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