Lakeroadster's X-FLR6 Rocket Build (AKA the TINTIN Rocket)

[lakeroadster]

I saw a photo on the Retro Rockets Facebook page of Belgian cartoonist Hergé Comic Series named "Explorer's Of The Moon" circa 1954.

Today I spent some time on CAD and on Open Rocket running some simulations to see if the rocket on the cover art is feasible for a flying model.

The plan is to turn the body on my wood lathe out of pine or basswood, and build 3 ply laminated balsa fins and balsa fin pods.

Looks like E15 or E30 will be the most economical motor. Clusters are possible, once I've proven it stable.

Upon further review it needs the fin pods updated for more of a boat tail look.

Here's some photo's, screen shots and renderings.

 

[kuririn]

Also known as Tintin's moon rocket. I was a big fan of the Tintin illustrated books as a kid.
Looking forward to this build.

 

[GlenP]

In the original concept I think the fin pods were landing shock absorbers, not engines. But that does look like a good candidate for clustering.

 

[lakeroadster]

Doggies.... they are the best people we'll ever know.

 

[BABAR]

In the original concept I think the fin pods were landing shock absorbers, not engines. But that does look like a good candidate for clustering.

I am a big fan of clusters, but not for outboard sides of fins. Exception might be for tiny motors mainly for smoke and show that have no significant thrust relative to the main central motor. Cluster motors that far off the cross section CG (as opposed to the longitudinal CG used for stability) present a high risk of throwing trajectory waaaay off vertical if one fails to light or lights late.

 

[dhbarr]

I'll just leave these here, in case they become useful:

https://forum.ausrocketry.com/viewtopic.php?t=3370

https://forum.ausrocketry.com/viewtopic.php?t=5486

 

[ThirstyBarbarian]

I’m interested in sci-fi style rockets and outboard pods. When I was looking into it, I was advised that you should fly the rocket on a strong central motor that is capable of flying the rocket on its own, and airstart the pods with electronics.

 

[lakeroadster]

I’m interested in sci-fi style rockets and outboard pods. When I was looking into it, I was advised that you should fly the rocket on a strong central motor that is capable of flying the rocket on its own, and airstart the pods with electronics.

Where's the excitement in that?

The pod mounted motors tend to steer the rocket.

Canting the motors to point to the rockets CG will help minimize the steering issue.

 

[BABAR]

Where's the excitement in that?

View attachment 381396

There are portions of model rocket flight where excitement should be intentionally avoided as much as possible.

 

[lakeroadster]

There are portions of model rocket flight where excitement should be intentionally avoided as much as possible.

“To the timid and hesitating everything is impossible because it seems so.” – Sir Walter Scott

 

[lakeroadster]

Updates and details..

 

[Daddyisabar]

Everyone loves the TinTin rocket!

 

[jlabrasca]

A flying cardstock model of Tintin's rocket.



Weirdly, Freddy Krueger makes an appearance shortly before lift-off.

Instructions here

https://www.nysi.org.uk/kids_stuff/rocket/rocket.htm

In the original concept I think the fin pods were landing shock absorbers, not engines. But that does look like a good candidate for clustering.

Matt Bondi published a cut-away of the Objectif Lune rocket


Can't find a link to a high resolution image anymore, but if you look closely -- alligators in the swimming pool in the pod. Presumably because Capitaine Haddock needed them for wrestling, or because Professeur Tournesol forget to check for alligators while taking on ballast...

 

[jqavins]

Cluster motors that far off the cross section CG (as opposed to the longitudinal CG used for stability) present a high risk of throwing trajectory waaaay off vertical if one fails to light or lights late.

Even if they all llight perfectly simultaneously, I'm told, normal variation in performane can be enough to throw the flight far out of whack.

Anyone know if it would be acceptable under NAR or TRA rules to use non-motor smoke generators, or would those be considered fireworks?

 

[dhbarr]

If I wanted smoke generators I'd use some of the RC loads.

 

[Tobor]

Very cool Lakeroadster. Looking forward to seeing this come to life.

Subscribed.

 

[BABAR]

Even if they all llight perfectly simultaneously, I'm told, normal variation in performane can be enough to throw the flight far out of whack.

Anyone know if it would be acceptable under NAR or TRA rules to use non-motor smoke generators, or would those be considered fireworks?

I don’t know that it has been tried with this intent, but if you intentionally recessed the motors to get Krushnic effect, regular motors will give you pretty much all the smoke a regularly placed motor would give, but far less thrust. I’d be concerned it might light the motor housing on fire around the nozzle, though.....

Oops, it has been suggested by LakeRoadster himself

https://www.rocketryforum.com/threads/krushnic-effect.145985/

https://www.nar.org/pdf/TCR1.pdf

 

[Tobor]

Anyone ever try a delay grain for effects?

 

[lakeroadster]

Even if they all llight perfectly simultaneously, I'm told, normal variation in performane can be enough to throw the flight far out of whack.

So true...

Some research on the ThrustCurve's site shows that NFPA 1125, Code for the Manufacture of Model Rocket and High Power Rocket Motors, allows an alarming amount of motor deviation from stated values....

• The total impulse must not have a standard deviation greater than 6.7%.
• The ejection delay must not vary more than 1.5 second or 20% (whichever is greater, up to 3s) from average.
• The average thrust must not vary more than 20% (or 1N for model rocket motors, 10N for high-power motors, whichever is greater) from average......

 

[G_T]

Even smoke generators provide a little thrust in some cases, and smoke/gas generation alters base drag. Burn rates are likely not perfectly matches so mass asymmetry is pretty much guaranteed. With that much leverage these effects are likely to cause unacceptible trajectory deviation. Were I to RSO that rocket, I'd never let it fly. Sorry. It's a cool rocket, but launching it is a bad plan.

