Preparations For Thrust Measurement And Error Discussion Of The Impulse Resonant Microwave Cavity

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M. S. McDonald et al. (2017), JBIS, 70, pp.415-424

Refcode: 2017.70.415
Keywords: Torsional pendulum, Force measurement, Non-contact RF power transmission, Thermal drift, Microwave cavity, Vacuum

This paper reports on preparations for independent validation and verification (IV&V) of a recently proposed speculative class of spacecraft propulsion which we label an "impulse drive". The most prominent example device, and the only one offering peer-reviewed experimental results, is the closed resonant microwave cavity of White et. al. from NASA Johnson Space Center. White reports anomalous thrust production with no conventional expulsion of reaction mass via a new and unconventional interpretation of physics. Such a device would have remarkable applications for spacecraft propulsion, but the positive experimental results to date, while suggestive, are near the limits of state of the art measurement resolution and subject to significant confounding errors due to thermal drifts and other subtle effects. Our objective is to rigorously weed out potential false positive thrust signals with null and control experiments, create an impartial baseline dataset to either validate or refute claims of anomalous thrust, and if merited form a solid foundation for further experimental and theoretical investigation. We duplicate the resonant geometry (length, diameter, taper) of White's experimental apparatus in a replica cavity with mechanical construction and driving microwave circuit of our own design, with careful attention to maximizing driving RF power capability and cavity resonant quality factor Q. We report on the fabrication and initial thermal testing of our replica cavity and the development of a noncontact RF power interface we dub a "finger joint" to permit frictionless power transmission to a freely swinging torsional thrust stand arm. No thrust measurements have been completed to date; this paper only presents experimental methods and risk reduction test results in preparation for performance measurements on a torsional thrust stand at vacuum. Potential sources of error including thermal drift, RF effects, magnetic tearing via dipole coupling, and electrostrictive response in the cavity dielectric insert are discussed.

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