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--- ideas:flight_support [2006/07/08 16:44] – rocketboy
+++ ideas:flight_support [2013/05/07 07:55] (current) – [Radar Reflector] rocketboy
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 ====== Flight Support ======
 ===== Radar Reflector =====
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 {{:ideas:corner.jpg|:ideas:corner.jpg}}
-Size - in order to work effectively each side of the corner must be at least 1.5 wavelengths - this gives a size of about 15cm to cover down to S band RADAR (3GHz = 10cm wavelength) - this makes a suitable reflector about 30cm (1 foot) tip to tip.
+FAR101 says "the reflector will present an echo to surface radar operating in the 200 MHz to 2700 MHz frequency range".
+Size - commercial radiosonde radar refelctors are about 50cm tip to tip.
 A very lightweight reflector (less than 30g) can be constricted using carbon fiber kite spars and metalized plastic foil (as used in space blankets).
-Can anyone confirm that aircraft radar (airborne and ground based) is S band or higher?
 ===== Pyrotechnic Cutdown Device =====
 This device is used to detach the payload from the balloon (or release items attached to the payload). Its an igniter (used in amateur rocketry) inside a small hard plastic tube (sealed with epoxy at both ends) - when fired the igniter has enough explosive force to shatter the tube (and hence release the balloon) - it works a treat in all the tests I have done, including some at -30dec C and in a vacuum chamber.
+__**WARNING: wear full eye area wrap around safety goggles when testing these devices.**__
 {{:ideas:release.jpg|:ideas:release.jpg}}
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 The igniter needs about 2amps @ 3Volts for just a few milli seconds to fire - it can even be fired from a charged 4700uF capacitor.
+{{ideas:cct0.gif|}}
+The ignitor on the right hand side of the circuit can be replaced by a small 6V bulb for testing - the bulb will light briefly when fired. Once you are happy with the circuit try an igniter.
+[''adeptium/STARS Project'': Not happy about the use of a wet cap for near-space use, but Farnell supplies an AVX 3300uF tantalum, 4-10V operating range, rated to -55C with no loss of capacity.  I'm going to try with one or two of these.]