RTLS Overview
If an engine fails during the first 4 minutes of ascent, the shuttle cannot achieve orbit. For the first 3 minutes or so of ascent, it cannot even reach a TAL. The only runway near enough to be reached is one near the launch site. In order to reach this runway, the shuttle must literally reverse course and fly back the way it came. The turn to reverse course is called powered pitcharound PPA , and the timing of PPA is critically important. Since the orbiter is powerless once the main engines...
Glide Range and Energy
After MECO, the shuttle has a certain amount of energy that determines how far and how long it can glide. This amount of energy is a function of the speed and altitude of the shuttle. The initial energy state, determined by the speed and altitude at the time the SSMEs are shut down, decreases continually during GRTLS, reaching zero at orbiter wheels stop. The horizontal distance or range that the shuttle can glide with a given amount of energy is determined by the vehicle's lift and drag...
RTLS TRAJ Display
The shuttle cannot fly at all without its computers. This means that if a serious problem disables all the PASS computers, the crew has no choice but to engage the BFS. However, it is possible that some combination of software errors and or hardware failures might cause the otherwise healthy PASS computers to be unable to fly the shuttle successfully. To provide an alternative to engaging the BFS, the capability has been provided for crewmembersto fly the shuttle during ascent. The manual...
Backup Flight System
The BFS is an independent software system which normally resides in the fifth GPC GPC 5 . If any failure or combination of failures renders the PASS computers unable to control the shuttle, the crew engages the BFS. Once engaged, the BFS assumes sole control of the shuttle vehicle and remains in control until after landing or until the problem with the PASS computers is found and fixed on orbit. Both the commander CDR and pilot PLT can engage the BFS by depressing the pushbutton PB on top of...