Mach Effect progress

[dkfenger]

Conclusion: you cannot ignore the nature of a non-inertial frame of reference and have more than a toy model.

That's not 'analysis'. That's somewhere between handwaving and giving up.

GR and SR closely follow Newtonian results in well defined regimes - inertial frames, minimal spacetime curvature, velocities well below c.

Oh, and I have been following this for some time, though I'd missed your innumeracy until recently. Does explain a lot, though.

I ask again, do you have *any* useful numbers for what sort of static thrust a M-E thruster should be able to develop for a given input power? Assume that the new ceramics scale as Dr. Woodward hopes.

I'll try to work out the rest myself - I've got a 200-level physics text that covers both SR and GR, a basic working knowledge of tensor calculus, and some decent mathematical software to play with.

[GIThruster]

Well you're not asking again. This is the first time you've asked for real M-E numbers.

The highest thrusts Jim has gotten were 130uN with about 1 watt dissipated. This is higher than the thrust efficiency of a Hall thruster.

However I would remind you of what was just quoted from Goat Guy posted over a year ago at NBF: it does not matter what number you choose for K. If it does not vary, any thruster will go overunity. Just as he notes:

"Which is to say the kinetic energy rises per the square of time ... since the K and E and M are constants. But, the energy put into the system is linear over time."

This problem arises because people just won't get it through their thick skulls that k is not constant (or better, "invariant").

It's not handwaving to note this problem only comes up with people who didn't pay attention how to avoid this mistake when their high school teachers told them DON'T DO THIS and who can't be bothered to learn what non-inertial frames entail.

[GIThruster]

Lets take another exmaple.

Since V is relative, lets look at the case of a chemical thruster with 3 minutes of fuel aboard. Use the numbers in GG's example and start with the thruster leaving it's boost stage 1 minute before it is due to go overunity.

The thruster will appear to go overunity, and it is a chemical thruster.

The reason is, the thruster is accelerating, and in order to relate the constant force exerted by the thruster in its own rest frame, one needs to use a transform that will vary the force as seen from the launch frame, or the frame the thruster is accelerating in.

This problem occurs with all thrusters, regardless of type.

[Skipjack]

The highest thrusts Jim has gotten were 130uN with about 1 watt dissipated.

That would equal 1.3 newton at 10 KW. That is about 20 times as much as a hall effect thruster. Do you have any numbers about how much a 10 KW ME thruster would weight?

[GIThruster]

Do you have any numbers about how much a 10 KW ME thruster would weight?

I'm sorry, I don't. The current test article is not in any way optimized for weight because it needs to have things like an easily accessible Faraday cage and it uses a bulk hunk of brass as it's reaction mass. Commercial grade thrusters wouldn't necessarily have these drawbacks, since for example they could use lighter weight Bragg reflectors. Also if Jim moves to CCTO next one expects this would drop the weight significantly since there's no lead in it, and at higher frequency you use a thinner ceramic mass but should get higher thrust. So using today's thrust to weight (which to the best of my knowledge has never been measured) would not tell one what to expect even in the next generation of pre-prototypes.

My guess though, is that the test item as exists today, with all the extra weight, masses out at much less than a comparable Hall thruster complete with its propellant for a 10 year mission. The issue is getting these M-E thrusters to last that long, and this is well served by going to a ceramic that is cubic and so cannot depolarize the way PZT does. PMN and CCTO are both cubic at the temperatures they're commonly used at.

[Skipjack]

Do you have any numbers about how much a 10 KW ME thruster would weight?

I'm sorry, I don't. The current test article is not in any way optimized for weight because it needs to have things like an easily accessible Faraday cage and it uses a bulk hunk of brass as it's reaction mass. Commercial grade thrusters wouldn't necessarily have these drawbacks, since for example they could use lighter weight Bragg reflectors. Also if Jim moves to CCTO next one expects this would drop the weight significantly since there's no lead in it, and at higher frequency you use a thinner ceramic mass but should get higher thrust. So using today's thrust to weight (which to the best of my knowledge has never been measured) would not tell one what to expect even in the next generation of pre-prototypes.

Ahh ok, I was hoping that you guys had already made some calculations on what future thrusters could look like, provided the theory works out.

[GIThruster]

If you want my guess (yes, I'm sometimes willing to guess) it will use a thin film of CCTO sitting on a multi-layer Bragg reflector and running in the Ghz region, without a preload apparatus. I don't know why FBAR's don't require preloads to avoid decomposition, but I would certainly love to find out. They must generate billions of gees. So far as I can tell they ought to go bits flying everywhere and they don't. Running without a preload would simplify a huge number of issues and enormously drop the mass.

[dkfenger]

Well you're not asking again. This is the first time you've asked for real M-E numbers.

Ah, sorry. I rewrote the post where I asked for K scaling a few times, and I must have edited that bit out in the final version.

The highest thrusts Jim has gotten were 130uN with about 1 watt dissipated. This is higher than the thrust efficiency of a Hall thruster.

However I would remind you of what was just quoted from Goat Guy posted over a year ago at NBF: it does not matter what number you choose for K. If it does not vary, any thruster will go overunity.

I think I have a way around that, but I probably won't dig into it in detail until the weekend. First I have to find that text...

Is the power to thrust ratio expected to improve with the higher frequencies and the new materials? Do you have even a ballpark guess for how much?

[djolds1]

OMGG!!

what??? Chrismb got so surprised by GIT´s admission that he refered to himself in FIRST PERSON!!!!

what does the M in OMG stands for?? "MY"!! That´s first person. Chrismb should have written OHG ("Oh his God")

ROFL!

