Getting closer to starting my build and wanted to share the project. I've been away from HPR for around ~30 years, got back into the hobby last year as a way to live vicariously through my two little boys. Achieved L1 and L2 certifications last year at Rocstock 50 and decided to start planning my L3 certification.
This first post will provide background and general approach, will post additional parts as the project develops, this may take some time as I'm trying to avoid re-work by re-confirming the design as I gather the components, have about 95% of items, but I'm keen on double checking everything and iterating as needed as I get the last few items. Also this Virus thing has thrown in a spanner into life, so build updates may come sporadically.
Been in communication with RocStock TAP members on this project and following the prescribed process to a T.
Beyond achieving L3 certification, want to scratch build a design that (1) looks good, (2) carries a HD camera, (3) highly re-usable - easy to re-launch the same day multiple times, (4) fly on a wide range of motors (really, really wide range), (5) robust recovery system and (6) incorporate know-how of the people who have pushed the envelope and succeeded and more importantly failed, but have been gracious to share their experiences on forums such as this one.
The rocket will be 85 inches long, with a conical (4:1) nose cone, 3 fins, tail cone, modular fin can (for L3 attempt will fly it with a 75MM motor mount).
Inspiration/goals for the design comes in all forms:
(1) From my prior time in rocketry - loved the feeling of launching, recovering and relaunching the same rocket over and over again. Especially when changing up the motors, thrilling to see how they would perform.
(2) Love long duration motors, want to build a rocket that can stay under the Lucerne waiver and use an L395 motor - 12 second duration.
(3) On-board rocket videos are awesome, especially looking at the horizon.
(4) Clean sheet design, but leverage what works and others have tested - don't re-invent the wheel, but approach things fresh.
From this, I made the following choices:
Plan on multiple flights before going for the L3 certification on a M1101. Want to test out all the systems and airframe robustness, will likely have its maiden voyage on a K motor then step up to a L motor (unless it needs more shake down flights on K motors) before going for an M launch.
My pie in the sky goal, is to take it to Balls and push it to max, be great to fly the same rocket to 2-3k feet and then go gangbusters without really changing anything on main part of the rocket.
See through picture
75MM fincan version - L3 cert design
98MM min diameter version - fin can swapped out for a full aluminum fin can (post L3 if it works)
This first post will provide background and general approach, will post additional parts as the project develops, this may take some time as I'm trying to avoid re-work by re-confirming the design as I gather the components, have about 95% of items, but I'm keen on double checking everything and iterating as needed as I get the last few items. Also this Virus thing has thrown in a spanner into life, so build updates may come sporadically.
Been in communication with RocStock TAP members on this project and following the prescribed process to a T.
Beyond achieving L3 certification, want to scratch build a design that (1) looks good, (2) carries a HD camera, (3) highly re-usable - easy to re-launch the same day multiple times, (4) fly on a wide range of motors (really, really wide range), (5) robust recovery system and (6) incorporate know-how of the people who have pushed the envelope and succeeded and more importantly failed, but have been gracious to share their experiences on forums such as this one.
The rocket will be 85 inches long, with a conical (4:1) nose cone, 3 fins, tail cone, modular fin can (for L3 attempt will fly it with a 75MM motor mount).
Inspiration/goals for the design comes in all forms:
(1) From my prior time in rocketry - loved the feeling of launching, recovering and relaunching the same rocket over and over again. Especially when changing up the motors, thrilling to see how they would perform.
(2) Love long duration motors, want to build a rocket that can stay under the Lucerne waiver and use an L395 motor - 12 second duration.
(3) On-board rocket videos are awesome, especially looking at the horizon.
(4) Clean sheet design, but leverage what works and others have tested - don't re-invent the wheel, but approach things fresh.
From this, I made the following choices:
- 4:1 conical nose cone - (1) not looking for the most aero design, would have gone with a 5:1 or 6:1 VK. In fact a Conical shape helps in trying to stay under the lucerne waiver. It looks cool, and my kids can easily draw the rocket using crayons.
- HD carbon fiber airframe, sourced from public missiles (slotted cut to length) - reduce weight where possible, but overbuild the rocket to handle the largest 98MM motor there is (O)
- Airframe will be in two pieces, and not have the traditional location of the break and a different nose cone attachment than typical.
