Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!husc6!yale!mfci!colwell From: colwell@mfci.UUCP (Robert Colwell) Newsgroups: sci.space.shuttle Subject: Re: Atlantis is home! Message-ID: <862@m3.mfci.UUCP> Date: 19 May 89 13:11:02 GMT References: <272@skipper.dfrf.nasa.gov> <9090001@hp-lsd.HP.COM> <4453@ttidca.TTI.COM> Sender: colwell@mfci.UUCP Reply-To: colwell@mfci.UUCP (Robert Colwell) Organization: Multiflow Computer Inc., Branford Ct. 06405 Lines: 39 In article 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