Lakeroadster's Finless Rocket Utilizing Gas-Dynamic-Stabilization
- Thread starter lakeroadster
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lakeroadster
When in doubt... build hell-for-stout!
Allow me to introduce "Thunk!". I've been thinking, or is that thunking, about some of the comments and tried to incorporate those into this redesign. It is also an upscale to a BT-55.
You'll notice a series of small fins, in an attempt to get the rocket to spin while under power, which will add stability to the rocket when the motor shuts off and thus GDS is no longer providing stability.
You'll notice a series of small fins, in an attempt to get the rocket to spin while under power, which will add stability to the rocket when the motor shuts off and thus GDS is no longer providing stability.
- This version is designed to launch from inside a piece of 2" pvc pipe. That disc on the back is meant to seal the rocket to the pipe I.D. In doing so the pressure generated by the motor should give the rocket a projectile launch out of the tube.
- It's a 24 mm design, so that allows for a wider array of motors.
- The thought here is to launch it with the spinner fins and the rear disc. If it performs well I can modify it so the rear disc just slides onto the body, thus once the rocket leaves the pvc, the rear disc would slide off the rocket. Also, one set of the spinner fins could be removed.
- The nose cone will have a threaded stud for adding / removing nose weight.
I need to re-think (thunk) the rear seal.. while in the pvc, the pressure generated by the motor will escape up through the GDS openings. 
Maybe have the seal attached to a coupler that slips inside the base and seals the GDS holes. Then when the rocket pops out of the pvc, the ring and the coupler fall off the back of the rocket?
Thoughts?
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GlenP
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If the disc is aft of the vents, will you get any piston effect in the tube?
I would still stick the spinner fins near the aft end, and maybe not put them in a position at the front to reduce static stability. Hard to tell though once it gets spinning if that really matters or not.
I would still stick the spinner fins near the aft end, and maybe not put them in a position at the front to reduce static stability. Hard to tell though once it gets spinning if that really matters or not.
lakeroadster
When in doubt... build hell-for-stout!
You are right.
I need to redesign the rear sealing ring. Maybe have it attached to a coupler that slips inside the base and plugs the GDS holes. Then when the rocket pops out of the pvc, the ring and the coupler fall off the back of the rocket.
I'll take a look at that tomorrow. Thanks for you input.
lakeroadster
When in doubt... build hell-for-stout!
Here's a preliminary set of drawings for Thunk.
Redesigned Items:
Redesigned Items:
- The sealing ring sub-assembly is a separate item and is a loose slip fit into the bottom of the rocket. It seals the GDS hole to allow for a piston style launch of the rocket.
- The launch silo tube will have a cat whisker aperture (kind of like corn broom bristles) such that it will help to restrain the sealing ring when the rocket exits the tube.
- Motor hook is externally attached
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lakeroadster
When in doubt... build hell-for-stout!
Rev 01
- Added some 1/4" dowels to stiffen the lower body tube, due to the GDS cut-out
- Added a rear stiffener ring to prevent damage at ground hit
- Relocated the motor hook so it engages the motor through the GDS port
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lakeroadster
When in doubt... build hell-for-stout!
Rev 02
Added sheets 5 through 10
Added sheets 5 through 10
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lakeroadster
When in doubt... build hell-for-stout!
THUNK! Rendering.
The thought came to me today that it may well toast itself inside the pvc silo if the piston effect doesn't work...
The thought came to me today that it may well toast itself inside the pvc silo if the piston effect doesn't work...
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lakeroadster
When in doubt... build hell-for-stout!
Build Day One: Custom Turned Nose Cone
Found this hiding inside a piece of 2 x 2 pine in our wood shed. Go figure?
Found this hiding inside a piece of 2 x 2 pine in our wood shed. Go figure?
lakeroadster
When in doubt... build hell-for-stout!
Drawing Set, Rev 03, Re-post #1 of 2
I needed to add a drawing to the set... and since I can no longer update post #38, I'll just add all the drawings again here.
I needed to add a drawing to the set... and since I can no longer update post #38, I'll just add all the drawings again here.
lakeroadster
When in doubt... build hell-for-stout!
Drawing Set, Rev 03, Re-post #2 of 2
lakeroadster
When in doubt... build hell-for-stout!
Learning to do decals in Open Rocket...
lakeroadster
When in doubt... build hell-for-stout!
Build Day 02: Motor Mount - Body Tubes - Stiffener Dowels
lakeroadster
When in doubt... build hell-for-stout!
Build Day 3: GDS Ports & Motor Mount Installation, Post 1 of 2
lakeroadster
When in doubt... build hell-for-stout!
Build Day 3: GDS Ports & Motor Mount Installation, Post 2 of 2
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lakeroadster
When in doubt... build hell-for-stout!
