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#240
by
Stormbringer
on 07 Aug, 2014 04:34
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well don't overlook another possibility. if these things work the final form might not be a single big device or set of big devices. the final form might be thousands (or millions) of tiny ones in some sort of array
a drive on a chip.
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#241
by
aero
on 07 Aug, 2014 05:13
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well don't overlook another possibility. if these things work the final form might not be a single big device or set of big devices. the final form might be thousands (or millions) of tiny ones in some sort of array a drive on a chip.
Yes, they could be pretty small but the size of the resonance cavity is driven by the frequency of the RF power. At 2 GHz the cavity is about 7 cm x 3.5 cm (length doesn't matter) and working with higher frequencies gets more challenging. But that's all I know about that.
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#242
by
GregA
on 07 Aug, 2014 05:25
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Yes, every floor could have them, which alters the structural strengthening needed.
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#243
by
Stormbringer
on 07 Aug, 2014 05:48
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But if the driver freq was in terahertz or...? or the form of the device was the solid state version Woodward favors?
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#244
by
IslandPlaya
on 07 Aug, 2014 05:52
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Getting back to EM Drive, am I correct in thinking that the higher the frequency the more power consumed and the smaller the RF resonator?
I'm trying to guess how large a mature EM Drive might be physically? (Assuming that it does mature.) I'm pretty sure that the power sources would be a lot bigger than the EM Drive itself.
From what I've read it doesn't look like there is any reason to hang the drives off the tail end of the spaceship, rather just set them in the electronics bay, or maybe in the Captain's cabin. Of course they would need to be attached to a thrust structure. If you wanted redundancy you could just weld 20 or so of the 5% sized EM Drives on the stern of your spaceship.
I'm hoping that by the end of the year we can start speculating configurations in earnest.
I like this. Do we need to wait until further confirmation to speculate on spacecraft configs?
We all know that the propellant-less thrust effect may be false, but shirley it is worth exploring.
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#245
by
Stormbringer
on 07 Aug, 2014 05:55
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I favor in between the outer hull and the pressure vessel wall with various orientations to provide agility.
EDIT: maybe a couple of panels of them or maybe 4 panels mounted on gimbals to change the orientation through a spherical 360 degrees.
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#246
by
IslandPlaya
on 07 Aug, 2014 06:00
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I think a puller config would be best. So mount these things at the prow. Yes?
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#247
by
Stormbringer
on 07 Aug, 2014 06:04
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they really could go anywhere if they were attached to some significant structure of the ship like a keel or the 'tween hulls. so up front should work. but why not go for a configuration that negates the need for a separate set of maneuver engines thrusters? make them mobile or have some for each axis.
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#248
by
Stormbringer
on 07 Aug, 2014 06:10
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i guess if you had them inside the pressure hull you could maintain or replace modules while in a shirt sleeve environment. your engineers would thank you.
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#249
by
IslandPlaya
on 07 Aug, 2014 06:33
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I guess you would have separate cavities for each axis. You would need them fore and aft for rotation.
They all would have to be superconducting. I think that would be best done outside the pressure hull. Not sure.
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#250
by
aero
on 07 Aug, 2014 07:25
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Why would they need to be superconducting, the test articles weren't?
And I wonder if somehow some RF electronics wizard could manage to change thrust direction electronically. Doesn't matter to much, these things are small and low mass. But before I can decide whether to mount them inside or outside the pressure hull, I'd like to know for sure that the hull doesn't interfere with the drive and that the drive isn't a safety hazard for the crew. If that's all OK I might mount the control thrusters inside the pressure hull in cabinets near the same relative locations where we currently mount them.
As for the main drives, I think I would distribute them throughout the ship to reduce the need for massive force transfer structures from the engines to the rest of the ship structure. I might even double them up with each pair having a forward and a reverse thruster. Heck, I might even do away with the bow and stern idea, and build a double ender, with a bow on both ends. That way there would be no need for a turn over maneuver, just put it in reverse. Of course the thrusters could be swiveled, instead. There are no rigid fuel lines, just a flexible microwave cable. Need to look at reliability to decide.
