Great !Next need to solve for the expression (f0^2 - f2^2) where (f0 => L1+L2=0 and f2 =>L1+L2=L ??)Hmmm, let me think about that for a second. What we want to do is isolate the (p*pi/L)^2 term so it will cancel out leaving the Doppler shifts in the accelerated frame. ie. (f0^2 - f2^2)
@ RODALI'm struggling w/ the best way to explain it. We want to get the expression (f0^2 - f2^2) such that the frequencies f0 and f2 are evaluated at the two ends of the cavity at the same wavenumber. They are the frequencies (energies) that would appear at the ends of the cavity if it were accelerated to the point that the dispersion between the ends were to disappear.Yes, dispersion curve intersections at constant k.No by df I just mean f1-f2 ie del fFrom f^2 evaluations at the ends (ie (f1^2-f2^2) = del f * 2f0 etc.[Excuse the quick..I'm being otherwise distracted at the moment]
Quote from: Notsosureofit on 03/06/2015 12:03 am@ RODALI'm struggling w/ the best way to explain it. We want to get the expression (f0^2 - f2^2) such that the frequencies f0 and f2 are evaluated at the two ends of the cavity at the same wavenumber. They are the frequencies (energies) that would appear at the ends of the cavity if it were accelerated to the point that the dispersion between the ends were to disappear.Yes, dispersion curve intersections at constant k.No by df I just mean f1-f2 ie del fFrom f^2 evaluations at the ends (ie (f1^2-f2^2) = del f * 2f0 etc.[Excuse the quick..I'm being otherwise distracted at the moment]This time, instead of purely geometrical terms for the truncated cone with only one medium like(b^2)*((1/Rs)^2 - (1/Rb)^2) one gets terms due to the different speed of light in mediums 1 and 2 for example(b^2)*((L1/c1)^2 -(L2/c2)^2)=> this is quite pedagogical to understand your point, and Mulletron's point that a cylindrical cavity with two different dielectric mediums maybe as or more effective than a truncated cone with only one medium
this is quite pedagogical to understand your point, and Mulletron's point that a cylindrical cavity with two different dielectric mediums maybe as or more effective than a truncated cone with only one medium
Quotethis is quite pedagogical to understand your point, and Mulletron's point that a cylindrical cavity with two different dielectric mediums maybe as or more effective than a truncated cone with only one mediumYou can add meep to that camp. Or at least for all indications you can but I should make some controlled runs to confirm it. If I ran a truncated cone and a cylinder, what frequency and cylindrical dimensions would I use in order that it be a fair comparison to the truncated cone? Dielectric constant? Or, if you prefer, what cylinder and cone dimensions are consistent? Same resonant frequency and mode or same "size" "volume" but since we're addressing a space thruster, maybe integrated structural mass? Cylinders tend to be smaller and simpler.
