Paul March works at NASA on the EMDrive, Cannae drive experiments. He is providing information about the experiments on the NASA spaceflight forum.
How High RF issues are being managed
Please note that the entire RF system including its voltage controlled oscillator, phased locked loop, RF amplifier, RF coupler and coaxial transmission lines are hard mounted on the moving torque pendlum arm with the test artricle as it would be in flight. The only power lines that comes across the liquid metal contacts (LMC) are the +5.0Vdc control and +28.0Vdc and their associated ground power lines for each circuit. The Maxwell stress forces created in the LMC pots due to these dc power currects are calculated to be in the nano-Newton range and just act to restore the LMC metal pins to the center of the LMC pots that hold the Galanstan. In otherwords these Maxwell centering stress forces just increase the effective C-flex spring constants by less than a tenth of a percent even when drawing ten amps through the plus and minus 28Vdc bus wires. And yes, all these power wires are twisted and and shielded throughout their runs to cancel out most of B-fields associated with the RF amplifer and control power feeds. Even with all that though, we appeared to still have a small residual interaction between these stray power line shield B-fields interacting with the stray B-fields from the magnetic damper, so we’ve already upgraded the magnetic damper design to further reduce this problem. Here are some pictures with the new magnetic damper design and buildup pictures.
Other Experiment details and the upcoming vacuum experiments
The units for all the E-field measurements in our 2014 JPC paper is volts per meter (V / m).
As to the torque pendulum dimensions, the center of the two C-flex bearing blocks is 2.38″ above and below the centerline of the 24.00″ long by 1.50″ square aluminum pendulum arm. The long end of the pendulum arm is 15.5″ from the torque pendulum’s center of rotation, which makes the other short-end of the pendulum arm 8.5″ from the center of rotation. And all the pendulum’s aluminum structural elements are electrically bonded together and then grounded to the vacuum chamber’s 304 alloy stainless steel walls that is in turn grounded to the facility’s green wire safety ground system. This grounding arrangement’s function is to preclude the buildup of electrical patch charges on the various parts of the pendulum and vacuum chamber during operations.
BTW, the reason Eagleworks NASA didn’t test in vacuum for these test series was that our 35W RF amplifier, that was mounted on the torque pendulum arm as the counterbalance mass for the test articles, was that it’s electrolytic capacitors would pop at the low pressures, thus disabling it. Eagleworks NASA have since obtained two ~100W RF amplifiers that are hermetically sealed that will allow tests down to ~5×10^-6 Torr vacuum pressures in the near future, at least once current phase locked loop design issues are resolved.
The Eagleworks Lab’s torque pendulum is a conventional horizontal torque pendulum with two C-flex torsional bearing blocks with one bearing block mounted directly above the torque pendulum arm and the other below it on the same rotational axis. From memory the distance between the bearing blocks to the torque pendulum arm is around 4.0″, but I’ll [Paul March] re-measure it today to make sure. The length of the aluminum pendulum arm is 24.00 inches with the center of rotation being offset from its center of mass by about 4.0″ before adding additional masses, but again I’ll re-measure it today to get its current dimensions. The Riverhawk C-flex torsion bearing’s spring constant is a nominal 0.007 in-Lb/deg., but that varies with the mass load mounted on the torque pendulum arm and selected balance point of the test article mass and its counterbalance mass on the other end of the pendulum arm relative to the torque pendulum’s center of rotation. Each bearing block is rated for ~25.0 Lb of vertical mass load, so we nominally restrict ourselves to a 25 pound total load limit on the torque pendulum arm to give ourselves a 100% support mass margin.
Previous coverage of the NASA Cannae drive and EMdrive tests
Abstract – Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum
This paper describes the test campaigns designed to investigate and demonstrate viability of using classical magnetoplasmadynamics to obtain a propulsive momentum transfer via the quantum vacuum virtual plasma. This paper will not address the physics of the quantum vacuum plasma thruster (QVPT), but instead will describe the recent test campaign. In addition, it contains a brief description of the supporting radio frequency (RF) field analysis, ssons learned, and potential applications of the technology to space exploration missions. During the first (Cannae) portion of the campaign, approximately 40 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 935 megahertz and 28 watts. During the subsequent (tapered cavity) portion of the campaign, approximately 91 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 1933 megahertz and 17 watts. Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level. Test campaign results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.
