The Way to Choose Structure Materials for High Frequency Ion Thrusters
Aerospace propulsion engineering
Аuthors1*, 2**, **, 3***, 4**, 4, **, 4****, 4*****, 4******
1. Central research institute for special machinery, Zavodskay str., Khotkovo, Moscow region, 141371, Russia
2. Research Institute of Applied Mechanics and Electrodynamics (RIAME),
3. Russian Institute of Chemical Technology named after D.I. Mendeleev, 3, Miusskay. st., Moscow, 125047, Russia
4. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
Selection of high frequency ion thruster materials and development of manufacturing processes for critical structural elements.
This study traces the results of tryout technology development for manufacturing ion thruster critical structural elements: dome-shaped perforated electrodes made of carbon-carbon composite material and ceramic discharge chambers.
To manufacture units of corundum, the technology of hot high-pressure casting with thermally-plastic slurry is used. The technology for manufacturing units of silicon nitride comprises the following processes: unit formation by hot casting of a composite paste comprising silicon powder, corundum filler and a binder, and unit final formation in nitrogen environment by sintering the silicon nitride. For the electrode manufacturing a sandwich-type carbon textolite with shifted direction of each next layer relative to the previous one by 600 is used. The sandwich carbon textolite is covered with laminating surface layers consisting of carbon material of the felt type. The sandwich is compacted pyrolytically (by gas-phase saturation with pyrolytic carbon). Laser beam is used to form apertures in electrodes. A technological process for aperture making at the stage of carbon-filled plastic workpiece formation has been developed. For this purpose the bottom layer of carbon felt was formed to the metallic plate with pins placed in accordance with the aperture grid for electrode. The carbon fibers with needed linear density were laid in three directions into the grooves between pins. The obtained sandwich was impregnated with a binder and closed by a stamp. After that the carbon-filled plastic workpiece in pressed state was subjected to thermal processing. To check up behavior of the chosen materials in the real structure, experimental investigations were performed by using a thruster model operating within the wide ranges of power (from 30 W up to 300 W), flow rate (from 0.2 mg/s up to 0.9 mg/s), and frequency (from 1800 kHz up to 2100 kHz). We tested not only chambers, but different matching devices also
It was revealed experimentally that high frequency ion thruster parameters change insufficiently with the replacement of discharge chamber material by a cheaper ceramics.
As a result of the works performed it is possible to conclude that in our country the technology for manufacturing basic structural elements for high-frequency ion thrusters has been restored within a relatively short period of time. The new solutions for manufacturing electrodes of carbon-carbon composite material were tried out in view of the electrode perforation. It is shown that at the stage of thruster tryout it is possible to use cheaper silicon-nitride ceramics.
Keywords:structural materials for ion thrusters, electrodes, composite carbon-carbon material, discharge chamber, ceramic material
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