EM Drive

Point out news stories, on the net or in mainstream media, related to polywell fusion.

Moderators: tonybarry, MSimon

Aero
Posts: 1200
Joined: Mon Jun 30, 2008 4:36 am
Location: 92111

Re: EM Drive

Postby Aero » Fri Aug 08, 2014 1:13 am

Tom - I sure would be interested in following your progress should you decide to make one of these drives. I bet I'm not alone in my interest. Much better if you do it than some anonymous laboratory that none of us know except by reputation. You we could believe, and if it is a conspiracy then you could tell us how much your pay-off was to claim success. :lol:

Also, you could put a strain gauge on it to tell if it is pressure or something else causing the detected force. Assuming you can make it work that is, but I'm pretty sure you could if there is anything there. Just don't forget the dielectric RF resonator, it doesn't work without that.
Aero

birchoff
Posts: 200
Joined: Sun Jul 27, 2014 7:11 pm

Re: EM Drive

Postby birchoff » Fri Aug 08, 2014 1:36 am

Tom Ligon wrote:Also sounds like they were running at high vacuum. Turbopumps, outgassing for a couple of days ... I'll read in more detail.


This part is a bit suspect. the NTRS Abstract claims they didnt test at high vacuum. The paper describes how they tested at high vacuum. Then the "Summary and Forward Work" says due to not having a vacuum capable RF Amp they didn't test at vacuum. I personally have interpreted this inconsistency to mean they haven't done a hard vacuum test. Would be interested to hear what you think.

Tom Ligon
Posts: 1871
Joined: Wed Aug 22, 2007 1:23 am
Location: Northern Virginia
Contact:

Re: EM Drive

Postby Tom Ligon » Fri Aug 08, 2014 1:56 am

birchoff wrote:
Tom Ligon wrote:Also sounds like they were running at high vacuum. Turbopumps, outgassing for a couple of days ... I'll read in more detail.


This part is a bit suspect. the NTRS Abstract claims they didnt test at high vacuum. The paper describes how they tested at high vacuum. Then the "Summary and Forward Work" says due to not having a vacuum capable RF Amp they didn't test at vacuum. I personally have interpreted this inconsistency to mean they haven't done a hard vacuum test. Would be interested to hear what you think.


I'll have to review the whole paper.

Depending on the model, a microwave oven magnetron likely WILL operate in a vacuum chamber. We found a model (tearing down an discarded microwave from RWB's kitchen) that was capable of vacuum sealing its antenna end into a chamber. I had a 4.5" CF cover plate machined to accept it, and added a reflecting cone. We launched microwaves into PXL-1 with ti quite nicely. There's no fine tuning a microwave oven magnetron, though ... you would have to fine tune the antenna, cavity, etc.

They were using coax, so could have used hermetically sealed coax connectors, and put the electronics into a gas-filled box, in the chamber.

I want a close look at the torque data. A torsion beam apparatus has an enormous moment of inertia relative to the torsion filament's torque. I'm curious about the dynamics. The pulses look about 30 seconds long, the instrument responds in maybe a second. How much movement is involved and what does this torsion element look like ... need to check. It seems amazing that the reading can stabilize in a second. But the calibration scheme sounds credible.

One of my jobs in the UAV biz was moment of inertia tests of UAVs to get data for flight dynamics calculations. We used a 2-filament support scheme (bifilar pendulum method). You measure the period of oscillation, and even with two filaments these things oscillate a long time. A single filament offering almost zero torque seems like it ought to oscillate like crazy with an extremely long period. Realizing they use magnets and a conductor to dampen it, still, it has to move for that to work. I know torsion filaments have been around for a long time and do work, but my gut says 1 second responses are on the fast side. The instrument is probably fine, but I'd want to think hard on it.

I've made strain gage torque-measuring devices, but not for micronewtons. MAYBE that would work. To get sensitivity up usually also means raising power dissipation in the strain gages, and heat dissipation would be worse in a vacuum. Working with tiny gages is not conducive to sensitivity due to power density. Working with very thin-walled small diameter tubing also limits heat dissipation. I can datalog at 18 bits, and 24 bit ADCs are common now ... one could imagine one has the sensitivity but then actually try it and find out that any signal is buried in noise and overcome by drift from 10 sources. I'd be happier with newtons. 0.4 N at a kW would be great.

Notice that they got interference feeding DC to the apparatus due to shifts in the magnetic field around the leads.
Last edited by Tom Ligon on Fri Aug 08, 2014 2:09 am, edited 1 time in total.

