Re: [amsat-bb] Spacefraft Aerodynamics [was:Re:AO-40: Plans for April-June 2001]

["Ken Ernandes" <n2wwd@xxxxxxxxxxxxxx>]

----- Original Message -----
From: Douglas Braun & Nadia Papakonstantinou <doug@dougbraun.com>
To: Margaret Leber <maggie@voicenet.com>
Cc: <amsat-bb@AMSAT.Org>
Sent: Thursday, April 05, 2001 11:07 AM
Subject: Re: [amsat-bb] Spacefraft Aerodynamics [was:Re:AO-40: Plans for
April-June 2001]


> At the atmospheric pressures where the satellite is, the classic concepts
> of "laminar" and turbulent" flow do not hold.  The reason is that the
> gas molecules are able to travel a significant distance (several cm?)
before
> colliding with another gas molecule.  Thus, the aerodynamic forces on
> the S/C can better be modeled by stream of individual particles than
> by fluid flow.  I believe that the drag would be almost exactly
> proportional to the frontal area (i.e. silhouette) of the S/C.
>
> Perhaps somebody who has studied this subject more recently
> than me (i.e. in the last decade or two) can give a more detailed
> and accurate explanation.

Generally your coefficient of drag (CD) is somewhere around 2.2 for a
spacecraft, which is a tad worse than a normally-oriented flat plate (CD =
2.0), which would represent the frontal area silhoutte.

73, Ken N2WWD


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