Teaching the Shuttle G&C to fly
contingency aborts... The avionics can now note the failure inertial speed of engines and determine the contingency procedure to be executed (here's a two engine failure in the BLUE region as an example).
The AP knows how to do the procedure for BLUE and GREEN in powered flight (the others are to come) and can compute dynamically optimum Nz after handing over to unpowered flight). My current vision is to be able to do an East Coast / Bermuda abort eventually. And perhaps to support bail-out by using the parachutist piggy-backed on the Shuttle sim
Single engine flight dynamics is bitchy in more than one way. First, the fact that the trajectory predictors inevitably drop like a rock is slightly depressing. Second, it's really crucial to get the roll channel off the engines - I spent two hours figuring out why I had no pitch authority before I figured out that the DAP was still trying to utilize a thrust vectoring roll.
Even single engine roll control (SERC) isn't without pitfalls, because it needs to be active right when the OMS fuel dump happens - the solution is to do mirror-imaging, rather than, say, firing the left pod up thrusters, one inhibits left pod down thrusters for a moment (and vice versa).
It's very subtle (the upward flame is missing on the left) but this is rolling the Shuttle under SERC with a fuel dump going on:
I absolutely love implementing all these little details about the Shuttle. It's ingenious how it all works together.