Also, Grumman advised that, from the standpoint of landing stability, a five-legged LEM was unsatisfactory. Under investigation were a number of landing gear configurations, including retractable legs.
Also Grumman reported that a preliminary analysis showed the reaction control system plume heating of the LEM landing gear was not a severe problem. (This difficulty had been greatly alleviated by the change from five to four landing legs on the vehicle.
At this same meeting, Grumman presented a comparison of radially and laterally folded landing gears (both of 457-centimeter (180-inch) radius). The radial-fold configuration, MSC reported, promised a weight savings of 22-2 kilograms (49 pounds). MSC approved the concept, with an 876-centimeter (345-inch) adapter. Further, an adapter of that length would accommodate a larger, lateral fold gear (508 centimeters (200 inches)), if necessary. During the next several weeks, Grumman studied a variety of gear arrangements (sizes, means of deployment, stability, and even a "bending" gear). At a subsequent LEM Mechanical Systems Meeting, on November 10, Grumman presented data (design, performance, and weight) on several other four-legged gear arrangements - a 457-centimeter (180-inch), radial fold "tripod" gear (i.e., attached to the vehicle by three struts), and 406.4-centimeter (160-inch) and 457-centimeter (180-inch) cantilevered gears. As it turned out, the 406.4-centimeter (160-inch) cantilevered gear, while still meeting requirements demanded in the work statement, in several respects was more stable than the larger tripod gear. In addition to being considerably lighter, the cantilevered design offered several added advantages:
The astronauts' review was held on October 5 and 6. It included demonstrations of entering and getting out of the LEM, techniques for climbing and descending the ladder, and crew mobility inside the spacecraft. The general inspection was held on the 7th and the Review Board met on the 8th. Those attending the review used request for change (RFC) forms to propose spacecraft design alterations. Before submission to the Board, these requests were discussed by contractor personnel and NASA coordinators to assess their effect upon system design, interfaces, weight, and reliability.
The inspection categories were crew provisions; controls, displays, and lighting; the stabilization and control system and the guidance and navigation radar; electrical power; propulsion (ascent, descent, reaction control system, and pyrotechnics ; power generation cryogenic storage and fuel cell assemblies ; environmental control; communications and instrumentation; structures and landing gear; scientific equipment; and reliability and quality' control. A total of 148 RFCs were submitted. Most were aimed at enhancing the spacecraft's operational capability; considerable attention also was given to quality and reliability and to ground checkout of various systems. No major redesigns of the configuration were suggested.
As a result of this review, the Board recommended that Grumman take immediate action on those RFC's which it had approved. Further, the LEM contractor and MSC should promptly investigate those items which the Board had assigned for further study. On the basis of the revised M-5 configuration, Grumman could proceed with LEM development and qualification. This updated mockup would be the basis for tooling and fabrication of the initial hardware as well.
vertical velocity - 3.05 m (10 ft) per sec
horizontal velocity - 1.22 m (4 ft) per sec
pitch - 3 degrees
roll - 3 degrees
yaw - random
attitude rates - 3 degrees per sec
At touchdown, all engines (descent and reaction control would be off. "It must be recognized," MSC emphasized, "that the vertical and horizontal velocity values . . . are also constraints on the flight control system."
At the same time, Grumman advised MSC that it considered impractical a contrivance to simulate lunar gravity in the drop program for test Mockup 5. Grumman put forth another idea: use a full-sized LEM, the company said, but one weighing only one-sixth as much as a flight-ready vehicle. SMD officials were evaluating this latest idea, while they were reviewing the entire TM-5 program.
In another study, a one-sixth scale model of the LEM landing gear was dropped from several feet to a platform which could be adjusted to different slopes. Impact data, gross stability, acceleration, and stroke of the landing gear were recorded. Although the platform landing surface could not duplicate the lunar surface as well as the computer, the drop could verify data developed in the computer program. The results of these studies would aid in establishing ground rules for lunar landings.
Shea replied, "We are currently evaluating the LEM lunar landing system with the Apollo contractors and the NASA Centers. We believe that the landing problem is being covered adequately by ourselves and these contractors." Shea added that a meeting would be held at Grumman April 21 and 22 to determine if there were any deficiencies in the program, and that he would be pleased to have Bellcomm attend the meeting and later make comments and recommendations.
Also Grumman representatives summarized the company's study on the design of the footpads. They recommended that, rather than adopting a stroking-type design, the current rigid footpad should be modified. The modification, they said, would improve performance as much as would the stroking design, without entailing the latter's increased weight and complexity and lowered reliability. SMD was evaluating Grumman's recommendations.
Grumman was also studying substitution of an aluminum-mylar nonrigid outer heatshield with plastic standoffs for current rigid ascent and descent heatshields. The potential inert weight saving would be about 84 kg (185 lbs). Lee requested that Thermo-Structures Branch stay in close contact with these developments.