Uncertainty Propagation in Integrated Airframe Propulsion System Analysis for Hypersonic Vehicles
Air{breathing hypersonic vehicles are based on airframe{integrated SCRAMjet engine. The elongated forebody which serves as the inlet of the engine is subject to harsh aerothermodynamic loading which causes it to deform. Unpredicted deformations may produce unstart, combustor chocking or structural failure due to increased loads. This study presents a framework allowing one to assess the impact of aerothermoelastic deformations on the engine performance prediction. Aerothermoelastic deformations are calculated for trajectories and angle of attack and transferred to a SCRAMjet engine analysis. Uncertainty associated with deformation prediction is propagated to the engine performance analysis. The importance of modeling the aerodynamic heating and aerothermoelastic deformations at the cowl of the inlet is noted. The cowl deformation is the main contributor to uncertainty and sensitivity of the propulsion system analysis.
Thermostructural concepts for hypervelocity vehicles
In the design of hypervelocity veh~cles (HVV). a key driving parameter is the structural mass fraction of the system. The mass fraction greatly influences the performance and payload capabilities of the vehicle. For example. a reduction of one pound of structural weight would effectively translate into an additional pound of payload, or alternatively, approximately ten fewer pounds of propellant. Through the optimization of thermostructural concepts. a significant increase in overall mission perfbrmance can be reallred. Such an optimiration requires not only good familiarity with the available material optlons and therrnostructural concepts. but also a thorough knowledge of the thermal. inertial, aerodynamic, and control loads on the vehicle as a consequence of hqpervelocity flight conditions. This optimiration process the establishment o l aeroheating and other critical loads, the consideration of material alternatives, and the formulation of thermostructural concep t wa the primary l'i~cus ol' t h ~ \ study. A suborbital vehicle (Figure I ) and the aswciated trajectory (Figure 2 ) a i described in Rckrence I were chosen as stud) baselines. These selections wcrc Idlowed b> a series of interrclated design and anal] tical tazks. during which a number of thcri~~ostructural trade \tudie\ \\el-c conducted. The primary results ol'the stud! include detailed w i g h t estlmates h r the candidate thernio~tructural concepts and the selecSUB-ORBITER SYNERGETIC PLANE CHANGE
Effect of high temperature creep and oxidation on residual room temperature properties for several thin sheet superalloys
Superalloys are being considered for the primary heat shields and supports in the thermal protection system of both hypersonic transport and space shuttle vehicles. Since conservative design philosophy dictates designs based on residual material properties at the end of the service life, material characterization after exposure to the environmental conditions imposed by the flight requirements of these two classes of vehicles is needed on the candidate alloys. An investigation was conducted to provide some of the necessary data, with emphasis placed on oxidation, creep, and residual properties of thin-gage sheet material.