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 ASPO Manager's proposal resulted from experience that had arisen because of unfortunate terminology used to designate the extra fuel. Originally the fuel budget for various phases of the mission had been analyzed and a 10 percent allowance had been made to cover - at that time, unspecified - contingencies, dispersions, and uncertainties. Mistakenly this fuel addition became known as a "10% reserve"! John P. Mayer and his men in the Mission Planning and Analysis Division worried because engineers at North American, Grumman, and NASA had "been freely 'eating' off the so-called 'reserve'" before studies had been completed to define what some of the contingencies might be and to apportion some fuel for that specific situation. Mayer wanted the item labeled a "10% uncertainty."
Shea recommended also that the capacity of the LEM descent tanks be sufficient to achieve an equiperiod orbit, should this become desirable. However, the spacecraft should carry only enough propellant for a Hohmann transfer. This was believed adequate, because the ascent engine was available for abort maneuvers if the descent engine failed and because a low altitude pass over the landing site was no longer considered necessary. By restricting lunar landing sites to the area between ±5 degrees latitude and by limiting the lunar stay time to less than 48 hours, a one-half-degree, rather than two-degree, plane change was sufficient.
In the meantime, Shea reported, his office was investigating how much weight could be saved by these propellant reductions.
On this same date, Grumman concluded negotiations with Allison Division of General Motors Corporation for design and fabrication of the LEM descent engine propellant storage tanks (at a cost of $5,479,560).
Resizing of the LEM propulsion tanks was completed by Grumman. The cylindrical section of the descent tank was extended 34.04 millimeters (1.34 inches), for a total of 36.27 centimeters (14.28 inches) between the spherical end bells. The ascent tanks (two-tank series) were 1240.54 centimeters (48.84 inches) in diameter.
Intermediate objectives for the Apollo program were outlined: the qualification of a manned CSM capable of earth reentry at parabolic velocities after an extended space mission; qualification of a manned LEM both physically and functionally compatible with the CSM; and demonstration of manned operations in deep space, including lunar orbit. The most significant basic test plan objective formulated during the study was the need for flexibility to capitalize on unusual success or to compensate for unexpected difficulties with minimum impact on the program.
Only one major issue in the test plan remained unresolved - lunar descent radar performance and actual lunar touchdown. Two possible solutions were suggested:
The complete findings of this joint study were contained in a five-volume report issued by North American and submitted to MSC early in February 1964. (This document became known informally as the "Project Christmas Present Report.")
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.
Shea had asked MSC's Maxime A. Faget to be chairman of a committee to accomplish the review, and would also ask the following individuals to serve: C. H. Lambert, W. F. Rector III, and J. G. Thibodaux, all of MSC; L. F. Belew, MSFC; M. Dandridge and J. A. Gavin, Grumman; I. A. Johnsen, Lewis Research Center; C. H. King, OMSF; Maj. W. R. Moe, Edwards Rocket Research Laboratory; and A. O. Tischler, NASA Office of Advanced Research and Technology.
The Committee should
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."
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.
During the latter part of the month, Crew Systems Division (CSD) engineers also looked into the several approaches. In contrast to Grumman, CSD calculated that, at most, an all-gaseous system would be but 4.08 kg (9 lbs) heavier than a supercritical one. CSD nonetheless recommended the former. It was felt that the heightened reliability, improved schedules, and "substantial" cost savings that accompanied the all-gaseous approach offset its slim weight disadvantage.
During late April, MSC ordered Grumman to adopt CSD's approach (gaseous systems in both stages of the vehicle). (Another factor involved in this decision was the lessened oxygen requirement that followed substitution of batteries for fuel cells in the LEM.)
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.
The PA-1 rig was designed and was being fabricated to accommodate small propellant tanks, and there were no plans to update it with larger ones. Therefore, advantages of flexibility, running tests of longer sustained durations, and with the final tank outlet configurations would not be realized. Grumman was requested to take immediate action to have the rig accommodate the larger tanks and install the smaller tanks by use of adapters or other methods.
TWX, James L. Neal, MSC, to GAEC, Attn: R. S. Mullaney. April 30, 1965.
During the Month
Grumman reported two major problems with the LEM's descent engine:
Required leak check operations were also requested at a maximum pressure of 142 newtons per sq cm (206 psia), with a design limit of 186 newtons per sq cm (270 psia). The test fluids would be compatible with the titanium alloy at the test pressures. The test would be conducted in the Altitude Test Stand, where adequate protection existed for isolating and containing a failure. MSC Director Robert R. Gilruth approved the request the same day.