Re: What kind of heat-shield was meant for such a craft?
The baseline thermal protection was tiles (all over the vehicle), but since the vehicle was mounted on the nose of the launch vehicle, and the Titan II uses room-temperature propellants anyway, there would be little chance of damage on launch unless you hit a bird or something. Some damage on landing was assumed, but of course at that point repairs are easy.
A backoff position was an ablative, replacable outer shell, but that made a lot of other design issues more difficult.