Aero
Posts: 1200
Joined: Mon Jun 30, 2008 4:36 am
Location: 92111

Re: EM Drive

Postby Aero » Fri Aug 08, 2014 2:04 am

birchoff wrote:
Tom Ligon wrote:Also sounds like they were running at high vacuum. Turbopumps, outgassing for a couple of days ... I'll read in more detail.


This part is a bit suspect. the NTRS Abstract claims they didnt test at high vacuum. The paper describes how they tested at high vacuum. Then the "Summary and Forward Work" says due to not having a vacuum capable RF Amp they didn't test at vacuum. I personally have interpreted this inconsistency to mean they haven't done a hard vacuum test. Would be interested to hear what you think.


I interpreted it to mean that the system is configured to test articles in vacuum and they described how that works, but they did not test these articles in vacuum because of the power supply capacitors. I don't know why they didn't replace the capacitors but it may have been an off-the-shelf power supply that they didn't feel confident to modify.

Or it could be that they were under time pressure and didn't have time to allow the chamber to pump down even if they had used vacuum compatible power supplies. After all, they wrote that it takes several days to draw down to vacuum, for each time they open the door. That would have added a lot of time to their already tight schedule (6 days of testing, IIRC).
Aero

Tom Ligon
Posts: 1871
Joined: Wed Aug 22, 2007 1:23 am
Location: Northern Virginia
Contact:

Re: EM Drive

Postby Tom Ligon » Fri Aug 08, 2014 2:14 am

Did I see in there that they used the electronics as the counterweight?

I think I would have put the electronics as close to the axis as possible, to minimize any effect power would have creating torque due to stray magnetic effects. Put an inert mass out to counterweight the pendulum.

GIThruster
Posts: 4686
Joined: Tue May 25, 2010 8:17 pm

Re: EM Drive

Postby GIThruster » Fri Aug 08, 2014 3:07 pm

"Stray magnetic effects" are very easy to identify and cope with. You can just walk around the balance with a magnet and look for coupling. If you find it, there are plenty of simple solutions, so magnetic coupling is really not top of the list of priorities.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

hanelyp
Posts: 2255
Joined: Fri Oct 26, 2007 8:50 pm

Re: EM Drive

Postby hanelyp » Fri Aug 08, 2014 6:01 pm

I'm looking at photon pressure through the feed line producing forces of similar magnitude to what I'm seeing cited for measurements, especially if there's a feed mismatch at the device end.
The daylight is uncomfortably bright for eyes so long in the dark.

Aero
Posts: 1200
Joined: Mon Jun 30, 2008 4:36 am
Location: 92111

Re: EM Drive

Postby Aero » Fri Aug 08, 2014 11:52 pm

We saw that high school students can make operable fusors. How much more complicated would it be to make an EM thruster? How did it come about that HS students started making fusors for their science projects? Was it Tom going around giving talks to science students and telling them how to make one? I ask, because I don't know.

Anyway, the EM Drive has been around for a few years now, I wonder if there have been projects tried but failed so we didn't hear about them. Probably. I wonder if there have been any projects tried with some success that we still didn't hear about?

Edit add: There was a link given in the OP, back in Sept. 2009, http://emdrive.com/ which has been added to since. There is some good information there. I particularly liked the professional English translation of the Chinese paper from 2012. For one thing, they discovered the problem that was causing the thrust measurement to bounce around when they run power up from 300 watts to 2500 watts. It turned out to be the klystron they used. It did not uniformly output the power that was input. When they measured the klystron output and used that data with their thrust measurements, they found the thrust to power behaved much more rationally.
Aero

GIThruster
Posts: 4686
Joined: Tue May 25, 2010 8:17 pm

Re: EM Drive

Postby GIThruster » Sat Aug 09, 2014 2:19 pm

Aero wrote:We saw that high school students can make operable fusors. How much more complicated would it be to make an EM thruster?

According to Paul, the trouble they had the first time around was they could not pull hard enough vacuum because they had chosen a copper cavity and the vapor pressure of copper would not allow the vacuum they needed to avoid corona discharge. So the required vacuum is likely very hard and difficult to see it as part of a high schooler's capability, though one never knows. One does know however that such a thing, even if inside the ability of a high schooler, is VERY expensive. These vacuum systems and stainless chambers are six digit items, and the balance and thruster go on top of that. So even if you have the labor for free as with students, you're looking at serious funding.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

John Gallagher
Posts: 20
Joined: Sat May 10, 2008 3:35 pm
Location: Winter Park Florida

Re: EM Drive

Postby John Gallagher » Sat Aug 09, 2014 3:48 pm

I must have missed something here. The vapor pressure of copper is way down in the UHV range even at 500C. Are they talking about outgassing due to electroformed copper or is this just bull pulled out of the quantum vacuum? :lol:

