Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2104343 times)

Offline SeeShells

  • Senior Member
  • *****
  • Posts: 2326
  • Every action there's a reaction we try to grasp.
  • United States
  • Liked: 2956
  • Likes Given: 2589
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

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
About Bae's PLT:
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.

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
The search function aren't that super here euuuuu.
To be blunt, it totally sucks :(

Offline jmossman

  • Member
  • Posts: 72
  • San Jose, CA
  • Liked: 58
  • Likes Given: 173
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 »

Online Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5260
About Bae's PLT:
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.

See:  http://ykbcorp.com/downloads/Bae_photon_propulsion_STAIF2_Paper_Circulation.pdf

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Props to anyone who spots the error in my calculation

Offline phaseshift

  • Full Member
  • *
  • Posts: 104
  • Seattle, WA
  • Liked: 84
  • Likes Given: 97
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

Offline zellerium

  • Full Member
  • *
  • Posts: 171
  • Pittsburgh, PA
  • Liked: 279
  • Likes Given: 400
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.

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Accurate to about 5% = 1-cos(18o). Could be better were you to use my observation about the distortion in the 1" dimensions.

Online aero

  • Senior Member
  • *****
  • Posts: 2743
  • 92129
  • Liked: 704
  • Likes Given: 237
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

Offline phaseshift

  • Full Member
  • *
  • Posts: 104
  • Seattle, WA
  • Liked: 84
  • Likes Given: 97
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

Offline phaseshift

  • Full Member
  • *
  • Posts: 104
  • Seattle, WA
  • Liked: 84
  • Likes Given: 97
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

Offline phaseshift

  • Full Member
  • *
  • Posts: 104
  • Seattle, WA
  • Liked: 84
  • Likes Given: 97
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

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1364
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 »

Offline Iulian Berca

  • Member
  • Posts: 14
  • Romania
  • Liked: 64
  • Likes Given: 3
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 ?

Online Rodal

  • Senior Member
  • *****
  • Posts: 5838
  • USA
  • Liked: 5919
  • Likes Given: 5260
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 »

Offline Notsosureofit

  • Full Member
  • ****
  • Posts: 656
  • Liked: 704
  • Likes Given: 1364
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 »

Offline LasJayhawk

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"

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
Collins used to make top line ham receivers back in the day

Offline ThinkerX

  • Full Member
  • ***
  • Posts: 303
  • Alaska
  • Liked: 112
  • Likes Given: 59
Quote
The search function aren't that super here euuuuu.

Basically, you have to use a defined google search to find past items of interest on this thread. 

Tags: