Long time, no update on the GBI mk18 (Great Big Inductor, 18mm).
I flew it with the slight base flange a couple times. Mixed results that were kind of encouraging, but I wasn't entirely pleased with them.
First flight on a B6-2 traced a Z in the sky. No exaggeration. For whatever reason it made two rather sharp turns at about ~100 and ~150 ft up.
It also ripped the shockcord from my thin cardboard nose bulkhead, so the epoxy and paper shroud nose separated and landed on its own (that thing's rock solid).
LCO made the most of it: "And we have smooth capsule deployment. Booster away!"
I reattached the shockcord with epoxy this time. Second flight on a C6-3 traced a kind of logarithmic path to deployment. Slight wiggle at burnout, but nothing crazy.
Worth noting is that both these flights had only barely noticeable black spots in the induction tube from exhaust. Looks like the additional airflow did a great job of protecting the tube interior.
For the third flight, I cut off the flange, and put a coupler in the end to friction fit either the flange, or a new ring piece with the same height and diameter. Both of them were made to match what looks like a loading ring on the real ground-based interceptor. This ring is on no way sufficient to stabilize a conventional rocket of this dimension, but I wanted to see how it affected the GBI mk18's behavior.
It was the best flight of my inductor yet on a C6-5. Almost perfectly straight.
Unfortunately, my Estimeter jammed the parachute and it nose dived onto its open body tube. The chute is kinda charred.
Further inspection shows that the rougher coupler caught more of the exhaust and started to char, which then caught and dislodged the ring piece, burning it too.
Plus the motor hook pushed forward and crimped the motor tube a bit.
Autopsy results:
I'm going to save the nosecone, extract the shockcord from the old motor mount and make a new body/induction section.
It won't have the coupler in the back, I'll build it with the ring from the start, make the portholes cleaner, and actually paint it!
After the ring testflight, I'm encouraged for the chances of upscaling. If this rebuild works out, GBI mk24 will be greenlit!