MSC prognosticated that, during landing, exhaust from the LEM's descent engine would kick up dust on the moon's surface, creating a dust storm. Landings should be made where surface dust would be thinnest.

Grumman and NASA announced the selection of four companies as major LEM subcontractors:

1. Rocketdyne for the descent engine
2. Bell Aerosystems Company for the ascent engine
3. The Marquardt Corporation for the reaction control system
4. Hamilton Standard for the environmental control system

Grumman began discussions with Rocketdyne on the development of a throttleable LEM descent engine. Engine specifications (helium injected, 10:1 thrust variation) had been laid down by MSC.

Aviation Daily reported an announcement by Frank Canning, Assistant LEM Project Manager at Grumman, that a Request for Proposals would be issued in about two weeks for the development of an alternate descent propulsion system. Because the descent stage presented what he called the LEM's "biggest development problem," Canning said that the parallel program was essential.

A bidders' conference was held at Grumman for a LEM mechanically throttled descent engine to be developed concurrently with Rocketdyne's helium injection descent engine. Corporations represented were Space Technology Laboratories; United Technology Center, a division of United Aircraft Corporation; Reaction Motors Division, Thiokol Chemical Corporation; and Aerojet-General Corporation. Technical and cost proposals were due at Grumman on April 8.

Grumman reported that it had advised North American's Rocketdyne Division to go ahead with the lunar excursion module descent engine development program. Negotiations were complete and the contract was being prepared for MSC's review and approval. The go-ahead was formally issued on May 2.

Grumman selected Space Technology Laboratories (STL) to develop and fabricate a mechanically throttled descent engine for the LEM, paralleling Rocketdyne's effort. Following NASA and MSC concurrence, Grumman began negotiations with STL on June 1.

Rocketdyne reported to Grumman on the LEM descent stage engine development program. Revised measurements for the engine were: diameter, 137 centimeters (54 inches); length, 221 centimeters (87 inches) (30.5 centimeters (twelve inches) more than the original constraint that Grumman had imposed on Rocketdyne).

After a detailed comparison of titanium and aluminum propellant tanks for the LEM descent stage, Grumman selected the lighter titanium.

Space Technology Laboratories received Grumman's go-ahead to develop the parallel descent engine for the LEM. At the same time, Grumman ordered Bell Aerosystems Company to proceed with the LEM ascent engine. The contracts were estimated at $18,742,820 and $11,205,415, respectively.

At a LEM Mechanical Systems Meeting in Houston, Grumman and MSC agreed upon a preliminary configuration freeze for the LEM-adapter arrangement. The adapter would be a truncated cone, 876 centimeters (345 inches) long. The LEM would be mounted inside the adapter by means of the outrigger trusses on the spacecraft's landing gear. This configuration provided ample clearance for the spacecraft, both top and bottom (i.e., between the service propulsion engine bell and the instrument unit of the S-IVB).

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:

• A reduced stowed height for the LEM from 336.5 to 313.7 centimeters (132.5 to 123.5 inches).
• A shorter landing stroke (50.8 instead of 101.6 centimeters) (20 instead of 40 inches).
• Better protection from irregularities (protuberances) on the surface.
• An alleviation of the gear heating problem (caused by the descent engine's exhaust plume).
• Simpler locking mechanisms.
• A better capability to handle various load patterns on the landing pads.

MSC approved Grumman's $19,383,822 cost-plus-fixed-fee subcontract with Rocketdyne for the LEM descent engine development program.

ASPO Manager Joseph F. Shea asked NASA Headquarters to revise velocity budgets for the Apollo spacecraft. (Studies had indicated that those budgets could be reduced without degrading performance.) He proposed that the 10 percent safety margin applied to the original budget be eliminated in favor of specific allowances for each identifiable uncertainty and contingency; but, to provide for maneuvers which might be desired on later Apollo missions, the LEM's propellant tanks should be oversized.

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.

Grumman selected AiResearch Manufacturing Company to supply cryogenic storage tanks for the LEM electrical power system. Final negotiations on the cost-plus-incentive-fee contract were held in June 1964.

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).

ASPO concurred in Grumman's recommendation to delete the redundant gimbal actuation system in the LEM's descent engine. A nonredundant configuration would normally require mission abort in case of actuator failure. Consequently, in making this change, Grumman must ensure that mission abort and the associated staging operation would not compromise crew survival and mission reliability.

MSC decided to supply television cameras for the LEM as government-furnished items. Grumman was ordered to cease its effort on this component.

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.

North American, Grumman, and MIT Instrumentation Laboratory summarized results of a six-week study, conducted at ASPO's request, on requirements for a Spacecraft Development Program. Purpose of the study was to define joint contractor recommendations for an overall development test plan within resource constraints set down by NASA. ASPO required that the plan define individual ground test and mission objectives, mission descriptions, hardware requirements (including ground support equipment), test milestones, and individual subsystem test histories.