GIThruster
Posts: 4686
Joined: Tue May 25, 2010 8:17 pm

Re: EM Drive

Postby GIThruster » Sat Aug 09, 2014 5:31 pm

It's been some years since that conversation but I relayed it as best I can. Could be I am wrong but remember that even a good vapor pressure is not good enough when you begin pulling E-6 or better.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

Tom Ligon
Posts: 1871
Joined: Wed Aug 22, 2007 1:23 am
Location: Northern Virginia
Contact:

Re: EM Drive

Postby Tom Ligon » Mon Aug 11, 2014 1:42 am

Aero wrote:We saw that high school students can make operable fusors. How much more complicated would it be to make an EM thruster? How did it come about that HS students started making fusors for their science projects? Was it Tom going around giving talks to science students and telling them how to make one? I ask, because I don't know.



What came about was that I showed a very crude fusor to the Tesla Coil Builders of Richmond at a Teslathon put on a the home of Richard Hull. Richard very quickly out-built me and then he and several others in the group pretty much created the Amateur Fusion Movement, leading to fusor.net and all those kids building fusors. The spark can't take much credit for the force of the explosion when the powder keg goes off. Me, spark. TCBOR: keg.

The result was that TCBOR renamed itself HEAS (High Energy Amateur Science?), and switched from mostly Tesla coiling to Fusors and a number of other sparks and sizzles experiments. Some time in there, Richard literally inherited the Electric Spacecraft Journal, a publication that would love papers on EM propulsion.

I have not been over to hang around at fusor.net for some months, but I'd not be surprised to find a line of tinkering in this going on there, and some of that crew have the equipment on-hand to work on it. This would be a perfect HEAS project.

Aero
Posts: 1200
Joined: Mon Jun 30, 2008 4:36 am
Location: 92111

Re: EM Drive

Postby Aero » Mon Aug 11, 2014 2:34 am

Well Tom, as you are proven to be a "Spark," maybe you would shoot a spark in a few directions to see if something ignites, or has ignited? But then I guess you might be reluctant to divert effort from successful experimentation, fusors, to something which may never actually work, EM Thrusters. I understand. It's not as simple as saying, "Hey guys, waste some time to see if you can make one of these work." But then, maybe they would like to waste some time to see what the flaw in the set-up is that causes White, Ling and Shayer to publish positive results.

And there's also the problem that a working fusor is kind of flashy, but a barely detectible EM Thruster force, not so much.
Aero

GIThruster
Posts: 4686
Joined: Tue May 25, 2010 8:17 pm

Re: EM Drive

Postby GIThruster » Mon Aug 11, 2014 5:57 pm

Tom Ligon wrote:Depending on the model, a microwave oven magnetron likely WILL operate in a vacuum chamber. We found a model (tearing down an discarded microwave from RWB's kitchen) that was capable of vacuum sealing its antenna end into a chamber. I had a 4.5" CF cover plate machined to accept it, and added a reflecting cone. We launched microwaves into PXL-1 with ti quite nicely.

IIRC, back when Paul and Sonny were building their first Shawyer resonator in 2007, what they found was they could not use a $20 microwave oven magnetron because it is not intended to cope with standing waves found in a resonator. It's only intended for the low power wave generation it is used for and for standing waves they had to purchase a much higher power tube from Russia. If you're seriously interested in this kind of project I suggest you contact Paul and ask his advise on this. He's a very approachable and amiable guy.

I've made strain gage torque-measuring devices, but not for micronewtons. MAYBE that would work.

My survey of all the micronewton balances and such available today suggests that the ARC Lite style used by the Austrians, Jim and Eagleworks is much better than the only viable alternative which is a suspension pendulum. Strain gauges have all sorts of troubles, from coupling to too short a period. You don't want a short period to measure these thrusts, and you want the balance to be well damped. You can get the specs for this sort of balance from several places, probably including Paul. Note though, that the balance is only a small portion of the requirement to work with micronewton thrusts. You need the instrumentation. You need decent vacuum, at least E-3T. That means a chamber and pumps, etc. Qualifying the setup normally takes about a year. Building the thruster is usually the easiest part of this task. Even the power supply for it normally requires more than to build the thruster itself.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

hanelyp
Posts: 2255
Joined: Fri Oct 26, 2007 8:50 pm

Re: EM Drive

Postby hanelyp » Mon Aug 11, 2014 9:53 pm

If not accounted for standing waves can shred your experimental results with high voltages, currents, and higher than expected forces.
The daylight is uncomfortably bright for eyes so long in the dark.


Return to “News”

Who is online

Users browsing this forum: No registered users and 9 guests