Tumble Drag Bugfix

A bug prevents the BasicTumbleStepper from ever calculating the drag, zero is always used.

Changes to Tumble Transition

• Do not switch to the tumble stepper under thrust.
  • If a stage wants to switch to tumble under thrust emit a warning.
• If a booster stage wants to tumble before apogee, let it.
• If the sustainer wants to tumble, only allow it after apogee.
  • If the sustainer wants to tumble before apogee emit a warning.

Before / After Comparison of Flight Paths

Before this change the lower stages of the three stage example model all appear to follow a parabola without air resistance:

After this change they fall much slower, with much more influence from the wind:

These images are from some playing around I am doing with visualizing many simulations. Things worth knowing are:

• The red dots on the ground are high speed impacts
• The green dots are slow, soft landings
• In the "After" image the fuchsia color is tumble recovery.
  • The "Before" image does not show tumble in fuchsia, but the lower stages do always begin to tumble just after apogee.