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:

1. Landing of an unmanned spacecraft. If this failed, however, there would be little or no gain, since there was not yet a satisfactory method for instrumenting the unmanned vehicle for necessary failure data. If the landing were successful, it would prove only that the LEM was capable of landing at that particular location.
2. Designing the LEM for a reasonably smooth surface. This would avoid placing too stringent a requirement on the landing criteria to accommodate all lunar surface unknowns. A block change to the LEM design could then be planned for about mid-1966. By that time, additional lunar data from Ranger, Surveyor, and Lunar Orbiter flights would be available. The group agreed the second solution was more desirable.

1. ASPO concur with the proposed plan as a planning basis for implementation;
2. ASPO issue a Development Test Plan to all three contractors (preferably within 30 to 60-days);
3. each contractor analyze the effect of the plan upon spacecraft, facility, and equipment contracts; and
4. ASPO and the contractors conduct periodic reviews of the plan once it was formalized.

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.")

MSC directed Grumman to integrate LEM translation and descent engine thrust controllers. The integrated controller would be lighter and easier to install; also it would permit simultaneous reaction control system translation and descent engine control. Grumman had predicted that such a capability might be required for touchdown.

The first full-throttle firing of Space Technology Laboratories' LEM descent engine (being developed as a parallel effort to the Rocketdyne engine) was carried out. The test lasted 214 seconds, with chamber pressures from 66.2 to 6.9 newtons per square centimeter (96 to 10 psi). Engine performance was about five percent below the required level.

MSC authorized AiResearch Manufacturing Company and the Linde Company to manufacture high- pressure insulated tanks. This hardware, to be available about May 15, would be used in a study of the feasibility of a supercritical helium pressurization system for the LEM.

MSC gave its formal consent to two of Grumman's subcontracts for engines for the LEM: (1) With Bell Aerosystems for the ascent engine ($11,205,416 incentive-fee contract) (2) With Space Technology Laboratories for a descent engine to parallel that being developed by Rocketdyne ($18,742,820 fixed-fee contract).

Space Technology Laboratories (STL) began using its new San Juan Capistrano, Calif., test facility to static fire the firm's LEM descent engine. Hereafter, the bulk of STL's development firings were made at this site.

Rocketdyne conducted the first firing of the prototype thrust chamber assembly for its LEM descent engine.

Representatives from a number of elements within MSC (including systems and structural engineers, advanced systems and rendezvous experts, and two astronauts, Edward H. White II and Elliot M. See, Jr.) discussed the idea of deleting the LEM's front docking capability (an idea spawned by the recent TM-1 mockup review). Rather than nose-to-nose docking, the LEM crew might be able to perform the rendezvous and docking maneuver, docking at the spacecraft's upper (transfer) hatch, by using a window above the LEM commander's head to enable him to see his target.

A good many factors pointed to the merit of this approach:

- A rectangular window 18 by 38 centimeters (seven by 15 inches) above the commander's head could readily be incorporated into the LEM's structure, with only minimal design changes. The weight penalty would be between 4.5 and 6.8 kilograms (10 and 15 pounds) (excluding possible effects on the vehicle's environmental control system). On the other hand, eliminating the front docking mechanism would save about 11 or 14 kilograms (25 or 30 pounds). A docking aid on the CM was essential, but the device "would pay for itself in increased reliability and decreased design load requirements and fuel requirements." Additionally, instead of two docking aids on the LEM (as currently envisioned), only the upper one would be needed.
- The top-only docking arrangement would simplify the docking operation per se. The crew would no longer have to transfer the drogue from the top to the front hatch prior to rejoining the CM. [The need for depressurizing the spacecraft to perform this task thus was obviated.] As an additional "fringe benefit," the front hatch could possibly be reconfigured to make it easier for the crewmen to get out of and back into their craft while on the moon.
- The overhead window would enable the LEM commander to see the moon during powered descent and ascent portions of the flight, and thus would afford the crew a visual attitude and attitude reference.

There existed, naturally, some offsetting factors: the pilot's limited view of his target (thought to be of "no major consequence"); and his being unable quickly to scan his instrument panel (which was not essential). Also, the maneuver called for the pilot to fly his vehicle, for a considerable period, in a rather strained physical position (i.e., with his head tossed backward). But because of the many inherent advantages, the group concluded, LEM-active docking at the upper hatch was acceptable as a backup method for docking. (CM-active docking still would be the normal procedure, because that vehicle could "perform the docking maneuver more easily and more reliably than can the LEM . . . Deletion of the front docking capability on [the] LEM will not alter this relationship, therefore the LEM should be required to dock only when the CSM or the crew member inside is incapacitated. If the CSM is incapacitated returning to it is of questionable importance.") They recommended that Grumman be directed to proceed with this concept for the LEM.

