Experimental Results

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Forces, Power, Frequency and Dimensions

The current best estimates for the parameters of various test articles run by public and private research labs (NASA Eagleworks, SPR Ltd., and NWPU) is here, along with the reported forces. Note that complete dimensions are not known in most cases, and some had to be determined via indirect methods (e.g., estimation from photographs). See Building for details on drives built by do-it-yourselfers.

Credit to Dr. Rodal and others for the great effort in compiling these. Please note some caveats for this data, at that link.

Description Mode Shape Pressure (Torr) Cavity Length (m) bigDiameter (m) smallDiameter (m) Shawyer Design Factor Dielectric Frequency (Hertz) Power (W) Q Force (mN) Force / PowerInput (mN/kW) Force/Power Multiple of Photon Rocket
Cannae Superconducting Ambient 0.03 0.220 0.200 None 1.047*10^9 10.5 1.1*10^7 8-10 761.9 - 952.4 228400 - 285500
Shawyer Experimental Ambient 0.156 0.16 0.1025 0.497 Yes 2.45*10^9 850 5900 16 18.82 5640
Shawyer Demonstration Ambient 0.317 to 0.187 0.28 0.17027 0.484[1] None 2.45*10^9 421-1200 45000 102.30 80-243 23980 - 72830
NASA Brady et.al. a TM212 [2] Ambient 0.2286 0.2794 0.15875 HDPE 1.9326*10^9 16.9 7320 0.0912 5.396 1617.2
NASA Brady et.al. b TM212 [2] Ambient 0.2286 0.2794 0.15875 HDPE 1.9367*10^9 16.7 18100 0.0501 3.000 899.12
NASA Brady et.al. c TE012 Ambient 0.2286 0.2794 0.15875 HDPE 1.8804*10^9 2.6 22000 0.05541 21.310 6386.7
NASA March et.al. TM212 5*10^(-6) 0.2286 0.2794 0.15875 HDPE 1.9371*10^9 50 6726 0.055 1.100 329.64
Iulian Berca Tests 3 & 3.1 (averaged w/up/down directional effects subtracted) [3] TM212[4] Ambient 0.2286 0.2794 0.1588 None 2.45*10^9 (magnetron) 800 n/a 2.84 3.55 1063.82
Fearn, Zachar, Woodward & Wanser - piezoelectric MET thruster[5] 39300 170 22000 0.002 0.01176 3.526

Environmental pressure unit: 1 Torr = [math]\cfrac{1}{760} [/math] of a standard atmosphere.

Comparison to Photon Rockets

For a perfectly-collimated photon rocket, the force per power input is as follows:

Photon Rocket Force / PowerInput (mN/kW) = 0.003337

If the results above are validated, the EM Drive would greatly exceed that ratio.

References

  1. Forum posts by @phaseshift, @Rodal, and @Rodal - The Design Factor is reported as 0.844 in at least three of Shawyer's references; however using a Design Factor = 0.844 gives a much smaller diameter in conflict with the ratio of the small diameter to the big diameter shown in the picture of the Demonstrator in Shawyer's publications, so it is assumed that was an unintentional typo (0.844 instead of 0.484, which results in a small diameter that agrees with the published image). The smallDiameter shown here was recalculated from the revised Design Factor (0.484). The cavity length is estimated as 0.317 to 0.187. The larger number takes into account the full length of the cylindrical part of the EM Drive Demo and the smaller number corresponds only to the length of the truncated cone section. Please notice that the Demo has a variable length actuated by a gear mechanism, in order to tune the cavity to achieve resonance emdrive_2.jpg .
  2. 2.0 2.1 Mode shape is noted as TM211 in Brady et.al.'s report. However, calculations show that TM211 should take place at a significant lower frequency and that this mode must have been TM212. Notice that Brady et.al. b took place practically at the same frequency as March TM212 test in vacuum
  3. The tests by Iulian Berca were not logged in a scientifically rigorous manner. See http://www.masinaelectrica.com/emdrive-independent-test/. However, because of the high profile nature of the tests, they are included here merely to give a rough comparison to the more scientifically rigorous tests. The measured thrust in this table is an average of multiple runs in tests 3 and 3.1, subtracting out the likely effects of hot air. @deltaMass calculated the net thrust for the EmDrive across both tests to be 0.29gf effective thrust, which is 2.84mN. See here.
  4. Iulian used the same dimensions as NASA's truncated cone, but without a dielectric. Mode shape is predicted to be TM 212 according to Rodal's exact solution calculation (2.42 GHz) and to NASA's COMSOL FEA analysis
  5. [1]Forum post by @Rodal - Included here because Prof. Woodward's device is also a propellant-less concept, and because Paul March (NASA) maintains that Prof. Woodward's Mach Effect theory might also be, in his opinion, an explanation for thrust for the EM Drive.