High Emissivity Arcjet Anode
Technology Description Improved cooling of the anode can increase the efficiency and lifetime of arcjet thrusters. Smooth tungsten anodes have low emissivity ~0.3 that severely limits radiative cooling. Traditional methods for increasing tungsten emissivity have are problematic: ceramic coatings tend to flake off under high temperature cyclic arcjet operation and surface roughening by arc and sputter texturing does not succeed on tungsten. ESLI's novel approach to the problem was to texture surfaces with small diameter fibers. The process involved the application of short fibers and a chemical vapor deposition coating to obtain high-density, well-oriented, large aspect ratio microcavities on substrate materials such as tungsten, carbon and refractory ceramics. Potential Benefits Radiative cooling of the anode can be increased 300% by improvements in emissivity, resulting in increased arcjet power and lifetime. Development Status ESLI performed a Phase 1 SBIR contract with the U.S. Air Force to develop high emissivity anode materials for arcjet propulsion and other optical and thermal applications. Samples were prepared and characterized to aid modeling of the infrared optical properties of fiber-coated surfaces and to guide design. Sample tungsten surfaces were then prepared and characterized at high temperature to assess feasibility of the approach for use in arcjet anode applications. |
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