With a little help from my friends: 2-stage 54mm min diameter

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rocketace

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Time to get high with a little help from my friends!

I have had a lot of fun with extreme flights with 38mm motors and now I am ready for a new challenge. I am in beginning design stage of a 54mm to 54mm 2 stage rocket that will be all minimum diameter. I have been doing a lot of research on current and past extreme projects from all you fine/crazy people. I am working on this project with a buddy of mine, but I want to document as much as I can here so yall can pick apart everything to find potential areas we over looked.

Goal:
First and foremost…safety.
After that…To get as high as possible with a 54mm motors in a 2 stage. But no Loki, sadly just not in the budget for this build.

Design-Overall:
The design is far from finalized, but after bouncing around dozens of configurations. The below is my current top ideas.

Airframe:
Current plan is 4-5layers (trying to match the tail cone diameter) of CF 3k Twill with 820 epoxy from sollercomposites.com. Mandrel will be a Blue Tube full length coupler. Since we will be using tape wire for sustainer ignition and possibly booster separation, some test layups will be done to figure out what ID we will need.

Nose cone:
Keeping it simple here by just using a Wildman FG nosecone. I will be adding a sled at the top for a GPS tracker.

Fins:
1/8” FG attached with RocketPoxy. Tip to tip is still TBD. I don’t think it will be needed for the flight profile, but it would be nice to have so I don’t have to worry if it has a hard landing. However, the current design has the sustainer OD airframe as the coupler which complicates things for tip-2-tip. A partial tip-2-tip is possible as well.

Recovery set up:
This is the main focus at the moment. So many design choices! I am highly leaning towards single recovery bay for each stage with the main held closed by a cable cutter. The ISC would be the nose cone of the booster. However, a 2 bay design isn’t ruled out yet nor is a chute cannon….

Recovery gear:
Most parts from Top Flight. Harness will be 1/8” TK, Main chutes planned to be 40” but not sure if I want to do 1.7oz or 1.1oz yet. Drogue or drogue-less has not been decided but I am leaning towards using a drogue. Booster drogue would be a standard 12” X-type and sustainer I am thinking a 12” Ultra-X-Type. Sizes are not finalized and any recommendations would be appreciated, especially if you have any data on decent rates for a rocket around 5lbs after burnout.

Electronics:
This is the second focus as the moment. There is no easy place to put the electronics, especially in the sustainer. If I put the altimeters just above the motor we will have to figure out if we can still arm wirelessly (like a slot antenna in one of Jims posts). If it is not right above the motor then we have to figure out how to incorporate quick disconnects for the sustainer ignition wires. Anyway, below is the current planned electronics to be used. Information in the parenthesis will be the arming method.

Sustainer:
Featherweight GPS - Ttracker (Magnetic switch)
Split 4K – Camera (TBD )
Raven V4 – Airstart – Backup Apogee/Main – (Wifi for power and 2 Screw switch for shunt and short)
PerfectFlight SLCF –Primary Apogee/Main (Screw switch)…Now I just need to time it right to get one

Booster:
EggFinder GPS – Tacker (Magnetic switch)
Eggtimer Quantum – Separation – Backup Apogee/Main – (Wifi switch)
PerfectFlight MAWD – Primary Apogee/Main (Screw switch)

A few notes: I might switch out the PF MAWD to something else that is a smaller package. Also, LabRat Pull switches might replace some screw switches.

Interstage coupler:
The current design has a coupler that will be external to the airframes. This will add a bit of drag, but as long as the booster separates after it burns the drag penalty shouldn’t be too bad. The coupler will be FG so the tracker and wifi switch can operate. The sustainer fins will be ~2.5 from the bottom to leave room to slide it in the coupler.

Motors:
I currently have 2 AT-K250 and a CTI K300. I will be using those for the sustainer motors. I am crossing my fingers on the K300 casing holds together… For the booster I am thinking of using the AT 54-2800 motors. If I want to keep it in the L range I can use the L1090 with the K250 and the K1050 with the K300. After we fly it as high as possible, we might want to go as fast as possible! That motor combo is TBD.

Flight Tests:
Flight test 1 - Sustainer only) One of the K250s I will use as a sustainer only flight test. This will be to test the stability of the rocket, recovery sequence, as well as testing how long the K250 takes to pressurize with whatever igniter we decide to fly with. I am also contemplating doing a smaller initial shake down flight an a small J first.

Flight test 2 – Full stack wo/sustainer motor) Motor is TBD, but probably will be a big J or small K, but I want to mimic launch rail exit velocity as close as I can. This will test the full stack stability, separation, and recovery sequence. Also, this will demonstrate a safe recovery if sustainer doesn’t light.

Safety:
Using a shunt and a short for sustainer ignitor separate from other switches
Having an altitude and velocity check for sustainer ignition
Utilizing a wifi switch for arming Raven that will control sustainer ignition (aiming for no ladder)
Will be following a checklist and arming sequence to reduce hazards as much as possible
Test flights to prove stability, stage separation, recovery, and to check the checklists.

Of course at this point actual values, checklists, shunts, ect are all TBD. Much testing will be needed during this project.

Test rocket:
On top of all this I should mention I have yet to do any HPR two stage rockets. I have kept up with and looked at many 2+ stage flights on here over the past 10+ years and I believe I am ready for the challenge! Once the design (and before the construction) for the above rocket is complete I am planning on building a less extreme 2 stage that will use the same electronics, recovery, and staging configuration. I will use this rocket as my test bed to gain experience in the world of HPR 2 stage. Due to current on hand materials, I am planning for this rocket to be made out of thick walled 2.5” OD cardboard, 0.125-0.25” plywood fins, 3D printed nosecone, 38mm MMT in booster, 29mm MMT in the sustainer. This rocket will also have a few test flights before its first full 2 stage flight. This test rocket will be a big step and serve as a proof of concept and to validate that we are on the right track.



Initial Rocksim design:
RockSim.jpg


Possible Sustainer configurations:
PPT Sustainer.jpg

Possible Booster configurations:
PPT Booster.jpg

Rejected ideas:
Rejected Designs.jpg

So...Feel free to follow along and please provide any input you may have!
 

JimJarvis50

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Jason,

Looks like a very fun project. Come find me at the shootout and we can discuss. We'll need to talk about how Ravens are used for staging.

Jim
 
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