In August Hacked covered the rumor, then confirmed by NASA, that a paper by the NASA Eagleworks team, titled “Measurement of Impulsive Thrust from a Closed Radio Frequency Cavity in Vacuum,” to be published in December’s issue of American Institute of Aeronautics and Astronautics (AIAA)’s Journal of Propulsion and Power, a prestigious peer-reviewed scientific journal, will reveal promising experimental results on the controversial, “impossible” EmDrive propulsion system. Now, a NASA Eagleworks paper that could be the December paper, or a draft, has been leaked.
The EmDrive results are often dismissed because they appear to violate the fundamental conservation laws of physics, but possible models for the anomalous thrust effect have been proposed that, while belonging to highly imaginative areas of theoretical physics, could explain the controversial results without violating fundamental conservation laws.
The leaked paper was first shared in the NasaSpaceFlight forum, which is often the primary source of updates for all things EmDrive, and a Reddit thread that was then removed at the request of the Eagleworks authors, then posted with a commentary by tech news site Next Big Future. Of course, the paper could be removed again, and therefore those who want to read it before December might want to download it now.
However, at this moment it isn’t clear if the leaked paper is the final version that will be published. In fact, according to a reply to a request for clarifications that I posted to the NasaSpaceFlight forum, the leaked paper is very likely not the same paper that will appear in AIAA’s Journal of Propulsion and Power in December, or at the very least, it’s only an early draft. “The results are not new, dating back to 2014-2015, “leading users to suspect that we do not have the current sum of research by Eagleworks.”
However, even if there are no really new results, the fact that previously announced Eagleworks results have been confirmed, reviewed by independent experts, and accepted for publication in a top technical journal, is good news in itself.
Measured Performance Much Higher Than Other Propellant-Less Propulsion Schemes
“A vacuum test campaign that utilized an updated integrated test article and optimized torsion pendulum layout has been completed,” note the NASA researchers. “The test campaign consisted of a forward thrust element that included performing testing at ambient pressure to establish and confirm good tuning, and subsequent power scans at 40, 60, and 80 W with three thrust runs performed at each power setting for a total of nine runs at vacuum.”
“The test campaign consisted of a reverse thrust element that mirrored the forward thrust element,” continue the Eagleworks scientists. “The test campaign included a null thrust test effort of three tests performed in vacuum at 80W to try and identify any mundane source of impulsive thrust; none were identified.”
“Thrust data from forward, reverse, and null suggests that the system is consistently performing at 1.2 ± 0.1 mN/kW which is very close to the impulsive performance measured in air.”
“A number of error sources were considered and discussed. While thermal shift was addressed to a degree with this test campaign, future testing efforts should seek to develop testing approaches that are immune to CG shifts from thermal expansion. As indicated in the error section, a modified Cavendish balance approach could be employed to definitely rule out thermal. Although this test campaign was not focused on optimizing performance and was more an exercise in existence proof, it is still useful to put the observed thrust to power figure of 1.2 mN/kW in context.”
“The current state of the art thrust to power for a Hall thruster is on the order of 60 mN/kW. This is an order of magnitude higher than the test article evaluated during the course of this vacuum campaign, however, for missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements.”
“The 1.2 mN/kW performance parameter is over two order of magnitude higher than other forms of “zero-propellant” propulsion such as light sails, laser propulsion, and photon rockets having thrust to power levels in the 3.33-6.67 µN/kW (or 0.0033-0.0067 mN/kW) range.”
Images from Wikimedia Commons and NASA.