Grumman and NASA announced the selection of four companies as major LEM subcontractors:
Grumman began fabrication of a one-tenth scale model of the LEM for stage separation tests. In launching from the lunar surface, the LEM's ascent engine fires just after pyrotechnic severance of all connections between the two stages, a maneuver aptly called "fire in the hole."
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.
RCA completed a study on ablative versus regenerative cooling for the thrust chamber of the LEM ascent engine. Because of low cooling margins available with regenerative cooling, Grumman selected the ablative method, which permitted the use of either ablation or radiation cooling for the nozzle extension.
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.
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 proposed a two-tank ascent stage configuration for the LEM. On January 17, 1964, ASPO formally concurred and authorized Grumman to go ahead with the design. The change was expected to reduce spacecraft weight by about 45 kilograms (100 pounds) and would make for a simpler, more reliable ascent propulsion system. ASPO also concurred in the selection of titanium for the two propellant tanks.
MSC defined the LEM terminal rendezvous maneuvers. That phase of the mission would begin at a range of 9.3 kilometers (five nautical miles) from the CSM and terminate at a range of 152.4 meters (500 feet). Before rendezvous initiation, closing velocity should be reduced to 61 meters (200 feet) per second by use of the ascent engine. The reaction control system should be used exclusively thereafter.
Grumman began initial talks with Bell Aerosystems Company looking toward concentrating on the all-ablative concept for the LEM's ascent engine, thus abandoning the hope of using the lighter, radiatively cooled nozzle extension. These talks culminated in July, when Bell submitted to Grumman a revised development and test plan for the engine, now an all-ablative design.
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).
The MSC Primary Propulsion Branch (PPB) completed a study on the current LEM ascent engine and performance that might be gained if the chamber pressure and characteristic exhaust velocity efficiency were increased. PPB also evaluated the use of hard versus soft chamber throats. A study by Bell Aerosystems Company had predicted a slightly lower performance than the MSC investigation (which estimated a drop of about six points below specification values if the current design were retained). PPB thought that specifications might be reached by increasing the chamber pressure to 82.7 newtons per square centimeter (120 psia) and the exhaust velocity efficiency to 97.3 percent, and by using a hard, rather than a soft, throat.
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. Additional Details: here....
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.
The current thrust buildup time for the LEM ascent engine was 0.3 second. To avoid redesigning the engine valve-which was already the pacing item in the ascent engine's development - MSC directed Grumman simply to change the specification value from 0.2 to 0.3 second.
At the same time, engineers at the Center began studying ways to increase the engine's thrust. Because of the LEM's weight gains, the engine must either be uprated or it would have to burn longer. Preliminary studies showed that, by using a phase "B" chamber (designed for a chamber pressure of 689.5 kilonewtons per sq m (100 psia)), thus producing chamber pressure of about 792.9 kilonewtons (115 psia), the thrust could be increased from 1,587 to 1,814 kg (3,500 to 4,000 lbs). Moreover, this could be accomplished with the present pressurization and propellant feed systems.
Bell Aerosystems Company tested a high-performance injector for the LEM ascent engine. The new design was similar to the current one, except that the mixture ratio of the barrier flow along the chamber wall had been changed from 0.85 to 1.05. Bell reported a performance increase of 0.8 percent (about 2.5 sec of specific impulse). Subsequent testing, however, produced excessive erosion in the ablative wall of the thrust chamber caused by the higher temperature. The MSC Propulsion and Power Division (PPD) felt this method of increasing the ascent engine's performance might not be practicable.
At the same time, PPD reported that Bell had canceled its effort to find a lighter ablative material (part of the weight reduction program). A number of tests had been conducted on such materials; none was successful.
The persistent problem of combustion instability in the LEM ascent engine, unyielding to several major injector redesigns, was still present during test firings at Bell Aerosystems. Following reviews by MSC and Grumman, the "mainstream effort" in the injector program was "reoriented" to a design that included baffles on the face of the injector. Largely because of this troublesome factor, it now appeared that the ascent engine's development cost, which only four months earlier Bell and Grumman had estimated at $20 million, would probably approach $34 million. Bell also forecast a 15.4-kg (34-lb) weight increase for the engine because of a longer burn design and a strengthened nozzle extension.
