[amsat-bb] Re: Since We Are Off Topic Somewhat....

Ransom, Kenneth G. (JSC-OC)[BAR] kenneth.g.ransom at nasa.gov
Thu Feb 14 16:42:10 PST 2008

The amount of time spent in the atmosphere at high velocity (I'd have to do some digging to give some real time data but basically it is as follows).
One the way up, the rocket goes through the 100 km of air during the slower part of the change of velocity and spends very little time in the atmosphere at the higher velocity.
On the way down, the object starts to encounter the atmosphere at maximum velocity and therefore maximum friction. It will be in the atmosphere for the a much longer period since it comes in a very shallow angle. The object will have that friction nearly the entire trip to the ground even though the drag from the atmosphere will slow the object. 
Kenneth - N5VHO


From: amsat-bb-bounces at amsat.org on behalf of Joe
Sent: Thu 2/14/2008 5:55 PM
Subject: [amsat-bb] Since We Are Off Topic Somewhat....

Hi All,,

Since we are somewhat off topic for the moment with the conversation
about the bird to come down shortly..
Ok,  the question is,  and i've asked it to several other places, and
yet to even get a answer,

The question is,,,

Space shuttle launches,,  starts off at sea level,  and in less than ten
minutes goes from  zero to 17K MPh (or so)  And gets to orbital altitude.

Time to come down,, the de-orbit burn happens to slow it down just a bit
to cause the orbit to more or less decay.. It's at orbital altitude..
and moving at about 17K MPh..  45 minutes or so later it's back on the
ground and moving at zero MPh..

So in actuality it comes down from space even slower than going up. 
Yes?  45 min vs 10.

Ok,  same goes with any satellite,,

How come,  going up,,  0 to 17K MPh through the atmosphere, all  is
fine..  BUT

coming down,,  17K MPh  to 0  unless it has protection  it will  burn up
in the atmosphere from friction with the air.

why is it different?

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