... I don't see any place for leaks in the axial direction....
What you are saying is that these EM thruster devices need to be checked with a smoke trails, like air flow in a wind tunnel is highlighted. Hold a lighted punk stick next to it and turn the device on. Wouldn't their be some time delay between power on/off and thrust on and off?
Quote from: aero on 10/22/2014 05:49 pm...Does anyone want to take a crack at estimating the dimensions of the flight thruster. It operated at 3.85GHz and weighed 2.92 Kg. That is a new operating frequency data point for us if we can get dimension. If nothing else, we should be able to get the taper angle pretty accurately, as well as the ratios of big/little and big/height.Please provide a link for this " flight thruster.. operated at 3.85GHz and weighed 2.92 Kg.", and if possible attach a picture. Thanks
...Does anyone want to take a crack at estimating the dimensions of the flight thruster. It operated at 3.85GHz and weighed 2.92 Kg. That is a new operating frequency data point for us if we can get dimension. If nothing else, we should be able to get the taper angle pretty accurately, as well as the ratios of big/little and big/height.
The time delay is not noticeable. I don't know if the time delay difference between this device and the EM thrusters could be detected. I don't think it can be with the data we have available to us.
Quote from: aero on 10/22/2014 06:19 pmThe time delay is not noticeable. I don't know if the time delay difference between this device and the EM thrusters could be detected. I don't think it can be with the data we have available to us.Actually the time delay is visible in these two plots of thrust data vs time. The first one is from Shawyer's 2008 paper. His 2013 and 2014 IAC papers don't have this kind of raw data. Both the up and down thrust roughly follow an exponential rise after power is applied and there is continued acceleration after the power is turned off.The second plot is from the JSC paper - Brady, White, et al. This also has a roughly exponential rise and continued thrust after RF power is turned off until the Cal pulse wipes it out.Both experiments have a thermal effect signature.
What about the gauge constant for the springs? How far does it have to move for the force to be read ?
Quote from: Notsosureofit on 10/22/2014 07:03 pmWhat about the gauge constant for the springs? How far does it have to move for the force to be read ?<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>
Quote from: Rodal on 10/22/2014 07:05 pmQuote from: Notsosureofit on 10/22/2014 07:03 pmWhat about the gauge constant for the springs? How far does it have to move for the force to be read ?<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>Yes, but how much displacement are we talking about and how long does it take to get there?
I made a kludge estimate of the Flight thruster dimensions operating at 385 GHz.w-small = 7.062943185 cmw-big = 11.02062266 cmheight = 7.114289902 cm...
Quote from: Notsosureofit on 10/22/2014 07:07 pmQuote from: Rodal on 10/22/2014 07:05 pmQuote from: Notsosureofit on 10/22/2014 07:03 pmWhat about the gauge constant for the springs? How far does it have to move for the force to be read ?<<Displacement of the pendulum arm is measured via a Linear Displacement Sensor (LDS). The primary LDS components consist of a combined laser and optical sensor on the fixed structure and a mirror on the pendulum arm. The LDS laser emits a beam which is reflected by the mirror and subsequently detected by the optical sensor. The LDS software calculates the displacement (down to the sub-micrometer level) based upon the beam reflection time. Prior to a test run data take, the LDS is positioned to a known displacement datum (usually 500 micrometers) via mechanical adjustments to its mounting platform. Gross adjustments are performed via set screws. Fine adjustments are performed using manually-operated calibrated screw mechanisms and a remotely controlled motorized mechanism that can be operated with the chamber door closed and the chamber at vacuum. The remote adjustment capability is necessary since the LDS datum will change whenever a change to the test facility environment affects the roll-out table or the chamber – e.g., whenever the chamber door is closed or latched and whenever the chamber is evacuated. Once the LDS displacement is adjusted in the final test environment, further adjustment between test run data takes is usually not required.>>Yes, but how much displacement are we talking about and how long does it take to get there?Also Paul March wrote in this thread: << The Riverhawk C-flex torsion bearing's spring constant is a nominal 0.007 in-Lb/deg., but that varies with the mass load mounted on the torque pendulum arm and selected balance point of the test article mass and its counterbalance mass on the other end of the pendulum arm relative to the torque pendulum’s center of rotation. >>However this torsional spring constant greatly disagrees with the natural frequency quoted by Paul March. The natural frequency quoted by Paul March indicates a much stiffer spring constant.
....A much higher frequency might indicate flex in the arm itself. (i should explain that I've built quite a few of these type and always found that to be a problem, also used force feedback for zero displacement...but that was a while ago)
Quote from: Notsosureofit on 10/22/2014 07:59 pm....A much higher frequency might indicate flex in the arm itself. (i should explain that I've built quite a few of these type and always found that to be a problem, also used force feedback for zero displacement...but that was a while ago)A higher frequency because you think that the frequency is due to beam bending rather than torsion of the bearing?In other words, this would mean that the frequency Paul March is referring to would not be the lowest frequency.I did some calculations some time ago based on known stiffness of the Faztek beams (1.5" by 1.5"), and the bending frequency would be way too high compared to Paul March's stated frequency assuming the inverted pendulum to be effectively clamped by the bearings as a cantilevered beam. So if the frequency given by Paul March is related to beam bending it would have to be also due to substantial flexibility from the bearings (not providing a perfect clamp).
Quote from: Rodal on 10/22/2014 08:06 pmQuote from: Notsosureofit on 10/22/2014 07:59 pm....A much higher frequency might indicate flex in the arm itself. (i should explain that I've built quite a few of these type and always found that to be a problem, also used force feedback for zero displacement...but that was a while ago)A higher frequency because you think that the frequency is due to beam bending rather than torsion of the bearing?In other words, this would mean that the frequency Paul March is referring to would not be the lowest frequency.I did some calculations some time ago based on known stiffness of the Faztek beams (1.5" by 1.5"), and the bending frequency would be way too high compared to Paul March's stated frequency assuming the inverted pendulum to be effectively clamped by the bearings as a cantilevered beam. So if the frequency given by Paul March is related to beam bending it would have to be also due to substantial flexibility from the bearings (not providing a perfect clamp).Tough call w/ all that stuff hanging out there. Can't see too much in the pictures and not too crazy about the way the chamber is set on. Could be anything that vibrates. What were the frequencies ?
The natural oscillation period of the pendulum arm when loaded with the RF amplifier, its RF plumbing and the test article was around 4.5 seconds.