New, Old , Now in AZ

Aug 13, 2022
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Hiya! I'm Mike. Long ago, I flew competition in the NARAM-16/19 time frame with a comeback for -23. The last competition was as a member of the Squirrels, NAR T006. As a fresh Mechanical Engineer out of the U of Md., I started a career in the Defense side of solid propulsion which did not allow time for the hobby. However, in those years, I learned much that will help now that I've picked it back up in retirement, and I also got to build lottsa 2.75" and 66mm rockets, paid for by others. In March '22, I went to to the G. Harry Stine Memorial Launch at the SSS field in the Kofa desert in AZ. and was reinfected with the rocket obsession.

Despite being a total novice at dual deployment and totally uncertified in HPR, I find I have many strong opinions about such systems and how they should operate. My training in Missile Propulsion Maintenance School made me feel somewhat appalled by the procedures for preparing a dual deploy rocket for flight and I decided to make my rockets differently. So, as any engineer would do, I set about laying out my requirements:
1. No handling loose black powder on the range! (Well, beyond what AeroTech has you do to perform a reload) Mankind may have used loose propellant for firearms for 400 years and fixed ammunition for only 100 years so far, but I think the advantages are plain....
2. No opening the AV bay on the range for normal operations. (yeah, I backed down on this one....)
3. No tools required for deployment preparation (Again, tools to support the AeroTech reload gotta be supported.)
4. NO POWERED STARTERS with ANY body parts within 2'!!!!
I can't tell you the coolllddd feeling in my gut when I realized folks were carting around armed, autonomous systems. Lucky we're only talking a few grains of BP. But a fully armed air-start? Behind the Line? I'm scared.

So, now I find myself with an obsession, an attitude, and a retirees income.... A DIY Altus Mega would seem the answer. Sparkfun, Adafruit, lottsa choices...

I built up a GPS, LoRa, AtMega32u4 version with a mirrored base station equipped with an OLED display and took it to Kofa for the SSS April Launch. I found the LoRa comm and the 400mAh LiPo combination seemed to work for as far as I felt like walking, constantly telling me where the other unit was. The OLED is NOT the display to use in full sun. The AtMega32u4 also was working torward the edge of it's memory so, future work changes to the SAMD M0 processor and an eInk display with an LED ring. (the Altus uses the STM32, dual core...)

It's August and I'm finishing the design of a ejection starter circuit that will fit on an Adafruit Feather board footprint. It incorporates an arming circuit, a monitor circuit (read, autonomous continuity checking) as well as handles the actual initiation pulse. Drone battery offerings are have really improved lately and I have a 3S 350mAh 30C I'll use to start my ejections. The starter itself is also DIY with 1" of 40ga Chromel 30 wrapped around a toothpick and coated with 4f BP glued on with a ping-pong ball dissolved in acetone. (Yes, I shoot BP muzzleloaders, too.) The Feather board is connected to the starter with an artful collection of silicone-coated wire, bits of BT20, BT-50, centering rings and copper foil tape. This will allow the toolless, no-touching-BP, ejection cartridge change I've required. I'm using the cheap ADXL345 accel in my design since I don't really care about motor performance for these flights, it's more about drag calculation and tilt sensing for these. The BME280 is a cheap baro sensor that should be able to do the job. These are used for elevator floor sensing for heavens sake, I oughtta be able to use it to tell up from down at apogee and 150m AGL for a main.

And now I see the new, fully integrated LILYGO T-Beam with GPS and LoRa for < $60usd...

I'm not making this into a shiny object chase, waiting on cooler flying weather in the desert....

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