Lakeroadster's 2 Stage Red Nova

[lakeroadster]

Chevrolet Nova's and Model Rocket Fin Flutter... a couple things that bring back good memories from my youth.

Fin Flutter

In high school (late 1970's) I did a scratch build using a BT-50, except I used cardboard for fins. The rocket did fine on the required string-swing test and showed it to be a stable bird.​

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It was launched on the baseball field at school. Powered by a C6-5 it was my first rocket that experienced severe fin flutter. The rocket launched and made a bbbuuuurrrrr sound, then nearly stopped maybe 20 feet into the flight, when it slowed down the flutter stopped and the rocket sped skyward, only to again be slowed by the fin flutter.​

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As I recall it did that 3 times that flight. Once the motors thrust portion expired the rocket crashed before the chute popped, due to the low apogee.​

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It sure was a crowd pleaser though.​

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Chevrolet Nova's

My 1st car was a Forest Green 1970... next was a Firethorn Red 1977​

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David Warren posted an Estes Red Nova he was building over on the Estes Facebook page and I inquired as to if it was a 2 stage? It wasn't. I know it's been done before, but I'm thinking this would be a nice addition to the build pile.

The screen shots below are from a model / simulation I did in Open Rocket. I started with an ORK file that @EXPjawa posted here on TRF. Thanks!

It was pretty simple making it into a 2 stage, and with a custom turned pine nose cone the rocket will not even require any ballast for stability. The rear extensions on the booster fins are thin cardboard... which with any luck should replicate the fin flutter anomaly. Should be interesting to see the rocket slow down a couple times, speed back up and then fire the second stage.



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I also ran a 2 stage simulation inspired by @Dotini and his ring fin rockets. The ring fin doubles as a display stand.

Ring fin is made by wrapping glued paper around a mold and then cutting it to size on my wood lathe. It is attached to the rocket with 3/16" round dowels, with the dowels penetrating through the body wall and onto the motor tube for extra rigidity.

 

[jqavins]

Nice work. Good luck with duplicating the "flutter braking" effect. Repeating an accident is always challenging.

I like that ring mounting a lot, and may just steal it.

I urge you to make sure the booster isn't stable after separation. Core samples are bad, even from low altitude.

I built a Red Nova last year, and with my Quest Terrier Orion two stage conversion in progress (it's been in progress for about eight years now) I was thinking another Nova might be next for the treatment.

Does anyone know if the Red Nova kit is based on any "real" rocket/missile? A quick Google search seems to indicate it is not.

 

[lakeroadster]

I urge you to make sure the booster isn't stable after separation. Core samples are bad, even from low altitude.

Thanks for the tip. I just ran the simulation and the booster is indeed marginally stable. But if I add some ballast at the rear centering ring I can tip the scale.

Does anyone know if the Red Nova kit is based on any "real" rocket/missile? A quick Google search seems to indicate it is not.

I did a deep dive prior to building the OR sim, hoping to find the actual full scale rocket to confirm dimensional data, only to find, it appears, that the Estes model rocket is indeed the full scale rocket.

 

[neil_w]

[removed]

 

[lakeroadster]

I guess that makes it a 1:1 scale model of the Estes Red Nova. MOVE THIS THREAD TO THE SCALE FORUM PRONTO

Still stirring the pot I see.

 

[neil_w]

Still stirring the pot I see.

Just goofing (apparently unsuccessfully), not stirring

 

[boatgeek]

Thought experiment:
Do the cardboard extensions contribute significantly to stability?
On the plus side: they're fins, and once they start fluttering, they're adding drag which is pretty much directional guidance
On the minus side: they're flexible enough to flutter, so they might not stay straight under normal aerodynamic forces

I tend to lean more toward the plus side on this, but it's an interesting thought. I would very much like to see a video of this flying that replicates the original flutter.

 

[lakeroadster]

Do the cardboard extensions contribute significantly to stability? .....

Stability with the fin extensions = 1.36 cal
Stability without the fin extensions = 0.537 cal
Stability data shown above includes the 2 ounces added to the booster to make it unstable / non ballistic.

I wonder if the deceleration from flutter could be enough to uncouple the booster from the upper stage?

 

[neil_w]

I wonder of the deceleration from flutter could be enough to uncouple the booster from the upper stage?

That's a really interesting question. I've always doubted that any sort of drag separation events are possible in the LPR domain, especially on a booster that is not going to achieve high velocity before staging. But if the booster fins flutter, and the interstage coupler is on the looser side.... I dunno, it doesn't seem impossible. I would tend to think that some Scotch tape between the couplers would be enough to solve the problem, but on a gap-staged design there's no real way to do that at the engine mount. Hmm.

Have to say, I love the look of the extensions but I'm a bit puzzled at the desire to induce flutter. BP multistage rockets already have enough trouble maintaining vertical trajectory; compromising the performance of the booster would seem to just increase the chance of cruise-missiling the sustainer.

 

[boatgeek]

Stability with the fin extensions = 1.36 cal
Stability without the fin extensions = 0.537 cal
Stability data shown above includes the 2 ounces added to the booster to make it unstable / non ballistic.

I wonder if the deceleration from flutter could be enough to uncouple the booster from the upper stage?

Oh, I'm sure the extensions help the stability in the computer. I was more thinking about whether that transferred from simulation to reality. @neil_w makes an interesting point about directional stability. If you do replicate the speeding up/slowing down cycle of the original, and staging happens during the slow point, you might not have very good directional stability on the sustainer. Again, a fascinating experiment if you get to flying.

