Engines, Large and Small

When Grumman began designing the lunar module in January 1963, its major subcontractors began work on the vehicle's integral subsystems: Bell Aerosystems, ascent engine; Rocketdyne Division of North American, descent engine; The Marquardt Corporation, reaction control system; and Hamilton Standard Division of United Aircraft Corporation, environmental control. Identifying rocket engines as the most critical subsystem, Grumman started their development first. The lander had 18 engines: 2 large rockets, one for descent to the moon and another for return to lunar orbit, and 16 small attitude control engines clustered in quads and pointing up, down, left, and right, around the ascent stage.22

During the spring of 1963, Grumman hired Bell to develop the ascent engine, basing the selection on Bell's experience in Air Force Agena development and hoping that the technology from that program might be applicable to the lunar module. Grumman placed heavy emphasis upon high reliability through simplicity of design, and, in fact, the ascent engine did emerge as the least complicated of the three main engines in the Apollo space vehicle (the descent and service module engines were the other two).* Embodying a pressure-fed fuel system using hypergolic (self-igniting) propellants, the ascent engine was fixed-thrust and nongimbaled, capable of lifting the ascent stage off the moon or aborting a mission should a landing not be feasible.

There was one major concern about the ascent engine, and that was the usual worry about the ablation material burning off too fast and causing damage to the thrust chamber. Some ablative material eroded during firing tests at Bell's plant near Niagara Falls and at the Arnold Engineering Development Center in Tennessee. But this erosion was not severe enough to warrant changes in the combustion chambers. In late 1964, Arnold was also the site of a fire-in-the-hole (FITH static firing test on a full-scale vehicle to supplement Grumman's previous scale-model test. The FITH flight test had to wait for later trials at White Sands.

Not everything went well with ascent engine development, however. About a year after the program began, the subsystem manager in Houston discovered that Grumman and Bell were using testing criteria left over from the Air Force Agena program. Since the Agena was unmanned, these were less stringent than NASA demanded for manned spacecraft. More rigorous standards were belatedly imposed by Houston, and a problem was revealed. In "bomb stability" tests, where the engine had to recover from combustion instability caused by an explosive charge within the combustion chamber, the ascent engine "went unstable" (failed to return to normal operation), and structural damage followed. This problem would have to be resolved before the engine could be trusted to bring a crew back from the lunar surface.23

The lunar module descent engine probably was the biggest challenge and the most outstanding technical development of Apollo. A requirement for a throttleable engine was new to manned spacecraft. Very little advanced research had been done in variable-thrust rocket engines - NASA's principal effort in this field, the hydrogen - fueled RL-10 used in the S-IV stage of the Saturn, antedating work on the lunar module engine by only a few months. Rocketdyne proposed a method known as helium injection, introducing inert gas into the flow of propellants to decrease thrust while maintaining the same flow rate. Although Bethpage and Houston agreed that this seemed a plausible approach to throttleability, it would be a major advance in the state of the art, and the MSC Apollo office directed Grumman to carry out a parallel development program and select the better design.

On 14 March 1963, Grumman held a bidders' conference, attended by representatives from Aerojet-General, Reaction Motors Division of Thiokol, United Technology Center Division of United Aircraft, and Space Technology Laboratories, Inc. (STL). In May, STL (which had lost out in the original bidding for the engine) was selected to develop the competitive motor. STL proposed a pressure-fed hypergolic system that was gimbaled as well as throttleable. The engine's mechanical throttling system used flow control valves and a variable-area injector, in much the same manner as does a shower head, to regulate pressure, rate of propellant flow, and the pattern of fuel mixture in the combustion chamber.

With two subsystem contractors working on such radically different throttling techniques, NASA planners, as Rector later said, "thought one or the other would stub his toe real quick . . . , that it would be obvious that we should go one [way] or the other - but it wasn't happening. They were both . . . pretty good. . . ." STL and Rocketdyne continued this head-to-head competition for the final-and lucrative-engine development and qualification contract through the end of 1964.24

In November 1964, Joseph Shea, Apollo spacecraft manager in Houston, told NASA Apollo Program Director Samuel Phillips in Washington that he had established a committee** of propulsion experts from Grumman, the Marshall and Lewis centers, NASA Headquarters, and the Air Force to review the contractors' efforts and recommend a choice. Selection of one firm over the other rested with Grumman and MSC, in the final analysis, and, Shea stated, "I do feel that we should have the intelligence at our disposal to appreciate all ramifications of [Grumman's] final recommendation."

