<DOC>
<DOCNO>
717
</DOCNO>
<TITLE>
motions of a short 10degree blunted cone entering a martian atmosphere
at arbitrary angles of attack and arbitrary pitching rates .
</TITLE>
<AUTHOR>
peterson, v.l.
</AUTHOR>
<BIBLIO>
nasa tn-d 1326 .
</BIBLIO>
<TEXT>
the dynamic behavior of two probe vehicles entering a martian atmosphere
 in a passive manner with arbitrary initial angles of attack and pitching
rates to 12degree per second has been determined . results for an
entry velocity of 21,700 feet per second and an entry angle of -40degree
 were obtained from machine calculated solutions of the six-degree-offreedom
rigid-body equations of motion using experimental aerodynamic
characteristics for the vehicles . one of the vehicles had a flat base
and was statically stable in two attitudes /nose forward and base forward/
. the other vehicle, derived from the first by adding a conical
afterbody, was statically stable in only one attitude /nose forward/ .
a 10-rpm vehicle spin rate, believed ample for the purpose of
distributing solar and aerodynamic heating over the vehicle surface, and
 model atmospheres encompassing the probable extremes for the planet
were also considered .
it was found that while the motion of the flat-based vehicle could be
oscillatory about either the nose-forward or base-forward stable trim
attitudes when aerodynamic heating rates were high, the range of initial
 angles of attack resulting in base-forward orientation was reduced by
more than a factor of 3. when initial pitch rates were increased from
body having only nose-forward stability showed that oscillatory angles
of attack at maximum heating-rate conditions probably would not exceed
about 25degrees although angles of attack when heating rates were 50
percent of maximum could be as high as 40degree . values of these upper
bound angles of attack were essentially independent of initial pitch
rates for the range considered . furthermore, the envelope of maximum
probable angles of attack was increased only slightly when the vehicle
was given a 10-rpm spin rate . the relationship between maximum amplitudes
of oscillation and heating rates through high heating portions of
the trajectories was preserved when model atmospheres believed to encompass
the extreme possibilities for mars were used in the calculations
</TEXT>
</DOC>