Build Day 4: Spin Inducing Tabs
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lakeroadster
When in doubt... build hell-for-stout!
Build Day 5: Started Building The Rear Closure
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lakeroadster
When in doubt... build hell-for-stout!
I chucked the rocket into the wood lathe and turned down the tip chord of the spin tabs so the rocket will have a loose slip fit into it's launch silo, a piece of 2" sch 40 pipe.
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lakeroadster
When in doubt... build hell-for-stout!
Updated Flight Simulation to Open Rocket 22.02.beta.01
All the pieces parts, like the stiffeners and tape rings were just for "visuals" before, now they are actually body tubes and transitions. I'm lovin' the new OR..
All the pieces parts, like the stiffeners and tape rings were just for "visuals" before, now they are actually body tubes and transitions. I'm lovin' the new OR..
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lakeroadster
When in doubt... build hell-for-stout!
Now that Thunk! is built I updated the Open Rocket file to an "As Built" configuration.
The rocket has small fins, what I call spin tabs, that are there to get the rocket to spin during the GDS phase, such that when the rocket's motor burnout occurs the rocket will maintain stability throughout the coast phase.
Maximum roll rate, per Open Rocket, is 65 rotations per second (3,900 rpm's)
which happens 0.04 seconds before motor burnout occurs... which is pretty much ideal in regard to timing.
By the time the rocket reaches apogee the spin rate has dropped to 6.23 rotations per second (374 rpm)
I wonder what roll rate would really be needed to maintain stability during the coasting phase?
I can't imagine the 3,900 rpm will be accurate.. seems like that much rpm would destroy the rocket. It's a very symmetrical design, except for the steel motor hook... but that's probably enough of an imbalance to hinder it from reaching such a high rpm.
Any thoughts?
The rocket has small fins, what I call spin tabs, that are there to get the rocket to spin during the GDS phase, such that when the rocket's motor burnout occurs the rocket will maintain stability throughout the coast phase.
Maximum roll rate, per Open Rocket, is 65 rotations per second (3,900 rpm's)
which happens 0.04 seconds before motor burnout occurs... which is pretty much ideal in regard to timing.By the time the rocket reaches apogee the spin rate has dropped to 6.23 rotations per second (374 rpm)
I wonder what roll rate would really be needed to maintain stability during the coasting phase?
I can't imagine the 3,900 rpm will be accurate.. seems like that much rpm would destroy the rocket. It's a very symmetrical design, except for the steel motor hook... but that's probably enough of an imbalance to hinder it from reaching such a high rpm.
Any thoughts?
lakeroadster
When in doubt... build hell-for-stout!
1st day of the year above 60 degrees... The new members of the fleet are heading for the fence... time to break out of paint jail!
Primer
Primer
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With that awesome paint he really has confidence it is stable, he really knows what he is doing! GDS is the bees knees.
lakeroadster
When in doubt... build hell-for-stout!
2 days ago it was snowing... and today 62 F. and sunny. Time to spray some color on ole Thunk!
It is soooo nice that just about every day is a dry, sunny paint day in the Wild Wild West!
lakeroadster
When in doubt... build hell-for-stout!
Removed the masking tape and newspaper. Still need to hand paint the fin tabs and the lower stiffener rods... once the weather gets warm again.
lakeroadster
When in doubt... build hell-for-stout!
Hand painted the stiffener rods and bottom closure ring. My hand painting skills are about a 5 out of 10...
lakeroadster
When in doubt... build hell-for-stout!
Went to Home Depot and bought all the parts needed to build the launch silo.
Some assembly required, super easy to find all the parts... Who Knew?
Some assembly required, super easy to find all the parts... Who Knew?
Reminds me of the old Apogee warehouse in the Springs.
lakeroadster
When in doubt... build hell-for-stout!
Worked on the launch silo some this afternoon. It's in redesign mode.
I was going to have the whip go through the sidewall as shown below. Once I did a mockup, I realized this will make attaching the launch controller leads to the motor ignitor difficult, very difficult.
The plan now is to make a sort of cartridge that attaches to the threaded plug. That way I can bench load the rocket, attach the whip and then slide that into the silo, and thread the plug / cartridge in.
This will also allow me to make some sort of impingement / blast deflector as a part of the cartridge to protect most of the whip wiring and the lower threads in the coupling and plug.
I was going to have the whip go through the sidewall as shown below. Once I did a mockup, I realized this will make attaching the launch controller leads to the motor ignitor difficult, very difficult.
The plan now is to make a sort of cartridge that attaches to the threaded plug. That way I can bench load the rocket, attach the whip and then slide that into the silo, and thread the plug / cartridge in.
This will also allow me to make some sort of impingement / blast deflector as a part of the cartridge to protect most of the whip wiring and the lower threads in the coupling and plug.
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