Path: utzoo!attcan!uunet!yale!mfci!colwell From: colwell@mfci.UUCP (Robert Colwell) Newsgroups: sci.space.shuttle Subject: Re: Atlantis is home! Message-ID: <871@m3.mfci.UUCP> Date: 23 May 89 13:04:44 GMT References: <272@skipper.dfrf.nasa.gov> <9090001@hp-lsd.HP.COM> <4453@ttidca.TTI.COM> <862@m3.mfci.UUCP> <3305@kalliope.rice.edu> Sender: colwell@mfci.UUCP Reply-To: colwell@mfci.UUCP (Robert Colwell) Organization: Multiflow Computer Inc., Branford Ct. 06405 Lines: 38 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