<DOC>
<DOCNO>
274
</DOCNO>
<TITLE>
analysis of quartz and teflon shields for a particular
re-entry mission .
</TITLE>
<AUTHOR>
adams,e.w.
</AUTHOR>
<BIBLIO>
heat transfer and fluid mech. inst. 1961, 222.
</BIBLIO>
<TEXT>
  the transient performance of
ablation type heat protection shields is
treated herein for the surface of
a vehicle returning from outer space to the
earth .  the vehicle weighs 8640 kg,
has a ballistic factor of 500 lb ft, reenters
with a speed of 11 km sec at
ratio of 0.5, and is subjected to a
maximum deceleration of 7.7 times the
gravity constant .
  by use of well known equations
for the heat transfer and the mass transfer
at a heated surface, a numerical
calculation method is derived which, for
the investigated ablation processes,
yields exact transient solutions of the
fundamental system of partial differential
equations .  the method is applied
to various quartz shields and to one
teflon shield, which all evaporate so
readily under the conditions of the
problem at hand that practically no flow
of molten shield material exists .
the solutions also show comparatively small
temperature changes parallel to the surface .
  the results show that the nose
of the vehicle is cooled predominantly by
the evaporation of the quartz or the
teflon,. the rest of the vehicle's surface
is cooled by radiation of the quartz
or evaporation of the teflon .  the large
mass transfer effects on the nose of
the vehicle are detrimental since the resulting
low surface temperatures prevent
the radiative heat transfer out of
the shield, which does not involve any
mass loss, from being the desirable
governing cooling factor .
</TEXT>
</DOC>
