Steps to reproduce

1. Start a new game

2. Select "Mars High"

3. Set autopilot to "Fly to vicinity"

4. Accelerate to 1 km/s
   Observed: ship speed jumps between 999 m/s and 1.00 km/s each frame
   Expected: ship speed does not change

5. Wait until decelerating near starport
   Observed: ship thrust fluctuates each frame
   Expected: ship thrust is smooth and constant

My pioneer version (and OS): current master b66733d49