Hermes Fin Flutter Analysis

Fin flutter is a mode of harmonic oscillation between caused by coupling of the pitch/torsion and aerodynamic forces on the fin.  Conditions for a fin to potentially flutter is determined mostly by the velocity, altitude (air density), and fin dimensions, where the thickness and span (distance extending out of the rocket) tend to make the biggest difference.  The data for Hermes fins shows the flutter velocity for a given fin size at different altitudes where the flutter velocity is the speed at which you would expect the fins to flutter.  This velocity was calculated for both quasi-steady and unsteady environments, which have to do with the relative change in pitch or angle of attack; therefore for Hermes we expect a quasi-steady environment, but would like the fins to be robust against instabilities.  These methods were calculated in a program called AeroFinSim, modeling the fin motion with beam deflection and spring-mass system dynamics. The chart coloring has to do with how close the flutter velocity is to the expected flight velocity and whether it is within a 1.4 safety factor.