[al_c]

Too heavy. The other orbiters were made later and lighter but they too had to undergo mods to make them lighter. Plus, the main engines, SRB's and external tank had to be modified in order to reach the orbital inclination of the ISS.

Too heavy? How heavy is the ISL?

[al_c]

ISL = ISS. Sorry.

[FReepaholic]

>>...Too heavy?...<<

Takes more energy to reach the orbital inclination of the ISS. Columbia is too heavy for the amount of thrust the Shuttle stack provides.