GDSCR - Gas Dynamic Stabilization Cluster Rocket

[lakeroadster]

Here's a Scratch Build / Scratch Design rocket that uses dual 24mm motors with rear eject recovery. It uses GDS, Gas Dynamic Stability, under thrust and spin tabs in order to ensure stability during the coast phase.

It also has a payload bay so it can carry an altimeter.

 

[Daddyisabar]

Singing:

Tiny spin fins, on my rocket, make me happy, make me feel fine.

Tiny spin fins, make it stable all over.
With a feeling that I'm gonna, fly it till the end of time.

 

[BABAR]

This one is a challenge, since you have succeeded before, I expect this will work. Is OpenRocket really able to input the effect of GDS and Spin Tabs. I am guessing neither is readily amenable to your wonderfully documented Swing Tests.

Question: this is quite different from your usual rear eject “spools”, although similar I think to your canted motors fighter jet rocket (I fergit the name.). How do you put a rear cone or cover that contains the parachute, that resists both gravity and acceleration forces but YIELDS to ejection forces? Seems like you need a Goldilocks touch, not too tight, not too loose.

 

[lakeroadster]

This one is a challenge, since you have succeeded before, I expect this will work. Is Open Rocket really able to input the effect of GDS and Spin Tabs. I am guessing neither is readily amenable to your wonderfully documented Swing Tests.

Open Rocket:​

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I use transparent fins and override the mass, CG and drag. This gives it the GDS stability, but negates the actual fins themselves​

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The little fins are canted and they provide the roll in Open Rocket​

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Question: this is quite different from your usual rear eject “spools”, although similar I think to your canted motors fighter jet rocket (I fergit the name.). How do you put a rear cone or cover that contains the parachute, that resists both gravity and acceleration forces but YIELDS to ejection forces? Seems like you need a Goldilocks touch, not too tight, not too loose.

On my F-79 I used fingers cut from a Nytril glove to hold the parachute in place.​

On this one... I'll just have to pack the chute "Just right".​

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[lakeroadster]

Day 01

 

[lakeroadster]

Day 02

 

[BABAR]

Are the insides of the “shroud/manifolds” lined with anything to resist ejection charge temperatures?

 

[lakeroadster]

Day 03

 

[lakeroadster]

Are the insides of the “shroud/manifolds” lined with anything to resist ejection charge temperatures?

Nope Oh, the humanity...​

 

[lakeroadster]

Rotation tabs revised to rotation canards...

 

[Daddyisabar]

Always a good thing when the fins move forward!

 

[lakeroadster]

Gas Dynamic Stabilization

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[Daddyisabar]

Beefy wood glue fillets!

Sunday, Sunday, Sunday!
Grab the kidz and come on down to see double barrel GDS in widely spaced pods, ducted rear ejection with canted canards to induce spin on the triple wide body! It's a Spinzilla fest for the entire family!

 

[BABAR]

How do you get motors in and more importantly out?

 

[Rschub]

I will be curious to see which way it spins, pro fin or anti fin twist direction.

 

[lakeroadster]

How do you get motors in and more importantly out?

As a wise man once said "It is amazing what you can do when you don't have a choice."​

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Actually they slide in easily. The BT-50 is sized to accept the motors... eazy peazy.​

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Removable metal engine retainers will be used. More to follow...​

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[lakeroadster]

Nose Cone - Bulkhead & Metal Motor Clips

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[lakeroadster]

Updated Simulation and Photo Studio

 

[NTP2]

You have made some thing too cool, again

 

[jqavins]

Getting the high roll rate, and keeping it through the coast phase, when the three body tubes make it like spinning a 1×3 board seems, um, sporty. You have a very good track record with far out designs, so I think you have a chance. Still, um... wow. (I also wonder what happens with GDS when the forces are off center, which they will be due to engine performance variations. But symmetry is overrated, and the roll drag gives me a lot more concern.)

 

[BABAR]

Gas Dynamic Stabilization

View attachment 607377​

How did you do the vents? do you have an extra long "jawed" hole punch? Those vents look perfectly clean and round, but a long distance from the tail end. I've had this problem on a number of my birds (although the hole needed to be about 2 and 1/4 inches from the tail), and my solutions were far less neat and elegant..

 

[BABAR]

Will the forward fins/canards be canted or just have a positive airfoil on one side? I believe the latter technique was used on the StovePipe

http://www.spacemodeling.org/jimz/eirp/eirp_56a.png

 

[lakeroadster]

How did you do the vents?

Just your basic hole punch...​

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Will the forward fins/canards be canted or just have a positive airfoil on one side?

Canted 30 degrees (Open Rocket only allows 15 degrees)​

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Getting the high roll rate, and keeping it through the coast phase, when the three body tubes make it like spinning a 1×3 board seems, um, sporty. You have a very good track record with far out designs, so I think you have a chance. Still, um... wow. (I also wonder what happens with GDS when the forces are off center, which they will be due to engine performance variations. But symmetry is overrated, and the roll drag gives me a lot more concern.)

Open Rocket shows a maximum roll rate of 3.72 rev/sec (223 rpm) at burnout. That roll rate slows to 0.32 rev/sec at chute deployment. I anticipate the rocket will go unstable sometime prior to chute deployment. But I canted the fins 30 degrees, not 15.​

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I also attempted to "balance" the rocket by putting the motor clips on one side and the launch lug on the other side. Thunk! exhibited some wobble during it's accent due to an offset motor clip, but nothing to severe. You could see the corkscrew in the motor smoke.​

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[lakeroadster]

Spin Tabs

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[Daddyisabar]

Hey dad! That guy has a rocket with crooked fins up front, no fins in back, widely spaced motors in pods and cheese grater holes punched in the motor tubes and rear ejection! Why doesn't our rocket look like that? Why does no one else's rocket look like that...DAD?

Well son, it's...a...I don't know.

 

[BABAR]

Not sure how much it matters, but the motor side pods are gonna act a bit like fins in creating air resistance to AXIAL rotation. Kinda like egg beater blades or mechanical bread dough kneaders.

I am impressed that OpenRocket can calculate roll rate at all, so no idea whether it accounts for this.

Your big fillets may earn their thickness, as at a rapid roll rate the pods are gonna experience at least some degree if centrifugal force, and the motors start with a good bit of mass.

 

[Daddyisabar]

The rotation will make the GDS calculations reach Vulcan levels of complexity. Calling Mr. Spock to do my mindsim!

 

[Daddyisabar]

The smoke trail will look like a double helix coil of self replicating DNA...AND THAT IS THE MEANING OF LIFE!

Chapter 3: Launching Silly Rockets. Yes, I have an idea for a silly rocket and have come to the Department of Silly Rockets for government funding.

Sorry, Elon and Jeff already have it all.

 

[Rschub]

I am betting on roll reversal due to the deflection of air over the pods, if anyone is keeping score.

 

[jqavins]

Do you mean you're betting on roll in the opposite direction from what the canted canards would otherwise cause? I'll take that bet. With all due respect to Lakeroadster's brilliant madness, I'm not going to bet heavily on success at all; however I would bet that, if there is a sufficient period of sufficient stability to observe a definitive direction of spin, that spin will be as intended.