NASA conducted a formal review of the LEM mockup M-5 at the Grumman factory. This inspection was intended to affirm that the M-5 configuration reflected all design requirements and to definitize the LEM configuration. Members of the Mockup Review Board were Chairman Owen E. Maynard, Chief, Systems Engineering Division, ASPO; R. W. Carbee, LEM Subsystem Project Engineer, Grumman; Maxime A. Faget, Assistant Director for Engineering and Development, MSC; Thomas J. Kelly, LEM Project Engineer, Grumman; Christopher C. Kraft, Jr. (represented by Sigurd A. Sjoberg), Assistant Director for Flight Operations, MSC; Owen G. Morris, Chief, Reliability and Quality Assurance Division, ASPO; William F. Rector III, LEM Project Officer, ASPO; and Donald K. Slayton, Assistant Director for Flight Crew Operations, MSC.

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.

NASA approved Grumman's selection of Airite to supply the LEM helium tanks, and the two firms started negotiations.

MSC's Systems Engineering Division reported on the consequences of eliminating the command and service module (CSM) rendezvous radar:

Coasting period:

During this phase of the mission, the rendezvous radar on the CSM would be used to track the LEM and the rendezvous radar on the LEM would be used to track the CSM. With the use of Mission Control through the Manned Space Flight Network (MSFN), three sources of information could be used as a vote for guidance system monitoring. Without the CSM rendezvous radar, the monitoring task would become more difficult; however, this was not to imply that it was impossible. The conclusion was that CSM rendezvous radar was highly desirable, but not absolutely necessary.

Lunar descent and ascent:

During powered flight, the CSM would be tracking the LEM. This was desirable because if the LEM guidance computer (LGC) failed, it was very doubtful that the astronauts could manually acquire radar lock-on with the CSM. Also, if the LEM rendezvous radar failed, CSM lock-on would be highly desirable. There were several alternative solutions to this problem. First of all, Mission Control through the MSFN could relieve the problem. If this did not satisfy all requirements, it was possible for the LEM rendezvous radar to track the CSM during powered descent and ascent. If the LGC then failed, the tracking acquisition would no longer be a problem. In summary, there did appear to be other ways of fulfilling the functions of the CSM rendezvous radar during the powered phases.

Lunar surface:

While the LEM was on the lunar surface, it would be tracked with the CSM rendezvous radar in order to update launch conditions. This could be accomplished by the LEM tracking the CSM and the MSFN.

Rendezvous:

This was the most critical phase for the use of the rendezvous radar on the CSM. If the LEM primary guidance system should fail (i.e., the LGC, inertial measurement unit (IMU), and LEM rendezvous radar), navigation information for long-range midcourse corrections would be provided by the rendezvous radar on the CSM. The MSFN, however, could supply this information. The terminal rendezvous maneuver would become a problem if the LEM rendezvous radar failed and there was not a rendezvous radar on the CSM. It had not been established that the MSFN could supply the required terminal rendezvous information. If MSFN could, a restricted mission profile would have to be employed. There were other methods of supplying terminal rendezvous information such as optical tracking. The scanning telescope or sextant on the CSM could be used with the IMU and Apollo guidance computer on the CSM to derive navigation information, meaning that the LEM would require flashing lights. There was a delta-V penalty associated with using angle-only information in place of range range rate and angle information, its importance depending on the accuracy of the angle data and the range/range rate data.

ASPO Manager Joseph F. Shea informed Apollo Program Director Samuel C. Phillips that it was his desire to review the progress of the two subcontractors (Space Technology Laboratory and Rocketdyne) prior to the final evaluation and selection of a subcontractor for the LEM descent engine.

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

1. establish review criteria during a planning meeting at MSC during the week of November 30, 1964;
2. visit the two subcontractors' facilities during the week of December 7, 1964, for review of technical status, manufacturing resources, and test facilities; and
3. prepare a written report and brief appropriate NASA personnel on their findings by December 18, 1964.

From MSC, Grumman received updated criteria to be used in the design of the LEM's landing gear. The gear must be designed to absorb completely the landing impact; it must also provide adequate stability for the vehicle under varying surface conditions, which were spelled out in precise detail.) Maximum conditions that MSC anticipated at touchdown were:

vertical velocity - 3.05 m (10 ft) per sec

horizontal velocity - 1.22 m (4 ft) per sec

spacecraft attitude

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."

Grumman ordered its major subcontractors supplying electronic equipment for the LEM to implement revised test programs and hardware schedules (in line with the new design approach). A similar directive went to RCA to modify the attitude and translation and the descent engine control assemblies as required for the new concept of an integrated assembly for guidance, navigation, and control of the spacecraft.

Parallel development of the LEM descent engine was halted. Space Technology Laboratories was named the sole contractor; the Rocketdyne contract was canceled. Grumman estimated that the cost of Rocketdyne's program would be about $25 million at termination.

