[Joe Barnard] made a solid propellant rocket motor, and as one does in such situations, he put it through its paces on the test stand. The video below is not about the test, nor is it about the motor’s construction. Rather, it’s a deconstruction of the remains of the motor in order to better understand its design, and it’s pretty interesting stuff.
Somewhere along the way, [Joe], aka “BPS.Space” on YouTube, transitioned from enthusiastic model rocketeer to full-fledged missile-man, and in the process stepped up his motor game considerably. The motor that goes under the knife — or rather, the bandsaw — in this video is his “Simplex V2,” a completely DIY build of [Joe]’s design. For scale, the casing is made from a 6″ (15 cm) diameter piece of aluminum tubing over a meter in length, with a machined aluminum forward closure and a composite nozzle assembly. This is a pretty serious piece of engineering.
The closure and the nozzle are the focus of the video, which makes sense since that’s where most of the action takes place. To understand what happened during the test, [Joe] lopped them off and cut them roughly in half longitudinally. The nozzle throat, which was machined from a slug of graphite, fared remarkably well during the test, accumulating only a little slag from the propellant, a combination of powdered aluminum, ammonium perchlorate, and HTBP resin. The lower part of the nozzle, made from phenolic-impregnated linen, did pretty well too, building up a pyrolyzed layer that acted much like a space capsule’s ablative heat shield would. The forward closure, whose sole job is to contain the inferno and direct the exhaust anywhere but up, took more of a beating but stood up to the challenge. Especially interesting was the state of the O-rings and the way that the igniter interfaced with the closure.
Post mortems like these are valuable teaching tools, and while it must be heartbreaking to destroy something you put so much work into, you can’t improve what you can’t measure. Hats off to [Joe] for the peek inside his world. Continue reading “A Look Inside A DIY Rocket Motor”
