Sonic boom rise times
Quote:
CliveL, are there any documented records of the trials in "Boom Alley" we could use to settle some of the issue? Unquote:
Christiaan, there isn't anything particular to "Boom Alley", but there is enough data around to quantify the issue.
SSD, you were quite right when you said that the shock waves diverge as they get farther from the aircraft; that could be as much as 25% of the aircraft length at the ground. Near the aircraft the rise time would be proportional to length/speed of sound.
To cut a long story short, plotting all the available data leads to a pretty good expression for the rise time:
T = 0.011*LOA + 0.0001*FL
To give you a feel for the numbers, the measured value for an F18 at FL600 is 0.18 secs, for Concorde at FL520 about 0.25 secs or for an F104 at FL190 0.08 secs.
After that it would depend on your own perceptions I think, but I could easily envisage either a single or double bang for a fighter size aircraft depending on altitude.