An applicability of the electrodynamic heat shield system to super-orbital reentry vehicles was investigated. In the case of the super-orbital reentry flight, due to the strong ionization reactions inside the shock layer, the heat shield system which utilizes the electromagnetic force is expected to work well. In the present study, in order to evaluate the reentry heating reduction by this heat shield system, we performed a CFD analysis including thermochemical non-equilibrium effects and an electromagnetic force. The flight condition used for the present study is that the velocity is 11.6km/s at the altitude of 64km at which the stagnation point heat flux of the MUSES-C reentry capsule is considered to be the maximum value. From our CFD results, we found that the heat flux to the vehicle could be reduced by up to 50%. Additionally, it was also found that the drag coefficient increased with the magnetic field strength, and the maximum value of the drag coefficient was 2.0 with the magnetic field strength of 0.6[T].
The characterization of pseudo-shock wave which is made by interaction between a shock wave and boundary layer is important for various aerospace engineering purposes including the isolator in a scram jet engine. In the present paper, two-dimensional numerical simulation was conducted to reveal physically how the shock-boundary layer interaction produces a pseudo-oblique shock wave for a supersonic channel flow with a slender obstacle located at the center downstream. It is found that a high-speed jet against the supersonic main flow which is issued from the attachment point of a shock wave with the channel wall is the main mechanism for the formation of a series of reverse flow regions in the pseudo-shock wave.
A sidewall-compression-type scramjet engine was tested under M4 flight conditions. Tested engine had an inlet, a constant cross-sectional area isolator, a constant cross-sectional area combustor (designated as combustor-1), a diverging combustor (designated as combustor-2), and an internal nozzle. In the previous study under M4 flight conditions, the maximum thrust increment by the fuel injection within the combustor-1 was 1,380N at an equivalence ratio of 0.31, and further fuel injection resulted in the combustor-inlet interaction (designated as CII). To suppress the CII, we attempted (1) a two-stage fuel injection within the combustor-1 and the combustor-2 and (2) a boundary layer bleed on the top wall, in the present study. The former was to suppress heat release around the first-stage fuel injectors in the combustor-1 at a given total fuel mass flow rate, and the latter was to decrease interaction length by decreasing a boundary layer thickness on the top wall. With the two-stage fuel injection, the maximum thrust increment was 2,230N at an equivalence ratio of 0.63. Next, the boundary layer bleed was carried out, and the maximum thrust increment was 2,300N at an equivalence ratio of 0.66. Thus, both two-stage fuel injection and boundary layer bleed led to 60% higher maximum thrust increment than that obtained in the previous study. Finally, both two-stage fuel injection and boundary layer bleed were applied simultaneously to obtain the largest thrust performance, and the maximum thrust increment was 2,560N at an equivalence ratio of 0.95. As a result, we obtained 80% higher maximum thrust increment than that in the previous study by these methods. The thrust achievement factor, which was defined as the ratio of the maximum thrusts obtained from experiment and theoretical prediction, under this condition was estimated as 70%.
For the development of Pulse Detonation Engine (PDE), effects of injected volume and distribution of purge-air gas on multiple-cycle operations of PDE were investigated. In order to improve the uniformity of a mixture, the experimental PDE had four sets of fuel and oxidizer injector in the opposite side at same axial location. In addition, an injector for the air purging was added on the thrust wall so that the direction of purging flow was discussed. In single cycle experiments, the air purging did not affect the pressure and propagation velocity of detonation wave, hence it is only effective for exhausting the burned gas. The amount of injected purging gas was varied in multiple-cycle experiments to find the optimum amount of purging for stable detonations. The results showed that the amount of air purging increased as the cycle frequency increased and the axial injection rather than the radial was effective to exhaust the burned gas.
An extensible elastica is a rigorous mathematical model of the Bernoulli-Euler beam whose cross-sections remain plane and normal to the axis after deformations. The principle of virtual work for the extensible elastica expressed in terms of the normal strain and rotation of the axis is derived from the principle of virtual work in the three-dimensional elasticity. And it is shown that the derived principle yields the exact equilibrium equations for a beam in the large deformations and rotations. Utilizing linear constitutive equations, we get the theorem of stationary potential energy expressed also in terms of the axial strain and rotation. And, from the Trefftz criterion on the second variation of the potential energy, we get the buckling equations for the extensible elastica, which give the buckling load higher than the Euler load for a cantilever elastica subjected to compressive end load.
This paper presents a method of navigation and control for a space robot (chaser) flying around a troubled satellite (target) on a circular orbit around the earth to approach the target satellite. Orbital dynamics of the chaser is represented by the Hill’s equation. The technique based on LOS angle of approaching the target is proposed. We prove the validity of the technique on the situation that the chaser approach the target satellite after the circular trajectory, which is periodically free motion.
A 2-degrees of freedom PID controller is designed for a maneuvering acceleration control system. This design method is based on the combination of PID and IPD controller. Results show that (1) IP controller is superior to PI controller for the damper loop controller, (2) the selection of PI or IP controller as for the acceleration controller depends on the tradeoffs between the responsibility and the reduction of inverse response.
ETFE film covered solar array was developed for arc mitigation in LEO environment. We used ETFE film because its transmittance is excellent at the wavelengths from 300 to 900nm. In LEO, however, the film will encounter serious space environment, such as AO and UV. Electrical power output may decrease due to degradation of transmittance. To study the effects of AO and UV radiation on ETFE film, we used a combined space effect test facility at JAXA. Although the film color turned white after the test, there was no change of film transmittance. Because of AO-induced erosion, texture structure was formed on the film surface, that trapped incident light and made it pass the film after scattering.