roberts@CMR.ICST.NBS.GOV (John Roberts) (01/24/89)
Surely an SR-71 at surveillance altitude doesn't sound too loud from
the ground - that would spoil the surprise (:-)
Concordes regularly fly by here (~20-40 miles north of Washington, DC).
Though they are undoubtedly subsonic, they are by far the loudest planes
in the area. Fighter planes a few hundred feet up would probably be louder,
but we don't get many of them around here.
John Roberts
roberts@cmr.icst.nbs.govwooding@daisy.UUCP (Mike Wooding) (01/26/89)
In article <8901240814.AA07708@cmr.icst.nbs.gov>, roberts@CMR.ICST.NBS.GOV (John Roberts) writes: > > Surely an SR-71 at surveillance altitude doesn't sound too loud from > the ground - that would spoil the surprise (:-) Since it can and probably does fly at several times the speed of sound when spying, it probably doesn't matter how loud it is. It's been gone long time when it's heard on the ground. m wooding
jackz@hpscdc.HP.COM (Jack Zeiders) (01/27/89)
> hpscdc:sci.space / roberts@CMR.ICST.NBS.GOV (John Roberts) writes: >Surely an SR-71 at surveillance altitude doesn't sound too loud from >the ground - that would spoil the surprise (:-) At Beal AFB last fall the SR-71 made a speed run at Mach 3 or so at altitude. The pilot dumped fuel creating a visible contrail, if he had not there would be little chance of seeing the aircraft as the altitude was reported as 60k feet. I had a 1000mm lens and could not see the black aircraft. Perhaps this was because of the ground glass focusing screen. The sonic 'boom' was a muted pop-pop that could go easily unnoticed if you were unaware of it. At take off the SR-71 is very noisy, The 'A' models apparently somewhat more so. Jackz
alastair@geovision.uucp (Alastair Mayer) (01/30/89)
In article <2556@daisy.UUCP> wooding@daisy.UUCP (Mike Wooding) writes: >In article <8901240814.AA07708@cmr.icst.nbs.gov>, roberts@CMR.ICST.NBS.GOV (John Roberts) writes: >> >> Surely an SR-71 at surveillance altitude doesn't sound too loud from >> the ground - that would spoil the surprise (:-) > > Since it can and probably does fly at several times the speed > of sound when spying, it probably doesn't matter how loud it is. > It's been gone long time when it's heard on the ground. For those that want a quantitative analysis, figure the Blackbird is going Mach 3 at >70,000' (although it's generally beleived that the SR-71 will do Mach 4 and >80,000 feet, these figures aren't officially confirmed). By the time it takes the sound the more than a minute to reach the ground from 70K feet, the plane is 3*70 K feet (horizontal distance) from where it was when the sound started -- about 40 miles. Like the man said, it's been gone a long time when it's heard on the ground. In any case, the boom is going to be somewhat attenuated after travelling that far. -- "The problem is not that spaceflight is expensive, | Alastair J.W. Mayer therefore only the government can do it, but that | alastair@geovision.UUCP only the government is doing spaceflight, therefore | al@BIX it is expensive." |