Responsive Access Small Cargo Affordable Launch (RASCAL ...

Table 5: POST Trajectory Constraints.
Max Axial Acceleration 6 g's
Max Dynamic Pressure 2000 psf
Max Angle of Attack 20 degrees
Max Dynamic Pressure at Release 1 psf
Final Orbit Apogee 270 nmi
Final Orbit Perigee 270 nmi
Final Orbit Inclination 98 degrees
Due to the complexity of the RASCAL trajectory the airbreathing, and rocket portions of
the trajectories were calculated separately to get approximate “guesses” for the combined
trajectories. These outputs with their appropriate initial conditions are then combined
into one POST input file which is then optimized to minimize the propellant consumed
by the stages.
The first stage input deck was set up to use the MIPCC engines as defined in the
propulsion section. This input file starts with an initial weight, accelerates the aircraft
until an appropriate time when the aircraft begins the zoom maneuver. This zoom
maneuver involves increasing the altitude while still firing the MIPCC engines. Once the
aircraft reaches the MIPCC limits of 88,000 ft and Mach 4 the engines shut down. The
aircraft then continues to gain altitude by trading kinetic energy for potential energy. The
first stage then coasts until the flight path angle drops to 20 degrees (other flight path
angles were used, but 20 degrees results in the smallest vehicle). The first stage input
deck actually tries to maximize the velocity of release to give the second stage as much
energy as possible. The dynamic pressure constraint of release combined with this
optimization scheme also results in an altitude in excess of 200,000 ft at release.
Once the first stage is optimized the second stage begins at the altitude, velocity,
azimuth, latitude, longitude, and flight path angle of the end of the first stage. The
second stage ignites after a coast of 5 seconds after release from the aircraft to get a
significant distance between the stages. The second stage hybrid then ignites until the
ideal ∆V provided by the second stage reaches 11,000 fps. This ∆V number was set in
the RASCAL design, but it was traded and found to be close to the optimal point. After
the second stage falls away the third stage ignites after a five second delay. The third
stage then fires until the proper orbit is reached. The entire upper stage input file is
designed to optimize the weight consumed. The final weight at the end of the run is then
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