lb, speed of Mach 3, 80,000 ft I had heard that them Falcon copies were good, but damn... -- Hope you don't die. -- I'm fucking winning Quote Share this post Link to post Share on other sites
lawrocket 3 #17 October 16, 2003 Okay, we know those speeds. That's a very good answer. But, the question I asked is at what altitude is a sonic boom possible? My wife is hotter than your wife. Quote Share this post Link to post Share on other sites
aero04 0 #18 October 16, 2003 QuoteAt what altitude can an object create a sonic boom? QuoteFor example, when the space shuttle re-enters, at what altitude does the first sonic boom occur? I've never heard it when it passed over Cali to land in Florida. But it sure rattled my windows when it landed at Edwards... Any altitude within the atmosphere. If there is enough fluid (air) there to get some kind of flow over the wings, the possibility of shock waves exist. This altitude would be way up there, but I don't know where the standard atmosphere stops and space starts. Shock waves occur when your velocity passes the local speed of sound, ie, when you pass Mach 1. The speed of sound varies with temperature. The higher you go, the lower the temperature is, and the lower the speed of sound is. Sonic booms can be heard if a shock is present. A sonic boom is caused by a shock wave. A shock wave causes the local pressure, temperature and density to increase. By local I mean those 3 properties will increase at the shock wave. If I recall correctly, I remember one of my profs saying the sonic boom is caused by the pressure change. In other words, we hear a sonic boom as a result of the pressure change. *Looking it up now in my stack of aerospace books* Quote Share this post Link to post Share on other sites
kallend 2,151 #19 October 16, 2003 QuoteI think it differs according to air pressure. Not sure exactly what you mean, but the speed of sound is almost completely independent of pressure in air, but depends on temperature.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 2,151 #20 October 16, 2003 QuoteI recall someone saying in a thread about Col. Joe Kittinger, that you have to travel faster to achieve the speed of sound at altitude. No - the speed of sound is lower at altitude because the air temperature is lower.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
QuickDraw 0 #21 October 16, 2003 I think i meant air density, but ok you got me on the second one. -- Hope you don't die. -- I'm fucking winning Quote Share this post Link to post Share on other sites
billvon 3,120 #22 October 16, 2003 >No - the speed of sound is lower at altitude because the air >temperature is lower. True up to about 30,000 feet; above that altitude the atmosphere stops getting colder. Above about 65,000 feet it starts heating back up again; by 120,000 feet it can be the same as sea level. Since sonic booms from the shuttle occur above 100,000 feet, at some points the speed of sound for the orbiter may be _higher_ than sea level. Quote Share this post Link to post Share on other sites
aero04 0 #23 October 16, 2003 Quote>No - the speed of sound is lower at altitude because the air >temperature is lower. True up to about 30,000 feet; above that altitude the atmosphere stops getting colder. Above about 65,000 feet it starts heating back up again; by 120,000 feet it can be the same as sea level. Since sonic booms from the shuttle occur above 100,000 feet, at some points the speed of sound for the orbiter may be _higher_ than sea level. I did not know that. Learning something new every day. I've got my sophmore aerodynamics book in front of me, and at 82500 feet, the temperature begins to increase. Quote Share this post Link to post Share on other sites
QuickDraw 0 #24 October 16, 2003 So...in theory.. if the temperature and pressure were high enough, a brisk walk would do it ? -- Hope you don't die. -- I'm fucking winning Quote Share this post Link to post Share on other sites
billvon 3,120 #25 October 17, 2003 >So...in theory.. if the temperature and pressure were high enough, a >brisk walk would do it ? Sure, if you're an antelope and you're on Venus. Quote Share this post Link to post Share on other sites
