LOX System Prestart Conditioning on X-34

The X-34 is a reusable launch vehicle that will be carried underneath an airplane to altitude of 35000 feet where it will be launched. It utilizes a single Fastrac 60K rocket engine for propulsion. This engine burns RP-1 and Lox as propellants and has a single shaft Lox and RP-1 turbopump. With these features there are three important requirements that must be met during the prestart thermal conditioning of this engine and feed system. First, the Lox temperature prior to starting the engine must be cold enough to be in the predefined start box at that pressure. Second, the RP-1 in the single shaft turbopump in close proximity to the lox must not freeze significantly where it effects turbopump or engine operation. Third, the chill phase of the prestart countdown has been allocated 700lb of Lox which if exceeded starts to effect mission performance. Extensive testing and analysis has been performed to evaluate the chill characteristics of the Fastrac Engine as well as test facilities and X-34 Lox feed and bleed systems.