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Frequency yes, I recall they wanted an electrical engineer with a master's to design a new power supply though. Apparently they don't come off the shelf at the lower levels Woodward needs at the frequencies a better thruster would operate at.

kunkmiester wrote:Frequency yes, I recall they wanted an electrical engineer with a master's to design a new power supply though. Apparently they don't come off the shelf at the lower levels Woodward needs at the frequencies a better thruster would operate at.

Did they ever specify what frequency range they needed, and into what capacitance through what inductance, and with the varying parasitic resistances? And for that matter if a perfect sine was best, or if they needed more a catenary*?

*It needs a steady 2nd derivative of rate of charge, right? And if a catenary, to what loading profile vs 2pi?

I think it was talked about either in this thread, or in a previous MET thread. That was also where talk of the new dielectric and why it was chosen was.

I might look it up later, but as I recall they wanted something in the gigahertz range or even higher, and with a few hundred watts, apparently they don't make power supplies like that off the shelf. There was also trouble with a piezoelectric material that could run that high too.

Both the dielectric and electrostrictive materials (what you're calling the piezoelectric) have to operate in the GHz range and show no thermal decay or variance due to thermal effects. The current colossal dielectrics do not work well in the GHz range and tend to decay due to thermal effects. The latter is the issue limiting the lifetime of these materials.

There are the colossal dielectric materials (k=50,000 or greater) that are being developed by industry for better capacitors and what not. There are also the "colossal" electrostrictive materials being developed by industry for MEMS applications. These are the materials technologies necessary to realize effective MET's. Thermal decay is one effect that limits the lifetime of these materials. The electrostructive material is physically active (e.g. mechanical) and there are lifetime issues with this as well.

Are we seriously talking about a device mechanically vibrating at GHz frequencies? micro-meter acoustic wavelengths? (Assuming sound speed through material faster than through air.)

hanelyp wrote:Are we seriously talking about a device mechanically vibrating at GHz frequencies? micro-meter acoustic wavelengths? (Assuming sound speed through material faster than through air.)

https://en.wikipedia.org/wiki/Radio_fre ... cal_system

painlord2k wrote:

hanelyp wrote:Are we seriously talking about a device mechanically vibrating at GHz frequencies? micro-meter acoustic wavelengths? (Assuming sound speed through material faster than through air.)

https://en.wikipedia.org/wiki/Radio_fre ... cal_system

I think from reading the linked article those are MEMS devices where the MEMS movement is far slower than the GHz range, but it is moving to tune and select circuits operating in that range.

MEMS devices certainly operate in the 100's of MHz, though. If I remember the MET equation correctly, for stable materials but with a far higher freq, in the 100's of MHz but far lower k, the thrust should be on the order of 100's of mN, plenty for pointing and station keeping, and unequivocal proof of concept.

I would imagine devices running at far lower frequencies will happen eventually, if only by hobbyists. Once details are worked out, they should be easier to make. High school science projects should be easy, building space ships in garages less so. That's part of the excitement for some of these technologies though, they don't take giant assembly lines, billion dollar lithography plants, or such to produce. While you probably wouldn't want to build a spaceship in your garage, fab shops making custom craft shouldn't be hard.

kunkmiester wrote:I would imagine devices running at far lower frequencies will happen eventually, if only by hobbyists.

I hate to tell you, I thought my clear point was the lower frequency devices are what has been built and tested. Because of the way thrust scales with frequency, I was suggesting a 100's of MHz MEMS device should be built, because it hasn't been done yet.

kunkmiester wrote: While you probably wouldn't want to build a spaceship in your garage

You're kidding, right?

Having been in the Air Force, and in manufacturing...let me put it this way, Spacex has been QC issues, imagine what that will look like in most garage shops.

I'd love to have a spaceship in the garage, but I'd hate to have the paperwork that comes with it these days.

kunkmiester wrote:Having been in the Air Force, and in manufacturing...let me put it this way, Spacex has been QC issues, imagine what that will look like in most garage shops.

This claim has been debunked. SpaceX has no QC issues. The problem they ran into is a rare occurrence that even more rigorous testing could not have discovered. Also want to remind that Lockheed, Boeing and ATK have all had their share of problems in the early days. SpaceX is innovating very quickly. That is why they are running into problems that no one has ever seen.

In you innovate faster than others, you run into problems faster than them.
It is like approaching the speed of light.

"Speed Kills"

Sage advice I received years ago. :p

I'll have to retract that, it makes it sound much worse than it is. If they have trouble with that though, imagine trying to do it in a garage.

Point remains, to get a reasonably safe ship, you either need a lot more paperwork than I'd like to do in a garage, or a lot of work to build systems that take less work to certify. Just putting a pile of Mach effect thrusters in the bottom of a Dragon will be way too expensive for a garage, and will take too much work to keep man rated.

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