 

[jqavins]

Also, since the extensions' effect on the stability in silico may be un- or partially-realized, I'd be nervous about the marginal stability computed without them.

Another way to destabilize the booster would be to add fins at its top, butting up to the trailing edge of the sustainer fins. They would probably have little effect on the full stack's stability if they're small, but would be seriously destabilizing canards on the booster alone. And would weigh less than the tail weight. They hurt the look in that the stack is no longer an exact Red Nova. I wonder if there's a sweet spot where they decrease the booster stability sufficiently, don't hurt the stack stability significantly, and don't look obtrusive.

And none of that helps with good vertical staging if the staging occurs in a fluttery, slow moment. I strongly suspect that that part is uncontrollable.

All in all, a difficult challenge, which makes the success all the sweeter.

 

[lakeroadster]

Have to say, I love the look of the extensions but I'm a bit puzzled at the desire to induce flutter. BP multistage rockets already have enough trouble maintaining vertical trajectory; compromising the performance of the booster would seem to just increase the chance of cruise-missiling the sustainer.

I think Joe answered this..

All in all, a difficult challenge, which makes the success all the sweeter.

In regard to staging complications.... for the initial flight I could always just launch it with tape at the booster to the sustainer coupler, not install a motor in the sustainer but place a BT-50 coupler in it's place, and use a D12-3 in the booster stage.

edit: (and tape up the outer vent holes in the booster).

Thoughts?

 

[icyclops]

Why are you adding the cardboard extensions for suspective fin flutter ? Am I missing something? I built one of these as a 2 stager and it flys great without back extensions. I just added 2 inches to the top body tube to stabilize the top stage along with the added weight of the 2nd motor. You don’t really notice the height difference that much. I cant see any reason to cause flutter or destabilize the 1st stage? Or maybe the entire rocket for that matter. I also added a top plugged very small diameter 6” long tube squished next to the 2nd stage motor mount that a tightly rolled 12” Mylar streamer can be inserted which pulls out on 1st stage separation. Can be folded in half and rolled to about 1/8” dia and the Mylar is slicker than crepe paper or nylon. Worked fine as the booster with streamer came down fast but no damage if you build and finish it proper.
1- D12-0
2- C6-5

 

[lakeroadster]

Why are you adding the cardboard extensions for suspective fin flutter ? Am I missing something?

To replicate this...

Fin Flutter

In high school (late 1970's) I did a scratch build using a BT-50, except I used cardboard for fins. The rocket did fine on the required string-swing test and showed it to be a stable bird.​

​

It was launched on the baseball field at school. Powered by a C6-5 it was my first rocket that experienced severe fin flutter. The rocket launched and made a bbbuuuurrrrr sound, then nearly stopped maybe 20 feet into the flight, when it slowed down the flutter stopped and the rocket sped skyward, only to again be slowed by the fin flutter.​

​

As I recall it did that 3 times that flight. Once the motors thrust portion expired the rocket crashed before the chute popped, due to the low apogee.​

​

It sure was a crowd pleaser though.​

 

[jqavins]

icyclops has reminded me of something I thought to say earlier. Maybe it would be a good idea to do one new and creative thing at a time. One two stage conversion of a Red Nova and one with deliberate flutter, rather than adding two complications at the same time. Among other reasons, that would eliminate the dangerous possibility of staging in a slow moment.

 

[lakeroadster]

icyclops has reminded me of something I thought to say earlier. Maybe it would be a good idea to do one new and creative thing at a time. One two stage conversion of a Red Nova and one with deliberate flutter, rather than adding two complications at the same time. Among other reasons, that would eliminate the dangerous possibility of staging in a slow moment.

No worries, I can fly it, with the booster attached, as a single stage: Post #12

 

[jqavins]

True as far as the flutter without staging. Not so for the staging without the flutter (unless you make the fin extensions detachable).

 

[lakeroadster]

True as far as the flutter without staging. Not so for the staging without the flutter (unless you make the fin extensions detachable).

The fins are designed as thru wall, 1/8" basswood ply. Just planning to glue the cardboard to the trailing edge. If there is to much flutter I can start trimming the length. Or even cut the cardboard extensions off all together & perhaps add a little nose weight.

 

[Daddyisabar]

A mindsim is a terrible thing to waste...

 

[dakota196]

If you are going to try to replicate the flight, then replicate it. Make the booster fins out of cardboard the way the original flew. And use all the construction techniques that you used then on the booster now. Your data will not be accurate unless you “duplicate” the data. Just my .02.

 

[lakeroadster]

If you are going to try to replicate the flight, then replicate it. Make the booster fins out of cardboard the way the original flew. And use all the construction techniques that you used then on the booster now. Your data will not be accurate unless you “duplicate” the data. Just my .02.

Great point and while I can't argue with your logic, my hard drive brain will not allow me to download remember the specifications to replicate a scratch built rocket I made over 50 years ago in high school shop class.

 

[dakota196]

Then make the fins out of cardboard, surface mount, and go from there. Booster is easy to mod after the verification flight.

 

[jqavins]

Then make the fins out of cardboard, surface mount, and go from there. Booster is easy to mod after the verification flight.

There is no way to recreate the past glory of a BT-50, cardboard finned, single stage rockets using a two stage modified Red Nova. Changes to the booster fins that make it a little closer to the 50 year old memory are irrelevant. Just let the man have his fun. This is rockets, but it ain't science.

 

[dakota196]

Just giving some analytical advice. To find answers you to an issue you need to recreate them. No harm intended.

 

[Daddyisabar]

If you really want flutter just add narrow FREE FLOATING cardstock segments to all the fins.