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

[Sil - ZL2CIA]

Sil - ZL2CIA wrote:
> 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
>   
Wikipeadia reckon 80% of the heating experienced by a re-entering 
orbiter (shuttle) is the result of compression, leaving 20% to friction.

The 90% figure might be more correctly applied to the Apollo re-entry 
vehicle. It was a very different shape.

Some highspeed vehicles did experience severe heating, notably the 
amazing X-15 craft.

The question is a good one, but the answer has needs to consider far 
more than frictional heating, since that accounts for only a small part 
of the energy that is converted to heat during re-entry.

I have no idea what the equivalent ratio is on the way up, but it is a 
delightful puzzle. Thanks Joe.

Sil
ZL2CIA

Sil