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the total payload weight and the dry weight. The dry weight can then be subtracted off
from the weights and sizing sheet to get the maximum payload.
Once both stages are optimized they are combined into one deck to verify the
results and to optimize the entire system. This input file is set up differently that the two
initial input files. The first stage deck already maximizes the velocity achieved by the
first stage. These initial guesses are then put into the combined deck which is set up to
minimize the weight consumed and therefore maximize the payload weight at the end of
the simulation. This method starts the total deck at a solution very near the ideal solution,
but then allows POST to determine if staging higher and slower is preferable to staging at
the maximum velocity while still satisfying the dynamic pressure constraint of 1 psf. The
optimized solution stages as soon as possible (while still meeting the dynamic pressure
constraint) thereby firing the second stage with the highest relative velocity. The results
of this trajectory are presented as Figure 16 and Figure 17. As these figures show that the
first stage provides only a small amount of the overall altitude and velocity that it
necessary to achieve orbit. The first stage does release the second stage outside the drag
of the atmosphere and that is where the majority of the benefit of the first stage is
achieved.
Mach Mach
30
25
20
15
10
5
0
3rd 3 Stage Ignition
rd Stage Ignition
2nd 2 Stage Ignition
nd Stage Ignition
0 200 400
Time of Flight (secs)
600 800
1800
1600
1400
1200
1000
800
600
400
200
Figure 16: Baseline Trajectory (Altitude and Mach Number).
0
Altitude (kft)
Mach
Altitude
22