[GIThruster]

Is the power to thrust ratio expected to improve with the higher frequencies and the new materials? Do you have even a ballpark guess for how much?

Yes. According to the value tables I've seen created by Paul March based upon the maths of Andrew Palfreyman, there are several qualities that can create significant scaling. However, each of these create their own unique issues and challenges.

The first is frequency. M-E and force rectification both scale exponentially with frequency. One trouble with this is, creating preloads that can keep up with these higher frequencies is a HUGE challenge. Hook's spring force laws are a BITCH.

Dielectric constant is a scaling factor. We want higher k materials and they are at hand.

Dielectric strength is an important factor. It doesn't much matter what the effective k is of a bulk material if the standoff it provides won't allow this to be used.

There is the issue whether to use piezo-ceramics or electrostrictors, or materials that have both qualities, like the PZT Jim is using at present. There's the issue that if you move to a material that provides one and not the other, you then need to provide a driving signal with the 1W+2W waveform and you can't get this with naive power systems suited only to a simple, screwed-up sine wave.

There are others. And there are the challenges that go with things like operating at higher frequencies and demanding more structural integrity from the ceramic. The tradeoff's are complex. All I an tell you now is, PMN, PMN-PT and CCTO are all in the running for next gen ceramics.

Want my guess? If we can conquor all the mitigating issues and run with ideal ceramics and power systems, we can see 10 or more orders magnitude improvement in thrust efficiency.

That's more than enough to enable human spaceflight.

Lets take an example. At 40 Khz, Jim's current PZT has a k of <1,000.

CCTO if properly prepared in nano-crystal, sintered properly and with electrodes properly applied with sputtering, or better diffusion bonding, has a k value at 40 Khz as high as 50,000.

IIRC, M-E production scales cubic with k, and force rectification is quadratic with k.

Do the math. We're looking at several orders magnitude improvement in stationary thrust efficiency just by moving to the next ceramic.

This is a BIG deal.

But note, CCTO is an electrostrictor. It does not provide a piezo-response at all, so you need to drive it with a complex 1w+2w waveform. Doing this with assurance requires some serious electrical engineering. That's what we expect to see in the next year, compliments of the Ivy League PhD EE who I met here on T-P 2+ years ago.

[chrismb]

---

[kurt9]

The CCTO's I've read about tend to loose their high dielectric constant at high frequencies. They are good up to about 100KHz. My understanding from Woodward's papers is that MHz operating frequencies is needed for effective propulsion device. They also have relatively high tangent loss. There is effort in the research community of these materials to overcome both of these limitations. Its not clear to me if they can.

Most CCTO work is thin-film material for thin-film applications (semiconductors, telecoms, etc.). Mach propulsion requires bulk form of these materials. Making these materials in nano-particle form is necessary to reduce the decay of these materials due to thermal effects, to increase operation lifetime.

[chrismb]

The chrismb post looks like it was withdrawn having thought better of trying to continue some debate with GIT.

But there is now a new chrismb post at viewtopic.php?t=4190 giving a full analysis and rebuff of any claim that propellant thrusters thermodynamically 'violate' over-unity.

In fact, the analysis also happens to show why a 'non-propellant thruster' is physically unrealistic.

It looks like chrismb was none-too impressed with the previous analyses, too many ways to argue they weren't right, so has preferred to use partial differential calculus to make the point rather than use a numerical argument.

Hopefully, that draws an end to chrismb posts. The forum has had enough of silly arguing between objective arguments and 'touchy-feely-handflappery' arguments.

[GIThruster]

The CCTO's I've read about tend to loose their high dielectric constant at high frequencies. They are good up to about 100KHz.

Yes, there is definitely a trade happening. I think though you still have 10^4 k values at 1 Mhz. It definitely depends upon things like what size crystals you use, how they're sintered, whether they're polished, how the electrodes are put on. There's an enormous difference for example between silver paint and gold sputtering. . .something like 40%. This is the kind of thing that needs a paid study to determine the best course.

[kurt9]

The CCTO's I've read about tend to loose their high dielectric constant at high frequencies. They are good up to about 100KHz.

Yes, there is definitely a trade happening. I think though you still have 10^4 k values at 1 Mhz. It definitely depends upon things like what size crystals you use, how they're sintered, whether they're polished, how the electrodes are put on. There's an enormous difference for example between silver paint and gold sputtering. . .something like 40%. This is the kind of thing that needs a paid study to determine the best course.

My understanding was that high MHz operating frequencies were desired for a thruster device. The higher frequency performance most likely can be improved with smaller grain-size (nano-crystalline?) and better sintering. This may also reduce the tangent loss as well. Bonding of the electrodes with sputtering process is necessary, although this requires a sputtering process system or at least access to one in a job shop. Much of this materials work has been beyond the very limited financial resources that Woodward has been able to put into this effort.

CCTO is the high dielectric materials that has received the most attention from researchers. However, there is a similar material. LSNO (La15/8Sr1/8NiO4) that offers 50K dielectric constant up to GHz operating frequencies. However, this material also has high tangent loss as well. I don't know if making these materials in nano-grain form and with the proper binding technique can reduce the tangent loss or if this is an intrinsic property of these materials that cannot be overcome.

In any case, these materials have to be made either in nano-particle form (e.g. nano-crystalline grain size) with the proper sintering or, much less likely, in single-crystal form, in order to overcome thermal degradation and improve operating life-time.

The electrical engineering involved in making the "circuit" is also quite daunting, as you have pointed out. Despite having a BSEE, I have not done much circuit design in my career and am clueless as to resolving this challenge.