Common Lunar Lander - Abstract
Common Lunar Lander

Jim Ruhnke, et. all

December 1991

Executive Overview

The Austin Cynthesis Corporation (hereafter referred to as "the Corporation") was formed to respond to a Request for Proposal for the design of a Common Lunar Lander (CLL) capable of carrying a lightweight (less than 500 kg), unspecified payload to the moon. The Corporation believes that such a system could make a large contribution towards the continued progress of the civil space program. The system could be utilized in further scientific study of the Moon by carrying payloads of scientific instruments custom-packaged for specific explorer missions. Additionally, it could help establish and/or support a manned lunar base, through the transfer of small amounts of building materials, communications equipment, a lunar rover vehicle, or other supplies. Due to its unique design philosophy, the potential missions the CLL could perform will truly be limited primarily by the payload designer.

The RFP received by the Corporation required the contractor to evaluate all mission phases: Earth launch, lunar transfer, lunar capture, and descent to the lunar surface. Additionally, the contractor was required to conceptually design a variety of potential payloads which the lander might be required to carry. To fulfill these requirements, the Corporation has divided the problem into three main parts: launch vehicle selection, lander design, and conceptual payload selection. Initial mass estimates led to the selection of a class of launch vehicles which included the Delta, Atlas, and Titan. As the design progressed, mass estimates eliminated the Delta as a possible launch vehicle, and the currently available Atlas/Centaur as well. However, planned upgrades to the Atlas/Centaur vehicle to be ready by 1993 should comfortably meet our needs.

The lander design itself has been broken into several subsystems: structure, power, thermal control, avionics, communications, and propulsion. The structures group has created a three-legged space frame design which provides for a two-meter diameter platform to which payloads will be affixed. This platform is hexagonal with diametric crossbeams. Small members may be connected between the main platform crossbeams to provide payload attachment points. At this time, the structure has been analyzed for particular static loads only; the short time available for the completion of the design precluded any attempt to perform dynamic modeling. Dynamic analysis is an important aspect of the structure design, however, and should be included in future phases of the design effort.

Because of the short mission duration of the lander itself (its mission will end when it has reached the lunar surface), the power group has determined fuel cells to be the optimum power source. Other than offering a limited amount of startup power, the lander itself will not be responsible for powering the payloads. For payload power requirements, the possibility of carrying a"common" power supply module as additional payload has been investigated. While there is no panacea available for supplying power to payloads using a standardized module, it would probably be practical to develop a "family" of power supplies from which a "best fit" for a particular mission could be chosen.

Thermal control of the lander will be accomplished using primarily passive systems to reduce weight and complexity. Spacecraft orientation, reflective paints, insulation, heat exchangers, and phase-change devices will be used to maintain the lander subsystems inside their operational temperature ranges. Additionally, the structure of the lander itself can be used as a heat sink for the payloads, if required.

The avionics subsystem has a difficult task, as the configuration of the lander will, in general, change significantly with payload mounting configurations particular to each mission. The avionics must either be configured before flight with specific information about the configuration of the lander, or else must be adaptable for a range of lander configurations. The pace of development of fully autonomous avionics systems indicates that an acceptable system would be available before the lander is scheduled to become operational.

The communications system is based on previous NASA explorer spacecraft. It is also shared between the lander and its payloads, as duplication of antennas, transmitters, and receivers is deemed unnecessary. It is expected that communications requirements for the payloads will be minimal during lunar transit, so that the lander will dominate communications use, and that the lander itself will not require communications at all after landing.

Finally, the propulsion system for the lander will use fine (25 N) and coarse (450 N) reaction control jets for attitude control, a solid rocket motor for lunar capture, and one storable bi-propellant engine for de-orbit, lunar descent, and landing. The fine control jets will be used for precision attitude maneuvers during free flight, while the coarse jets will be used to compensate for moments generated by the thrust vector from a main engine not passing through the center of mass of the spacecraft.

While the RFP has tasked the Corporation with the conceptual design of multiple payloads for the lander, the primary task is the design of the lander itself and most resources have been spent there. While several ideas for payloads have been advanced, time allowed for only a handful to be examined in any detail. These ideas include a common power system to satisfy various payload power requirements, a lunar experiment package, a materials utilization and testing platform, a surface rover, and a ground communications relay station. Other sample payloads which were proposed but not studied in this project included ground-based communications relay stations, families of transport containers (with options for power, pressurization, etc), modular building components, and a ballistic payload distribution system (to scatter small, shock-resistant items in an area around the lander).

This Final Design Report Document includes information on the requirements for the design project; the ideas proposed as solutions to the design problem; the work which has been completed in support of the design effort; justifications, validations, and verifications of decisions made during the project; and suggestions for future work to be done in support of the project. A project schedule, including current status of the items included on the schedule, as well as cost and management summaries is also included.