The flow mechanism on transient unstart and restart phenomena due to compound choking and/or disturbances in the combustion chamber of a scramjet engine were investigated experimentally and numerically. Experiment is conducted by using a Mach 3 blowdown tunnel. Engine unstart was initiated by blowing jet from the top surface of engine model. Shock movements in transient conditions were captured by 5 pressure transducers capable of 20kHz sampling and by optical measurements. The results were compared with numerical results which were performed by a quasi-three dimensional MacCormack differential scheme. Both results coincide qualitatively, and it is shown that the mechanisms of the transition from start to unstart in sheared inflow with boundary layer flow is different from that in uniform inflow. Namely, whole flow is dammed up by disturbance on unstart of uniform inflow, on the other hand in sheared inflow case shock waves arise first in boundary layer flow and pressurized boundary layer at the back of the shock pushes out the main flow. It is also found that the transition unstart is accompanied by movement of stronger shock waves than transient restart and the behavior of the shock waves is quite different between the transient unstart and restart.
This paper discusses a trajectory synthesis for low thrust Lunar orbiter travelling between a low Earth circular orbit and a low Lunar one. The low thrust trajectory discussed here is made up of three phases which are the Earth spiral ascending phase, the Lunar capture phase and the Lunar spiral descending phase, each of which plays proper roles in the transfers to the Lunar orbit. The Lunar capture phase is the most important one in which the orbiter is guided from a parking orbit of around 150, 000km radius to an elliptical orbit with the eccentricity of about 0.3 by thrusting only in the one side of the orbital arc, attracted by the Lunar gravitational force and put into the Lunar sphere of influence on the conditions to achieve near circular but unstable Lunar orbit, and finally transferred to a stable circular orbit by using the low thrust with acceleration levels of the order of 10-5G. In this paper, the conditions to establish the Lunar capturing are considered and expressed as numerical relations of the entry radius and velocity into the Lunar sphere of influence. Such relations are derived from trajectory simulations. Also typical trajectories to the Moon are shown as samples to evaluate the time of flights, consumed propellant weights and the orbital control capabilities.