How would you improve the Shuttle design?

[KASASpace]

You do realize that Energia give 5 tiem the payload of Proton, more or less, right?

Now, do you realize that if scramjets have bad TWR, than so would a normal jet. You see, the Vespucci effect can be utilized to accelerate the to mach 2 at mach 0.7. So, use an epic solid rocket to get to that speed and bring up an RL-10, weighs about 600 lbs. YOu might want to look it up.