Grid Fin Reentry Steering

Reusable rockets like SpaceX's Falcon 9 don't just fall back to the pad — during reentry, four lattice-like grid fins bite into the thickening atmosphere and steer the tumbling-fast booster onto a precise cross-range target using pure aerodynamics, no engine required until the very last seconds. This simulator models that phase: deflect the fins to correct a starting position error and fight a crosswind, or hand off to a proportional-derivative autopilot, while dynamic pressure — and with it, how much steering authority the fins actually have — rises and falls in real time as air density and speed both change through the descent.