Study On Air-breathing Engine Performance And Boost Trajectory Of Laser Propulsion Vehicle

In this paper, the air-breathing engine performance and boost trajectory of laser propulsion vehicle were studied. The laser propulsion vehicle was famous Myrabo Lightcraft. The flight characteristics of engine varying with altitude and flight velocity in air-breathing mode, the flight stability and boost trajectory were analyzed by means of theoretical modeling and numeral simulation.At first, inlet flow model for Myrabo Lightcraft air-breathing engine was presented by air dynamics. The ratio of inlet gap flow velocity to free stream velocity was set equal to 5/3 in subsonic flight regime, and the characteristics of inlet flow in supersonic regime was modeled by axis-symmetric cone's flow theory based on its unique configuration. For the impulse generation and transfer model, CJ detonation theory and Sedov's self-similar solutions were used. A complete analytical performance projection for the engine of Myrabo Lightcraft in air-breathing mode was thus presented. The numerical results showed that Coupling Coefficient reduces gradually by Mach number increasing for a constant altitude.Then, based on flight stability of Myrabo Lightcraft, this paper built the impulsion model of laser propulsion and developed Myrabo lightcraft's three-degrees of freedom movement model. This paper framed a new algorithm to solve the conflict between the precision and efficiency. By numerically calculating and analyzing the laser's repetitive impulse frequency, power and slope of lift curve changing procedure, effect factors of Myrabo lightcraft's stabilization in flight are studied. As a result, characteristic saw-tooth velocity is generated in vertical direction; there even has a lower frequency limit of laser repetitive impulse. In lateral pass, high frequency of laser pulse can generate rapider revert velocity and smoother curve than low frequency, and with the increase of slope of lift curve, Lightcraft can attain stabilization in short time.At last, this paper built movement model in boost track from ground to earth orbit, and analyzed the choice of engine model conversion point in both vertical and inclined launch mode. For shortest flying time, conversion point should generally occur in the flight point of 25 second, 25 kilometers, and 5 Mach; For heaviest mass of payload it should occur in the other flight point of 40 second, 43 kilometers, and 6 Mach.