Peter, this really does'nt apply to model rockets that are available here.
The engines are solid propellant manufactured to very strict standards and are
very similar to the Space Shuttle SRBs, etc. I can understand why such a hobby
is not available in Israel. In this country, you can go to most any hobby shop
and buy kits, parts to build rockets, and engines. Still, if your country would
allow the hobby under some kind of control (ie: engine purchase for educators),
it can be very educational, fun, and safe.

   I'm working on a response to Ed but, as is typical of this group, there has
already been many excellent replys. I have kind of a unique perspective as I
started back in the 60's with Estes rockets and engines. Back then they still
used fuzes that you lit with a match... Then the wire ignitor. Now days they
coat the ignitor with a material that improves the reliability of ignition.
I love this topic and this message is the first of a `flood' of messages that
I want to discuss from Ed's application to PIC-based payloads ;-)

   - Tom

At 02:24 PM 10/12/98 +0000, Peter L. Peres wrote:
>On Sun, 11 Oct 1998, Dr. Ed Edmondson, Jr. Ph.D. wrote:
>
>> little Estes toys.  Some things which should be simple in theory always tend
>> to end up like an open can of worms.  Once opened, you are never able to
>> return the worms to the original can!
>
>How nice that some people notice this early ;)
>
>> I still am looking for a clever way to dump the launch pulse down the
wires to
>> the fuze?  I was thinking that using an opto isolator and high current FET
>> might work.  It would isolate the main circuitry from the firing circuit.  A
>
>Just thought I'd mention some things books say about drivers for such,
>ahem, things:
>
>- The battery voltage is to be too low to fire the fuse if connected
>directly to it, for any length of time.
>
>- The output to the fuse should be AC coupled (transformer secondary) and
>matched to the line with suitable resistors.
>
>- The a.c. generating device should be run off a charge storage device
>(capacitors) charged at a voltage higher than the battery voltage.
>
>- The a.c. generating device should not be able to operate from un-boosted
>battery voltage.
>
>- The firing should occur after a large amount of cycles in the a.c.
>generating device (i.e. a few cycles are not enough).
>
>- The previous point opens the possibility of precision timed firing
>sequences (computer in each fuze counts pulses before firing).
>
>- None of this is new, the magneto detonators used way back before WW2 all
>worked like this, excepting the part on batteries (used none) and the part
>on precision firing (?).
>
>There is much more. This I've culled from mining & prospection explosive
>handling textbooks. They should be available in a university bookstore.
>Also describes fuzes and other interesting data, such as safety distances
>and procedures. Compulsory reading for rocket people imho. <g>
>
>hope this helps,
>
>Peter
>
>