Panel members visited both companies the week of 7 December 1964, but their findings were largely inconclusive. The progress of each firm was nearly identical. Both contractors, although experiencing minor troubles with injector designs, demonstrated satisfactory structural compatibility between injector and thrust chamber. After a year and a half, neither helium injection nor mechanical throttling had proved superior over the other. On 5 January 1965, Grumman decided to stick with Rocketdyne.25

Manned Spacecraft Center Director Gilruth appointed a five-member board*** to weigh Grumman's recommendations, review the findings of the earlier committee, and study a technical comparison prepared by Houston's Propulsion and Power Division. On 18 January this review board, in a surprising move, reversed Grumman's action and named STL instead of Rocketdyne. The board said that the

recommendation of STL is based upon the assessment that STL is in a more favorable position [and] is capable of supplying more management and superior resources to this program without interference of other similar programs. . . . there are potential benefits to be gained for the Gemini and Apollo attitude engine programs at NAA by the cancellation of the [Rocketdyne] descent engine development.****

This decision, unusual because Houston rarely vetoed a recommendation for a subcontractor made by a prime contractor, was sustained by Phillips at Headquarters. Shea and Contracting Officer James L. Neal then directed Grumman to proceed with STL.26

Grumman chose Marquardt to build the lunar module's third engine system, the small 100-pound-thrust attitude control thrusters. In 1960, Warren P. Boardman and Maurice Schenk of Marquardt had visited Robert Piland and Caldwell C. Johnson at Langley to discuss their firm's propulsion work. Piland and Johnson were intrigued with the idea for a bipropellant thruster that promised to be far superior to the monopropellant engine then used in Mercury. Testing of Marquardt's product - a dual-valve, pulse-modulated engine with a radiation-cooled combustion chamber - at the Lewis Research Center paved the way for its incorporation into Apollo. Marquardt at first supplied engines for both the command and service modules. In mid1962, NASA decided to use the Marquardt engine for the service module only, because the command module thrusters would be buried within the heatshield, making radiation cooling impossible. Rocketdyne would supply the command module thrusters, which were similar to those it was already developing for Gemini.

Marquardt would furnish attitude control engines and mounting structure and perform some tests of the propellant system. Grumman would provide tanks (purchased from Bell), propellant lines, and the pressurization system. Apollo officials had expected that the service module thrusters, with only slight modifications, could also be used in the lander, but common use proved difficult. The end results, though beneficial, fell far short of Houston's anticipations. Differing functional requirements, as well as unique environmental and design constraints, precluded direct incorporation of the service module thruster. Houston, however, complained that Grumman failed to take advantage of all the common-use technology available and attributed delays in procurement of many thruster components to this failure.27

After thruster tests at Bethpage and at Marquardt's Magic Mountain Facility in California during the first half of 1964, a technical problem emerged: the engine spiked, or backfired, at ignition, and a rapid rise in temperature and pressure caused the engine to explode. The spiking appeared so significant that Grumman wanted to develop a backup engine through another source, but Houston refused permission. Marquardt eliminated spiking by installing a small, tubular "precombustion" chamber inside the engine.28

* The rocket engine of the ascent stage developed about 15,500 newtons (3,500 pounds) of thrust, which produced a velocity of 2,000 meters per second from lunar launch to docking. The descent stage, a throttleable engine, reached a maximum of 43,900 newtons (9,870 pounds) and operated at a minimum of 4,700 newtons (1,050 pounds) for delicate maneuvers. Considerably larger than the two lunar module engines, the service module motor attained 91,200 newtons (20,500 pounds) of thrust.

** Committee members were Max Faget (chairman), Rector, Joseph G. Thibodaux, and C. Harold Lambert (MSC); Charles H. King and Adelbert O. Tischler (NASA Headquarters); Leland F. Belew (Marshall); Irving A. Johnson (Lewis); P. Layton (Princeton University); Major W. R. Moe (Edwards Rocket Research Laboratory, USAF); and Joseph M. Gavin and M. Dandridge (Grumman).

*** Members of the Subcontractor Review Board for the LEM Descent Engine were Faget (chairman), Dave W. Lang (Procurement), André J. Meyer, Jr. (Gemini), Joseph G. Thibodaux, Jr. (Propulsion and Power Division), and Rector.

**** Gemini manager Charles W. Mathews was having trouble getting reliable engines for his spacecraft from Rocketdyne. In its decision, the board was obviously supporting both his program and Apollo.

