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From: mikef@aplvax.UUCP (Michael A. Fallavollita)
Newsgroups: net.aviation,net.politics
Subject: Re: "A Design Proposal That Would Make Passenger Planes Safe"
Message-ID: <185@aplvax.UUCP>
Date: Fri, 17-Jan-86 01:58:45 EST
Article-I.D.: aplvax.185
Posted: Fri Jan 17 01:58:45 1986
Date-Received: Sun, 19-Jan-86 01:42:33 EST
References: <196@hropus.UUCP> <968@terak.UUCP> <865@masscomp.UUCP>
Organization: JHU/Applied Physics Lab, Laurel, MD
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> [article refering to "all-lifting-surface" aircraft.]

I'd like to add a little light to the subject of drag vs. speed.  All aero-
dynamic forces are usually thought of in terms of coefficients.  The aero-
dynamic forces all vary as the square of the velocity, ie. dynamic pressure.
There are three major components to the total drag coefficient:

      Component:  Based on:
	profile - design
	induced - square of lift coefficient, aspect ratio and wing shape
	   wave - becomes a LARGE factor at supersonic speeds.

Profile drag varys by design only. .  Wave drag is caused by
changes in entropy across the shock wave.  It does not exist below Mach 1
but increases drastically at Mach 5 and above.  The induced drag coefficient is
the hardest to get a handle on but it changes by the square of the lift co-
efficient and by the inverse of the aspect ratio.  It does not change as a
factor of speed.  Therefore up until Mach 1, the velocity drag curve is
a power curve.  Past Mach 1 up until Mach 5, things are within reason
but a lot harder to define.  At hypersonic velocities, above Mach 5, wave
drag takes off.  A lot of research is presently being done to:

	1)  find a way to decrease the effects of the shock waves,
	2)  Create an engine to go from subsonic to hypersonic speeds. (SCRAM)

Drag is always one of the major concerns of Aerospace engineers and one place
of ongoing research.

I hope someone out there followed this and cared a hoot.
(If it did thank Dr. JD Anderson, my Aerodynamics teacher.)

			Mike Fallavollita
			JHU APL
			(UMCP)