Direct Thrust Measurements of an EMDrive and Evaluation of Possible Side-Effects

Abstract

The EMDrive has been proposed as a revolutionary propellantless thruster using a resonating microwave cavity. It is claimed to work on the difference in radiation pressure due to the geometry of its tapered resonance cavity. We attempted to replicate an EM Drive and tested it on both a knife-edge balance as well as on a torsion balance inside a vacuum chamber. After developing a numerical model to properly design our cavity for high efficiencies in close cooperation with the EM Drive's inventor, we built a breadboard out of copper with the possibility to tune the resonance frequency in order to match the resonance frequency of the magnetron which was attached on the side of the cavity. After measuring the Q-factor of our assembly, we connected the EMDrive to a commercial 700 W microwave magnetron. After a thermal mapping of the surfaces, we performed thrust measurements with a knife-edge balance as well as with a torsion balance in vacuum chamber. Our measurements reveal thrusts as expected from previous claims after carefully studying thermal and electromagnetic interferences. For the first time, measurements were also performed in high vacuum. Due to a low Q factor of <50, we observed thrusts of +/-20 µN. We identified the magnetic interaction of the power feeding lines going to and from the liquid metal contacts as the most important possible side-effect that is not fully characterized yet. Our test campaign can not confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far. Nevertheless, we do observe thrusts close to the actual predictions after eliminating many possible error sources that should warrant further investigation into the phenomena. Nomenclature c = speed of light = 3×10 8 m/s f = frequency F = force P = power

Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum

“…T WAS previously reported that radio-frequency (RF) resonant cavities generated anomalous thrust on a low-thrust torsion pendulum [1,2] in spite of the apparent lack of a propellant or other medium with which to exchange momentum. It is shown here that a dielectrically loaded, tapered RF test article excited in the transverse magnetic 212 (TM212) mode (see Fig.…”

Proposal of a Handy Setup for Discriminating Parasitic Effects for the Measurement of Impulsive Thrust From a Microwave Cavity

“…This level of force seems high enough to be measurable with a commercial precision balance which has short response time as opposed to that of the torsion pendulum [1,2]. This type of measuring instrument has already been used to detect an EMDrive force [3,7], and it allows us to develop an accurate-enough, handy, and low-cost measuring setup.…”

“…This contentious atmosphere prompted other research teams around the world to publish their own studies on this topic, both on an experimental level [1][2][3] and on a theoretical one [4,5]. In 2016, in the first one of the few peer-reviewed papers, White et al, from Eagleworks Laboratories (NASA Johnson Space Center), stated that their cavity type, named QVPT (quantum vacuum plasma thruster), produced a force with a thrust to power ratio of 1.2 ± 0.1 mN/kW [1].…”

“…On the other hand, McDonald et al, from Naval Research Laboratory, resumed White's work and presented, in 2017, their preparations and suspicions of possible side-effects to independently validate or refute the observed phenomenon [6]. In parallel, since 2015 [3], Tajmar and Fiedler from TU Dresden have published several interesting papers about original thrusters. In the last one [2] about the EMDrive topic, Kößling et al presented the tests carried out in 2018.…”

On the exhaust of electromagnetic drive

“…Possible side-effects have been pointed out, and hence certain experiments have been inconclusive about the thrust. 10 Also credibility of some earlier experimental results has been recently reconsidered in relation to instrumental precision. 11 Since explanations 12,13 and their refutations [14][15][16][17] have not been conclusive, we bring up a new line of thought to the profound discourse that targets to important applications, most notably to keep satellites on orbits.…”