### Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2484806 times)

#### SeeShells

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3440 on: 05/15/2015 08:58 PM »
The search function aren't that super here euuuuu.

Why is the RF injected into the side of the EM Device. I know it's a basic question but can someone expand on it a little more?

Shells

#### deltaMass

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3441 on: 05/15/2015 09:15 PM »
The technique will come into its own when alignment over at least one million Km is feasible.

Now you'll notice that they were in a clean room (albeit in air) so that should give pause to anyone considering using this as a launch system for extremely light payloads directly from Earth's surface.  Nevertheless, a little noodling would not go amiss on this topic.

The available motive power is Q*P (Q=200, P=800 W in the video), so the force F = 2*Q*P/c (1.1 mN in the video), so the acceleration a = F/m (m=0.45 Kg, a = 2.5 mm/s2 in the video).

What would it take to get up to 1 gee for an Earth-based launch?
The acceleration needs to be increased by a factor of ~4000x.
Putting this all together we get
a = 2 Q P / (m c)
Leaving m alone for the moment, Bae states that Q could improve by a factor ~5x (200->1000).
Now we need 4000/5 = 800x improvement.
Using a 800 kW laser does that for us (1000x).
Alternatively we can use a lower mass and thus a lower power laser.

#### deltaMass

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3442 on: 05/15/2015 09:22 PM »
The search function aren't that super here euuuuu.
To be blunt, it totally sucks

#### jmossman

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3443 on: 05/15/2015 09:32 PM »
The search function aren't that super here euuuuu.

Why is the RF injected into the side of the EM Device. I know it's a basic question but can someone expand on it a little more?

Shells

No one else has chimed in, so I'll give this a shot.

I believe the choice of antenna position is predominantly a function of the antenna beam pattern, and the desire to couple maximum energy into the cavity.

A simple dipole antenna radiates/couples well in the perpendicular direction, so placing a dipole antenna perpendicular to the cavity wall would allow direct coupling into the dominant resonant direction (i.e.  between the concave/convex end plates).

(attached image from http://www.trevormarshall.com/byte_articles/byte1.htm)

I had proposed (many pages back) that the use of a waveguide to inject a magnetron's signal had the effect of a directional beam pattern that was much better at injecting energy than removing energy from the cavity. (since resonanting energy is dominantly between the end plates, a waveguide input roughly perpendicular to the walls would inject energy better than remove energy)  However, I'll readily admit my reasoning may be overly simplistic.

Thanks,
James
« Last Edit: 05/16/2015 12:22 AM by jmossman »

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3444 on: 05/15/2015 09:48 PM »
The technique will come into its own when alignment over at least one million Km is feasible.

Now you'll notice that they were in a clean room (albeit in air) so that should give pause to anyone considering using this as a launch system for extremely light payloads directly from Earth's surface.  Nevertheless, a little noodling would not go amiss on this topic.

The available motive power is Q*P (Q=200, P=800 W in the video), so the force F = 2*Q*P/c (1.1 mN in the video), so the acceleration a = F/m (m=0.45 Kg, a = 2.5 mm/s2 in the video).

What would it take to get up to 1 gee for an Earth-based launch?
The acceleration needs to be increased by a factor of ~4000x.
Putting this all together we get
a = 2 Q P / (m c)
Leaving m alone for the moment, Bae states that Q could improve by a factor ~5x (200->1000).
Now we need 4000/5 = 800x improvement.
Using a 800 kW laser does that for us (1000x).
Alternatively we can use a lower mass and thus a lower power laser.

#### deltaMass

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3445 on: 05/15/2015 10:16 PM »
Props to anyone who spots the error in my calculation

#### phaseshift

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3446 on: 05/15/2015 11:59 PM »
Does the Flight Thruster have a slightly concave top and convex bottom? Would appear so from the gaps.

Enhanced the photo as much as I can for those wishing to try to extract dimensions as this photo is better that the original as it has no distortion.

If we can find the dimensions of the bottom Rf connector flange, we can set pixels per cm and start doing measurements.

Most N connectors like that are 1" square, and the holes are .718" center line to center line.

Pixel away.

Thanks. Have fine rotated to vertical / horizontal and lined up. Attached if anyone else wants to have a go.

Using the enhanced photo I built a Google SketchUp model such that when overlayed with the image it matches.  Then I scaled the model so that the RF connector plate measured 1 inch along one side.  The resulting cone has dimensions of sD: 122.2mm, bD: 223.8mm, L: 153.98mm. Not sure the margin of error but the numbers should look fairly close I hope.
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

#### zellerium

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3447 on: 05/16/2015 12:06 AM »
Random thought but;

1-  Could someone please try an em cavity with the bottom (large curved end) not electrically bonded to the sidewalls & top. ie place a circular insulating gasket between the contact point of the sidewall bottom edge and the actual bottom curved plate,  just the wall/plate boundary NOT covering the internal surface area of the curved plate.

What do you think will be different if the bottom plate is electrically insulated?

I think we could easily incorporate this into our design, we have planned to leave a small clearance between the bottom movable plate and the frustum. Our bottom plate may not be as curved as Shawyer's, but we'll be able to provide a small amount of curvature by tighting the screws to different lengths.

#### deltaMass

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3448 on: 05/16/2015 12:15 AM »
Accurate to about 5% = 1-cos(18o). Could be better were you to use my observation about the distortion in the 1" dimensions.

#### aero

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3449 on: 05/16/2015 12:21 AM »
I have this, but don't know what the small end chord, large end chord, or the perpendicular distance between the chords should be, in terms of wavelengths. Or the drive frequency for that matter.

