In March 2002, the Defense Advanced Research Projects Agency (DARPA) began the Rapid Access Small Cargo Affordable Launch (RASCAL) program. DARPA established the goal of creating a launch system capable of responsively and routinely placing small payloads into orbit at significantly reduced cost. In that same month, DARPA selected six teams to conduct RASCAL system studies. This first phase was nine months long and ended with a single contract award to The Space Launch Corporation for Phase II.
Phase II was an 18-month design phase that advanced the design of the RASCAL system and allow for risk reduction testing. Although Phase II culminated in a very successful preliminary Design Review (PDR) DARPA decided not to proceed to Phase III.
The RASCAL system was designed to be a highly responsive, economical launch system capable of placing a 150 kg payload into low-Earth-orbit for $10,000 / kg. The RASCAL system consisted of a reusable aircraft as the launch platform and a two-stage expendable rocket vehicle (ERV) for accelerating a payload to orbital velocity. A significant feature of the RASCAL aircraft was the ability for exo-atmospheric flight (flight outside of the Earth's atmosphere). As a result of this ability, the satellite payload and rocket vehicle could be released from the RASCAL aircraft at an altitude where aerodynamic forces are negligible.
In order to fly outside the atmosphere, the RASCAL aircraft planned to utilize standard military jet engines with a 'bolt-on' modification known as Mass Injection Pre-Compressor Cooling, or MIPCC. MIPCC would allow the RASCAL aircraft to operate at higher velocities and altitudes (greater than 200,000 ft) than an aircraft with just standard jet engines. As MIPCC was considered an enabling technology for RASCAL, the RASCAL aircraft was referred to as the MIPCC Powered Vehicle, or MPV.
To reach altitudes in excess of 200,000 ft, the RASCAL MPV would perform a 'zoom maneuver'. In this maneuver, the MPV would accelerate to a high velocity while still in the atmosphere (less than 50,000 ft) and then begin a steep climb. Using MIPCC, the MPV would continue to accelerate while climbing until the engines were shut down at around 100,000 ft. Even with the engines shut down the MPV would continue to climb due to momentum and eventually would coast to an altitude of 200,000 ft.
Once the MPV reaches an altitude of 200,000, where atmospheric forces are negligible, the ERV is released from within the MPV. After the ERV is released, the first stage of the ERV ignites and carries the payload to orbit.
