The reason why Novas start hanging behind you in space might be because of lag, ping etc.
They are fairly easy to hit against larger cruisers, some transports and Battleships. I also hit a corsair gunboat with it once. You just need to fire them from larger distance, then they can gain full speed and start tracking.
Btw, does -one- CD really blow it up? I was shooting Nova torpedoes with CDs once, and I needed 2 TCDs to blow it.