Quote from: zen-in on 03/05/2015 03:21 amQuote from: frobnicat on 03/04/2015 08:46 pm@ Rodal :See attached picture to share my mental image. Tilt over-exaggerated for illustration. Grey : solid rotating assembly (no deformation implied) Orange/brown : fixed assembly (no deformation implied) Blue : the ground slab of the vacuum chamber (no deformation implied) For now, assume a perfect axis of rotation around Z : only one degree of freedom of Grey relative to Orange, the "official" rotation around Z, no compliance implied, Grey kept in the XY plane, plane has same tilt as Orange (XY parallel to Orange platform).@Star-Drive Can you confirm this is a correct way to understand that there is a tilt in the axis of rotation ?One aspect of this tilt in the axis of rotation that hasn't been discussed is the requirement for imbalance. The difference in moments on either side of the beam only has to be very slight for it to always come to rest at the same location +/- a micron or two.Yes, a difference in centre of mass can make long lasting difference in position. The following statement tries to summarize rigorously :Statement A : Any shift in centre of mass of a part (relative to fixation to the balance arm) along a direction orthogonal to a compliant (not infinite stiffness) axis that is not strictly vertical can induce a change in angular rest position around said compliant axis.This can be quite important as a (thermal) longitudinal (Y+ or Y-) shift in CoM of the frustum assembly would be orthogonal to axis Z, but so long as this most compliant by far axis Z (the natural axis of the pendulum) was believed to be strictly vertical there would be no change in angular rest position of the arm (around Z). Only transient angular positions shifts could be induced by such thermal CoM shifts, the arm position (around Z) would be quickly enough restored to unmodified rest position (return to baseline) by the spring restoring torque of flexure bearings, and then time of ~45s during which a sustained displacement where recorded could be used as an effective argument that this couldn't be due to thermal expansions alone.Note that now that the Z axis is no longer vertical the argument is no longer valid.QuoteA small CW tilt along the X axis of the balance arm would explain the apparent drift in the baseline seen in some of the thrust waveforms. When the cavity has the orientation shown below its CM shifts to the left. This would reduce the tilt, resulting in an increase in brightness of the reflected light the LDS measures; due to the mirror position being closer to an optimal perpendicular position wrt the light beam. The increase in brightness corresponds to a decrease in distance; hence the negative slope. With the device mounted the other way the shift in CM increases the tilt. This reduces the reflected light and is registered as an increase in distance. Is this what you are saying ?Indeed the X axis is not vertical (it is horizontal, or almost), so the above statement A does apply if we consider rotations around X are not against infinite stiffness. But preliminary rough estimations gave me relative displacements of rest optical length of at least one order of magnitude below signal. Even if not infinitely stiff, the added torsion compliance of faztek beam around X and compliance of tandem flexure bearings around X is not enough. For reasonable thermal CoM's shifts, this is stiff enough , and the optical lever is small enough (optical length d measured at small distance below X) that it would make very little contribution to the signal.QuoteNo actual motion of the beam occurs. This apparent motion is an optical artifact. This assumes the Philtec distance sensor is used on the far side. If it is used on the near side a small CCW tilt along the X axis of the beam would produce the same effect; except requiring much less rotation from the change in CM.For this twist around X effect, no actual rotation of the beam around Z would occur, but the beam is deformed. I wouldn't qualify that as an "optical artifact". Sorry I'm becoming quite finicky on wordings lately That would be a real mechanical motion, only not a motion around the "official" Z axis.We have all reasons to believe the Philtec linear sensor is used in the far range, see attached chart's horizontal units. The initial report (anomalous...) clearly states that it is used around 500µm, the vertical readings of the charts are consistent, and Paul March confirms :Quote from: Star-Drive on 03/02/2015 12:21 amQuote from: frobnicat on 03/01/2015 09:12 pm...- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant.......The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror in microns, so the numbers on the left hand side of the force plots measure the distance from the end of the fiber-optic laser head to its mirror target mounted on the torque pendulum arm. The data sheet for same is attached....Still, there is a factor 10 disparity between the apparent stiffness readings (LDS readings against calibrations pulses alone) and the stiffness needed to explain the 4.5s pseudo-period of oscillations, so this can put a doubt on the readings of vertical scale, a factor 10 here could explain a lot of things.Regardless of this nagging problem of late, now that we know that Z deviates from strict verticality by a quarter bubble, from statement A above there is now a real possibility that a thermal CoM shift along Y changes angular rest position around the official Z, of relative magnitude compatible with signals, as rotation around Z has a very low stiffness (the restoring torque of flexure bearing around their natural axis of rotation). And such change in angular rest position around Z would record as false "sustained thrusts" in the charts.Statement B : The validity of real sustained thrust signals now rests on the amount of deviation of Z from vertical, resolution of the contradictions between apparent stiffness around Z, and careful assessment of thermal expansions in vacuum. The sustained duration alone no longer suffice.
