Helmut Horn and the Origin of the Saturn V Iterative Guidance Mode (IGM)

摘要

The development of the Iterative Guidance Mode (IGM), a closed loop, exo-atmospheric, explicit guidance algorithm that ran on a digital flight computer, was one of many technological innovations that enabled the success of the Apollo Program. Circa 1960 or 1961, Helmut Horn, a Peenemiinde veteran and branch chief at the NASA Marshall Space Flight Center, embedded a simplified and modified version of Derek Lawden's bilinear tangent steering law in the equations of motion to obtain computer generated, approximately optimal powered flight trajectories. Such a method could potentially provide optimal trajectories much faster and more reliably than existing calculus of variations optimization software. Horn's idea led to development of IGM to serve as on-board guidance for several Saturn I, and all Saturn IB and Saturn V launch vehicles.