From the Full paper
Eagleworks tested one tapered (frustum) cavity, aka Shawyer’s EmDrive; and two Cannae drives which are also asymmetric but different resonant cavities. The Cannae drive is said to work on a purported different principle than the EmDrive, according to its inventor Guido Fetta (a net Lorentz force imbalance of electrons upon top vs bottom wall of the cavity). According to this purported working principle, one Cannae drive had radial slots on its rim as required by Fetta in order to produce net thrust, and the second Cannae drive didn’t have those slits and was intended to be a “null test device”. But the Cannae null test article… also produced net thrust (20 to 40 µN of net thrust depending of the forward or backward direction).
The null device having thrust means that the Cannae drive theory that the slits mattered was not true. However, this is irrelevant as to whether the Cannae drive produces thrust. Another theoretical explanation is needed but the anomalous thrust remains
We’re talking of net thrust because of course the setup was also tested with a null 50 ohm load connected, in order to cancel the effect from the drives and detect any detect any spurious force due to EM coupling with the whole apparatus (which exists, at 9.6 µN) and this “null” spurious force was evidently subtracted from any thrust signal due to the drives then tested on the pendulum.
All tests articles (the EmDrive version, the Cannae drive version, and even the Cannae “null test” version) had a dielectric embedded within. This is a hint for a different theoretical explanation involving EM fields, proper acceleration, mass fluctuation and dielectrics. Maybe Mach effects (due to Mach’s principle), as supposed by Woodward and Fearn within the GR theory, or within a scalar-tensor theory of gravity according to Minotti.
Fetta’s experimental results are detailed. Also, numerical work and what he believes are the Principles.
EMDrive thrust does not seem to scale with higher Q with these tests
What space missions are possible with early versions if this is true?
Based on test data and theoretical model development, the expected thrust to power for initial flight applications is expected to be in the 0.4 newton per kilowatt electric (N/kWe) range, which is about seven times higher than the current state of the art Hall thruster in use on orbit today. The following figures show the value proposition for this class of electric propulsion. A conservative 300 kilowatt solar electric propulsion roundtrip human exploration class mission to Mars/Deimos. A 90 metric ton 2 megawatt (MW) nuclear electric propulsion mission to Mars that has considerable reduction in transit times due to having a thrust to mass ratio greater than the gravitational acceleration of the Sun (0.6 milli-g’s at 1 AU). The same spacecraft mass performing a roundtrip mission to the Saturn system spending over a year around two moons of interest, Titan and Enceladus. Even in this last class of mission which requires only a single heavy lift launch vehicle, the mission has less mission duration than is common with a current conjunction-class Mars mission using chemical propulsion systems and which would require multiple heavy lift launch vehicles. 300 kW SEP Roundtrip Mission to Mars Deimos (50 day stay) departing from DRO 300 kW SEP
What are the next research steps ?
The lessons learned with antenna design and location have been factored in and the design of both the drive and sense antenna s have been explicitly optimized to excite the RF thruster at the target frequency and mode (e.g.,the optimal location has been analytically determined). The thrust performance of this next generation tapered test article has been analytically determined to be in the 0.1 newton per kilowatt regime. Vacuum compatible RF amplifiers with power ranges of up to 125 watts will allow testing at vacuum conditions which was not possible using our current RF amplifiers due to the presence of electrolytic capacitors. The tapered thruster has a mechanical design such that it will be able to hold pressure at 14.7 pounds per square inch (psi) inside of the thruster body while the thruster is tested at vacuum to preclude glow discharge within the thruster body while it is being operated at high power. A phase lock loop (PLL) solution has already been implemented and evaluated at the 1 GHz frequency range, and is being tailored to be able to support testing at multiple set points all the way up to 2.5 GHz. The near term objective is to complete a Q -thruster breadboard test article that is capable of being shipped to other locations which possess the ability to measure low thrust for independent verification and validation (IV&V) of the technology. The current plan is to support an IV&V test campaign at the Glenn Research Center (GRC) using their low thrust torsion pendulum followed by a repeat campaign at the Jet Propulsion Laboratory (JPL) using their low thrust torsion pendulum. The Johns Hopkins University Applied Physics Laboratory has also expressed an interest in performing a Cavendish Balance style test with the IV and V shipset
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