MSC contacted Grumman with reference to the LEM ascent engine environmental tests at Arnold Engineering Development Center (AEDC), scheduled for cell occupancy there from May 1, 1965, until September 1, 1965. It was MSC's understanding that the tests might begin without a baffled injector. It was pointed out, however, that the first test was expected to begin July 1, and since the recent baffle injector design selection had been made, time remained for the fabrication of the injector, checkout of the unit, and shipment to AEDC for use in the first test.
Since the baffled injector represented the final hardware configuration, it was highly desirable to use the design for these tests. MSC requested that availability of the injector constrain the tests and that Grumman take necessary action to ensure compliance.
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:
Bell Aerosystems Company received Grumman's go-ahead to resume work on the thrust chamber of the LEM ascent engine. Bell conducted a dozen stability tests using an injector fitted with a 31.75 mm (1.25 in), Y-shaped baffle. Thus far, the design had recovered from every induced disturbance (including widely varied fuel-to-oxygen ratios). Also, to ease the thermal soakback problem, Bell planned to thicken the chamber wall.
The thrust mount for the LEM ascent engine cracked during vibration testing. The mount would be strengthened.
During the same period, Bell tested the first one-piece ablative chamber for the ascent engine (designed to replace the molded-throat design, which developed cracks during testing . In firings that totaled over eight minutes, Bell engineers found that the unit suffered only negligible throat erosion and decay of chamber pressure.
H. I. Thompson Company's first combustion chamber with a tape-wrapped throat successfully withstood a series of four test firings. If further testing confirmed its performance, reported the resident Apollo office at Bethpage, N.Y., the design would be used in the LEM's ascent engine. (It would replace the current compression-molded throat, which suffered from excessive cracking.)
The first firing of the LEM ascent engine test rig (HA-3) was successfully conducted at White Sands Missile Range, New Mexico. A second firing on April 23 lasted 14.45 sec instead of 10 sec as planned. A third firing, lasting 30 sec, completed the test series. A helium pressurization system would be installed before additional testing could begin.
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):
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.
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.
William A. Lee, ASPO Assistant Manager, asked Systems Engineering Division to study the feasibility of an abbreviated mission, especially during the initial Apollo flights. Because of the uncertainties involved in landing, Lee emphasized, the first LEMs should have the greatest possible reserves. This could be accomplished, he suggested, by shortening stay time; removing surplus batteries and consumables; and reducing the scientific equipment. Theoretically, this would enable the LEM pilot to hover over the landing site for an additional minute; also, it would increase the velocity budgets both of the LEM's ascent stage and of the CSM. He asked that the spacecraft's specifications be changed to fly a shorter mission:
Bell Aerosystems Company successfully cycled a LEM ascent engine propellant valve 500 times (double the specification requirement). Also, the company conducted a full-duration altitude firing with an ablative nozzle extension to verify heating characteristics.
ASPO reported a number of significant activities in its Weekly Activity Report.
A LEM ascent engine exploded during altitude firings at Arnold Engineering Development Center (AEDC). In subsequent investigations, Bell Aerosystems researchers concluded that the failure probably resulted from raw propellants being accidentally forced into the engine at the end of the second run, thus damaging the injector. Additional Details: here....
MSC requested Grumman to review the following ascent and descent pressurization system components in the propulsion subsystem for materials compatibility with certain propellants:
Bell Aerosystems reported on stability and ablative compatibility testing of the first bipropellant-cooled injector baffle for the ascent engine of the LEM. Combustion was stable; however, streaking on the injector face forced Bell to halt ablative testing after only 60 seconds of operation.
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).
MSC suggested that Grumman Aircraft Engineering Corp. redesign the injector for the Bell Aerospace Go. ascent engine as a backup immediately. The Center was aware of costs, but the seriousness of the injector fabrication problem and the impact resulting from not having a backup was felt to be justification for the decision.
A fire broke out in the Bell Aerosystems Test Facility, Wheatfield, N.Y., at 2:30 a.m. April 20. Early analysis indicated the fire was started by overpressurization of the ascent engine's propellant- conditioning system, which caused the system relief valve to dump propellant into an overflow bucket. The bucket in turn overflowed and propellant spilled onto the floor, coming into contact with a highly oxidized steel grating. Contact was believed to have initiated combustion and subsequently an intense, short-duration fire. Additional Details: here....