22. Neal TWX to Small, 29 Jan. 1963; MSC news release 63-14, 30 Jan. 1963; Grumman, "LM System Description," from information package for Apollo 11, July 1969; Bell Aerosystems, "Bell Aerosystems Company and Apollo 11," news release, July 1969; Aerojet-General, "Fact Sheet about the Main Rocket Engine for the Apollo Command and Service Modules," news release, July 1969; William R. Hammock, Jr., Eldon C. Currie, and Arlie E. Fisher, "Descent Propulsion System," AER TN S-349 (MSC-05849), review copy, October 1972; Clarence E. Humphries and Reuben E. Taylor, "Ascent Propulsion System," AER TN S-341 (MSC-04928), review copy, May 1972; Chester A. Vaughan et al., "Lunar Module Reaction Control System," AER TN S-315 (MSC-04567), review copy, December 1971.

23. Dave W. Lang TWX to NASA Hq., Attn.: Brackett, 5 Feb. 1963; Clyde B. Bothmer to George M. Low, "Bell Aerospace Contract for LEM Engine," 11 Feb. 1964; LEM Program Management Meeting, Grumman NASA, 22 April 1964; Rector TWX to Grumman, Attn.: Mullaney, 21 Aug. 1964; minutes of LEM Ascent Propulsion Subsystem Schedule and Technical Status Meeting at Grumman, 16-17 Sept. 1964; ASPO Weekly Management Reports, 23-30 July 1964 and 21-28 Jan. 1965; Rector TWXs to Grumman, Attn.: Mullaney, 2 Sept. 1964; Rector and Gavin interviews; Alexander L. Madyda to LEM PO, "Response of GAEC Propulsion to MSC Requests and Directions," 5 Nov. 1964.

24. House Committee on Science and Astronautics, Astronautical and Aeronautical Events of 1962: Report, 88th Cong., 1st sess., 12 June 1963, p. 145; Neal to Grumman, Attn.: Snedeker, "Descent Engine Subcontract," 12 Aug. 1963; Rector interview; Charles W. Mathews to Asst. Dir., Research and Dev., "Procurement Plan for Apollo Supporting Research - Throttleable Engine Development," 16 Aug. 1962; Robert H. Voight to Asst. Mgr., ASPO, "Parallel Development LM Descent Engine, Grumman Aircraft Engineering Corporation, Audit Report MSC 11-67A," 8 March 1967; RASPO Grumman Activity Report, 10-16 March 1963, p. 1; Carl D. Sword TWX to Grumman, Attn.: Snedeker, 27 May 1963; MSC news release 63-92, 29 May 1963; R. F. Mettler TWX to Charles W. Frick, 20 Nov. 1962; Gavin interview; Jack N. Cherne, "Mechanical Design of the Lunar Module Descent Engine," paper presented at the 18th International Astronautical Congress, Belgrade, Yugoslavia, 24-30 Sept. 1967, p. 1; Rector TWX to Grumman, Attn.: Mullaney, 5 May 1964; Roger D. Hicks to Chief, Propulsion and Power Div. (PPD), "Report of trip to Rocketdyne and STL, July 8 and 9, 1964," 10 July 1964; MSC Weekly Activity Report for Assoc. Admin., OMSF, NASA, 28 June-4 July 1964, p. 3; Rector and Mullaney interviews.

25. Shea to Maj. Gen. Samuel C. Phillips, 25 Nov. 1964; Shea TWX to STL, Attn.: J. Elverum, 30 Nov. 1964; Robert W. Polifka to Chief, PPD, "Trip to White Sands Missile Range, . . . STL, . . . and Rocketdyne . . . in review of Rocketdyne and STL LEM descent engine injector development, August 16-21, 1964," 26 Aug. 1964; Voight to ASPO, 8 March 1967; Maxime A. Faget to Mgr., ASPO, "LEM Descent Engine Subcontractor Review," 23 Dec. 1964, with encs.; Gavin to MSC, Attn.: Rector, "Selection of the LEM Descent Engine Contractor," 5 Jan. 1965.

26. Gilruth to Asst. Dir., Eng. anti Dev., "LEM Descent Engine Subcontractor Review Board," 8 Jan. 1965 (identical memos sent to Chief, Procurement and Contracts Div.; Senior Asst., Gemini Prog. Off.; Chief, PPD; and LEM PO, ASPO); Faget to Dir., MSC, "LM Descent Engine Subcontractor Review Board Report," 20 Jan. 1965, with enc., subject as above, 18 Jan. 1965; Mathews to NASA Hq., Attn.: William C. Schneider, "Rocketdyne Performance on the Gemini Program, . . ." 29 April 1964, with encs.; Charles W. Yodzis to Chief, PPD, "Evaluation of Parallel LEM Descent Engine Contracts," 11 Jan. 1965; Voight to ASPO, 8 March 1967.