Evaluations of the three-foot probes on the LEM landing gear showed that the task of shutting off the engine prior to actual touchdown was even more difficult than controlling the vehicle's rate of descent. During simulated landings, about 70 percent of the time the spacecraft was less than 0.3 m (1 ft) high when shutdown came; on 20 percent of the runs, the engine was still burning at touchdown. Some change, either in switch location or in procedure, thus appeared necessary to shorten the delay between contact light and engine cutoff (an average of 0.7 sec).

Grumman reported three major problems with the LEM:

1. To enable the manufacturer to complete the design of the aft equipment bay, NASA must define the ground support equipment that would be supported by the LEM adapter platforms.
2. Space Technology Laboratories' difficulties with the descent engine injector (the combustion instability in the variable-thrust engine)
3. The need for a lightweight thrust chamber for the descent engine, one that would still meet the new duty cycle.

Initial flights of the LLRV interested MSC's Guidance and Control Division because they represented first flight tests of a vehicle with control characteristics similar to the LEM. The Division recommended the following specific items for inclusion in the LLRV flight test program:

• The handling qualities of the LEM attitude control system should be verified using the control powers available to the pilot during the landing maneuver. The attitude controller used in these tests should be a three-axis LEM rotational controller.
• The ability of pilots to manually zero the horizontal velocities at altitudes of 30.48 m (100 ft) or less should be investigated. The view afforded the pilot during this procedure should be equivalent to the view available to the pilot in the actual LEM.
• The LEM descent engine throttle control should be investigated to determine proper relationship between control and thrust output for the landing maneuver.
• Data related to attitude and attitude rates encountered in landing approach maneuvers were desirable to verify LEM control system design limits.
• Adequacy of LEM flight instrument displays used for the landing maneuver should be determined.

MSC's Structures and Mechanics Division was conducting studies of lunar landing conditions. In one study, mathematical data concerning the lunar surface, LEM descent velocity, and physical properties of LEM landing gear and engine skirt were compiled. A computer was programmed with these data, producing images on a video screen, allowing engineers to review hypothetical landings in slow motion.

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.

An evaluation was made of the feasibility of utilizing a probe-actuated descent engine cutoff light during the LEM lunar touchdown maneuver. The purpose of the light, to be actuated by a probe extending 0.9 m (3 ft) beyond the landing gear pads, was to provide an engine cutoff signal for display to the pilot. Results of the study indicated at least 20 percent of the pilots failed to have the descent engine cut off at the time of lunar touchdown. The high percentage of engine-on landings was attributed to

1. poor location of the cutoff switch,
2. long reaction time (0.7 sec) of the pilot to a discrete stimulus (a light), and
3. the particular value of a descent rate selected for final letdown (4 ft per sec).

Grumman officials presented their findings on supercritical versus gaseous oxygen storage systems for the LEM (supercritical: state of homogeneous mixture at a certain pressure and temperature, being neither gas nor liquid). After studying factors of weight, reliability, and thermal control, as well as cost and schedule impacts, they recommended gaseous tanks in the ascent stage and a supercritical tank in the descent stage. They stressed that this configuration would be about 35.66 kg (117 lbs) lighter than an all-gaseous one. Though these spokesmen denied any schedule impact, they estimated that this approach would cost about 2 million more than the all-gaseous mode. MSC was reviewing Grumman's proposal.

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.)

Grumman ordered Space Technology Laboratories to increase the lifetime of the thrust chamber in the LEM's descent engine. This required substantial redesigning and was expected to delay the engine's qualification date about seven months.

William F. Rector, the LEM Project Officer in ASPO, replied to Grumman's weight reduction study (submitted to MSC on December 15, 1964). Rector approved a number of the manufacturer's suggestions:

• Delete circuit redundancy in the pulse code modulation telemetry equipment
• Eliminate the VHF lunar stay antenna
• Delete one of two redundant buses in the electrical power system
• Move the batteries for the explosive devices (along with the relay and fuse box assembly) from the ascent to the descent stage
• Reduce "switchover" time (the length of time between switching from the oxygen and water systems in the descent stage to those in the ascent portion of the spacecraft and the actual liftoff from the moon's surface). Grumman had recommended that this span be reduced from 100 to 30 min; Rector urged Grumman to reduce it even further, if possible. He also ordered the firm to give "additional consideration" to the whole concept for the oxygen and water systems:
  1. in light of the decisions for an all-battery LEM during translunar coast; and
  2. possibility of transferring water from the CM to the LEM.

• Delete the high intensity light. Because the rendezvous radar had been eliminated from the CSM, Rector stated flatly that the item could "no longer be considered as part of the weight reduction effort."
• Combine the redundant legs in the system that pressurized the reaction control propellants, to modularize" the system. MSC held that the parallel concept must be maintained.
• Delete the RCS propellant manifold.
• Abridge the spacecraft's hover time. Though the Center was reviewing velocity budgets and control weights for the spacecraft, for the present ASPO could offer "no relief."

Space Technology Laboratories' major problems with the LEM descent engine, Grumman reported, were attaining high performance and good erosion characteristics over the entire throttling range.

