Hi, I'm Erik Anderson and I've been an Orion fan for years. I had no idea there were more of us!
I only found this place as I was reseaching online Orion links for my Orion simulator for Orbiter.
Orbiter is a free space simulator which has a steep learning curve but true physical realism. It's also got a very open API so third parties (me, in this case) can do lots of crazy things with the code. It's available at: http://www.orbitersim.com
So, practical upshot: there is now a working computer sim of Orion vehicles. I flew a 20-meter Orion from Earth to Europa the day before yesterday; you can too. And it is -- I've already mentioned -- free.
I'm also looking for practical suggesions for improvements. I'm sure I didn't get everything perfect the first time around...C++ isn't even my native language!
But if anyone was likely to be as excited about this as I am, I figure this is the crowd....
I've played the simulator; 'tis good, but has no collision model.
I'd like to see an add-on containing a station/spacecraft model with an asteroid mesh and a couple Orions docked to it, so it can be moved to different (and possibly catastrophic) trajectories.
That's probably Orbiter's biggest weakness: as a one-man show, it doesn't get features the author doesn't feel like implementing. And he feels collision modeling would be a LOT of work. A few people have been begging him, but so far no luck.