Rotational Dynamics

I’ve long been an advocate for thinking carefully about rotational dynamics in space colony design.  For any given object, some spin directions may be inherently unstable, as you can see in this video.  In the spacecraft industry, there is a well-known rule of thumb that the desired spin axis must have a moment of inertia at least 1.2 times that of any other axis.  However, this rule was largely unknown in the space habitat community, resulting in a lot of designs that wouldn’t work in real life.  (This is the insight that led to co-authorship of the Kalpana One paper; the original design had to be substantially revised for stability.)

Now it’s time to apply those same insights to the High Frontier game.  A grossly unstable design should wobble, and end up tumbling end-over-end, just as it would in real life.  However, when we tried to simulate this using the built-in physics engine in Unity, we ran into trouble.  No matter what we did, we couldn’t get a rotating object to tumble.  We can knock it off its original axis, sure, but as soon as we stop poking it, it just spins happily around whatever its new axis happens to be. Continue reading