Historical research guide · 0486 · 2014
Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum
David A. Brady · Harold G. White · Paul March · James T. Lawrence · Frank J. Davies
In one minute
In August 2013 a NASA Johnson Space Center team — David Brady, Harold ’Sonny’ White, Paul March, James Lawrence and Frank Davies — spent eight days measuring two radio-frequency cavities on the Eagleworks torsion pendulum, a balance that resolves forces down to single-digit micronewtons. The cavities, designed by Cannae LLC, were driven at about 935 megahertz inside a closed stainless steel vacuum chamber held at ordinary air pressure. The pendulum moved: roughly 30 to 50 micronewtons, on both articles, including the one built as a null. Swapping the cavity for a plain radio-frequency load gave no force, which told the team the signal followed the cavity rather than the cabling. Their stated conclusion is careful and worth quoting exactly — the force is not attributable to any classical electromagnetic phenomenon, and may therefore be showing an interaction with the quantum vacuum virtual plasma. They named their own next steps too: automatic frequency control instead of a hand-tuned source, and independent verification at other facilities.
Connection
This is the measurement that put propellantless radio-frequency thrust on chapter 8’s table, made by a NASA group with a named apparatus and a stated force. It is also chapter 1’s evidence ladder in action, because the authors asked for exactly the thing that came next: Martin Tajmar’s SpaceDrive group at TU Dresden rebuilt the experiment on an instrument sensitive below a nanonewton, catalogued the thermal and cable artefacts that manufacture a convincing thrust signature, and found every reading inside the noise at or below the light-pressure limit. That replication is on this site at /library/stm-0d21110734, and the two sheets should be read together — the open regime both papers point at is the superconducting cavity, where the quality factor rises by orders of magnitude and nobody has yet looked.
From the source
An electric propulsion test article consisting primarily of a radio frequency resonant cavity excited at approximately 935 megahertz produced approximately 30 to 50 micronewtons of thrust, measured on a low-thrust torsion pendulum capable of detecting force at a single-digit micronewton level.Abstract, paragraph 2
Thrust was observed on both test articles, even though one of them, the null article, was built without the internal physical modifications that were expected to produce thrust — a result the authors report rather than set aside.Abstract, paragraph 5
Replacing the test article with a radio frequency load, and reversing the orientation of the article, were both run as controls, to verify that the force was not being generated by effects unassociated with the test article.Abstract, paragraph 2
The team’s interpretation of the result is that the radio frequency resonant cavity thruster design is producing a force that is not attributable to any classical electromagnetic phenomenon and is therefore potentially demonstrating an interaction with the quantum vacuum virtual plasma.Abstract, final paragraph
The campaign ran inside a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure, and the resonant frequency had to be held by hand throughout; the authors name automatic frequency control as the first thing to build before the next run.Abstract, paragraphs 2 and 6
The paper closes by naming independent verification and validation at other test facilities as its own future test plan — the measurement that would settle the question, and the one Tajmar’s group at TU Dresden went on to make.Abstract, final sentence
The way in
https://doi.org/10.2514/6.2014-4029How to cite it
David A. Brady, Harold G. White, Paul March, James T. Lawrence, Frank J. Davies (2014) Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum doi:10.2514/6.2014-4029