Quote:
Originally Posted by freebeard
I read it as for any particular shape of varying fineness ratio.
Above 250, a pointed nose is better than a bluff nose.
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Correct!
Above 250-mph ( 405 km/h ) a road vehicle is entering transonic flow, where air begins to compress, and parts of the body may be capable of generating shock-wave drag.
Hucho gives us a glimpse into this world in his 2nd-Edition book, regarding record vehicles.
The rocket-powered 'Blue Flame' is attributed with a subsonic drag of Cd 0.20, which climbs to Cd 0.60, or 0.65 ( if memory serves me ) around Mach-1, in standard air.
You see the same with the Space Shuttle, North American X-15, and NASA lifting bodies.
The U.S. Army's Aberdeen Proving Grounds has published drag figures for a handful of artillery projectiles, which also depicts these exponential drag increases, from subsonic to supersonic velocities, at constant air density.