Tube Devil 54 - The supersonic flight of a tube-finned rocket

Site: Holtville Havoc

Date: 03/01/19

Rocket: Tube Devil 54 - modified Go Devil 54

Motor: CTI - K260 - 2285Ns 6G54mm Classic Long Burn

Max Altitude: 12723'

Max Velocity: 1246fps (847mph)

Electronics - Missile Works RTX in the nose cone, Missile Works Altimeters RRC3 and RRC2+ in the AV-Bay

Weight on the pad 4394g (9.67#)

The first flight of this was on a CTI I303 to 2846' at 461fps. It underperformed the simulation but I imagine the camera taped to the side was partially responsible. Otherwise the flight went off perfectly with a small drogue at apogee and 48" main at 500' slowing it to 22fps.

While this was built with a supersonic flight in mind eventually, its second flight at Holtville was not intended to bust mach, just tickle it. The Open Rocket simulation had max altitude of 10,605' and max velocity of 685mph. Fortunately, the waiver was 18K. The winds were low and the almost 9 second burn took it straight up. I had eyes on it to apogee and only saw it again when the RTX guided me to it. It landed about 8500' east of the pad site in perfect condition.

Here is the data from the RRC3 altimeter:



And a screen cap from the KML generated by the RTX on Google Earth:





Something about the build:

I used an Aero Pack 54mm motor retainer held in place with one 6-32 screw, screwed to a T-nut epoxied inside the retainer. Having the retainer removable makes it easier to thread smaller motors onto the retainer and to change the harness if necessary. I've used this technique on several 38mm rockets with Giant Leap hard point anchors:















The fins are standard G12 black fiberglass cut at 50 degrees for the leading edge and 25 degrees for the trailing edge. These angles were determined by a painstaking process of "what looks good" and "let's taper the aft end so it doesn’t break if it hits hard" and "what is the easiest to repeat with the chop saw." I'd like to think they made some aerodynamic sense as well but no actual calculations were made to that end.

The weight of the fin set is 429g and the epoxy holding them on is 472g (just over one pound.) There is more epoxy than fin. I was not worried about 54mm G12 tubing failing at mach as much as the fins ripping off, and so far so good.




I have my eye on a K300 or L265 for the GHS launch next fall.

(And I ordered a 3" Go Devil on Wednesday from Madcow Rocketry along with the parts to make a Tube Devil 75.)

YES! If you want to go faster make your fintubes shorter next goround, base around 1 body diameter and keep your most excellent angles.

Congrats, people keep hanging onto the myth that you can't scoot a tuber; but we know better :-D

EDIT: PS: How did you choose to do the repeatable angles?

What dhbarr said about tube fin aspect ratios.

You might even want to drop below 1:1

I’d still like to see 6 fins and hit mach.

It’s been done already (Ari Krupnik) so it is possible.

dhbarr said:

YES! If you want to go faster make your fintubes shorter next goround, base around 1 body diameter and keep your most excellent angles.

Congrats, people keep hanging onto the myth that you can't scoot a tuber; but we know better :-D

EDIT: PS: How did you choose to do the repeatable angles?

Click to expand...

Neural Paralyzer & Turtleosis also.

fantastic project, and this line is complete perfection:

These angles were determined by a painstaking process of "what looks good" and "let's taper the aft end so it doesn’t break if it hits hard" and "what is the easiest to repeat with the chop saw."

supersonic tube fines

I've heard that having the full 6 fins contributes to the strength greatly.

Hopefully Fastasleep's fiberglass tubes won't be as susceptible to shred as paper/bluetube

Nytrunner said:

I've heard that having the full 6 fins contributes to the strength greatly.

Hopefully Fastasleep's fiberglass tubes won't be as susceptible to shred as paper/bluetube

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My L2 rocket, Tubula Rasa, has a similar profile to the Tube Devil but with 4" bluetube. I have a number of videos looking down past the tube fins. I haven't flown it faster than around 600 mph but the vibration you can see is just scary. I've never considered pushing those big thin fins past mach.

FastAsleep said:

but the vibration you can see is just scary.

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I'd love to see the tube fin flutters!

The first time I saw my L2 fly and watched the video I was like "I'm 95% sure that fin doesn't normally have a 5deg bend in it....."

Nytrunner said:

I'd love to see the tube fin flutters!

The first time I saw my L2 fly and watched the video I was like "I'm 95% sure that fin doesn't normally have a 5deg bend in it....."
View attachment 379204

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Here is the Tube Devil, rock solid:


And Tubula Rasa, not so much:

Mode shapes! That takes me back to Vibration Mechanics!

Nytrunner said:

Mode shapes! That takes me back to Vibration Mechanics!

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I never had vibrations that was an elective. Opted for compressible gas dynamics. Anyways I’d love to see the math on predicting tube fin flutter.

That would be (not) fun. I remember circular object vibrations from a specific source like a displacement or active vibration/forcing function. Not determining that from airflow down the surface.

Andrew_ASC said:

I never had vibrations that was an elective. Opted for compressible gas dynamics. Anyways I’d love to see the math on predicting tube fin flutter.

Click to expand...

I'm pretty sure it would devolve into a bunch of hideous differential equations scattered with semi-arbitrary damping/flexibility factors* pretty quickly. I'll just stay on this side of the room, thankyouverymuch.

* The kind of factors that range from 0.5 to 1.5 and change your answers by an order of magnitude depending on where on that scale you land.

Remember that for a given fin thickness seven smaller fins is dramatically stronger as well as faster.