Gerald

PS - Now if you had a single internal smoke generator and piped the smoke to the three pods using matched plumbing, that might be possible. Not easy to engineer, but possible.

 

[jqavins]

Remember the cherry bomb size smoke bombs most of us had as kids? I was thinking of devices something like those, but cylindrical, and with a bigger vent hole. The thrust from those was barely enough to make them roll a little on the ground, and with a sizable hole instead of the small fuse penetration the thrust would be undetectable. The mass imbalance might be an issue, but I feel comfortably certain it would be a small one. Imagine there were a two gram lump of clay on one fin, or one (purely decorative) pod were twice the size of the others; no big deal, right? I'd never argue if the RSO says "no", but I wouldn't hesitate to launch a rocket with those in fin pods and a decent thrust central motor on my own at the park.

 

[lakeroadster]

Were I to RSO that rocket, I'd never let it fly. Sorry. It's a cool rocket, but launching it is a bad plan.
Gerald

Yet another reason I fly on BLM property with nothing around for a square mile. Nobody there but me, my stuff, and my creations.

 

[G_T]

When in college I used one of those little cherry smoke bombs to provide thrust for a paper airplane. It climbed and flew along like a little jet. Then caught fire. Not the safest experiment!

With the smoke bomb, that little hole is actually too large to cause useful nozzle effects. You're just getting mass flow and a little pressure. Therefore enlarging it will only alter the burn rate a bit perhaps, but not really alter the total impulse.

It takes very little mass imbalance, drag imbalance, or thrust imbalance, to cause a small short light rocket to deviate rather quickly from vertical. You need all the forces and the center of mass to be colinear.

Gerald

 

[burkefj]

Steve jurvitson had a scary mess of a flight with fin tip motors at ldrs last year, he said its neat when it works... I'd stay away..

 

[lakeroadster]

Honestly, it sim's just fine on a E15. I can't envision flying it with (4) motors.

I've thought about making the wing pods adjustable, so they could be canted to point them toward the rockets CG... That would allow them to point straight up for single motor launches, or canted for 4 motor launches. Hold my Tang, I got this..

 

[jqavins]

When in college I used one of those little cherry smoke bombs to provide thrust for a paper airplane. It climbed and flew along like a little jet. Then caught fire. Not the safest experiment!

With the smoke bomb, that little hole is actually too large to cause useful nozzle effects. You're just getting mass flow and a little pressure. Therefore enlarging it will only alter the burn rate a bit perhaps, but not really alter the total impulse.

It takes very little mass imbalance, drag imbalance, or thrust imbalance, to cause a small short light rocket to deviate rather quickly from vertical. You need all the forces and the center of mass to be colinear.

Gerald

A smaller hole causes the pressure to be greater (for a given burn rate) and therefore the exit velocity as well. That's why putting you thumb over the end of a hose and allowing a small exit gets you much better range on the water "jet". And the smaller jet hit's your target with greater force, which indicates (Newton's third law) that its thrust is grater as well. Of course the simple hole is not a compression-expansion nozzle (we are in agreement) so none of the subtleties of a good nozzle apply.

The exit hole on those smoke bombs is (if the image in my head is accurate; it's been a long time) about four mm. The ID of an 18 mm casing is 13 mm. That's roughly a 10.5:1 area ratio.

Sounds like a ground test is in order. Make a smoke bomb (Abby Hoffman's recipe should do nicely, or a slow burning BP such as with baking soda filler) with an 18 mm casing plugged at one end, and put it on a test stand.

As for off-center drag, there's no reason to expect any if the pods are made well. And, launch lugs make little or no difference (granted, they are much closer to the center line). Poorly build rockets with things like random slight canting of fins and other defects, up to a point, still fly safely if not well.

Finally, with regard to the mass imbalance, remember that we're not talking about the mass of a smoke generator in one pod and not the others. We're only talking about the transient imbalance due to different burn rates while all three are burning. The burn rates should be essentially the same assuming they are all the same composition, so the mass differences will be trivial. Come to think of it, the same goes for what little thrust there is; it's not one pod's thrust that matters but rather their transient differences; the differences between small and similar quantities is is tiny.

 

[G_T]

Base drag is a function of gas evolution rate from the smoke generators.

Do you think you can light all three simultaneously? Do you think you can get fairly identical burn times? Do you think they even have the same starting mass?

Lots of leverage turns a small force into considerable torque for a low moment of inertia object.

Gerald

 

[burkefj]

Just remember blm land can still catch fire like anywhere else if you send a burning cartwheeling rocket into the brush, just be sure to have a very large clear area, I'll get off my soap box now Love the tin-tin rocket.

Yet another reason I fly on BLM property with nothing around for a square mile. Nobody there but me, my stuff, and my creations.

 

[lakeroadster]

Honestly, it sim's just fine on a E15. I can't envision flying it with (4) motors.

Base drag is a function of gas evolution rate from the smoke generators.

Do you think you can light all three simultaneously? Do you think you can get fairly identical burn times? Do you think they even have the same starting mass?

Lots of leverage turns a small force into considerable torque for a low moment of inertia object.

Gerald

Just remember blm land can still catch fire like anywhere else if you send a burning cartwheeling rocket into the brush, just be sure to have a very large clear area, I'll get off my soap box now Love the tin-tin rocket.

A 1 square mile launch area.. for a rocket that sim's to under 500 feet with an E15. We're good.

Really fella's? It's LPR not HPR. Don't be such buzz kills.

 

[G_T]

Then as long as people, cars, etc, are out of range. This is probably a missile not a rocket. It is not about being a buzzkill. I think it is a cool project. It is about being reasonably safe - not starting areas on fire, not killing anyone.

Gerald