Computational simulations are expected to provide for initial design choices.
A capability for real-time computational simulation of aeroheating has been developed in support of the Hyper-X program, which is directed toward demonstrating the feasibility of operating an air-breathing ramjet/scramjet engine at mach 5, mach 7, and mach 10. The simulation software will serve as a valuable design tool for initial trajectory studies in which aerodynamic heating is expected to exert a major influence in the design of the Hyper-X airplane; this tool will aid in the selection of materials, sizing of structural skin thicknesses, and selection of components of a thermal-protection system (TPS) for structures that must be insulated against aeroheating.
The Hyper-X airplane will include an inlet/combustor/nozzle assembly attached to an airframe. The forebody of the inlet will consist of a leading edge and a tungsten ballast. Movable wings and vertical tail rudders will give the autonomous airplane controllability. Mounted inside the airframe will be all the active systems needed to fly and to demonstrate the ramjet/scramjet engine. The fuel-burning and flight hardware will be instrumented to collect and telemeter flight data.
Because of the short duration of flight, critical areas on the airframe TPS will be limited to the leading edges on the nose, cowl, and side walls of the inlet and the horizontal wings and vertical tails. In addition to other aeroheating effects, gap heating is expected to occur at horizontal wing roots, and at vertical rudder roots by amounts that will vary with movement of the rudders.
The present capability for real-time computational simulation of aeroheating makes it possible to predict temperature as a function of time at critical heating locations on the Hyper-X airplane. Simulations of this type are used extensively to select acceptable flight trajectories by eliminating ones for which structural-design temperature limits would be exceeded (see figure). Other real-time simulations can be performed, using software modules that enable evaluation of other aspects of operation and design, including aerodynamics, reaction control system, flight guidance, and airplane structures. At speeds in excess of mach 2, aeroheating is considered important enough to affect design parameters, so that it becomes necessary to include a software module for simulation of aeroheating.
Thus far, a mathematical submodel of a nose with a solid carbon/carbon leading edge has been incorporated into the mathematical model used in the simulation of aeroheating. This submodel model includes 14 temperature nodes. Other submodels of aeroheating of the tail rudder and the leading edges of the horizontal and vertical tails were undergoing development at the time of reporting the information for this article.
This work was done by Les Gong of Dryden Flight Research Center. For further information, contact the Dryden Commercial Technology Office at (661) 276-3143. DRC-98-76