Still toying with numbers. I divided the COP I posted previously by Q and got this: Experiment COP COP/Q "Shawyer (2008) a" 5,643 0.96 "Shawyer (2008) b" 64,156 1.43 "Juan (2012) TE011" 64,156 2.00 "Juan (2012) TE012" 94,435 1.89 "Brady et al. (2014) a" 1,618 0.22 "Brady et al. (2014) b" 899 0.05 "Brady et al. (2014) c" 6,388 0.29 I don't know that it has any meaning but now at least the number values are near the ideal photon rocket thrust. That is, the thrust of an ideal photon rocket using the stored energy of the cavity/second comes close to the experimentally derived thrusts.

Couple things:Won't get back to the lab til monday for measurements from pictureBoth end plates have something else going on. Looks likr the top one has a tuning plate(?) of some kind, not motorizedWhy the extra plate below the bottom, can't see in picFound another paper that was bothering me in the piles behind the desk"Ionization instabilities and resonant acoustic modes", Physics of Plasmas, V8, N0.11, p.5018It was concerned w/ the coupling of ions w/ dust particles. Reminds me of RF w/ axions (Ya, I'm still chasing the axion connection) no cavities involved, but "It is found that an unstable dust-acoustic mode of nonzero real frequency can be generated via a resonance phenomenon." ... "As the charge on dust particles exceeds a threshold, multiple low-frequency modes with large growth rates are excited suddenly."I just had to throw that in cuz I finally found the d**m thing ! (You youngsters can play w/ it for now)Ok, so in practical terms it means you can (theoretically)induce feedback into the coupling constant if you can set up the dispersion relations properly.

OK - I took out all possible sources of loss and inefficiency by simply replacing the actual measured trust with Prof. M's new formula predicted values. Formula thrust Experiment COP COP/Q COP/Q "Shawyer (2008) a" 5,643 0.96 0.44 "Shawyer (2008) b" 64,156 1.43 0.82 "Juan (2012) TE011" 64,156 2.00 0.82 "Juan (2012) TE012" 94,435 1.89 0.82 "Brady et al. (2014) a" 1,618 0.22 0.46 "Brady et al. (2014) b" 899 0.05 0.46 "Brady et al. (2014) c" 6,388 0.29 0.46 Now the values are all geometry because Q is multiplied the formula and divided out. The values though are getting into the range of what a COP based on an ideal photon rocket should be. I could factor cosine losses into the thrust formula but that's a lot of trouble for little benefit.This formula says to me that what is wanted is a big cavity with the ratio (w_big/w_small) large, and height/length, (s) large. Height/length, (s) large is the new factor in Prof. M's latest formula and s is the variable name he uses. It seems that current tech could deal with that but of course the larger the cavity is, the heavier it is so the T/W ratio suffers at some point.

Please forgive an idle speculation on a Sunday evening from the peanut gallery.QuoteThanks. I was really gettin' kinda full, all by myself in that there gallery.

Thanks. I was really gettin' kinda full, all by myself in that there gallery.

we must seriously address the question of the role of resonance and Q in a cavity

Quote from: aero on 10/19/2014 09:53 PMOK - I took out all possible sources of loss and inefficiency by simply replacing the actual measured trust with Prof. M's new formula predicted values. Formula thrust Experiment COP COP/Q COP/Q "Shawyer (2008) a" 5,643 0.96 0.44 "Shawyer (2008) b" 64,156 1.43 0.82 "Juan (2012) TE011" 64,156 2.00 0.82 "Juan (2012) TE012" 94,435 1.89 0.82 "Brady et al. (2014) a" 1,618 0.22 0.46 "Brady et al. (2014) b" 899 0.05 0.46 "Brady et al. (2014) c" 6,388 0.29 0.46 Now the values are all geometry because Q is multiplied the formula and divided out. The values though are getting into the range of what a COP based on an ideal photon rocket should be. I could factor cosine losses into the thrust formula but that's a lot of trouble for little benefit.This formula says to me that what is wanted is a big cavity with the ratio (w_big/w_small) large, and height/length, (s) large. Height/length, (s) large is the new factor in Prof. M's latest formula and s is the variable name he uses. It seems that current tech could deal with that but of course the larger the cavity is, the heavier it is so the T/W ratio suffers at some point.Very interesting. On this topic, have people commented on this paperPhotonic Laser Propulsion (PLP): Photon Propulsion Using an Active Resonant Optical Cavity ?http://arc.aiaa.org/doi/abs/10.2514/6.2007-6131He claims to have measured 35 microNewtons thrust at 1.7 watts with propellant less photon rocket amplification in an optical cavityThis is a much higher thrust/power input than normal photon rockets and even superior to NASA Eagleworks truncated cone experiments

Taking into account the frequency drift and bandwidth issues that the researchers have tuning the device under resonance, with concomitant drift in Q (which therefore cannot be a constant during the measurements) these results are quite interesting!