What is your antenna like. A centered dipole (vertical in the images) works well, and the longer the better it seems to me.
« Last Edit: 05/16/2015 12:24 AM by aero »
Retired, working interesting problems

#### phaseshift

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3450 on: 05/16/2015 12:23 AM »
Accurate to about 5% = 1-cos(18o). Could be better were you to use my observation about the distortion in the 1" dimensions.

It's an actual 3D Model and the projection lines up to a pixel, so the 'distortion' should be accounted for.
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

#### phaseshift

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3451 on: 05/16/2015 12:25 AM »
Random thought but;

1-  Could someone please try an em cavity with the bottom (large curved end) not electrically bonded to the sidewalls & top. ie place a circular insulating gasket between the contact point of the sidewall bottom edge and the actual bottom curved plate,  just the wall/plate boundary NOT covering the internal surface area of the curved plate.

What do you think will be different if the bottom plate is electrically insulated?

I think we could easily incorporate this into our design, we have planned to leave a small clearance between the bottom movable plate and the frustum. Our bottom plate may not be as curved as Shawyer's, but we'll be able to provide a small amount of curvature by tighting the screws to different lengths.

After building the 3D-Model I'm 'fairly certain' there is a rubber gasket between the end plates and cone.  It's 1/16 of an inch thick in the model which reflects what I see in the image.
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

#### phaseshift

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3452 on: 05/16/2015 12:29 AM »
A little more detail - hidden edges can be seen in the xray rendering.
"It doesn't have to be a brain storm, a drizzle will often do" - phaseshift

#### Notsosureofit

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3453 on: 05/16/2015 12:34 AM »
Random thought but;

1-  Could someone please try an em cavity with the bottom (large curved end) not electrically bonded to the sidewalls & top. ie place a circular insulating gasket between the contact point of the sidewall bottom edge and the actual bottom curved plate,  just the wall/plate boundary NOT covering the internal surface area of the curved plate.

What do you think will be different if the bottom plate is electrically insulated?

I think we could easily incorporate this into our design, we have planned to leave a small clearance between the bottom movable plate and the frustum. Our bottom plate may not be as curved as Shawyer's, but we'll be able to provide a small amount of curvature by tighting the screws to different lengths.

After building the 3D-Model I'm 'fairly certain' there is a rubber gasket between the end plates and cone.  It's 1/16 of an inch thick in the model which reflects what I see in the image.

Typically, it would be a copper gasket w/ bevels on the plate edges, but rubber o-rings could be used.  In any event, they would be used to make it vacuum tight.  (the copper gaskets are ~1/16")
« Last Edit: 05/16/2015 12:36 AM by Notsosureofit »

#### Iulian Berca

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3454 on: 05/16/2015 12:38 AM »
The search function aren't that super here euuuuu.

Why is the RF injected into the side of the EM Device. I know it's a basic question but can someone expand on it a little more?

Shells

It was first question in my mind also. Why not on top or bottom ?

#### Rodal

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3455 on: 05/16/2015 12:57 AM »
I am back with an updated draft after some terrible news around about NASA dismissing these researches. They should not as, otherwise, it could happen as with Galilei having his detractors even not trying to look in the telescope, just dismissing on faith.

I have analysed the case of the frustum and the results appear to be striking. One must admit that geometry comes to rescue not just general relativity. For this particular geometry the cavity can be made susceptible to gravitational effects if your choice of the two radii of the cavity is smart enough. This is something to be confirmed yet, just my theoretical result, but shocking anyway.

As usual, any comment is very welcome.
In page 8, equation 34 of http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=830137,
for the integral on dr', should the limits, instead of

0 to ((r2-r1)/h) z' + r2

be

r1 to ((r2-r1)/h) z' + r1 ?
« Last Edit: 05/16/2015 01:00 AM by Rodal »

#### Notsosureofit

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3456 on: 05/16/2015 01:02 AM »
I am back with an updated draft after some terrible news around about NASA dismissing these researches. They should not as, otherwise, it could happen as with Galilei having his detractors even not trying to look in the telescope, just dismissing on faith.

I have analysed the case of the frustum and the results appear to be striking. One must admit that geometry comes to rescue not just general relativity. For this particular geometry the cavity can be made susceptible to gravitational effects if your choice of the two radii of the cavity is smart enough. This is something to be confirmed yet, just my theoretical result, but shocking anyway.

As usual, any comment is very welcome.
In page 8, equation 34 of http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=36313.0;attach=830137,
for the integral on dr', should the limits, instead of

0 to ((r2-r1)/h) z' + r2

be

r1 to ((r2-r1)/h) z' + r1 ?

Good Point !  But volume integral ?     0 to ...    ((r2-r1)/h) z' + r1 /l0  ?  (seems circular that way)

It's Eq. 18 that still bothers me a bit.  Invoking the Heaviside step function is OK, but I don't see the addl. components being detectable outside the cavity w/o a non-linear term.  Maybe I'm missing something ?

« Last Edit: 05/16/2015 01:35 AM by Notsosureofit »

#### LasJayhawk

##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3457 on: 05/16/2015 01:08 AM »
The search function aren't that super here euuuuu.

Why is the RF injected into the side of the EM Device. I know it's a basic question but can someone expand on it a little more?

Shells
Beats me. And it looks like the placement would put part of the big end in the near near field and loading the bejesus out of the source.

I've also noted they use a simple loop antenna, but there seems to be no consideration to what we called at Collins the "look angle"

#### deltaMass

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##### Re: EM Drive Developments - related to space flight applications - Thread 2
« Reply #3458 on: 05/16/2015 01:14 AM »
Collins used to make top line ham receivers back in the day

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