The simulation voltage on the conductor was chosen so that the parameter d> for the simulation was the same as found in low earth orbit. In low earth orbit a solar array voltage of 200 V in an flow of 5 eV oxygen gives <I> = 40. In order to compare our results with the work of Kuninaka & Kuriki the choice £=48 was made. This corresponds to a array of about 1.6 m in length. The array was modelled as composed of five segments where the potential on segment j is obtained from equation (2). The force on an array of potential drop △ 0 was obtained as the result of the sum of five simulations with simulation voltage (j=l, 2... 5). For each simulation we had Aegmen/( ^orbita/^) = 4.09. Therefore to obtain the length of the array such that £=48 we calculated the force on the dielectric of length (Forbltal/(yp,) tai/^p,)) analytically (ns + 5) and included it in the total force. This approach is justified by the noninteracting limit since any dielectric outside the sheath of a conductor will be bombarded by ions which are only accelerated by the weak potential on the dielectric. This gives the ratio of conductor area to total array area as ac = 0.044. We chose the accommodation coefficients in the same way as in Kuninaka & Kuriki [2] i.e. crn=0.7 cos 0, and crt = 0.6 where 0,- is the incident angle of the ions (except for Fig. 10). Numerical Result Since we divide the 1.6 m array into five segments, each solar cell corresponds to 32 cm by 32 cm with 1.4 cm interconnector. In order to check the validity of the noninteracting assumption in actual scale of solar array, we performed one PIC simulation for a 8 cm X 8 cm solar cell with a 3.5 mm interconnector in addition to the large scale PIC simulations mentioned above. In Fig. 3 we show the potential contours in steady state for a conductor biased to —250 V with a dielectric on either side with an ion flow at P=~90. The e^=s»t,P’Jrbita] contour is seen to reach almost half way out over the dielectric. This indicates that for this voltage, dielectric length and angle of attack the noninteracting limit is the appropriate limit in which to evaluate the force on the array. Conversely, if the lowest voltage on the array is — 250 V then the interacting limit where all the sheaths are overlapping will clearly overestimate the force on the array. In Fig. 4 we show the ion velocity vectors at steady-state for the same conditions as in Fig. 3. This figure shows that the potential contour at which the streaming ions are affected is the j»z, P^rbital contour. The parts of the dielectric which fall outside the projected area of this contour are struck only by ions which stream directly to them and undergo almost no acceleration. In Fig. 5, we show the normalized components of the total force on each biased segment as a function of voltage. The reflection force on the dielectric is small and independent of the voltage on the conductor. This is because the dielectric takes a voltage very close to ground regardless of the conductor voltage. The ram-scattering force is independent of voltage from momentum conservation. The total force is mainly composed of the reflection force on the conductor and the ram-scattering force. The reflection on the conductor is a function of voltage since it is composed of neutralized ions which are emitted from the conductor after they have been accelerated by the potential. For voltages below — 200 V the ram-scattering force dominates while for voltages above this the reflection force dominates. This result was also observed in the work of Kuninaka & Kuriki.
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