Over the last few weeks I have been working on designing and building a BT-80 scale/sport-scale IRIS Hydra sounding rocket w/ booster. This is the later version of the IRIS sounding rocket that had 3 fins on the sustainer and a 3-tube booster w/ Sparrow engines inside and smallish booster fins.
Anyway, I finally nearly completed / built my first full prototype. When I originally looked at this design I thought it was going to be much easier than it turned out to be (just lots of interconnecting parts). The rocket is definitely the largest rocket I have built at 174cm/68.5" and 650g w/o chutes or engines (Big Bertha in pictures for size comparison).
I am designing this so it can be built with BT-80 or 2.6" thick-wall tubes and can use 24mm or 29mm engines (I am planning to launch with 3x D12 engines in the booster and 1x D12 engine in sustainer which gives me a 200m estimated flight - the lowest and least powerful launch combination that will work with this rocket). This model channels / vents two booster engines to hopefully ignite the sustainer engine and uses 1 booster engine (with delay) to eject a booster chute. Gap staging should be interesting (the little nozzle-extension part can be replaced with the pyramid tip for display). Nosecone is made in 3 quarter-twist locking parts and has mounting points for swappable nose weight (to go inside of tip or 2nd section) as well as generic mounting points for a sled (to position sled inside of 2nd or 3rd sections).
I need to add a bracket to the top of the booster section below the booster nosecone to help stabilize the weight of the sustainer, need to add the 3rd bracket details around the sustainer fins, and need to glue in motor blocks. I will also probably do a final coat of glue to clean up the fillets (still a bit wet in these pictures). Finally, I will also need to tweak parts to work with the 2.6" tubing version.
The scale data for this was provided by @Ez2cDave in this thread - https://www.rocketryforum.com/threads/iris-sounding-rocket-scale-data.155495/ (although I am still not 100% sure about the correct height for the sustainer fins on this model per my comments in that thread).
Anyway, I finally nearly completed / built my first full prototype. When I originally looked at this design I thought it was going to be much easier than it turned out to be (just lots of interconnecting parts). The rocket is definitely the largest rocket I have built at 174cm/68.5" and 650g w/o chutes or engines (Big Bertha in pictures for size comparison).
I am designing this so it can be built with BT-80 or 2.6" thick-wall tubes and can use 24mm or 29mm engines (I am planning to launch with 3x D12 engines in the booster and 1x D12 engine in sustainer which gives me a 200m estimated flight - the lowest and least powerful launch combination that will work with this rocket). This model channels / vents two booster engines to hopefully ignite the sustainer engine and uses 1 booster engine (with delay) to eject a booster chute. Gap staging should be interesting (the little nozzle-extension part can be replaced with the pyramid tip for display). Nosecone is made in 3 quarter-twist locking parts and has mounting points for swappable nose weight (to go inside of tip or 2nd section) as well as generic mounting points for a sled (to position sled inside of 2nd or 3rd sections).
I need to add a bracket to the top of the booster section below the booster nosecone to help stabilize the weight of the sustainer, need to add the 3rd bracket details around the sustainer fins, and need to glue in motor blocks. I will also probably do a final coat of glue to clean up the fillets (still a bit wet in these pictures). Finally, I will also need to tweak parts to work with the 2.6" tubing version.
The scale data for this was provided by @Ez2cDave in this thread - https://www.rocketryforum.com/threads/iris-sounding-rocket-scale-data.155495/ (although I am still not 100% sure about the correct height for the sustainer fins on this model per my comments in that thread).