Thermal Protection Using Endothermic Fuel Conversion

Abstract

The issue of thermal protection is one of the principal ones when developing hypersonic flight vehicles (HFV). Thermal protection characteristics determine to a considerable degree the appearance and performance of the vehicle as a whole. For the first time the problem of thermal protection has been particularly emphasized and given thought to in the rocket-and-space technology with emergence of the necessity to ensure highly reliable protection of the forebodies of ballistic missiles and space vehicles from aerodynamic heating during their high speed atmosphere reentry, as well as the necessity to protect combustion chambers and engine nozzles. The most widely used in the missile engineering became ablative coating protection (passive protection). This type of protection is largely used in the event of intensive though short-lived heating but with the repeated HFV flights there seems no escaping the necessity of finding some other solutions. For the prolonged atmosphere flights, the transition to the so called active thermal protection with the forced feed of the cooling agent to the protected surface becomes a must. It is not a rare occasion when the fuel itself is being used for thermal protection of the heat-stressed structural parts. In various HFV designs [1-3] they suggest usage as a fuel of liquid hydrogen or hydrocarbon fuels that undergo different transformations with heat absorption – hence their name “endothermic fuels”. Thanks to enhanced cooling resource and energy potentialities of decomposition products of the endothermic fuels they prove competitive with liquid hydrogen. Creation of the active thermal protection system on the basis of chemical endothermic transformation of the initial hydrocarbon fuel at the expense of utilization of the heat losses associated with airframe aerodynamic heating and propulsion operation is, as of today, a new challenge that faces scientists and designers working in the sphere of aerospace technology.