Small Experimental Electrodynamic Space Tether System. Electrical model

1Pirozhenko, AV, 2Mischenko, AV
1Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, Dnipro, Ukraine
2Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, Dnipropetrovsk, Ukraine
Space Sci.&Technol. 2018, 24 ;(3):03-09
https://doi.org/10.15407/knit2018.03.003
Section: Space Energy, Power and Propulsion
Publication Language: Russian
Abstract: 
For some decades, the scientists preserve an interest in the experimental research with electrodynamic space tethered system (EDSTS) in low Earth orbits (LEO). This interest is caused by the prospects of the EDSTS’s use for transport operations and for space debris deorbit. The cost reduction of such experiments is associated with the small tether system’s applying.
         The aim of this paper is to describe the electric model of passive EDSTS, in which additional contactors with plasma are not provided. The model is based on the probe theory and the equality of the electron and ion currents collected by the system in the ionospheric plasma. Model makes possible to calculate the EDSTS parameters ensuring the existence of the anodic and cathodic of the system parts for the selected orbit, as well as predicting the voltages and currents in the parts of the system.
          We examine the EDSTS of two bodies connected by a conductive cable, where either a cylindrical tether or a tape is considered as a cable. The flow of charges on the tether was calculated for the orbital-motion-limited regime of cylindrical Langmuir probes. The calculation of the current values on the end bodies of EDSTS is based on the models for large spherical probes. The collection of the ion current by a negatively charged body is one of the most difficult procedures to model processes and is the least experimentally verified. To calculate it, we used the Alpert-Lem model for a current limited by layer. We note that, since the coefficients of this theory for the electron current were found empirically, they can be different for the ion current and need experimental verification.
The main feature of the interaction of the considered EDSTS with the ionospheric plasma is its relatively short anode part. Calculations show that the positively charged part for arbitrary tether lengths does not exceed 2% of the total length.
          Unlike the previously known model, the proposed model allows us to simplify calculations and estimates of the effects of system interaction with plasma as well as to take into account a number of additional factors that can make significant corrections to the system operation.
Keywords: electrical model, electrodynamics space tethered system, spacecraft removal system
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