Infinite Wishes 🌻🏳️‍⚧️🚀

Is a weblog by Emma Humphries

Abortion and Trans Liberation are two facets of our right to bodily autonomy.

28 Mar 2022 » Postmortem of an AeroTech I200W failure at Snow Ranch

A model rocket launching and prematurely ejecting its parachute

The afternoon of February 5th, at Snow Ranch in Stanislaus County, California, I flew my AeroTech Mega Initiator on an AeroTech 29mm I200 RMS which had a failure.

Having reviewed my phone camera footage of the launch, the reason for the failure was a premature ejection charge firing, fractions of a second after the motor’s propellant grain ignited.

Single frame capture of motor firing ejection charge at ignition

I think the root cause of the failure was leaving out the forward seal disk when assembling the motor. This component is combined with an o-ring seal which prevents the premature ignition of the ejection charge. But there was no burn through of the case. There was some scorching on the nylon shock cord consistent with the grain burning from both sides.

Detail of correct assembly of motor with forward seal disk

via AeroTech website

Lessons learned:

  • Don’t assemble reloads in the field if you are rushed or uncertain.

Build the day before launch, or bring or buy a DMS motor

We had a bunch of folks flying high power and the pads were full. I rushed my prep.

I could had purchased an equivalent DMS motor from the vendor on-site.

  • Ask for help

I had questions and needed clarification on the instructions packed with the RMS reload. I could have asked a neighbor if they had time to clear up my questions.

  • Fly another day if you’re unsure

I could have launched the rocket with a properly assembled motor another day.

I had to make repairs to get this rocket flying again. HPR is already expensive. I lucked out and someone found the video camera which was flung out of its mount. I could had avoided this with a little patience.

Replies to this post are welcome. You can send an email, or a WebMention. Be kind, not clever.

Send a WebMention