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#251
by
aero
on 07 Aug, 2014 07:35
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I did some thrust calculations for the truncated cone EM Drive using F = .0912 mN at 17 W input power. I then ranged jet energy from 10 to 17 watts.
Calculated Isp ranges from 22,400 s (10 W) to 38,000 s (17 W)
Calculated mdot, ranges from 4.16E-10 kg/s (10 W) to 2.45E-10 kg/s (17 W).
That is a nice range to be in.
If I assume the power electronics are 60% efficient, jet energy is 10.2 W, so Isp = 22,800 seconds and mdot = 4.08E-10 kg/s.
Now all that is needed is a theroy of where that mdot comes from and where it goes to! It does occur to me that if we knew the amount of waste heat coming off the EM Drive we could estimate the jet energy from the experiment using total energy = jet energy + waste energy.
------------------
1) Thrust, F = mdot * Ve, and
2) jet energy, E = 0.5 mdot * Ve^2
substituting 1) into 2) clears mdot and gives
E = 0.5 F * Ve so Ve = 2* E /F . Now calculate mdot from 1).
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#252
by
Stormbringer
on 07 Aug, 2014 08:26
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well i don't know about shayer's...but is the thermal trace that woodward graphs the waste heat?
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#253
by
Star One
on 07 Aug, 2014 15:58
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For what it's worth I speed-read a lot of things and I'm good at it.
I am still going over the NASA paper properly.
So far I think that they have been very careful about outside influences.
Ion wind, heat based stuff not so much... I will continue pouring over it.
How about testing in hard vacuum with a Tesla cage around it?
You mean Faraday cage supposedly...
Yes I don't know why I said Tesla.
The reason I mentioned those two is I saw a number of online commentators claiming these are the sort of tests it needed to be subjected too.
Far be it for me too suggest they were setting deliberately high hurdles.
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#254
by
aero
on 07 Aug, 2014 18:33
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#255
by
Star One
on 07 Aug, 2014 19:01
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#256
by
IslandPlaya
on 07 Aug, 2014 20:13
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Here is an article with a more accepting slant. Still has errors but what can you do. The tests were NOT performed in vacuum.
http://www.wired.co.uk/news/archive/2014-08/07/10-qs-about-nasa-impossible-drive
It does make one very important point that is there is no agreed theory on how high temperature superconductors work but because they have been replicated so many times we know they do.
There has actually been a paper on high-temp superconductors published recently, explaining how they work. It is supported by computer codes to simulate them as well. Sorry can't find the link at the mo.
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#257
by
aero
on 07 Aug, 2014 20:28
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Here is an article with a more accepting slant. Still has errors but what can you do. The tests were NOT performed in vacuum.
http://www.wired.co.uk/news/archive/2014-08/07/10-qs-about-nasa-impossible-drive
It does make one very important point that is there is no agreed theory on how high temperature superconductors work but because they have been replicated so many times we know they do.
There has actually been a paper on high-temp superconductors published recently, explaining how they work. It is supported by computer codes to simulate them as well. Sorry can't find the link at the mo.
Doesn't matter. They worked for a long time before anyone figured out how. EM Drive, if verified to work, is in that stage before anyone has figured how.
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#258
by
aero
on 08 Aug, 2014 00:14
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Does anyone know if the classic EM Drive has ever been operated with a strain gauge attached to the end plates? That should be an easy way to prove or disprove the pressure idea of operation of the device.
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#259
by
sanman
on 08 Aug, 2014 02:30
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I, for one, am glad if the NASA team's test results announcement has created a flutter. At least this will encourage more experts to get involved in coming up with either a definitive proof or disproof on this matter. At least one way or the other, the matter can then be settled.
a drive on a chip.