The survivor of a failed space mission must prove his loyalties between the bizarre inhabitants of an asteroid colony and the mad doctor who controls the colony or face certain death in the void of space.

Cool.

I like this second attempt

Let's take a different approach:

The survivor of a failed space mission is stranded on an asteroid colony where he is swept up in a war between the bizarre asteroid inhabitants and their mad leader, but the survivor holds a secret that may doom them all.

Somewhat. It's deeper than that, but that's what it looks like when zoomed out.

What is the central conflict?

Is the central conflict just that the lead must prove his loyalty or die?
Just curious.