MSC directed Grumman to use supercritical helium only in the descent stage of the LEM; Grumman completed negotiations with AiResearch for the storage system.

Grumman and MSC engineers discussed the effect of landing impacts on the structure of the LEM. Based on analyses of critical loading conditions, Grumman reported that the present configuration was inadequate. Several possible solutions were being studied jointly by Grumman and the Structures and Mechanics Division (SMD):

• Strengthening the spacecraft's structure (which would increase the weight of the ascent and descent stages by 19 and 32 kg (42 and 70 lbs), respectively)
• Modifying the gear
• Reducing factors of safety and landing dynamics, including vertical velocity at touchdown

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.

Allison Division of General Motors Corporation completed an analysis of failures in the LEM descent stage's propellant tanks. Investigators placed the blame on brittle forgings. MSC's Propulsion and Power Division reported that "efforts are continuing to insure (that) future forgings will be satisfactory."

As a result of the decision for an all-battery LEM, MSC advised Grumman that power for the entire pre- separation checkout of the spacecraft would be drawn from that module's batteries (instead of only during the 30 minutes prior to separation). This change simplified the electrical mating between the two spacecraft and obviated an additional battery charger in the CSM. From docking until the start of the checkout, however, the CSM would still furnish power to the LEM.

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:

1. Space Technology Laboratories (STL) asked that the thrust chamber be lengthened by 13.9 cm (5.5 in). Weight penalty would be 11.3 kg (25 lbs).
2. STL concluded that, if used with Grumman's heatshield, the current nozzle extension would melt.

A tentative agreement was reached between Grumman and MSC propulsion personnel concerning the Propulsion System Development Facility's test scheduling at White Sands operations in regard to stand occupancy times relating to the ascent and descent development rigs. The tentative schedule showed that the ascent LEM Test Article (LTA)-5 vehicle would not start testing until April 1967. The PA-1 rig prototype ascent propulsion rig) would therefore be required to prove the final design and support early LEMs.

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.

ASPO requested the Apollo Program Director to revise the LEM control weight at translunar injection as follows:

• Ascent stage - 2,193kg (4,835lbs)
• Descent stage - 2,166kg (4,775lbs)
• Total LEM (fueled) - 14,515kg (32,000lbs)

ASPO Manager Joseph F. Shea reported the accomplishment of a number of important items.

- North American was directed to stop all work on systems installation on CSM 006. Test objectives would be reassigned to boilerplate 14 and CSM 008.
- The first deliverable LEM attitude and translation control assembly had passed acceptance test at RCA and was delivered to Grumman.
- The Design Engineering Inspection on LEM descent propulsion test rig PD-1 was completed and the rig shipped to WSMR/PSDF. The LEM ascent propulsion rig HA-4 was shipped to AEDC for ascent engine environmental tests.
- The LEM Technical Specification and the LEM Master End Item

Specification were incorporated into the Grumman contract on June 1, 1965.

Systems Engineering Division chief, Owen E. Maynard, reported to the Instrumentation and Electronic Systems Division (IESD) the results of a study on a LEM communications problem (undertaken by his own group at IESD's request). During phases of powered descent to certain landing sites (those in excess of 20 degrees east or west longitude), the structure of the spacecraft would block the steerable antenna's line of sight with the earth. Communications with the ground would therefore be lost. Maynard concurred with IESD that the problem could best be solved by rotating the LEM about its thrust axis.

Grumman advised MSC of major troubles plaguing development of the LEM's descent engine. These included problems of weight, chamber erosion, mixtures, valves, combustion instability, and throttle mechanisms (which Grumman said could delay delivery of LEM 1 and the start of qualification testing).

MSC requested Grumman to review the following ascent and descent pressurization system components in the propulsion subsystem for materials compatibility with certain propellants:

1. helium explosive valve;
2. pressure regulator;
3. latching solenoid valve;
4. pressure relief and burst disc; and
5. quad check valve.

MSC requested that Grumman study the feasibility of a "fire-till- touchdown" landing procedure for the LEM. Grumman was to investigate especially performance factors surrounding crushing of the descent engine skirt, or possibly jettisoning the skirt, and was to recommend hardware modifications required for this landing mode.

Bell Aerosystems Company reported that the LEM ascent engine bipropellant cooled injector baffle met all basic specification requirements, including those for combustion efficiency, ablative compatibility, and stability. Bell conducted a successful firing with an engine that had previously been vibrated to simulate launch boost and lunar descent. The contractor also completed a duty cycle firing at AEDC with hardware conditions set to the maximum temperatures believed attainable during a lunar mission.

