[amsat-bb] Re: New Cubesat - the Ultimate Fox Hunt

[Graham Shirville]

According to the  "Apollo 11 Owner's Workshop Manual" recently published by 
Haynes here in the UK
 page 71

"Atmospheric Heating"
Frictional heating was not just a problem during re-entry. During the 
acceleration after launch through the thicker, lower atmosphere, the apex of 
the command module would also be exposed to aerodynamic heating and needed 
protection by an additional cork and fibreglass shroud attached to the 
launch escape tower.
The far more intense re-entry heating is often mistakenly thought to be 
something to do with friction with the passing air. In fact the extra 
heating during re-entry is more comparable to the heat that builds up in a 
valve in a bicycle pump as air is compressed into a tyre. When any gas is 
compressed the amount of energy that it holds in a given volume rises. When 
the air in front of a blunt hypersonic craft cannot move aside fast enough 
it becomes compressed and so heats up for the same reason.
During re-entry the speeds, and therefore the compression, are so great that 
the temperature can easily rise into the thousands of degrees, approaching 
the same sort of temperature as on the surface of the sun (5,500C) . The 
advantage of the blunt shape has in this process over a more streamlined 
form is that by creating this compressed layer of air ahead of it, the main 
part of the craft is separated from the hottest and most damaging heat."

So all we need is a cubesat containing a deorbit propulsion system so that 
the landing point can be carefully selected, which has inside it, a 
miniature Apollo shaped capsule made of titanium with a heat shield on the 
blunt end and which has ceramic panels so that the inbuilt GPS can receive 
and the VHF or UHF or S band transmitter can transmit.:)

73

Graham G3VZV

PS The Haynes Manual is available from the RSGB

----- Original Message ----- 
From: "Sil - ZL2CIA" <zl2cia at amsat.org>
To: "Bob Bruninga" <bruninga at usna.edu>; "Amsat Reflector" 
<amsat-bb at amsat.org>
Sent: Monday, August 10, 2009 9:40 AM
Subject: [amsat-bb] Re: New Cubesat - the Ultimate Fox Hunt


> Bob Bruninga wrote:
>
>> The difference is that going up, you are going slowly in the higher 
>> density atmosphere which is continually lessening as you go up letting 
>> you go faster and faster with less and less friction.  THus, no 
>> multiplying build up of friction.
>>
>>
> Bob,
>
> I hesitate to say this, but I'm almost certain that re-entry heating is
> not caused by friction (well may be 10%). Most reliable sources, NASA
> included, attribute re-entry heating to shock wave compression of the
> air in front of the descending craft.
>
> Sil
> ZL2CIA
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