Quote from: frobnicat on 03/04/2015 08:46 pm@ Rodal :See attached picture to share my mental image. Tilt over-exaggerated for illustration. Grey : solid rotating assembly (no deformation implied) Orange/brown : fixed assembly (no deformation implied) Blue : the ground slab of the vacuum chamber (no deformation implied) For now, assume a perfect axis of rotation around Z : only one degree of freedom of Grey relative to Orange, the "official" rotation around Z, no compliance implied, Grey kept in the XY plane, plane has same tilt as Orange (XY parallel to Orange platform).@Star-Drive Can you confirm this is a correct way to understand that there is a tilt in the axis of rotation ?One aspect of this tilt in the axis of rotation that hasn't been discussed is the requirement for imbalance. The difference in moments on either side of the beam only has to be very slight for it to always come to rest at the same location +/- a micron or two.
@ Rodal :See attached picture to share my mental image. Tilt over-exaggerated for illustration. Grey : solid rotating assembly (no deformation implied) Orange/brown : fixed assembly (no deformation implied) Blue : the ground slab of the vacuum chamber (no deformation implied) For now, assume a perfect axis of rotation around Z : only one degree of freedom of Grey relative to Orange, the "official" rotation around Z, no compliance implied, Grey kept in the XY plane, plane has same tilt as Orange (XY parallel to Orange platform).@Star-Drive Can you confirm this is a correct way to understand that there is a tilt in the axis of rotation ?
A small CW tilt along the X axis of the balance arm would explain the apparent drift in the baseline seen in some of the thrust waveforms. When the cavity has the orientation shown below its CM shifts to the left. This would reduce the tilt, resulting in an increase in brightness of the reflected light the LDS measures; due to the mirror position being closer to an optimal perpendicular position wrt the light beam. The increase in brightness corresponds to a decrease in distance; hence the negative slope. With the device mounted the other way the shift in CM increases the tilt. This reduces the reflected light and is registered as an increase in distance.
No actual motion of the beam occurs. This apparent motion is an optical artifact. This assumes the Philtec distance sensor is used on the far side. If it is used on the near side a small CCW tilt along the X axis of the beam would produce the same effect; except requiring much less rotation from the change in CM.
Quote from: frobnicat on 03/01/2015 09:12 pm...- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant.......The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror in microns, so the numbers on the left hand side of the force plots measure the distance from the end of the fiber-optic laser head to its mirror target mounted on the torque pendulum arm. The data sheet for same is attached....
...- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant....
For this twist around X effect, no actual rotation of the beam around Z would occur, but the beam is deformed. I wouldn't qualify that as an "optical artifact". Sorry I'm becoming quite finicky on wordings lately That would be a real mechanical motion, only not a motion around the "official" Z axis.We have all reasons to believe the Philtec linear sensor is used in the far range, see attached chart's horizontal units. The initial report (anomalous...) clearly states that it is used around 500µm, the vertical readings of the charts are consistent, and Paul March confirms :Quote from: Star-Drive on 03/02/2015 12:21 amQuote from: frobnicat on 03/01/2015 09:12 pm...- That the vertical scale in the charts (indicated in µm, around 500) are relevant or not relevant.......The Philtec D63 fiber-optic displacement sensor measures distance from its target mirror in microns, so the numbers on the left hand side of the force plots measure the distance from the end of the fiber-optic laser head to its mirror target mounted on the torque pendulum arm. The data sheet for same is attached....Still, there is a factor 10 disparity between the apparent stiffness readings (LDS readings against calibrations pulses alone) and the stiffness needed to explain the 4.5s pseudo-period of oscillations, so this can put a doubt on the readings of vertical scale, a factor 10 here could explain a lot of things.Regardless of this nagging problem of late, now that we know that Z deviates from strict verticality by a quarter bubble, from statement A above there is now a real possibility that a thermal CoM shift along Y changes angular rest position around the official Z, of relative magnitude compatible with signals, as rotation around Z has a very low stiffness (the restoring torque of flexure bearing around their natural axis of rotation). And such change in angular rest position around Z would record as false "sustained thrusts" in the charts.Statement B : The validity of real sustained thrust signals now rests on the amount of deviation of Z from vertical, resolution of the contradictions between apparent stiffness around Z, and careful assessment of thermal expansions in vacuum. The sustained duration alone no longer suffice.
