1998 Undergraduate Team Engine Design Competition Sponsored by the AIAA/Air-Breathing Propulsion

1998 Undergraduate Team Engine Design Competition sponsored by the AIAA/Air-Breathing Propulsion Technical Committee

Title: Design of an RBCC Propulsion System for a Reusable, Single-State-to-Orbit Launch Vehicle

Abstract

Construction and operation of the International Space Station (ISS) will require frequent launches from various points on earth. To keep operational costs to a minimum, a small fleet of reusable, single-stage-to-orbit (SSTO) launch vehicles is required. The use of chemical rocket propulsion would require advances in light-weight materials and structures in order to manufacture such a launch vehicle at a practical gross lift-off weight (GLOW). It is proposed that the high performance potential of air-breathing propulsion be exploited in a rocket-based combined-cycle (RBCC) engine to enable reusable, SSTO launch vehicles at a practical GLOW.

The fraction of a vehicle’s GLOW that must be propellant (propellant fraction required or PFR) to achieve SSTO is related to the specific impulse (Isp) of the propulsion system. The PFR of an SSTO vehicle propelled by chemical rockets is about 89%, which leaves only 11% for the propellant tanks, engines, miscellaneous structures, subsystems, and payload. Further, these structural systems are to be reusable, and must be more robust than their expendable counterparts.

In a rocket-based combined-cycle (RBCC) engine, the chemical rocket and ramjet cycles are integrated into a common flowpath. Optimization of the rocket’s high thrust-to-weight ratio (T/W) with the ramjet’s high Isp along the flight trajectory provides the potential for a reduction in the PFR to achieve SSTO. The benefits of this reduction in PFR are offset however, by the increased weight associated with the use of air-breathing propulsion. The vehicle designer’s task is therefore one of balancing overall propulsive efficiency and weight to satisfy minimum GLOW and reusability requirements for a given payload.

The purpose of this RFP is for the conceptual design of an RBCC propulsion system that will minimize the GLOW of a vertical take-off, horizontal landing (VTHL) reusable launch system designed to carry 10,000 pounds to the International Space Station. Parametric propulsion component performance and structural weight information will be provided. Aerodynamic characteristics and scaleable weight statements for candidate vehicle designs will be provided.