Well, no. It's actually mass divided by cross sectional that matters, not just mass. Anyway my question wasn't about the underlying physics, but how I can engineer a solution.
I solved my problem by giving my rocket a flared bottom to increase drag. That slightly increases drag while launching too, but the speeds are so much lower on take off than re-entry that this doesn't matter in practice. In short, as you scale up rockets, you should scale up their radius more than their height if you want to keep aerodynamic properties the same.
As for stability, I found that the most reliable way is to add small stubby wings near the nose cone. No need for control surfaces, and by making each winglet symmetric (along a horizontal axis) they don't interfere much with launch either. In essence, they provide a restoring torque should the rocket stop pointing exactly retrograde. Although if you ever get more than a few degrees out of alignment nothing will stop you from entering a spin and ending up pointing prograde.
So, yeah, I solved my own problem, but hopefully this might be of use for someone else later.
Well, no. It's actually mass divided by cross sectional that matters, not just mass. Anyway my question wasn't about the underlying physics, but how I can engineer a solution.
I solved my problem by giving my rocket a flared bottom to increase drag. That slightly increases drag while launching too, but the speeds are so much lower on take off than re-entry that this doesn't matter in practice. In short, as you scale up rockets, you should scale up their radius more than their height if you want to keep aerodynamic properties the same.
As for stability, I found that the most reliable way is to add small stubby wings near the nose cone. No need for control surfaces, and by making each winglet symmetric (along a horizontal axis) they don't interfere much with launch either. In essence, they provide a restoring torque should the rocket stop pointing exactly retrograde. Although if you ever get more than a few degrees out of alignment nothing will stop you from entering a spin and ending up pointing prograde.
So, yeah, I solved my own problem, but hopefully this might be of use for someone else later.
6 months ago