As I said, solved as far as practically required, as your comment illustrates. The viability of the scramjet being actually useful for anything is up for debat

As I said, solved as far as practically required, as your comment illustrates. The viability of the scramjet being actually useful for anything is up for debate. Either you can fly slower with a jet, or leave the atmosphere altogether with a rocket. Flying at orbital speeds within the atmosphere is of very, very marginal utility, given the number of complexities involved.