- The nose cone (Madcow fiberglass) has a shoulder that typically has a coupler glued in place, then that coupler woudl slide into the main airframe. I'm inverting this, the coupler will be glued into the top of the airframe, with it exposed past the top of the airframe and the nose cone sliding onto the coupler. Couple of reasons for this, (1) Coupler acts a stop for the 98MM aeropak motor retainer, (2) the coupler double ups the main airframe above the aeropak retainer, creating a very strong airframe to take on the biggest motors, (3) allows use of the inside of the nose cone base as space for recovery gear, (4) noticed others pushing the envelop had failures of the airframe where there is a break in the airframe, typically a bit of distance from the top of the nose cone (usually the AV/Payload bay meeting the rest of the airframe), hence wanted to move the break in the airframe as far forward as possible.
- The rocket has another break, but this is found at the bottom, it will have a "fin can" made out of the same HD carbon fiber, but it will only be as tall as needed to attach the fins. This fin can will not be glued to the airframe, instead it will have a coupler glued in place, and that coupler will slide into the bottom of the airframe. Using an aeropak 98MM retainer for the motor, this allows (1) to use the motor to sandwhich the fin can between the end cap and the main airframe, (2) take away the compressive forces off most of the airframe and have the motor only be compressing a small section of the airframe (which is double walled) via the aeropak retainer (3) allow to change the fin can for different motors / fin designs as needed, thereby leveraging all the components and while in essence having a different rocket. Already have the components to switch it to a 98MM min diameter configuration, for example.
- 3 Fins made out of aluminum, sourced from Binder Design (awesome craftsmanship). Doing research was tempted to use carbon fiber or fiberglass fins, however if the rocket is ever pushed to the max, fin flutter could have been a concern, gave some thought to using 4 or more fins to reduce the risk of fin flutter by having "shorter" spans. However, decided to go with aluminum since I rather over build this component and not worry about potential cracks one could not see/notice developing, again going to inspiration of item (1) above. Fins will extend beyond the bottom of the airframe to the tailcone. The shape is inspired by the wing tips of F22 fighter, and did not want them to extend past the bottom of the rocket to reduce fin damage on landing. They will be attached in a traditional through the wall method, will create epoxy dams to affix them to multiple surfaces not just the motor mount tube.
- 3D printed tailcone. Reason is it looks cool and aerodynamic, I'm sure it helps a bit with base drag, but it is more an artistic feature, did not spend time trying to come up with the most aero shape, it is conical in design, for visual symmetry with the nose cone. The tailcone is not a load bearing part and will not be touching the motor case in any way (don't want it to melt), will be using a fiberglass motor mount tube and even the motor end cap will not directly touch the tailcone.
- Will be using dual egg timer protons for deployment activation. will use centrifugal tube charge in a PVC charge tube holder to separate the rocket at apogee. 24" drouge chute (rocketman). At lower altitude main chute (rocketman) will deploy by a tender descender moving the connection of the drouge chute from the main airframe (it will disconnect it) to the top of the deployment bag (rocketman). The main chute will be held inside the main airframe until the drouge pulls it out. Grateful to all that posted videos of their chute deployments, really insightful to see what worked and what did not and the near misses of tangles that magically un-tangled before the main. This led me to using a deployment bag and designing it to stay inside the main airframe.
- AV bay will be a slide in sled from the top of the rocket that will be followed by the recovery gear. The AV sled will be locked in place to the top of the aeropack retainer, then the recovery gear will be place inside the main airframe and bottom of the nosecone. The AV sled will have the two eggtimer protons, each with its own battery and screw switch accessible via vent holes, it will also have a HD camera recording the flight, the camera will look out horizontally via window epoxied in place. The window will be flush with the curvature of the airframe, using a watch lens cover that perfectly matches the curvature of the 98MM airframe, eliminating any potential drag from a camera setup while giving clear views.
- The nose cone will house a Eggtimer GPS transmitter. I'm splitting the nose cone into two functional areas to maximize the use of space, the top half will house the GPS TX and battery and the lower part will have a portion of the recovery gear.
Plan on multiple flights before going for the L3 certification on a M1101. Want to test out all the systems and airframe robustness, will likely have its maiden voyage on a K motor then step up to a L motor (unless it needs more shake down flights on K motors) before going for an M launch.
My pie in the sky goal, is to take it to Balls and push it to max, be great to fly the same rocket to 2-3k feet and then go gangbusters without really changing anything on main part of the rocket.
See through picture
75MM fincan version - L3 cert design
98MM min diameter version - fin can swapped out for a full aluminum fin can (post L3 if it works)
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