27. MSC, Consolidated Activity Report, 24 Feb.-23 March 1963, p. 7; Piland note, 9 Dec. 1960; Charles J. Donlan to LeRC, Attn.: Bruce T. Lundin, "Proposed program with Lewis Research Center for evaluating developments in bipropellant reaction control systems," 17 Nov. 1960, with enc.; Donlan to NASA Hq., Attn.: Low, "Support from Lewis Research Center for evaluating developments in satellite attitude controls for application to Project Apollo," 6 Dec. 1960; A. B. Kehlet et al., "Notes on Project Apollo, January 1960-January 1962," 8 Jan. 1962, p. 12; D. Brainerd Holmes to Assoc. Admin., NASA, "Change in Subcontractors for Apollo Command Module Reaction Control Jets," 24 July 1962; Caldwell C. Johnson TWX to North American, Attn.: E. E. Sack, "Command and Service Module Reaction Control System Engines," 31 July 1962; Decker TWX to Sack, 25 March 1963; Small to Decker, "Review of GAEC Specification . . . for the Reaction Control System," 30 April 1963; Neal TWX to Grumman, Attn.: Snedeker, 15 July 1963; Maynard to Grumman, Attn.: Mullaney, "Reaction Control Subsystem, . . . Bell Aerosystems Company Proposal, . . . dated November 1963," 3 Dec. 1963; Faget to Systems Evaluation and Dev. (SEDD), Spacecraft Research, and Life Systems Divs., "Investigation of similar or near similar systems, subsystems and components on Mercury, Gemini and Apollo (including Lunar Excursion Module) spacecraft," 17 Aug. 1962; Rector to Decker and Neal, "Proposed Reply to GAEC TWX LTX-150-7," 2 July 1963; Rector to Maynard and Alfred D. Mardel, "Differences in Development, Environmental, Quality Assurance, and Reliability Requirements between NAA/S&ID and GAEC for Potential Common Usage Items," 17 Feb. 1964; Rector to Grumman, Attn.: Mullaney, "LEM RCS Tank Specification No. LSP-310-405," 16 March 1964; B. Darrell Kendrick to LEM PO, "LEM RCS Propellant Tanks," 23 April 1964; abstract of Proceedings, LEM RCS Meeting on 9 April 1964; Witalij Karakulko to Chief, PPD, "Review of the problems associated with the common usage components of the LEM RCS," 22 May 1964; Rector to Neal, "Implementation of the common usage rule in LEM RCS components," 9 July 1964, with enc.; Shea to NASA Hq., Attn.: George E. Mueller, "Grumman," 1 Aug. 1964; Rector to Chief, SED, "LEM RCS Propellant Quantity Gaging System Design Approach," 30 Oct. 1964; Gaylor to Small, "Past RASPO Activity Report Status on C. U. RCS Components," 20 Oct. 1964.

28. ASPO Weekly Management Report, 30 July-6 Aug. 1964; Decker TWX to Grumman, Attn.: Mullaney, 26 Aug. 1963; LEM PO, "Problems," 14-20 May 1964; Richard B. Ferguson memo, "SM and LEM Reaction Control Engine Development?' 8 June 1964; Gary A. Coultas to Chief, Design Integration Br., "Trip report Service Module/LEM RCS engines, the Marquardt Corporation," 25 June 1964; Rector to Grumman, Attn.: Mullaney, "Thermal analysis of the SM/LEM RCS Engine," 20 July 1964, with encs.; Rector to LEM Proc. Off., "GAEC Request for Development of Backup Source for a 'Common Usage' RCS Engine," 21 July 1964; Henry O. Pohl to Chief, PPD, "Meeting with The Marquardt Corporation (TMC) and North American Aviation (NAA) to discuss the ignition pressure spike problem," 28 July 1964; Karakulko to Chief, PPD, "Trip report to The Marquardt Corporation (TMC)," 2 Dec. 1964; Marquardt, Apollo Service Module Reaction Control Engines, Monthly Progress Report, TMC Project 279, A-1011-26, 30 Sept. 1964, pp. iii, 30.