Moon landing

Abstract: Artemis is a Common Lunar Lander (CLL) design for the Space Exploration Initiative (SEI). Structure factors for the CLL's primary and secondary structures are listed in tabular form. Additionally, engineering drawings of various systems, including the propulsion and landing systems, are presented.

Abstract: Apollo Lunar-descent Guidance transfers the Lunar Module from a near-circular orbit to touchdown, traversing 17^o central angle and 15 km altitude in 11 min. A group of interactive programs in an onboard computer guide the descent, controlling altitude and the descent propulsion system throttle. A ground-based program precomputes guidance targets. This paper describes the concepts involved. Explicit and implicit guidance are discussed, guidance equations are derived, and the earlier Apollo explicit equation is shown to be an inferior special case of the later implicit equation. The paper describes interactive guidance by which the two-man crew selects a landing site in favorable terrain and directs the trajectory there. Interactive terminal-descent guidance enables the crew to control the essentially vertical descent rate in order to land in minimum time with safe contact speed. The attitude maneuver routine uses concepts that make gimbal lock inherently impossible. The throttle routine yields zero steady-state thrust-acceleration error or avoids operation within a thrust region forbidden because of hardware limitations. The ground-based program precomputes guidance targets which shape the trajectory to produce an efficient descent with adequate visibility and no transients at the final phasic interface.

Abstract: The article examines the reasons why the U.S. National Aeronautics & Space Administration (NASA) wants to return to the moon. 2009 marked the 40th anniversary of two events in space exploration, including the Moon landing of Apollo 11. Topics include the author's testimony before the U.S. Congress stating his opinion that returning to the moon would be for the adventurous nature of it, not the advancement of science, and would be financially costly.

Abstract: China launched its first lunar probe, Chang’E-1, at 6:05 p.m. (10:05 GMT), October 24, 2007. Chang’E-1 blasted off on a Long March 3A carrier rocket from the No. 3 launch tower in the Xichang Satellite Launch Center of southwestern Sichuan Province. China National Space Administration performed the lunar orbit injection maneuver for Chang’E-1 at 11:25 a.m. on November 5, 2007 (China Standard Time). Chang’E-1 was injected into the lunar orbit after the maneuver, and will begin to explore the moon in the following 1 year. It is the first step into its ambitious three-phase moon mission, marking a new milestone in the Chinese space exploration history.

Abstract: The ALHAT project is funded by NASA to develop an integrated AGNC (autonomous guidance, navigation and control) hardware and software system capable of detecting and avoiding surface hazards and guiding humans and cargo safely, precisely and repeatedly to designated lunar landing sites. There are important interdependencies driving the design of a lunar landing system including such things as lander hazard robustness, landing site conditions (terrain and natural lighting), trajectories, sensors, crew involvement, and others. The ALHAT system must be capable of operating in a wide range of lunar environments and supporting global lunar access for both crewed and robotic missions. This paper discusses the major factors driving the design of a lunar landing system as well as the current state of the technology development. The supporting analysis and testing results will be presented that show the system interdependencies and their relative importance, as well as the trades needed to optimize the landing system. The emphasis is on the final phase of the landing where hazard detection and avoidance (HDA) and hazard relative navigation (HRN) are the primary considerations in achieving a safe landing. The current sensor options being considered and the status of the development of those sensors are discussed.