Scratch build thread - 2.2" three stage

[Cameron Anderson]

Cold weather has forced me indoors for the winter to build. I got all my parts for my 3 stage last week. All airframe, couplers, anf bulkplates are from PML. Hardware is from Ace Hardware.

My goal is to create a modular system around 54mm airframe with interchangeable electronics bays and booster/sustainer combos.

Booster 1 (B1) - 22" long, 38mm motor mount. motor for 2 stage, J for 3

Electronics bays serve as interstage couplers.

E-Bay 1 (E1) - 4" long, contains RRC2 and 9v, apogee chute deployment for B1. B1 will always fly with E1.

Sustainer 1 (S1) - also 22" long, 29mm motor mount intended for i205 or H195.

E-bay 2 (E2) - 7" long, will only fly in three stage configuration. Will contain another RRC2 for S1 apogee chute deployment and PET2+ for S1 motor ignition and B1-E1/S1 separation.

Sustainer 2 (S2) - identical to S1.

E-bay 3 (E3) - 9" long, will always be upper e-bay for all flights (whether 2 or 3 stage). Will contain T3 GPS, RRC2 for S2 apogee drogue and S2 700' main, second PET2+ (for S1 sep and S2 motor ignition in 3 stage configuration, in two stage configuration it will seperate the booster and sustainer and light the sustsiner motor) and and power for those components.

Right now I'm working on the 38mm booster. I'll use an Aerotech 38/600 reload (i435 or i284) in the 2 stage configuration and a 38/720 (J500) in the three stage figuration.

Depending on motors and motor timing, 2 stage configuration is simming between 5,000 and 9,000 feet and 3 stage is 6,000 to 11,500 feet.

Depending on local weather, I"d like to fly in a month or two. More to follow.

 

[Cameron Anderson]

Finished B1 and E1. Used scrap airframe to cut a key which I glued to E1 and then cut a corresponding notch in B1.

I'm not sure if I am unnecessarily worried about airframe twisting or not. Either way, it's easily fabricated piece of mind.

 

[BABAR]

Looking good!

 

[Cameron Anderson]

S1 with fins tacked in place, still needs fillets. Total airframe height here is 47.5".

Also pictured is i205 motor for test.

 

[Cameron Anderson]

S1 motor mount is done with centering rings in place and ignitor conduit passing through all 3 rings.

I also finished my recovery retention assembly. I prefer apogee-drogue main-800 dual deployment. My shock cord anchors from both ends of my e-bay to the chutes. I anchor the drogue and of the line to a full airframe diameter bulkplate with an eye bolt. I then epoxy a small length of coupler in front of the bulkplate relative to the pulling force to further reinforce the retention point and prevent separation. I've done this for year's and never once lost retention.

 

[Cameron Anderson]

Using some allthread to feed the bulkplate assembly over the wire conduit.

 

[Cameron Anderson]

Finished major airframe assembly today. 38/720, i205, and H195 for scale.

Just need to pack the chutes, test sep charges, and load the electronics.

Booster 1 sep at 1,500 feet
Sustainer 1 sep at 4,400 feet
Sustainer 2 goes supersonic at 6,200 feet
11,955 apogee in current configuration.

 

[Cameron Anderson]

Prepping for a 2-stage test flight I'm 6 July instead of the full-up 3-stage stack first flight. Booster will be an AT RMS 38/600 i435R to an AT DMS H195BT sustainer.

Here are both sides of the av bay sled - batteries not secured, and altimeter events not wired in.

I have my timer leads secured - they are just long enough to clear the e-bay and tie into the stage separation charge and second stage ignitor respectively. They will be break away in design and just twisted to their respective leads and covered with some electrical tape so the e-bay can still seperate from the motor mount assembly for a streamer deployment as part of the sustainer DD recovery. Normally i'd use some sort of connector to break away but space is at a premium so I'm trying something new.

The T3 tracker will be powered up pre-flight to ensure tracking. The GPS and the timer don't have switches - again, in the name of space saving I'm using spliced power lines that I feed externally of the av bay, twist together before flight, tape, and push back through the pressure holes. I've done it before on min diameter airframe and it works well.

 

[Rob702Martinez]

Nice! Looking forward to the launch report.

 

[Cameron Anderson]

Camera wobble and whistle is due to the fact that I secured the camera to the airframe with gorilla tape.

 

[Cameron Anderson]

Lift off was nominal. I can't tell if the interstage coupler/av bay failed, if the separation charge blew early, or if the booster airframe suffered failure, but you can clearly see in the video that there is a shift in The stack prior to sustainer motor ignition. The top of the booster airframe suffered a crack a week ago when it was dropped...it was repaired with CA glue and epoxy and looked great, so I'm not sure that was the failure point. Incorrect timer detection of lift off and early sep charge firing is my assumption (timer setting of BECO +0.5 was confirmed post-flight).
Even with early charge firing, separation of the sustainer and interstate wasn't clean and sustainer engine ignition finally blew the two parts apart.

Here is a picture of BEI as the sustainer coasts away.

 

[Cameron Anderson]

I was building this rocket in parallel with a larger 3" custom 2-stage and trying different construction methods on each. I was far into the construction when I realized the phenolic tubing was strong enough for flight but too brittle for repeated flights and recovery. This airframe was always going to be a testbed, but unfortunately it would more than likely only make one flight. All my motor hardware, chutes, and electronics were recovered, but the interstate coupler suffered cstostrophic staging damage, the booster suffered catastrophic landing damage, and the sustainer suffered minor landing damage.

Booster apogee was 2,722'
Sustainer apogee was 5,915'

 

[Cameron Anderson]

Despite the damage, all my test objectives were met. Certain build features worked perfectly, others failed miserably.

 

[Wallace]

Nice! Phenolic is just too damn brittle without reinforcement of some sort. I too have learned that the hard way...