I first noticed this when I was playing multiplayer. Anyways, I sent all my combat vecs out and morale dropped from 99 to 0 very quickly. I brought 32 lynx back and it went back up 99! Curious, I tested this out on Eden Starship. It worked the same, but at a slower rate. Anyways, I could be wrong, but this is what I've come up with:
-Having friendly combat vehicles at your colony boosts morale.
*Don't know if allied vehicles help. Just making sure you knew I didn't mean ENEMY vehicles.
-Sending all combat vehicles away, leaving your colony unprotected, drastically hurts morale, mostly based on the distance your vehicles are from your base.
-The effect on morale changes based on the number of enemy combat vehicles.
*In multiplayer, morale quickly dropped from 99 to 0. I'm guessing this is due to the massive army of laser lynx I had to deal with, whereas in Eden Starship, morale increased/decreased slowly due to the small Plymouth army.
-This only seems to take effect if you have combat vehicles and/or a large quantity of them. Also, it only seems to take effect if your vehicles are a long distance from your colony. (a few miles shouldn't hurt, halfway across the world will). Interestingly, the morale boost only seems to take place if the vehicles are actually IN your colony.
Of course, it could all just be coincidences, or something I missed entirely, but for now, I tell everyone about it. So, you all go and prove me right or wrong I guess. Just like real scientists!