Rocketdyne Division of North American Aviation was selected for negotiation of a contract for the design, development, qualification, and delivery of four production models of an injector for the lunar module ascent engine. The project would serve as a backup to the injector program already being conducted by Bell Aerospace Corp. under subcontract to Grumman. The ascent engine was considered to be the most critical engine in the Apollo-Saturn vehicle. No backup mode of operation remained if the ascent engine failed.
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. Additional Details: here....
NASA Hq. requested MSC to forward by December 5 the Center's plan for providing qualified LM ascent engines with dynamically stable injectors for manned LM flights. The plan was expected to be based on ground rules established in July when a NASA team went to Bell Aerosystems Co. that the current BAC engine would be the prime effort with the Rocketdyne Division (North American Rockwell) injector development as backup. Headquarters asked that the plan contain the following elements:
MSC ASPO Manager George M. Low reminded NASA Apollo Program Director Samuel C. Phillips that at a meeting three weeks previous MSC had presented a Bell Aerospace Corp. qualification completion date for the LM ascent engine of March 28, and a Rocketdyne Division, North American Rockwell, completion by May 1, 1968. Additional Details: here....
A LM test failed in the Grumman ascent stage manufacturing plant December 17. A window in LM-5 shattered during its initial cabin pressurization test, designed to pressurize the cabin to 3.9 newtons per square centimeter (5.65 pounds per square inch). Both inner and outer windows and the plexiglass cover of the right-hand window shattered when the pressure reached 3.5 newtons per sq cm (5.1 psi). An MSC LM engineer and Corning Glass Co. engineers were investigating the damage and cause of failure.
The LM ascent engine program plan submitted to NASA Hq. on December 9 had been approved, Apollo Program Director Samuel C. Phillips told ASPO Manager George M. Low. Phillips was concerned, however, about the impact of recent unstable injector tests at Bell Aerosystems Co. on this plan. He said, "Resolution of these failures must be expedited in order to maintain present schedules. Also of concern, is the possible underestimation of the contractual and integration problems that will exist if the Rocketdyne (Division) injector should be chosen." Phillips asked that those areas receive special attention and that he be kept informed on the progress of both injector programs.
ASPO Manager George M. Low ordered LM Manager C. H. Bolender to establish a firm baseline configuration for the LM ascent engine to use during the entire series of qualification tests (including any penalty runs that might be required). Low's memo followed a telephone conversation the previous day with Apollo Program Director Samuel C. Phillips. Low cited to Bolender the need for a rigid design control on the engine. During a recent technical review, he explained, NASA officials learned that most qualification tests had been performed on one model (the E2CA injector), while all of the bomb stability tests had used another (the E2C injector). Ostensibly, the only difference between the two injectors was in the welding techniques. However, the first E2CA injector that was bomb-tested showed a combustion instability. Low emphasized that he was not charging that the different welding technique had caused the instability. Nevertheless, "this supposedly minor change (has) again served to emphasize the importance of making no changes, no matter how small, in the configuration of this engine." Once Bolender had set up the requested baseline configuration, Low stated, no change either in design or process should be made without approval by the Configuration Control Board.
Phillips followed up his conversation with Low a week later to express a deep concern regarding the ascent engine program, particularly small improvements in the engine, which could very likely delay the entire Apollo program beyond the present goal. The sensitivity of the engine to even minor design, fabrication, and testing changes dictated absolute control over all such changes. The ascent engine, Phillips told Low, was one of a very few Apollo hardware items in which even the most insignificant change must be elevated to top-level management review before implementation.
During an Apollo flight test program review at MSC, the question was left unresolved whether or not to perform a "fire-in-the-hole" test of the LM ascent engine (i.e., start the engine at the same instant the two stages of the spacecraft were disjoined - as the engine would have to be fired upon takeoff from the lunar surface) on either the D or E mission. Additional Details: here....
Christopher C. Kraft, Jr., MSC Director of Flight Operations, expressed concern to ASPO Manager George M. Low over the escalation of E-mission objectives; the flight now loomed as an extremely complex and ambitious mission. The probability of accomplishing all the objectives set forth for the mission, said Kraft, was very low. He did not propose changing the mission plan, however. "If we are fortunate," he said, "then certainly the quickest way to the moon will be achieved." Kraft did suggest caution in setting mission priorities and in "apply(ing) adjectives to the objectives." Additional Details: here....
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. Additional Details: here....