The LEM electrical power system use of the primary structure as the electrical ground return was approved after Grumman presentations were made to ASPO and Engineering and Development personnel. The descent-stage batteries would not use a descent-stage structure ground to preclude current flow through the pyrotechnic interstage nut and bolt assemblies. The ascent and descent stage batteries would be grounded to primary structure in the near vicinity of the ascent-stage batteries. In addition, several selected manually operated solenoids would ground. All other subsystems would remain grounded to the "single-point" vehicle ground. This change would be implemented by Grumman with no cost or schedule impact and would effect a weight savings of approximately 7.7 kg (17 lbs).

In reply to a letter from Grumman, MSC concurred with the recommendation that a 135-centimeter lunar surface probe be provided on each landing-leg footpad and that the engine cutoff logic retain its basic manual mode. MSC did not concur with the Grumman recommendation to incorporate the automatic engine cutoff logic in the LM design. MSC believed that the planned descent-stage engine's manual cutoff landing mode was adequate to accomplish lunar touchdown and had decided that the probe-actuated cutoff capability should not be included in the LM design.

MSC Director Robert R. Gilruth requested of Jet Propulsion Laboratory Director William H. Pickering that JPL fire the Surveyor spacecraft's vernier engine after the Surveyor landed on moon, to give insight into how much erosion could be expected from an LM landing. The LM descent engine was to operate until it was about one nozzle diameter from landing on the lunar surface; after the Surveyor landed, its engine would be about the same distance from the surface. Gilruth told Pickering that LaRC was testing a reaction control engine to establish surface shear pressure forces, surface pressures, and back pressure sources, and offered JPL that data when obtained.

Handling and installation responsibilities for the LM descent stage scientific equipment (SEQ) were defined in a letter from MSC to Grumman Aircraft Engineering Corp. The descent stage SEQ was composed of three basic packages:

1. the Apollo Lunar Surface Experiments Package (ALSEP) compartment 1, which included the ALSEP central station and associated lunar surface experiments;
2. ALSEP compartment 2, composed of the radioisotope thermoelectric generator (RTG) and Apollo lunar surface drill (ALSD); and
3. the RTG fuel cask, thermal shield, mount and RTG fuel element.

1. The SEQ would be installed in the LM descent stage while the LM was in the LM landing gear installation stand before LM-SLA mating, with the exception of the RTG fuel cask, thermal shield, mount and fuel element, and the ALSD.
2. The RTG fuel cask, thermal shield, mount and fuel element and the ALSD would be installed in the LM descent stage during prelaunch activities at the launch site.
3. Grumman would be responsible for SEQ installation with the exception of the RTG fuel element. The ALSEP contractor, Bendix Aerospace Systems Division, would provide the installation procedure and associated equipment. Bendix would also observe the installation operation and NASA would both observe and inspect it.
4. The Atomic Energy Commission (AEC) would be responsible for handling and installing the RTG fuel element. Bendix would provide procedures and associated equipment. Grumman and NASA would observe and inspect this operation. If for any reason the RTG fuel element was required to be removed during prelaunch operations, the AEC would be responsible for the activity. Removal procedures would be provided by Bendix. MSC requested that Grumman's planned LM activities at Kennedy Space Center reflect these points of definition.

Donald K. Slayton said there was some question about including extravehicular activity on the AS-503 mission, but he felt that, to make a maximum contribution to the lunar mission, one period of EVA should be included. Slayton pointed out that during the coast period (simulating lunar orbit) in the current flight plan the EVA opportunity appeared best between hour 90 and hour 100.

Two primary propulsion system firings would have been accomplished and the descent stage of the LM would still be attached.

Slayton specified that EVA should consist of a crewman exiting through the LM forward hatch and making a thorough orbital check of the LM before reentering through the same hatch. He said EVA on AS-503 would provide:

- flight experience and confidence in LM environmental-control-system performance during cabin depressurization;

- flight confidence in the Block II International Latex Corp. pressure garment assemblies;

- orbital time-line approximation of cabin depressurization times, forward hatch operation, flight crew egress procedures, and LM entry following a simulated lunar EVA;

- visual inspection and photography of LM landing gear for possible damage during withdrawal from the S-IVB stage;

- external inspection and photography of the LM to record window and antenna contamination caused by SLA panel pyrotechnic deployment;

- inspection and photography of descent engine skirt and adjacent areas for evidence of damage from two descent propulsion system firings;

- inspection and photography of possible damage to the upper LM caused by the SM reaction control system during withdrawal;

- possible additional data regarding EVA metabolic rates, etc., as applied to the Block II pressure garment assembly; and

- additional orbital confidence in the portable life support system operational procedures.

ASPO Manager Joseph F. Shea requested that the White Sands Test Facility be authorized to conduct the descent propulsion system series tests starting April 3 and ending about May 1. The maximum expected test pressure would be 174 newtons per sq cm (253 psia), normal maximum operating pressure. The pressure could go as high as 179 newtons per sq cm (260 psia) according to the test to be conducted.

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.

C. H. Bolender, ASPO Manager for the lunar module, wrote Joseph G. Gavin, Jr., Grumman LM Program Director, that recent LM weights and weight growth trends during the past several months established the need to identify actions that would reduce weight and preclude future weight growth.

