Future Reusable Launch Vehicles Research Articles

X-34 Vehicle Aerodynamic Characteristics

The X-34, being designed and built by the Orbital Sciences Corporation, is an unmanned sub-orbital vehicle designed to be used as a flying test bed to demonstrate key vehicle and operational technologies applicable to future reusable launch vehicles. The X-34 will be air-launched from an L-1011 carrier aircraft at approximately Mach 0.7 and altitudes to 250,000 feet. An unpowered entry will follow, including an autonomous landing. The X-34 will demonstrate the ability to fly through inclement weather, land horizontally at a designated site, and have a rapid turn-around capability. A series of wind tunnel tests on scaled models was conducted in four facilities at the NASA Langley Research Center to determine the aerodynamic characteristics of the X-34. Analysis of these test results revealed that longitudinal trim could be achieved throughout the design trajectory. The maximum elevon deflection required to trim was only half of that available, leaving a margin for gust alleviation and aerodynamic coefficient uncertainty. Directional control can be achieved aerodynamically except at combined high Mach numbers and high angles of attack, where reaction control jets must be used. The X-34 landing speed, between 184 and 206 knots, is within the capabilities of the gear and tires, and the vehicle has sufficient rudder authority to control the required 30-knot crosswind.

RADEM: An air launched, rocket demonstrator for future advanced launch systems

Critical features associated with future reusable launch vehicles include reduction of turn around effort, use of integral liquid hydrogen tanks, advanced structures and thermal protection, and re-usable LOx-hydrogen propulsion with low maintenance overheads. Many doubts associated with such designs could be removed by a sub-orbital demonstrator. An air launched vehicle would fulfil many of the objectives for such demonstration. British Aerospace, NPO Molnija, TsAGI and DB Antonov have made an initial study for ESA for such a demonstrator (RADEM), using earlier studies of operational launch systems with the An-225 /Hotol and MAKS proposals. The paper describes the results of this study, including the selection of two potential vehicle designs, and an approach to sub-system design and vehicle development to minimize the costs. It appears that such a vheicle, capable of flying to Mach 12 or beyond using currently available technology, could have a cost an order of magnitude less than that required for development of an operational vehicle.