A future multi-beam communication satellite requires to develop a large deployable antenna which has a total length of about 9m including two large main-reflectors and a tower. Thermal balance test for a such large sized antenna system is limited by volume of a space simulation chamber. And, the deployment mechanisms can not support the reflectors without damage under gravitational condition on the ground. In order to overcome the above problems, two step thermal design verification method is devised. First, the antenna component thermal analytical model was verified by the each component test at critical test cases. Next, the antenna system thermal analytical model was verified by the antenna system test at typical test cases. The antenna system test is performed by using supporting structures which support the hardpoints of each main-reflector in order to minimize the gravity force to the antenna deployment mechanisms. This paper describes the method of the thermal balance test and the result of thermal design verification for the whole antenna system.
This paper presents cooperative dynamic control methods for a dual armed free-flying robot for proximity maneuvering. A two-dimensional space robot model equipped with thrusters and dual three-degree-of-freedom arms is considered. Firstly, the equation of motion is derived by Kane's method. Secondly, we adapt it to point-to-point resolved motion acceleration control. We consider two cases: control with thrusters and without thrusters, and compare them. Thirdly, it is inappropriate to use thrusters for controlling the attitude because of the amount of propellant required. Thus, if a single arm is enough for a task, the other are is available to control the attitude. Several methods are discussed. Finally, when the robot avoids an obstacle or chases a moving target, point-to-point control is insufficient. We extend the control law to follow an arbitrary desired trajectory. Aligning with a target axis and chasing a moving target are demonstrated.
In this paper optimal returns of an AOTV (Aeroassisted Orbital Transfer Vehicle) from the high earth orbit within the limit of the aerodynamic heating are studied numerically, which minimize the characteristic velocities for decelerations and plane changes at the atmospheric flights and the impulses in space. As a result from computations optimal control methods are remarkably changed by the heat limit, but with them in these cases we can still keep the characteristic velocities small.
Numerical analyses have been conducted on radiative heat transfer from hypersonic, non-equilibrium air shock layers over a reentry body. The band method developed here enables one to conduct wavelength-dependent, three-dimensional radiative transfer calculation in which self-absorption effect is taken into account. The radiative heat transfer calculated here was found comparable with convective one. Atomic species and N2+ were found to be dominant radiators. Electrons play an essential role in determining radiative emission power. Due to a high electron temperature, a peak in emission power exists immediately behind the shock. At a high Mach number, since electron density is at a high level, another peak appears near the wall, thereby enhancing the radiative heat transfer at the stagnation point and enlarging the half-width of the radiative heat flux to the wall.
Optimal flight path of hand-launched papercraft is discussed as an initial value problem to maximize endurance. Typical paths are shown for two and three dimensional flight. It shows that the size of horizontal wing is of primary importance to attain height as well as endurance.
An infinite series solution presented for a thin rectangular fin is developed for the steady temperature distribution in a two-dimensional rectangular sandwich panel fin heated within a rectangular footprint region, and losing energy to environment by linearized radiation. The solutions approximate a spacecraft application where a heat dissipating electronic component is mounted to a heat-sink plate or a equipment panel. The comparison of numerical results obtained from the proposed method and the lumped nodal method shows that the formulations will be useful in evaluating heat-sink designs where geometry, heat loads, thermal properties, and environmental parameters change frequently.
The liquid droplet radiator (LDR) uses many streams of droplets to radiate heat to space. A droplet emitter of the liquid droplet radiator produces directed droplets streams from its orifices toward a droplet collector. During the flight, droplets loses heat by radiation. In order to constitute an effectivelly radiative droplet sheat and minimize the working fluid loss at the collector, uniformly formed and spaced droplet streams with a good aiming accuracy are required to be formed. To investigate the formation of such a uniform droplet stream, and develop the droplet emitter, a laboratory model with a single orifice was made. Diffusion pump oil (DC-704) was used as a working fluid, and squirted out from the orifice by applying pressure. In addition, pressure perturbation was caused by the piezoelectric ceramic to produce uniform droplets from the liquid jet coming out from the orifice. The formation characteristics of the liquid droplet stream was tested in a vacuum, and it was confirmed the liquid droplet stream thus produced reached the required level for the liquid droplet radiator.