He pointed out that the Configuration Control Board (CCB) at MSC had emphasized such actions, while recognizing the specific weight increases associated with design change actions resulting from the AS-204 accident. Several other design corrections or improvements had been implemented, such as increased plume protection, ascent engine reflection protection, descent stage upper-deck structural repair, and landing gear shielding. Bolender told Gavin, "We cannot afford to exercise ultraconservatism as an expedient to problem solving. The modification of the descent stage skin panels may be a case in point. . . . We have already asked that in consideration of minimum weight design, you reassess your recommendation to change to a uniform panel thickness." He requested that the objectives of the recent Super Weight Improvement program (a weight saving "tool" employed by Grumman) be reiterated in design activity and that weight reduction suggestions be solicited and evaluated for implementation. Bolender requested a biweekly review of weight reduction candidate changes and told Gavin he was asking Systems Engineering Division to maintain close coordination with Grumman and to report progress of the weight reduction and control activity at the regular CCB meetings.

ASPO Manager George M. Low discussed with Rocco Petrone of KSC the problem of high humidity levels within the spacecraft-lunar module adapter. Petrone advised that several changes had been made to alleviate the problem: air conditioning in the SLA and the instrument unit would remain on during propellant loading; and the rate of air flow into the SLA was increased. Also, technicians at the Cape had designed a tygon tube to be installed to bring dry air into the LM descent engine bell, should this added precaution prove necessary. With these changes, Low felt confident that the humidity problem had been resolved.

NASA launched Apollo 5 - the first, unmanned LM flight - on a Saturn IB from KSC Launch Complex 37B at 5:48:08 p.m. EST. Mission objectives included verifying operation of the LM structure itself and its two primary propulsion systems, to evaluate LM staging, and to evaluate orbital performances of the S-IVB stage and instrument unit. Flight of the AS-204 launch vehicle went as planned, with nosecone (replacing the CSM) jettisoned and LM separating. Flight of LM-1 also went as planned up to the first descent propulsion engine firing. Because velocity increase did not build up as quickly as predicted, the LM guidance system shut the engine down after only four seconds of operation, boosting the LM only to a 171 x 222 km orbit. Mission control personnel in Houston and supporting groups quickly analyzed the problem. They determined that the difficulty was one of guidance software only (and not a fault in hardware design) and pursued an alternate mission plan that ensured meeting the minimum requirements necessary to achieve the primary objectives of the mission. The ascent stage separated and boosted itself into a 172 x 961 km orbit. After mission completion at 2:45 a.m. EST January 23, LM stages were left in orbit to reenter the atmosphere later and disintegrate. Apollo program directors attributed success of the mission to careful preplanning of alternate ways to accomplish flight objectives in the face of unforeseen events.

Grumman President L. J. Evans wrote ASPO Manager George M. Low stating his agreement with NASA's decision to forego a second unmanned LM flight using LM-2. (Grumman's new position - the company had earlier strongly urged such a second flight - was reached after discussions with Low and LM Manager G. H. Bolender at the end of January and after flight data was presented at the February 6 meeting of the OMSF Management Council.) Although the decision was not irreversible, being subject to further investigations by both contractor and customer, both sides now were geared for a manned flight on the next LM mission.

However, Evans cited several spacecraft functions not covered during the LM-1 flight that would have to be demonstrated before attempting a lunar mission, notably control by the primary navigation and guidance system of the descent propulsion system burn as well as control of stage separation and firing of the ascent propulsion system. To demonstrate these functions fully, he said, some modifications in mission plans for the next two manned flights might be necessary.

The LM Descent Engine Program Review was held at TRW Systems, Redondo Beach, Calif., reviewing the overall program status, technical and manufacturing problems, and program costs. Program status reports showed that 28 engines had been delivered in the LM descent engine program to date, including all White Sands Test Facility engines and engine rebuilds and all qualification test and flight engines; 9 WSTF engines and 12 flight engines remained to be delivered. Grumman indicated all engine delivery dates coincided with the vehicle need dates.

ASPO Manager George M. Low and others from MSC met with Grumman's LM engineering staff, headed by Thomas J. Kelly, to discuss the descent stage heatshield and thermal blanket problems associated with reduced thrust decay of the descent engine at lunar touchdown.

Several significant decisions were reached:

- The touchdown probe was lengthened to 1.6 meters.
- Effective on LM-5 and later vehicles, Grumman would "beef up" (both structurally and thermally) the base heatshield.
- Grumman was to conduct a series of tests on overpressure of the descent engine.
- Grumman would begin design studies of a jettisonable descent engine skirt.
- Landing stability would be reexamined with the existing thrust tailoff profile (a study to be made either by Grumman or by Boeing; Low asked Maxime A. Faget, Director of Engineering and Development at MSC, to review this proposed test plan and to recommend where it should be conducted, for best cost, schedule, and technical capabilities).

