A design methodology of both space structure beam and construction robot is described from the point of total cost minimum. The study is experimentally investigated. At first, two types of beams are prepared. One is a deployable truss structure. This truss is stowed in a rocket fairing folded, and is then deployed in orbit. The other is a putting-pipe-in-socket type beam in which members are separated from the beam, and then these are put in joints in orbit. In this paper secondly, ground experiment on beam construction with an industrial manipulator system are reported. The experiment proves that the dual arm system can conduct both types of beam. Furthermore, it obtains useful system requirements for structure beams. In conclusion, a design of both space structure beam and construction robot is proposed.
A transportation system with low pressure drop using spiral flow has been developed. With this system, ceramic balls were transported at the rate of 190kg/h in a 15.0m long pipeline that was composed of a 5.0m vertical section and a 10.0m horizontal section with 34.0mm diameter. The pressure drop was dramatically decreased by about 40% from 6.91×102 [Pa/m] to 3.88×102 [Pa/m] as compared with the typical method. The particles movement was observed at the vertical section to discuss the low pressure loss. The particles moved as rotating without touching the inner pipe wall. The device to produce spiral flow is a nozzle with an annular slit, attaching to the conical cylinder. Pressurized fluid is forced through the side of the device into the buffer area and then through the angled annular slit into the conical cylinder. Due to the Coanda effect of this annular jet attaching to the nozzle wall, the flow downstream develops a spiral structure with steep axial velocity distribution and high stability that is much more ordered than typical turbulent flow. To accomplish the high performance transportation, particles should not touch the pipe inner wall. The requirements can be responded by the steep axial velocity profile and swirling motion of the spiral flow with large free vortex region.
A Stalker tube has been developed at the Nagoya University for the study of hypersonic and high enthalpy flows over a reentry capsule. Measured free-stream Mach number and total pressure are 12 and 0.1MPa, respectively. The flow duration is 150μs and the estimated flow enthalpy is 10MJ/kg. Paraffin models were exposed to the high enthalpy flows in this facility. An edge line of an ablating region surrounding a stagnation point is clearly recognizable on the model surface. The line would be identical to the isothermal one of paraffin's ablation temperature. Noncircular shape of the edge line implies the occurrence of local transitions of the flow from laminar to turbulent over the ablating surface. A picture taken by a high speed camera shows the shape of radiating region around the model.
Beam characteristics of a microwave discharge ion thruster were measured by several kinds of beam analyzers for the purpose of comparing its efficiencies with conventional DC discharge ion thrusters. Propellant utilization, ion cost, doubly charged ion fraction, and beam divergence were evaluated with throttling parameters, resulting in thrust efficiency of 64% when the microwave ion thruster was operated at the condition of mass flow rate of 1.6sccm, microwave power of 45W and acceleration voltage of 1.5kV.
Investigations on the spatial flowfield of hypersonic shock-wave/boundary-layer interaction have been performed by utilizing the electric discharge method. The model geometry used in this experiment is composed of a flat plate and a fin. In general, visualizations of such spatial flowfield were very difficult or impossible. However, in these investigations utilizing the electric discharge method which is the method for visualizing three dimensional hypersonic flowfield phenomena, the spatial flowfield phenomena could be visualized qualitatively. The experiment is carried out using a hypersonic gun tunnel whose main characteristics are that the Mach number is 10 and the duration is 10ms.
An emission current imbalance phenomena involved in the clusterization problem were experimentally investigated using a microwave neutralizer. The fundamental properties of current voltage characteristics was measured. The current imbalanced operation was experimentally demonstrated dependent on a current inflow from other electron source and the imbalanced modes of the microwave neutralizer were categorized. An advisable method to suppress the imbalance was proposed and performed experimentally.
For efficient use of solar electric propulsion, it is required to adjust operational parameters to the electrical power supply available on a spacecraft. For a microwave ion engine system, which is employed for asteroid sample return mission MUSES-C, such a throttling is conducted by varying the electrical power used for plasma generation via electron cyclotron resonance as well as by modifying the mass flow rate of xenon propellant. However, in some throttling conditions, microwave power deposition for plasma generation is prohibited, deteriorating propellant utilization efficiency. From probe measurement of a microwave ion source, the propellant utilization efficiency was strongly related to the plasma characteristics inside the discharge chamber. Very diffused plasma distributions were found in the case of low utilization efficiency, making contrast to localized plasma distributions for efficient propellant utilization.