i've seen 1 link that would direct me to a site that gave an equivalent of what would happen if a SATURN 5 let go on the pad, but not the Shuttle, was wondering what the force equivalent would be if the Shuttle would have exploded on the pad (SRB's, external tank, and the Shuttle itself lettin go all at once)
Volume 2 of a March 1981 study (links below) by the DOD gives the External Tank explosive force on the pad as equivalent to 54,000 pounds of TNT.
Rationale for the calculation is described in the paper.
If you want to read some interesting predictions about what would have happened if one SRB came off during first stage, etc, etc, these papers are for you.
SPACE SHUTTLE RANGE SAFETY COMMAND DESTRUCT SYSTEM ANALYSIS AND VERIFICATION