Design and analysis of lunar lander manual control modes

All Apollo landings were performed by the crew, manually commanding the lunar module (LM) attitude and rate-of-descent (ROD). In future missions, the astronauts will again need manual control of the flight path and attitude. Crew interaction mechanisms have been proposed to re-designate a landing aimpoint during the approach phase. However, manual control modes, crew control capability, and resulting vehicle performance during terminal descent have not been thoroughly investigated. A rate-control attitude hold (RCAH) mode was ultimately used in the LM for lateral flight and descent rate was controlled incrementally (P66), although other modes were considered and evaluated. These modes, as well as others proposed during Apollo, are reviewed and discussed in terms of their applicability to Altair. The ALHAT guidance, navigation, and control (GNC) algorithms for autonomous precision lunar landing were modified to include two manual flight control modes: RCAH with incremental ROD (A66) and incremental lateral velocity control with incremental ROD (A68) using Altair LDAC1-Delta vehicle parameters. Crew interactions with the ALHAT GNC system are described throughout the mission phases from lunar orbit to touchdown, focusing on manual control of flight path and attitude during terminal descent. These ALHAT manual attitude control modes are described and vehicle performance is discussed in terms of its estimated impact on handling quality ratings.