Same here. The EBay units I've got are #201065780928 and #131442703325 so far in case anyone want to try the same system.
Quote from: Notsosureofit on 03/03/2015 03:50 pmSame here. The EBay units I've got are #201065780928 and #131442703325 so far in case anyone want to try the same system.I've decided to try and live up to my screen name and throw my lot in with the replicators. I have a few questions before I kick off my effort:1) Why did you decide to go with #201065780928 rather than a frustrum of a cone? The #201065780928 part looks more like a rectangular slit shape rather than a cone shape. 2) How do you plan on hooking the MA86751B X band oscillator up to the waveguide assembly?3) It looks like the MA86751B X band oscillator is tunable from 9.9 GHz to 10.6 GHz with power output levels from 10 mW to 100 mW powered by 9-10 Volts DC. Did you pick this particular oscillator for a reason?4) Do you expect there to be a resonant frequency within the 9.9 GHz to 10.6 GHz frequency band?5) Do you plan on putting a dielectric toward one end of the waveguide assembly?6) With what material do you plan on capping each end of the waveguide assembly?Although I direct this friendly set of questions to Notsosureofit, Mulletron, and others who are attempting replications, I welcome any forum members to chime in with recommendations or insights. Can you imagine what would happen if the effect can be shown on such a small scale? It could cause some ripples and raise a quite a few eyebrows around the world.
....I'll just try a long ( 20 ft ?) pendulum First and see what happens. Vacuum later.
http://www.ebay.com/itm/AERCOM-Microwave-RF-Isolator-Circulator-2-4GHz-20dB-isolation-Low-I-L-TESTED-/281549538390?ssPageName=ADME:L:OU:US:1120Picked up one of these puppies on Ebay to protect my amp. Another example of broken time reversal symmetry in action.Got about an oz of very expensive liquid metal from here:http://www.amazon.com/Gallium-Indium-Eutectic-GaInSn-68-5%25/dp/B00KN92MWW/ref=sr_1_3?ie=UTF8&qid=1425074693&sr=8-3&keywords=galinstanSo back to the copper from way back: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326742#msg1326742...Been working with the supplier with a machine shop I posted about way back:http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326669#msg1326669 I'm going that route. The quote I got is: price: $120.00 layout + $51.63 for part + freight. So I have to pay the layout, then anyone else who wants one of these: but built in 16oz copper, with a smooth butt seam inside, and 1/4" flange around edges, can get one for about 50 bucks plus shipping. If all this works out, it'll fulfill my goal of making a replication by DIYers easier. For me, paying the layout plus price about breaks even with buying the sheet myself and fumblefuddeling around trying to solder up a cone at home. So I'm happy. I'll get back with more later, when the items are at home.
Quote from: Notsosureofit on 03/03/2015 03:50 pmSame here. The EBay units I've got are #201065780928 and #131442703325 so far in case anyone want to try the same system.I've decided to try and live up to my screen name and throw my lot in with the replicators. I have a few questions before I kick off my effort:....3) It looks like the MA86751B X band oscillator is tunable from 9.9 GHz to 10.6 GHz with power output levels from 10 mW to 100 mW powered by 9-10 Volts DC. Did you pick this particular oscillator for a reason?4) Do you expect there to be a resonant frequency within the 9.9 GHz to 10.6 GHz frequency band?.....
