The first stage ascent trajectory of the space shuttle uses an open-loop guidance scheme. A reference trajectory profile is designed preflight and loaded into the onboard general purpose computers. The reference trajectory is a trade-off among aerodynamic loads, heating constraints, and payload requirements.
In the space shuttle flights after Space Transportation System (STS) 51-L, the ascent design has been mission specific. As the program continues to mature, a standardization of ascent design will be pursued to reduce resource requirements for each flight. A day-of-launch (DOL) ascent trajectory, designed only hours before launch and based on real-time wind and atmosphere conditions, is currently being studied and will be tested in early 1990.