High-accuracy thrust measurements of the EMDrive and elimination of false-positive effects

Abstract

The EMDrive is a proposed propellantless propulsion concept claiming to be many orders of magnitude more efficient than classical radiation pressure forces. It is based on microwaves, which are injected into a closed tapered cavity, producing a unidirectional thrust with values of at least 1 mN/kW. This was met with high scepticism going against basic conservation laws and classical mechanics. However, several tests and theories appeared in the literature supporting this concept. Measuring a thruster with a significant thermal and mechanical load as well as high electric currents, such as those required to operate a microwave amplifier, can create numerous artefacts that produce false-positive thrust values. After many iterations, we developed an inverted counterbalanced double pendulum thrust balance, where the thruster can be mounted on a bearing below its suspension point to eliminate most thermal drift effects. In addition, the EMDrive was self-powered by a battery-pack to remove undesired interactions due to feedthroughs. We found no thrust values within a wide frequency band including several resonance frequencies and different modes. Our data limit any anomalous thrust to below the force equivalent from classical radiation for a given amount of power. This provides strong limits to all proposed theories and rules out previous test results by at least two orders of magnitude.

The law of momentum conservation in free microwave cavities containing coherent radiation

“…Using the same quality factor, for 1.5GHz, one finds t max = 2.94 µs. Such time is incompatible with the several seconds observed in many experimental tests [5,14,31] claiming to proof or disproof the effect. The later situation is probably the case, because after t max no other thrust is expected to occur in the system which nevertheless is under the action of other perturbation forces neglected here.…”

“…Consequently, one concludes that any displacement of the cavity body due to an interplay of partial momentum components within the system is unobservable under these conditions. This is specially true considering the existence of other neglected perturbations as discussed in [5] and [14].…”

“…with w(t, t ) a weight function, and ±∞ a representative limit of measurement time intervals much longer than ω −1 . The average is justified because in the measurement process of such velocity change (involving, in general, a mechanical set-up to measure torsions, see, e. g. [5,14]), the output is mechanically unresponsive to oscillations at the microwave frequencies. Such time average is accomplish by considering, for example, the weighting function…”

“…Despite the numerous attempts to explain the effect [10,11,12,13], no convincing theory was accepted to solve the apparent anomaly, and the interest in such devices faded away to some extent. Recently, it received a serious blow after sensitive experimental tests [14], suggesting all previous results were caused by mechanical stresses due to thermal dilatation of the cavity body. Despite this negative report, a thorough theoretical account of the role played by momentum conservation in such system is still missing because electromagnetic fields also carry momentum which is conserved for the whole system only.…”

Time-Domain Analysis of Electromagnetic Fields in Conical Cavities With Modified EAE

“…T HE exploration of electromagnetic fields within conical geometries has garnered significant attention due to its implications in advanced technologies, notably biconical transmission lines [1], conical antennas [2], and the concepts like the EMDrive (RF resonant cavity thrusters) [3], [4]. Stemming from the seminal works of Smith and Tai [5], [6], research in this area has continually evolved to demystify the complex behaviors exhibited by fields in these unique structures [7].…”