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The purpose of this note is to discuss, from the limited
information available, the order of magnitude of the strength and
the configuration of the shock waves, close to ground level,
generated from aircraft flying et supersonic speeds. The level
flight case is the only one considered in detail but brief reference
is also made to other manoeuvres such as the supersonic dive of
limited duration. The alterations in path and strength of a shock
wave in passing through the heterogeneous atmosphere are shown to
be very important. For normal temperature variation with altitude
the attenuation of shock strength, with distance downward from the
aircraft, will be decreased. A similar effect will occur when
shock waves are propagated against a wind, whose velocity increases
with height..
These results should be of interest to civil engineers
and others making estimates of the possible damage to buildings due
to the above cause. A preliminary, mainly qualitative discussion
of this part of the problem is included, which although not complete
should at least give some idea of the damage to be expected. In
this connection it is found that for aircraft flying at and above
5000 ft. at Each numbers up to 2 the damage to buildings should be
limited to a number of ‘freak’ cases of window breakage and similar
minor damage. In the case of aircraft diving at supersonic speeds
at a high altitude the excess pressures caused by the resulting shock
waves and their time duration are so small that the chance of any
damage occurring is almost negligible. |
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