Explode Harder

Electrosonic 2


welcome to the most advanced research project ever, based on Electrosonic, it will feature:

  • overall similar design to Electrosonic. cheap i know.
  • but
  • heavier epoxy-post-tube or PVC construction
  • external-mould nosecone
  • plastic or aluminium fins NO WARPING
  • internal spring-switch for apogee detection
  • motor fittings of steel
  • 2-stage one-piece motor, air-speed re-ignition
  • more powerful rechargeable onboard battery, no swapping
  • more powerful motor developed, 40mm.


    some other ideas that might show up are:

  • phone camera
  • on-board ignition of first stage
  • clockwork or electronic timer for parachute and/or failsafe
  • shrieking piezo location alarm
  • RC ignitor box / launch switch
  • basic altitude sighting and triangulation
  • motor test pressure and thrust monitoring
  • simulation

    12th May
    Work has started on this project. i've been investigating deployment systems, and have part of one working in a crude form. this is a most pressing issue considering what happened to Electrosonic I. though the air-speed switch has worked in quite ambitious rockets for Richard Nakka it has inelegancies:
  • sticks out
  • complex mechanism
  • easy to fool

    alternatives i'd found were magnetic sensing of orientation, photo-comparatory sensing of tip-over and a mechanical free-fall switch mechanism thing. the first two required electronics and the third, i couldn't actually find details about, when i went looking. the first, magnetic detection, relied on a hall-effect chip a bit like a compass, which turned out to be very expensive. it would otherwise no doubt have worked.

    so i proceeded with the 2nd. this involves comparing the voltages of two light-sensing circuits and outputting a voltage when the relationship between the two reverses. one sensor is pointed skyward and one soilward, and they can be either CdS light sensors, or light dependant resistors. all the components seemed relatively available so with some helpful correspondance from the originator of the system, i built a working one.

    there was a fair bit more trial and error and swearing than i have detailed, but i am confident that it will work, with a complete rebuild.

    then of course, i found the mechanical one

    both have shortcomings:
  • mechanisms need to be carefully constructed, electronics doesn't
  • the mechanism is bone-simple and can pass high current
  • the electronics is probably harder to fool

    without actually trying both its hard to know, but i think the mechanical one is harder to test on the ground and could come unstuck if the rocket goes off at an angle. the electronics is more likely to deploy, but it could do so at a high speed, also if the trajectory is crooked.

    maybe i should use both, i haven't decided.













  • Optical apogee detector test circuit =D


    20th May - Nozzle News is Good News

    i've worked out what the nozzles should be like, and am working on the nosecone.

    Bulkhead for bigger motor - blueprint

    Nozzle for smaller motor - blueprint

    Nozzle for bigger motor - blueprint

    i investigated "spinning" the nozzles, but my achievements have been a bit discouraging so far [pics], so i might have to have them machined from "Ledloy" steel.

    the nosecone will be cast in a 3-part plaster mould hopefully, and comprised of reinforced epoxy of some sort. before i can do that, i need to make a wooden blank... [drawing]




    nozzle renders from Blender



    August trans-winter drawings

    after a bit of discussion and to-and-fro with engineers i drew up these plans with a pencil. the idea was that they would be clearer and more legible, all i can really claim is that they have measurements explicitly labeled, instead of a grid you have to squint at.

    click for 1000px

    click for 1000px

    i haven't finished the nosecone form of course, but i have aquired a selection of neodymium-tipped darts. highly lethal, highly magnetical and in attractive red and green colours! do not eat.






    September 2012 - preparing to cast first stage



    September 12th, 2012

    Its been a long, long time, of hmm and ahh and oooeeer. Preparatory noises, extended indecision, not feeling the space and time to take the next step. The motor housing has been fitted in a testing stand and the pressure gauge has been hooked up, then it has simply sat in the corner, waiting for me.
    The next step is a bit of a leap - cook propellant I haven't made in AGES, in unprecedented quantities, with new ingredients and equipment [ok now im overplaying it] and mush it into liner/inhibitor tubes coated with R180 Epoxy, which has me intimidated already.

    December 11, 2017 - 8PM

    This motor was finally tested. After two years of it sitting in a test stand assembled and ready with ignitors in place, I set a date (and overshot it). Tested on my Dad’s farm a couple of days before he left for South America, it worked well and scared everything in earshot.
    The first stage fired straight away… followed by immediately the second stage. The nozzle blew off and was lost, all fuel was burned / ejected and the casing recoiled into the ground, and broke everything. A set of bathroom scales ($4, tip shop) was sacrificed and the motor casing is rippled, bent and bulged at the bulkhead end. Hydraulic fittings are mangled, pressure gauge survived though.
    Thrust and pressure were registered for a very short time and the nozzle was expanding the exhaust well. The design was ultimate faulty, likely packing to much fuel into a single stage, let alone two in the one casing. The difficulty in actually forming and inhibiting the propellant grains to the specification probably caused uncontrolled burning.

    December 21, 2017

    Ideas for the next design: 1. Keep it simple: a. 3d printed nozzles in sintered steel if feasible, or turned graphite, or cast concrete. b. simple threaded bulkhead c. sealed with setting material, Either Silicone RTV or putty. 2. Design changes: a. Casing of seamless steel, diameter 60+mm. b. 3x Bates grains and 1x Moon- or Slot-grain, half/half. c. single stage with high -to- sustaining thrust curve, moderate burn time.

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