An Evaluation of Two Alternate Propulsion Concepts for Bantam-Argus: Deeply-Cooled Turbojet+Rocket and Pulsed Detonation Rocket+Ramjet
The Bantam-Argus reusable launch vehicle concept is a smaller version of the original Argus single-stage-to-orbit launch vehicle design. Like the original Argus, Bantam-Argus uses a Maglifter launch assist system to provide an initial horizontal launch velocity. Bantam-Argus is designed to deliver 300 lb. payloads to low earth orbit and, like the full sized Argus, the baseline Bantam-Argus concept utilizes two liquid oxygen/liquid hydrogen supercharged ejector ramjets as prime motive power. This paper presents the results of an investigation of two alternate propulsion systems for the BantamArgus launch vehicle. First, a thermally integrated combined-cycle system consisting of two deeplycooled turbojets and two liquid rocket engines was evaluated. Second, a combination propulsion system utilizing two pulsed detonation rocket engines and two standalone ramjets was evaluated. The results show that both alternate propulsion systems have the potential to reduce both the dry weight and gross weight of the baseline Bantam-Argus concept (when resizing the vehicle while holding mission payload constant). The pulsed detonation rocket engine option is particularly attractive. However, these results must be treated with caution given the relative immaturity of the supporting propulsion data available for both alternatives. Trade studies on key performance parameters were p rformed to bound the potential gains to be expected from either alternative.
Prospects for Detonations in Propulsion
The application of detonations for propulsion has received widespread attention recently. Some of the attractions for utilizing detonations include the higher theoretical thermodynamic efficiency compared to deflagration-based systems, high power-to-weight ratio and few moving parts. Despite these attractive features, a number of fundamental physics and engineering challenges must be overcome before such propulsion systems can be practical. Specifically, focusing on the aerothermodynamic aspects of detonation-based propulsion, some of these issues involve the unsteadiness of the flow, mixing of fuel and oxidizer, detonation initiation and propagation, etc. These issues will be discussed within the context of different detonation-based engine architectures. The pathway from fundamental research to practical systems will be illustrated.
STATUS OF THE ADVANCED REUSABLE TRANSPORTATION TECHNOLOGIES PROJECT
The National Aeronautics and Space Administration (NASA) has established the Advanced Space Transportation Program (ASTP) to focus efforts on technologies that have the potential to greatly reduce costs of payload to orbit. The Advanced Reusable Transportation Technologies (ARTT) project at NASA's Marshall Space Flight Center (MSFC) has been established to investigate technologies associated with combined cycle air breathing propulsion through ground testing of critical components and the development of preliminary concepts for a full-size operational rocketbased combined cycle (RBCC) launch vehicle. Five contractors have been selected and are now well into their respective test and analysis efforts. Initial concept study efforts have been completed on a full scale operational RBCC-powered vehicle. Results from these studies indicate that a single-stage-to-orbit (SSTO) RBCC powered vehicle can be developed that will allow 25,000 pounds of payload to be delivered in a Space Station supply mission scenario. These studies indicate that the contractors preference for this vehicle is either a horizontal takeoff/horizontal landing or a vertical takeoff/horizontal landing machine that has a gross takeoff weight of approximately 1.2 million pounds and a dry weight slightly above 210,000 pounds. The vehicle is approximately 200 feet long. The average structural mass fraction of these vehicles with the engines installed is slightly below 0.8. The studies also indicated that the point at which the engine inlets will be closed and the rockets reignited for orbital insertion is favored to be in the range of Mach 8 to Mach 10.