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Re: Since We Are Off Topic Somewhat....



Also remember that during launch the space shuttle is facing directly 
into the direction of travel thus presenting the lowest drag (and 
least friction).  During re-entry the space shuttle lifts its nose a 
bit to expose more area of the underside of the craft to produce more 
drag.  This increases friction.  As the shuttle descends, air density 
increases which increases friction.  The shuttle slows due to this 
friction.  The decent path is a smaller rate of decent (lower angle) 
than launch which is nearly vertical at first.  This gives more time 
for slowing due to atmospheric friction.  All this produces very high 
temperatures.  Too steep a decent would increase temperatures beyond 
what the tiles on the skin of the shuttle can withstand and the 
shuttle would burn up just like a meteor.  Hope this helps understanding.

Ed (just an old retired NASA engineer - not quite rocket scientist).

At 05:04 PM 2/14/2008, Jim Jerzycke wrote:
>Because on the way up, as its accelerating, the air is
>getting thinner. On the way down it only has the drag
>of the atmosphere to slow it, so it caries more of its
>velocity into the thicker air.
>Jim  KQ6EA
>
>--- Joe <nss@mwt.net> wrote:
>
> > 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?
> >
> > Joe WB9SBD & NSS
> > _______________________________________________
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>
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