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Posted by <tapwater on April 6, 2006, 2:19 am
Please log in for more thread options Thank you for comprehending what I was trying to discuss. Now I have to
figure out why the people at aerospaceweb feel that the heating will be
greater. Their diagram shows only four or five large skips, I would try a
larger number of smaller skips. Also, for purposes of clarity I suppose,
they show the "outer limits of the atmosphere" as a line rather then a
region. In reality, the nitpickers could argue for years over where to draw
that line.
I still think a carefully plotted course could significantly reduce the
need for heat shielding. My rationale for hanging on to my theory is that a
fixed amount of mass, and a fixed amount of deceleration through friction
will always generate a fixed amount of heat. I can't figure out how to get
around that equation! HOWEVER, if you spread that heat over a greater time
period, then the instantaneous heat (heat measured at any instant) can be
reduced. A machine can tolerate 500F for 10 minutes better than it can
tolerate 1000F for 1 minute. (I'm pulling those numbers out of a hat, but
you get the idea). We have to find a way to EASE a spacecraft into the
atmosphere rather then slam it in.
> >They can't skip up to orbital speed, but they can get lift enough to get
to
> >thinner atmosphere where they either stall and descend again, or nose
down
> >and descend again. I'm talking about an oscillating downward flight path,
> >instead of a constant downward one, and an oscillating deceleration rate
> >instead of a constant rate.
>
> Aerospaceweb.org: Atmosphere & Spacecraft Re-entry Q&A
> <http://www.aerospaceweb.org/question/spacecraft/q0218.shtml>
> has a decent description of ballistic, glide, and skip re-entry
> trajectories, but about skip, they say:
>
> The attraction of the skip trajectory is that a vehicle can travel
> much farther downrange than either the ballistic or glide options
> allow. The primary disadvantage, however, is significantly higher
> aerodynamic heating since the friction heat absorbed during the
> skips grows at a higher rate and requires heavier shielding to
> protect the vehicle. As a result, skip entry has never been used
> for a manned spacecraft. A related technique known as aerocapture
> has been applied to unmanned craft, though the method is typically
> used to slow a vehicle and enter orbit around a planet rather than
> as a means of re-entry.
>
>
> --
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