Formation flight of spacecraft in eccentric orbits is considered in this paper. Symmetry of the eccentric orbits is assumed in a relative formation orbit, and under this assumption, relations of initial conditions in formation flight are derived. Some characteristic orbits are obtained from these relations, such as an orbit where a deputy spacecraft rotates around a chief spacecraft with relatively small variation in the distance between the two spacecraft, or an orbit where the deputy spacecraft moves on a local horizontal plane on which the chief spacecraft exists. Formation flight by plural spacecraft is possible by combining these relative orbits.
Microwave emissions due to hypervelocity impacts have been detected by heterodyne receivers in the ground experiments using an accelerator. We aim to establish the detection system of space debris impacts on a space structure via microwave. The emitted powers at several frequencies due to the impact velocity of 10km/sec are estimated from the characteristics at the experimental impact velocity. Considering the emitted power, the receiving antennas and the microwave frequencies, the maximum distances for detecting the microwave emission are 85m at 2GHz-band and 24m at 22GHz-band. The type and location of receiving antennas which can detect the impact on all habitation and experiment modules on the International Space Station are discussed. It is concluded that the impact can be sufficiently detected via a low gain antenna at 2GHz band.
Numerical simulations were conducted to predict the ejector pumping performance of a rocket-ramjet combined-cycle engine under a take-off condition. The numerical simulations revealed that the suction airflow was chocked at the exit of the engine throat when the ejector rocket was driven by cold N2 gas at the chamber pressure of 3MPa. When the ejector-driving gas was changed from cold N2 gas to hot combustion gas, the suction performance decreased remarkably. Mach contours in the engine revealed that the rocket plume constricted when the driving gas was the hot combustion gas. The change of the area of the stream tube area seemed to induce the pressure rise in the duct and decreasing in the pumping performance.
Features of a supersonic inductively coupled plasma small wind tunnel that can obtain high electric conductivity despite low input RF power are numerically examined by means of an axisymmetric r–z two-dimensional numerical analysis. The working gas is Argon. The stagnation pressure and temperature are 10kPa and 600K, respectively. The RF power is less than or equal to 1kW. Numerical results demonstrate that when the RF induction coil is set up in the supersonic region of nozzle (case-1), the plasma produced by RF Joule heating has much stronger thermochemical nonequilibrium state compared to the case that the RF induction coil is set up in the subsonic region of nozzle (case-2). As a result, the electrical conductivity in the test chamber in the case-1 is about two times higher compared to that in the case-2.
Miniature space GPS receivers have been developed by means of automobile-navigation technology. We expanded the frequency sweep range in order to cover large Doppler shift on orbit. We tested the performance in low earth orbits by means of a GPS simulator. The range error caused by the receiver is measured to be 0.9m in RMS. The receiver is tolerant for 20krad radiation. Receiver was on-boarded on INDEX (“REIMEI”) satellite, which was launched in 2005. Cold start positioning is confirmed repeatedly to finish within 30min on orbit. The short term random error of GPS positioning is as large as 1.5m for PDDP = 2.7 on orbit. The range error due to the receiver is 0.5m RMS from the flight data. These results on orbit are consistent with the simulation results by means of a GPS simulator. This miniature space GPS receiver is promising as an inexpensive space GPS receiver in commercial market.
An experimental and analytical investigation for a newly proposed electromagnetic-driven fan concept is described. Environmental friendliness in aviation is a key feature in the development of future air-breathing engines, and a desirable technology to be introduced is an electromagnetic motion fan system, because it will tremendously reduce the total operating emission, reduce weight, increase maintainability and increase energy efficiency. The proposed fan concept has a potential to satisfy the requirements and also possess many other applications such as vector thrust operation. The present paper shows the result of the testing of a concept verification model and the result revealed the importance of the controlling parameters to produce efficient power transmission. The accompanying analytical result further explains the motion mechanisms and gives suggestions for the novel design of the fan system.
We analyze theoretically how the radius of geosynchronous orbits would vary owing to the perturbations due to the sun/moon gravity, solar radiation pressure, and the oblate earth. The analysis is simple, as it uses a diagrammatic method to solve near-circular orbital motions. Results are obtained in seven terms of corrections to the radius of non-perturbed ideal orbits. Each correction term is derived, with clear physical meaning, from each component of the perturbing forces.