POWERED GUIDANCE DEVELOPMENT FOR APOLLO AND THE SPACE SHUTTLE

The 1950s era reference trajectory and correlated guidance techniques (Delta Minimum, Delta, and Q) were not capable of supporting space missions envisioned by 1960. The development of digital flight computers enabled explicit guidance algorithms to be developed using results from the calculus of variations. The Iterative Guidance Mode (IGM) and E Guidance were explicit guidance schemes that were successfully developed for and flown in the Apollo Program. Hypersurface targeting provided constraints to IGM for the Trans Lunar Injection burn. Powered Explicit Guidance (PEG) was developed later and successfully flew on the Space Shuttle from 1981 to 2011. PEG was a more capable algorithm that could support demanding Space Shuttle abort profiles.