ASPO Manager George M. Low wrote to Grumman President Llewellyn J. Evans to call his attention to the problem of continued propellant leaks in the LM.

"In spite of all of our efforts, last summer" (i.e., with the extensive plumbing rework done on LM-1 after its delivery to Florida), Low said, technicians at KSC found a leak on one of the lines on LM-3, even though no leaks had been observed during checkout at Bethpage. Investigating the problem, Low had learned that Grumman had made some propellant-system design changes that had led to installation of four-bolt flanges with single teflon O-ring seals - despite the fact that during the preceding summer NASA and Grumman had jointly agreed not to use this joint on the LM vehicle. This most recent problem, said Low, again points up the importance of strictest control of all design changes in the spacecraft. Because of the need for maintaining a lunar-configured LM as a design baseline, all spacecraft design changes had to be carried through the Apollo Configuration Control Board before implementation.

The Allison descent-stage propellant tank, being redesigned at Airite Division of Sargent Industries to a "lidless" configuration, blew up during qualification test at Airite. The crew noticed loss of pressure and therefore tightened fittings and repressurized. As the pressure went up, the tank blew into several pieces. Grumman dispatched a team to Airite to determine the cause and the necessary corrective action.

Howard W. Tindall, Jr., Chief of Apollo Data Priority Coordination within ASPO, reported an operational system problem aboard the LM. To give a returning Apollo crew an indication of time remaining to perform a landing maneuver or to abort, a light on the LM instrument panel would come on when about two minutes worth of propellants remained in the descent propellant system tanks with the descent engine running at 25-percent thrust. The present LM weight and descent trajectory were such that the light would always come on before touchdown. The only hitch, said Tindall, was that the signal was connected to the spacecraft master alarm. "Just at the most critical time in the most critical operation of a perfectly nominal lunar landing mission, the master alarm with all its lights, bells, and whistles will go off." Tindall related that some four or five years earlier, astronaut Pete Conrad had called the arrangement "completely unacceptable . . . but he was probably just an Ensign at the time and apparently no one paid any attention." If this "is not fixed," Tindall said, "I predict the first words uttered by the first astronaut to land on the moon will be 'Gee whiz, that master alarm certainly startled me.'" Tindall recommended either rerouting the signal wiring to bypass the alarm or cutting the signal wire and relying solely on the propellant gauges to assess flight time remaining.

The MSF Management Council, meeting at KSC, agreed that MSC would take the following actions for augmenting the capability of the Apollo system to accomplish a successful lunar landing mission and for planning further lunar exploration:

Capability Augmentation:

• Submit for Apollo Level I approval a plan for developing and procuring the A9L spacesuit.

• Submit a plan to the Apollo program Director describing how the portable life support system's improvement program procurement would be done.

• Proceed with the 1/6-g special test equipment. The plan - including scope, schedule, and cost estimates for this simulator - would be submitted to Apollo Program Director by 1 March.

• Proceed with the engineering definition of software and hardware required to precision-land the LM at sites anywhere on the front surface of the moon.

Lunar Exploration:

• Submit a plan for the buildup of the cannibalized ALSEP, listing experiments to be included, the estimated cost, and delivery schedule.

• Submit a plan for the procurement of additional ALSEPs including proposed quantities, estimated costs, and experiments.

• Proceed to define further a CSM lunar orbital science package and a lunar polar orbit mission science package, including instruments, costs, delivery schedule, and approach to CSM integration. Costs would include instruments and spacecraft integration.

• Proceed with the definition to increase the size of LM descent stage tanks and to improve the propellant pressurization system.

• Submit a plan for the procurement of a constant volume suit, including a description of any further development not under contract that MSC planned to add to any present contract by change order.

• Proceed with engineering change analysis of performance (including habitability) improvements to the CSM and LM.

In a report to the Administrator, the Associate Administrator for Manned Space Flight summed up the feeling of accomplishment as well as the problem of the space program: "The phenomenal precision and practically flawless performance of the Apollo 9 lunar module descent and ascent engines on March 7 were major milestones in the progress toward our first manned landing on the moon, and tributes to the intensive contractor and government effort that brought these two complex systems to the point of safe and reliable manned space flight.

The inevitable developmental problems that plagued the LM propulsion system were recurring items in our management reporting, and the fact that essentially all major test objectives were met during last Friday's flight operations is an outstanding achievement. The earth orbital simulations of the lunar descent, ascent, rendezvous, and docking maneuvers, taking Astronauts McDivitt and Schweickart 114 miles (183.4 km) away from the CSM piloted by Dave Scott and safely back, were a measure of the skill of the Apollo 9 crew and the quality of the hardware they were flying."

MSC appointed a panel to investigate a February 13 accident at the Aerojet-General plant in Fullerton, Calif., that had damaged a lunar module descent tank beyond repair. Panel findings were reported to a review board later in the month, which recommended needed safety measures.