2016-10-21

Tuesday, the hard work of the last four months finally produced some results. As you may recall, the last chamber I made was not able to resonate at the expected frequency. I originally thought it was, but then I discovered that it was actually a resonance in my measuring equipment and not in the chamber itself. I discovered this right before I presented my project at the International Space Development Conference in San Juan (it wasn't meant to be a scientific presentation, but it would have been pretty embarrassing to present something that turned out to be incorrect). Comparing the measurements of the cavity that the Tajmar team used in their model, I found that my chamber was 5 mm shorter. I've had trouble understanding why they made their model to those measurements. I didn't have the parts on hand to make a second chamber, and didn't have the money to buy new materials. Luckily, I did have the parts to try and make the variable-sized chamber that would be the next generation model. I've pressed on to try and finish that, and have made some progress on it, but most importantly I got much better at polishing. With a few new tools and learning new techniques that were better than just hand-polishing with sandpaper, I decided a couple of weeks ago to try polishing the original chamber with the new techniques and see if the problem with the resonance was actually due to incorrect measurements. 

And amazingly changing the polishing fixed the resonance problem! I got a resonance at about 2.40 GHz and at about 2.46 GHz. I didn't test it with the computer recording software plugged in, and when I attempted to show Mike Beach, the electronics expert that has been helping me at Artisan's Asylum, after the class he was teaching ended an hour and a half later it didn't work any more. I believe that this is because the copper oxidized enough in that hour and a half to reduce the reflectivity enough that it no longer resonated, but now I know how to fix that. (Really, Dr. Paul March gave me the hint about it months ago, but I thought I could get around it so I didn't buy the correct materials. Eight hours soaking in lemon juice, he told me, but I thought polishing right before the test was enough. I now keep all parts in a bath of 5% ascorbic acid whenever it's not in use).

The Q I measured yesterday was about 50, comparable to what the Tajmar experiments had, and I'm sure I can do better. Now that something is moving the needle, I am laying out a series of tests that I will be conducting over the next few days or weeks.

I am going to run tests, recording a control sweep and then recording frequency sweeps every 15 minutes to see the degradation of the resonance over time after at least a day of soaking in the ascorbic acid. The next step will be to see whether using galinstin as a liquid "gasket" between the copper parts of the chamber increases the Q factor; it may or it may not. The next step after that will be to incorporate the silicone spray Dr. March recommended to me to see how well it protects against oxidation. I didn't want to incorporate this spray until I knew the chamber worked in case a misapplication of the spray caused a problem that prevented the chamber from working.

Testing the chamber under full expected power will take a lot of preparation. I have partially constructed a faraday cage in which to test it that is big enough for some levers to amplify the measured force. It's a bit complicated, and getting power into the cage without it leaking the powerful microwaves out has been tricky.

I also have been starting to construct the experiment controller, with the foundation for control circuitry for the satellite inside it. That part is designed roughly in my head, and I've only just started to get it out into code.

I will keep you posted.