Development of the iterative guidance mode with its application to various vehicles and missions.

Abstract

The guidance errors at orbital insertion or lunar conic injection in the position magnitude, velocity magnitude, and the path angle, with respect to the specified terminal conditions that result from three-sigma vehicle perturbations including a single engine failure in the S-IC or S-II stages are: AR = ±20 m, AF = ±0.005 m/sec, and AT = ±0.001°. The velocity error at cutoff is due to the inability of the vehicle to achieve cutoff at the proper millisecond. The errors at lunar conic injection, assuming perfect navigation, result in less than 100 km error in attaining the specified radius of closest approach to the moon if no midcourse corrections are made. The basic criterion for evaluating the performance of the Saturn V navigation system is the midcourse correction velocity required to achieve the desired radius of lunar approach at the desired time. Table 1 summarizes the corrections required at two hr after injection onto the lunar trajectory. The data are based on a stay-time of 2.7 orbits. Environmental and propulsive uncertainties are included with the equation errors. The midcourse velocity requirements are well within the available velocity budget for a Saturn-V Lunar Landing Mission; the major portion of the budget is used to correct the platform hardware errors.