14 May 2004

Lightning feedback

Editor,

Concerning the article by Mark Kinsler on lightning (Research Opportunities in Lightning Protection for Amateur Scientists, The Citizen Scientist, 7 May 2004):

A number of years ago now I read an article on a NASA web page about lightning current measurements. This article described a means of measuring lightning currents in a cable that was almost as simple as the needle method, but possibly it could be calibrated more accurately. The device consisted of a strip of magnetic recording tape with a tone recorded on the tape. This tape was placed in a protective tube that also held the tape straight. The tube was then attached to the cable to be instrumented at right angles. After a strike, the current was determined by reading how far the tape had been erased from the cable.

Regarding the last paragraphs about nuclear weapon design, there are two possibilities here. One is the triggering mechanism as surmized, and the other is electromagnetic pulse (EMP) effect of nuclear weapons. One could be interested in designing weapons that maximize this effect. When designing equipment that has to survive EMP, the techniques are similar to protection from lightning. The triggering mechanisms on early nukes did use discharge tubes. See: http://bellsouthpwp.net/j/o/johngd/files/nuke/Trinitite_krytron.jpg

Here are a few interesting lightning links:
http://bat.nmt.edu/
http://bat.nmt.edu/fox/fox.html
http://thunder.msfc.nasa.gov/
http://bub2.met.psu.edu/default.htm
http://thunder.msfc.nasa.gov/validation/instruments.html#KSC-EFMN
http://www.lightningstorm.com/tux/jsp/gpg/lex1/mapdisplay_free.jsp

Jim Hannon

http://www.fmtcs.com/web/jmhannon/
WB0TXL

The magnetic tape method you cite has excellent potential for amateur science lightning monitoring. The EG&G Krytron tube shown in the photograph in the first link cited above had uses in addition to triggering nuclear weapons. I once published an article on how to use a Krytron as very fast, high current switch that delivered pulses having a peak amplitude of a few hundred amperes and a duration of a few tens of nanosceconds to high-power gallium arsenide semiconductor laser diodes. Editor.

A lightning question

Hello,

I found Mark Kinsler's article about lightning protection very interesting. I have often wondered if the lightning rods on my home have been hit.

The problem with current monitoring needles is that it is time consuming and difficult to keep measuring them to see if anything has happened.

I have been thinking about extending the tip of the lighting rods a few centimeters with a thin copper wire. The idea is that it would melt and vaporize if it is hit, so it would be easy to see the damage. Only at that point would the needle would be collected and measured.

A similar function would be an extension made of a resistive material, carbon for example, that would vaporize from the dissipated power.

With a pair of binoculars, the little wires could even be seen from the ground without having to climb the roof.

Is this practical? Any other similar visual indicators?

Thanks for all the great work with SAS.

Bertho Boman (in lightning prone Florida)