ENH: Tube Fins

[AlexKari]

I'm attempting to simulate the design for my Level 3 to try and find the maximum velocity, however rocketpy lacks any settings for tube fins.

Can there be tube fins added similar to how openrocket does it?

[Gui-FernandesBR]

@AlexKari no, there's no direct equivalence to tube fins on rocketpy.

I recommend you to use the Generic Aero surfaces instead.

[ting-hong-shieh]

Hi, I'd be interested in working on this. Since the issue is still open and labeled Help wanted, could you confirm whether a built-in tube-fin model is still wanted, or whether GenericSurface is now the intended solution?

I compared RocketPy's current aerodynamic-surface API with the linked OpenRocket calculator. Two differences affect the scope:

• OpenRocket makes the tube-fin center of pressure Mach-dependent: quarter-chord at Mach 0.5 and below, a polynomial through the transonic range, and an empirical expression at Mach 2 and above. RocketPy currently stores a fixed center of pressure for each Barrowman surface.
• OpenRocket also includes component friction and pressure drag. RocketPy's current Barrowman surfaces do not add axial drag; vehicle drag is supplied through the rocket's power-on and power-off drag curves.

If a dedicated model is welcome, would the following be an acceptable first PR?

• Add a TubeFins surface defined by tube count, length, inner radius, outer radius, and rocket radius.
• Implement the Ribner-based normal-force slope, OpenRocket's 20-degree angle-of-attack cap, and a fixed quarter-chord center of pressure for the documented subsonic range (Mach <= 0.5).
• Initially support tangent, non-overlapping, uncanted tube sets only, with validation for unsupported geometry.
• Add Rocket.add_tube_fins, serialization, focused unit tests, and documentation of the model limits.
• Defer Mach-dependent center of pressure, component drag, separated or overlapping tubes, cant, and side-force/yaw behavior.

This would keep the first change within RocketPy's current surface architecture. If full Mach-range CP or component drag is required for initial support, I can revise the proposal before starting implementation.