The problem is that you don't know whether the Shuttle is just floating there on a peaceful mission or going in on an attack run until maybe 3 minutes before th

The problem is that you don't know whether the Shuttle is just floating there on a peaceful mission or going in on an attack run until maybe 3 minutes before the nukes are dropped. Plus the big Soviet radars were pointed towards where US ICBMs would be coming from, not south where the shuttle would come from. Getting the capability to take out the shuttle would be really hard.