Your typical Space Shuttle Mission Part 2: Shuttle processing in a nutshell

Hooray! Discovery touches down after a successful mission! Time to work around the clock to get it ready!!! *pulls hair off*

Seriously. No sooner than the orbiter lands, lots of things start to be set in motion. The astronauts power down and safe up the orbiter, until they leave it, in which Kennedy Space Center employees take over (unless the unfortunate possibility of an Edwards Air Force Base, California landing occurred, in which it takes some days for the orbiter to be latched onto a Shuttle Carrier Aircraft so it’s taken back to Florida, THEN it starts).

The orbiter is towed to the nearby Orbiter Processing Facility, in which it’s prepared for its next mission, while being checked for any problems that may have occurred during the previous mission. Sometimes, payload is installed at this point.

In the meantime, the SRBs, refurbished from an earlier flight, arrive at KSC in pieces in trains, and a new External Tank arrives in a wharf (read: big ass boat). Both SRBs are taken to the Vehicle Assembly Building (the famous big, cube-like building in Kennedy Space Center), where a crawler-transporter with a mobile launcher platform on top is waiting. The lower segment of the SRBs are bolted to the mobile launcher platform (MLP), and are assembled from the bottom up.

The External Tank already comes in one piece. It is dragged out of the wharf and is towed to the VAB, where it is hoisted by a powerful crane and lowered between the SRBs, already completed and attached to the MLP. The tank is then latched onto the SRBs.

And finally! The orbiter clears the Processing Facility, is finally ready for its next mission, and is towed to the VAB, where it is also hoisted by a crane, and lowered in its position in front of the SRB/ET Stack. Then all connections and bolts are placed, and finally, the entire shuttle stack is complete! Following that is the rollout to the pad.

The bluish-gray thing below the white-gray platform is the crawler transporter, and the white-gray platform is the mobile launcher platform. From what you just read, the whole stack is bolted only in the SRB points. Therefore, the crawler has to go at speeds less than one mile per hour to avoid stressing those bolts and having the stack topple over. It must travel 3 to 4 miles to the launchpad. At best, it takes over 6 hours to get there. Once it does, the crawler lowers the MLP into the pedestals in the launchpad, and leaves it there, and goes back to a parking spot it has near the launchpad, where it will wait until launch is over, then it goes back to fetch the empty MLP for servicing and use for a later mission.

So the shuttle sits at the launchpad until the time of liftoff, where it will do its mission, and later come home, and the cycle starts all over again.