Electrosonic: the big picture.

Electrosonic rocket project:

grand plans and modest means

finally im building another rocket =D and taking pictures along the way. these previously-penned pages covered the design and planning and motor development:

Rocket vehicle airframe fins n cones etc R+D

Rocket motor nozzles n Kn ratios etc design + development

First launch, huge explosion, mayhem, panic, end of an era e.t.c.

so this page will cover the real thing - made more or less to spec, changed where necessarry or even made up on the spot to cover design blindspots! heres hoping it turns out well!

step 1:

in which i cut the fins out of 3mm plywood with my brand-newly repaired-from-a-lightning-strike, because-some-old-witch-didnt-want-it-anymore-surprisingly SCROLLSAW! variable speed, vac extract, dust puffer and lamp all working well! RRRRwwwwwWWRRRRRRRRRRRRRRRRRRRRRRRRRRRR! thankyou jaycar and helpful man who found the correct thyristors, diodes and fuse!

i'm attaching them with Epiglue, which is so tough it could beat up industrial diamonds im sure. then im sealing and glassing them at the roots with a handkerchief. astrohandkerchief that is. also sealed the mid coupler.

Recovery electrics!
here they are! an air-speed actuated, deceleration-sensing assembly with adjustable preload.
a CR2 lithium camera battery provides 3V and lots of current, and the radial retaining screws are used as test-terminals :) the ignitor screws down on the top face of the disc.


what should the parachute be like? i didnt really do any research or design on any parachute type paraphenalia, thinking i'd work it out when i got to it.
well now i am at it :) so this is the plan:

a shaped chute of large size to ensure a soft landing, strong for +150km/h ejection with a hole in the top for stability. should be lairy as all hell so as to be very easy to spot and track on the way down. must fit into the nosecone with all shrouds and stuff and come out readily when pulled.

im going to go with a conical shape, made of ripstop spinaker nylon of medium-weight, which the very helpful man at Hood sailmakers helped me choose and told me how to use. check out the colours, awesome. i made a couple of mockups out of newspaper first, and a 1.2 meter, 8-panel design suggested itself. here goes!

paper mockup on nylon stock from hood

nylon of both colours laid out

joining the panels for stitching with double-sided tape

the stitching, the madness! this is a three-step zigzag stitch.


something else i didnt give any thought, except that it be lairy and fun. heres one idea i painted in Blender...

i didn't end up using this paint scheme, partly for practicalities sake and also because it looks like a circus prop - there is high-visibility and then there's silly.
and i like silly, but then theres stupid. realising this i mixed some chromacryl together to get this very deep, fairly lairy orange which i whacked on willy-nilly:

then i took it outside to test the ejection system. i strapped it to a folding step-stool and shorted out the mercury switch via the test wiring - thats the clip-lead. then i used a steel bar to retain the flap, got a few meters away behind a bush and pulled the bar clear with a line...

the effect wasnt quite instantaneous, though prompt. it went pop-sssshhh and the nosecone moved as above. i experimented with charges including little firecrackers and plugged holes and used graphite powder on the coupler.

even two crackers dont produce very much gas at all. they moved the cone with the sudden pressure spike but more volume of gas was required to finish the job - the 5th attempt used an inch or so of 6mm paper tube, full of gunpowder, and fired the cone right out to the end of the tether. luckilly the only damage from all this was a bit of a recoil dent in the bottom of the mid-tube.

back to paint: i finished it off with some dots and stripes in chute colours here and there, to give it some personality :)