As stated above, the ion properties affect the interference of the HVSA more significantly than those of the electron. In this work the interference of the HVSA with the ionospheric plasma is studied about the ion collection, assuming almost all the area of the HVSA to have negative potential relative to the plasma. The assumptions are summarized as follows: 1. Ionospheric environment is regarded as collisionless plasma with no magnetic field. 2. Electrons are in thermal equilibrium and ions have zero temperature. 3. HVSA acts as a simple plate that has a conductive surface on one side and has an insulated on the other. The last assumption is explained as follows. In general the solar cell is mostly covered with glass, and the solar array potential appears only at the interconnects, which is covered with the plasma sheath. Since the sheath thickness is larger than the interval between the interconnects, the solar array is entirely covered with the sheath and electrically behaves as a single conductive plate. The angles of attack a based on the ion flow is shown in Fig. 2. The drag is defined as force along the ion flow. The conditions at a= —90, 0 and +90 are called ‘ram', ‘airplane' and ‘wake' modes, respectively, with regard to the relation between the conductive surface and the plasma flow. The position on the HVSA is indicated by the spanwise and chordwise locations as a percentage of the respective array dimensions. The Poisson's and the ion kinetic equations induce the Child-Langmuir equation on the assumption of one-dimensionality and neglecting the electron effect. Respective normalizations of the potential and the variable in space by VA and LA derive one of the scaling parameters, that is, CL, The 0 represents the effect of the electron term which is neglected in the Child-Langmuir equation. The CL and 0 are scaling parameters because some HVSAs having the same CL and 0 are governed by the same formula. The CL parameter has significance in the interaction of the HVSA because Inequality (3) assures the 0 is small enough to neglect the electron term in the Poisson's equation. The CL can be converted into and also can be considered normalized permeance which is used in the theory on the vacuum tube. The experimental simulation using small-size models [7] was conducted in the laboratory based on the similarity law, which requires more dense plasma than that in LEO. The scale experiment has the following advantages to respective to the real size experiment on the ground.
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