Doesn't have one???
Why not???
Unlike ordinary air travel, all data from the shuttle is simultaneously transmitted to Houston. Houston is the black box - it has all flight data up to the time of loss of communications (and perhaps beyond if there was another means of communication that we civilians don't know about).
They stated that they had a tape voice recorder but it would not have survived. They probably do not have much on-board data recording, because everything is being transmitted to the ground constantly. The only time it is not, is the few minutes of comm loss during the very high heat part of re-entry.