The Orion won't remain immobile,if the Sathanas moves 6000 m away the Orion can follow it...
You obviously didn't play the mission. Yes the Orion can follow it. But the Orion is slower than the Sathanas. It can't keep up. It takes about 15 minutes for the Sathanas to open up enough distance on the Orion but the second it does death is not far away for the Orion.
Uhm,yeah.I have created a subspace pursuit a few months ago,and the Orion was slower.I didn't remember it.
Axem:event.It was event.Making a Sathanas escape is not good for Shivan forces and boosts the morale of their enemy.Being destroyed is better,trying to inflict as many casualties as possible.
GTVA had the Colossus to face the Sathanas.The NTF couldn't respond to the Colossus' deployment in the battlefield.
The Orion can bring two BGreens on a single target + some Slashes.Enough to destroy a Deimos and of course an engine subsystem.The Sathanas is faster,but in my mission I had the orion inflicting most of the damage on the Sathanas,while the other warships(an Aeolus,a Deimos and a Sobek)inflicted only small damage.The Orion wasn't fast enough,but it has destroyed the Sathanas.I can attach here that mission,its old and my FRED skills have improved in the meantime.I will laugh like you.
My theory is mine,ok,but even if the method isn't correct,the Shivans do what I said.Another possible theory is that they have record of florid systems where life could be present(they fought the Ancients,maybe they have visited Vasuda or Sol).