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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| EmDrive | 5/5 | https://en.wikipedia.org/wiki/EmDrive | reference | science, encyclopedia | 2026-05-05T09:19:20.530876+00:00 | kb-cron |
The largest error source is believed to come from the thermal expansion of the thruster's heat sink; as it expands this would lead to a change in the centre of gravity causing the resonant cavity to move. White's team attempted to model the thermal effect on the overall displacement by using a superposition of the displacements caused by "thermal effects" and "impulsive thrust" with White saying "That was the thing we worked the hardest to understand and put in a box". Despite these efforts, White's team were unable to fully account for the thermal expansion. In an interview with Aerospace America, White comments that "although maybe we put a little bit of a pencil mark through [thermal errors] ... they are certainly not black-Sharpie-crossed-out." Their method of accounting for thermal effects has been criticized by Millis and Davies, who highlight that there is a lack of both mathematical and empirical detail to justify the assumptions made about those effects. For example, they do not provide data on temperature measurement over time compared to device displacement. The paper includes a graphical chart, but it is based on a priori assumptions about what the shapes of the "impulsive thrust" and "thermal effects" should be, and how those signals will superimpose. The model further assumes all noise to be thermal and does not include other effects such as interaction with the chamber wall, power lead forces, and tilting. Because the Eagleworks paper has no explicit model for thrust to compare with the observations, it is ultimately subjective, and its data can be interpreted in more than one way. The Eagleworks test, therefore, does not conclusively show a thrust effect, but cannot rule it out either. White suggested future experiments could run on a Cavendish balance. In such a setup, the thruster could rotate out to much larger angular displacements, letting a thrust (if present) dominate any possible thermal effects. Testing a device in space would also eliminate the center-of-gravity issue. Tajmar's team later used such a setup to show that past results had all been artefacts of thermal effects.
=== Electromagnetic interactions === These experiments used relatively large electromagnetic inputs to generate small amounts of thrust. As a result, electromagnetic interactions between power leads, between power lines and ambient magnetic fields, or between the apparatus and walls of a test chamber, could all have significant effects. Yang reported in 2016 that an interaction with the Earth's magnetic field had caused the fairly large apparent thrust in their 2012 paper. Tajmar looked for potential Lorentz force interactions between power leads in trying to replicate White's experimental setup. Another source of error could have arisen from electromagnetic interaction with the walls of the vacuum chamber. White argued that any wall interaction could only be the result of a well-formed resonance coupling between the device and wall and that the high frequency used imply the chances of this would be highly dependent on the device's geometry. As components get warmer due to thermal expansion, the device's geometry changes, shifting the resonance of the cavity. In order to counter this effect and keep the system in optimal resonance conditions, White used a phase-locked loop system (PLL). Their analysis assumed that using a PLL ruled out significant electromagnetic interaction with the wall.
== See also ==
== References ==
== External links == Official website, Cannae Official website, EmDrive Oberhaus, Daniel (5 June 2019). "A Mythical Form of Space Propulsion Finally Gets a Real Test". WIRED. Retrieved 7 June 2019. Broadcast 2722 EM Drive @ The Space Show Videos of presentations on EM Drive, Mach Effect, Cannae by March, Woodward, Tajmar and others at the 2016 Breakthrough Propulsion Workshop @ Space Studies Institute YouTube Playlist TMRO video podcast #EMPossibleDrive 9.16 with builder Dave Distler Archived 8 October 2016 at the Wayback Machine @25 minutes in EmDrive fails tests