Thanks, Jeff
I can imagine some guy standing under the ready to launch missile, holding a pad with a big red button that says "Launch" "OK, Sarge! Looks good! Should I press the button?"
In operation, I think all three solid fuel boosters would fire at once, to get the missile to the altitudes and speeds it would need to start the scramjet. The side boosters would drop off and eventually so would the main core. The lighter green adapter section would have some fuel for the scramjet - depending on the mission, it might just glide for a while or ignite the engine and blast into the target. The missile itself would have some fuel; you don't need much of a warhead if you're going between Mach 5 and Mach 10.