In this paper, first, the nonlinear flight trajectory controller for an aircraft is designed using singular perturbation theory. The control system consists of a slow-time scale subsystem and a fast-time scale subsystem. Since a digital computer is used to realize these subsystems, they are reduced to digital control systems. Then, the sampling periods for which the subsystems become stable are computed using linear discrete-time control theory. They are the good criteria for selection of the sampling periods for the flight controller.
The dynamic response of the LE-7 engine LOX pump under cavitating conditions was investigated by perturbation tests using cryogenic fluid in order to obtain data for the analysis of the H-II rocket POGO phenomena. Mass flow gain factor, Mb, and cavitation compliance, Cb, were determined by pressure data using resonant frequency. Mb and Cb show cavity volume change rates due to flow fluctuation and pressure fluctuation, respectively. A large accumulator was installed in the vicinity of the pump inlet in order to eliminate the upstream effects. The test results of Mb agreed well with the values calculated by equations presented in the literature. However, the test results of Cb were quite different from the calculated values.
A series of experiments was conducted for studying scramjet nozzles under Mach 8 flight conditions using a high temperature gas flow produced by combustion of monomethyl-hydrazine (MMH) and nitrogen tetroxide (NTO). The stagnation temperature was designed to be 3170K, and the stagnation pressure to be 1MPa. Scramjet nozzles with expansion ratios of 3 (EN3) and 5 (EN5) were examined. Delivered specific impulse (Isp) was found to be 17.3s (EN3) and 26.1s (EN5). Performances of nozzles were predicted using numerical codes, and energy release loss, kinetic loss and two-dimensional loss were identified. The two-dimensional loss was predicted to be 16.5% in the EN3 nozzle and to decrease to 7.0% in the EN5 nozzle. The kinetic loss due to chemical freezing was found to be about 4%. A friction loss evaluated from thrusts suggested laminar flow in the scramjet nozzle with the MMH/NTO experiments. Measured heat flux on nozzles also supported the laminar boundary layer. Experiments using a cold gas flow with the nozzles were also conducted to compare with the hot flow.