Thanks, Bert, awesome and inspiring information. And I enjoyed those reports. Hey, do you have copies of those books for sale?
It's high on my list as soon as H&H AoE III is finished.
BTW, do you know about the water bridges?
--
Thanks,
- Win
Hehehe.. I have some Skylab videos on Laser Disc from NASA, of which one is titled "water bridges".
Essentially 'fun with water and surface tension and surface adhesion in space'.
Jeff's cousin? :-)
What sort of switch would be used there? When I was a kid, I used to make banks of electrolytics (from old TV sets), charge them up, and dump them into coils using, pretty much, just wire contacts. They welded shut every shot. I could magnetize most anything.
John
http://205.243.100.155/frames/shrinkergallery.html
He has some how-to data there, IIRC.
http://205.243.100.155/frames/gallery/newgap5a.jpg
http://205.243.100.155/frames/Newgap2a.jpg
I'll bet that he gets more than one cycle on his MTBF 'numbers'.
Yeah - these are really curious. Under the right conditions, a cylindrical 2-4mm diameter liquid bridge of distilled water can stretch between two Pyrex beakers separated by up to 25mm. Just one more in a LONG list of amazing properties of water. Although this phenomenon was first discovered 117 years ago (by Sir William Armstrong), it has recently been rediscovered, and studied in much greater detail.
There's an excellent YouTube clip by physicists Elmar C. Fuchs, Karl Gatterer, Gert Holler and Jakob Woisetschlager (J. Phys. D: Appl. Phys.
41 (2008) showing a water bridge being extended using an adjustable HVDC supply voltage of up to 25 kV. Also included are thermal and density profiles:In the above experiments, a current-limited HVDC supply was connected between the two beakers, and a 42 nF capacitor was connected in parallel with the beakers. The current was found to be about 0.5 mA. Instead of using a string to start the process (ala Armstrong), the experimenters increased the voltage between beakers while they were placed side by side, until "Taylor Cones" (jets of electrostatically-repelled water) were ejected from the surface, and bridging the gap. The researchers also found that there was mass flow (usually from anode to cathode beaker) accompanied by rotational flow near the outer surface of the bridge. Interesting stuff!
Although I have all of the above books in my personal library, I don't have any extra copies at this time. However, they're all currently available via Amazon.
BTW, have you seen HV "air threads"? These were first reported by amateur researcher Charles Yost and subsequently studied by Bill Beaty? These tight filaments of air are probably related to ion wind... but the real mystery is how they can maintain such a tight stream? I'm not aware of any good explanations for these as yet. :^)
Physics is fun!
Bert
-- ******************************************************************** We specialize in UNIQUE items: coins shrunk by ultra-strong magnetic fields, Captured Lightning Lichtenberg figure sculptures, and scarce technical Books. Please visit us at http://www.capturedlightning.com********************************************************************
Oh. Brute force. I could have done something like that, operated by a hammer maybe.
John
Mecury contactors ain't cheap, or small.
High power switches ("power modulators") can be very simple or fairly esoteric. Lower power applications can use stacked IGBT's or SCR's. However, silicon cost rapidly escalates for higher voltage and current applications. Series stacks becomes necessary at voltages over 5 kV, dynamic voltage sharing and simultaneous triggering adds significant design complication, and current/voltage reversals may require anti-parallel high current free-wheeling rectifiers.
Thyratrons can handle moderately high-current pulses at higher standoff voltages, but they begin to run out of gas above 100 kA, and most thyratrons don't handle oscillatory discharges gracefully. Other low pressure switches, such as pseudospark and triggered vacuum gaps have also been developed, and these can handle maximum currents to about 500 kA. Current densities for gas volume gaps (thyratrons, ignitrons, and various vacuum triggered gaps) are limited to about 10+6 amperes/square meter.
Higher power switching is commonly done via pulse-rated ignitrons (which use refractory metal anodes to safely handle oscillatory current reversals), triggered spark gaps, or electromechanical switches. For hobbyists, a simple solenoid-driven switch, with massive brass (or tungsten-copper or tungsten-silver) contacts are very robust, relatively inexpensive, and very reliable. Very low-inductance "nail switches" are used for at even higher power levels. These use a conductive "nail" to puncture a polyethylene or Mylar dielectric sheet, creating a short circuit between bus bars that are configured as a low-Z transmission line. The result is a constrained, high pressure, low inductance, low resistance arc.
Electrically- or laser-triggered spark gaps are used in applications where tighter timing accuracy is needed or where multiple switches need to be triggered simultaneously. These use air or another dielectric gas under normal pressure, or higher pressures to increase standoff voltage. Insulating liquids are used (such as mineral oil) to further increase power density and hold-off voltage. Triggering can be via a high voltage triggering electrode or a high-energy laser pulse. In comparison to lower pressure gas volume switches above, current densities for gas, liquid, or solid spark gaps are of the order of 10+12 Amperes/square meter.
Bert
-- ******************************************************************** We specialize in UNIQUE items: coins shrunk by ultra-strong magnetic fields, Captured Lightning Lichtenberg figure sculptures, and scarce technical Books. Please visit us at http://www.capturedlightning.com********************************************************************
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That is what the big boys use on the multi-Megavolt DC interties.
Stack of 'em in a 30' x 12' x 12' box suspended 90' in the air in a VERY big room. They are like 7 inches in diameter and an inch thick (the actual Thyratron medium).
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properly
Does lightning have a return strike? So perhaps the bolt would ring and want to suck much of the energy captured back out again.
Grant.
-- http://bugs.id.au/
Stay out of conversations in which it is blatantly obvious that you are too retarded to grasp the depth of.
You're an idiot.
There is a reason why there is no longer a restaurant on top of Mt. Evans. That reason is because it DOES strike in the same place again.
After the third fire they decided not to rebuild again. That determination was made decades ago. Lightning was the reason.
post
It is typically a dumping of electrons INTO the Earth. They don't bounce back. Not rubber biscuits.
post
Although the space shuttle has recorded lightning strokes which also had an upward going 'sprite' that rose above the atmosphere (at least one visible layer). They have recorded many, in fact.
I have seen ball lightning twice in my life. Maybe they are little mini black holes...
These stacked power switches for DC Interties are actually Thyristors... modern optically-triggered SCR's. These replaced ignitrons in older inverters.
Thyratrons are gas-filled electron tubes. Similar sounding but completely different technologies.
Bert
-- ******************************************************************** We specialize in UNIQUE items: coins shrunk by ultra-strong magnetic fields, Captured Lightning Lichtenberg figure sculptures, and scarce technical Books. Please visit us at http://www.capturedlightning.com********************************************************************
Yes... I had a whole word typo. I read you writing thyratron, and thought of the thyristors up at Bonneville. A bit of dyslexia there...
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