Perhaps we need some more frobnicating , including re-running the formulas with the updated geometry (see http://physicsfromtheedge.blogspot.it/2014/10/emdrive-mihsc-dream-of-horizon-physics.html) and allowing for Sqrt[ 1/big^2 + 1/L^2] and perhaps all the other square roots as well. Also using the new formulas taking into account wavelength: http://forum.nasaspaceflight.com/index.php?topic=29276.msg1272925#msg1272925Also frobnicating with the photon rocket analogy...

#define Nrec 7t_data data_in[Nrec] ={ // w_big w_small lambda Q power force {"Shawyer (2008) a", 1.0 , 16 , 8 , C/2.45 , 5900 , 850 , 16 }, {"Shawyer (2008) b", 1.0 , 28 , 4 , C/2.45 , 45000 , 1000 , 214 }, {"Juan (2012) TE011", 1.0 , 28 , 4 , C/2.5 , 32000 , 1000 , 214 }, {"Juan (2012) TE012", 1.0 , 28 , 4 , C/2.45 , 50000 , 1000 , 315 }, {"Brady et al. (2014) a", 1.0 , 24.75 , 16.5 , C/1.933 , 7320 , 16.9 , 0.0912 }, {"Brady et al. (2014) b", 1.0 , 24.75 , 16.5 , C/1.937 , 18100 , 16.7 , 0.0501 }, {"Brady et al. (2014) c", 1.0 , 24.75 , 16.5 , C/1.88 , 22000 , 2.6 , 0.0554 },};

I have my sheets of copper and a dismantled microwave oven at the ready!

Quote from: Rodal on 10/19/2014 09:57 PMVery interesting. On this topic, have people commented on this paperPhotonic Laser Propulsion (PLP): Photon Propulsion Using an Active Resonant Optical Cavity ?http://arc.aiaa.org/doi/abs/10.2514/6.2007-6131He claims to have measured 35 microNewtons thrust at 1.7 watts with propellant less photon rocket amplification in an optical cavityThis is a much higher thrust/power input than normal photon rockets and even superior to NASA Eagleworks truncated cone experimentsDoes anyone have access to this full paper?From the abstract, It looks like his resonant cavity has a Q of 3000. At 35 muN thrust, 1.7 watts, and frobnicat's simplified rule of thumb, F/P = 1/c * Q predicts F = 17. muN . Only missing a factor of 2.I'd say that's close enough to add a constant factor of 2 as a possible choice in your formula search. Have we exceeded a million equation search yet?

Very interesting. On this topic, have people commented on this paperPhotonic Laser Propulsion (PLP): Photon Propulsion Using an Active Resonant Optical Cavity ?http://arc.aiaa.org/doi/abs/10.2514/6.2007-6131He claims to have measured 35 microNewtons thrust at 1.7 watts with propellant less photon rocket amplification in an optical cavityThis is a much higher thrust/power input than normal photon rockets and even superior to NASA Eagleworks truncated cone experiments

Have we exceeded a million equation search yet?

Quote from: aero on 10/19/2014 10:43 PMHave we exceeded a million equation search yet?No but 21769 is already quite a lot. The data set is sparse and with some uncertainties : the risk is overfitting. Scanning on more than 15 bits (32768 combinations) worth of explanation could easily bring up more perfect formula for the specific available data but with less generalisation power : worse at predicting next data points to come. Need more data points before it's worth looking at much more formulas. Not a problem of computing power, not before reaching many billions of formulas. At this stage with 7 data points, from a "phenomenological theoretically agnostic" point of view, simpler is better, and there is not that much simple equations.Note : the number of combinations of exponents and added terms were 94 millions but of those only 21769 unique representations (discarding equivalents) made sense in dimensional analysis (kg m s).