Quote from: Mulletron on 02/27/2015 09:00 pmhttp://www.ebay.com/itm/AERCOM-Microwave-RF-Isolator-Circulator-2-4GHz-20dB-isolation-Low-I-L-TESTED-/281549538390?ssPageName=ADME:L:OU:US:1120Picked up one of these puppies on Ebay to protect my amp. Another example of broken time reversal symmetry in action.Got about an oz of very expensive liquid metal from here:http://www.amazon.com/Gallium-Indium-Eutectic-GaInSn-68-5%25/dp/B00KN92MWW/ref=sr_1_3?ie=UTF8&qid=1425074693&sr=8-3&keywords=galinstanSo back to the copper from way back: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326742#msg1326742...Been working with the supplier with a machine shop I posted about way back:http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326669#msg1326669 I'm going that route. The quote I got is: price: $120.00 layout + $51.63 for part + freight. So I have to pay the layout, then anyone else who wants one of these: but built in 16oz copper, with a smooth butt seam inside, and 1/4" flange around edges, can get one for about 50 bucks plus shipping. If all this works out, it'll fulfill my goal of making a replication by DIYers easier. For me, paying the layout plus price about breaks even with buying the sheet myself and fumblefuddeling around trying to solder up a cone at home. So I'm happy. I'll get back with more later, when the items are at home.Mulletron, Can you provide me with the contact information (email) of the maker of the custom cone? What dimensions did you settle on? I appreciate that you are footing the bill for the layout, thereby lowering the cost for the rest of us. Kudos to you for that.
Quote from: DIYFAN on 03/06/2015 11:41 amQuote from: Mulletron on 02/27/2015 09:00 pmhttp://www.ebay.com/itm/AERCOM-Microwave-RF-Isolator-Circulator-2-4GHz-20dB-isolation-Low-I-L-TESTED-/281549538390?ssPageName=ADME:L:OU:US:1120Picked up one of these puppies on Ebay to protect my amp. Another example of broken time reversal symmetry in action.Got about an oz of very expensive liquid metal from here:http://www.amazon.com/Gallium-Indium-Eutectic-GaInSn-68-5%25/dp/B00KN92MWW/ref=sr_1_3?ie=UTF8&qid=1425074693&sr=8-3&keywords=galinstanSo back to the copper from way back: http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326742#msg1326742...Been working with the supplier with a machine shop I posted about way back:http://forum.nasaspaceflight.com/index.php?topic=36313.msg1326669#msg1326669 I'm going that route. The quote I got is: price: $120.00 layout + $51.63 for part + freight. So I have to pay the layout, then anyone else who wants one of these: but built in 16oz copper, with a smooth butt seam inside, and 1/4" flange around edges, can get one for about 50 bucks plus shipping. If all this works out, it'll fulfill my goal of making a replication by DIYers easier. For me, paying the layout plus price about breaks even with buying the sheet myself and fumblefuddeling around trying to solder up a cone at home. So I'm happy. I'll get back with more later, when the items are at home.Mulletron, Can you provide me with the contact information (email) of the maker of the custom cone? What dimensions did you settle on? I appreciate that you are footing the bill for the layout, thereby lowering the cost for the rest of us. Kudos to you for that.The cone is the same dims as the DUT at Eagleworks. What was built was based off of this: https://docs.google.com/file/d/0B4PCfHCM1KYoN2VURmltbVlfa3c/edit?pli=1It is in shipping to me att. I intend to make sure it is good to go, then if no changes are required, the guy who made it will list it on Ebay for around 50 bucks or so. Please give it a few days to arrive. I want to make sure there aren't any problems before it gets put up for sale. That way I accept the risk first. Here's what it looks like.
....3) It looks like the MA86751B X band oscillator is tunable from 9.9 GHz to 10.6 GHz with power output levels from 10 mW to 100 mW powered by 9-10 Volts DC. Did you pick this particular oscillator for a reason?4) Do you expect there to be a resonant frequency within the 9.9 GHz to 10.6 GHz frequency band?.....