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LM RCS


LM RCS Development Diary

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LM RCS Chronology


1962 November - .
  • Study of Apollo CSM-LEM transposition and docking - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM RCS; LM RCS; LM Weight. North American completed a study of CSM-LEM transposition and docking. During a lunar mission, after the spacecraft was fired into a trajectory toward the moon, the CSM would separate from the adapter section containing the LEM. It would then turn around, dock with the LEM, and pull the second vehicle free from the adapter. The contractor studied three methods of completing this maneuver: free fly-around, tethered fly- around, and mechanical repositioning. Of the three, the company recommended the free fly-around, based on NASA's criteria of minimum weight, simplicity of design, maximum docking reliability, minimum time of operation, and maximum visibility.

    Also investigated was crew transfer from the CM to the LEM, to determine the requirements for crew performance and, from this, to define human engineering needs. North American concluded that a separate LEM airlock was not needed but that the CSM oxygen supply system's capacity should be increased to effect LEM pressurization.

    On November 29, North American presented the results of docking simulations, which showed that the free flight docking mode was feasible and that the 45-kilogram (100-pound) service module (SM) reaction control system engines were adequate for the terminal phase of docking. The simulations also showed that overall performance of the maneuver was improved by providing the astronaut with an attitude display and some form of alignment aid, such as probe.


1963 January 30 - .
  • Selection of four companies as major Apollo LEM subcontractors - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Ascent Propulsion; LM Descent Propulsion; LM ECS; LM RCS. 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

1963 March 11 - .
  • Contract talks with Marquardt for Apollo LEM reaction control system - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Summary: Grumman began early contract talks with the Marquardt Corporation for development of the LEM reaction control system..

1963 March 14 - .
  • Bidders' conference for Apollo LEM mechanically throttled descent engine - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Descent Propulsion; LM RCS. 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.

1963 April - .
  • Apollo LEM reaction control system (RCS) to be equipped with dual interconnected tanks - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Grumman recommended that the LEM reaction control system (RCS) be equipped with dual interconnected tanks, separately pressurized and employing positive expulsion bladders. The design would provide for an emergency supply of propellants from the main ascent propulsion tanks. The RCS oxidizer to fuel ratio would be changed from 2.0:1 to 1.6:1. MSC approved both of these changes.

1963 July 19 - .
  • Marquardt begins development of the Apollo LEM reaction control thrusters - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Summary: Grumman directed the Marquardt Corporation to begin development of the LEM reaction control system thrusters. Negotiations had begun on March 11 on the definitive subcontract, a cost-plus-incentive-fee type with a total estimated cost of $10,871,186..

1963 August - .
  • Full-scale cardboard model of the Apollo LEM - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Landing Gear; LM RCS. Grumman built a full-scale cardboard model of the LEM to aid in studying problems of cockpit geometry, specifically the arrangement of display panels. This mockup was reviewed by MSC astronauts and the layout of the cockpit was revised according to some of their suggestions.

    Also Grumman reported that a preliminary analysis showed the reaction control system plume heating of the LEM landing gear was not a severe problem. (This difficulty had been greatly alleviated by the change from five to four landing legs on the vehicle.


1963 November 13-14 - .
  • Means for reducing the weight of the Apollo LEM - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Electrical; LM RCS. After careful study, Grumman proposed to MSC 15 possible means for reducing the weight of the LEM. These involved eliminating a number of hardware items in the spacecraft; two propellant tanks in the vehicle's ascent stage and consequent changes in the feed system; two rather than three fuel cells; and reducing reaction control system propellants and, consequently, velocity budgets for the spacecraft. If all these proposed changes were made, Grumman advised, the LEM could be lightened significantly, perhaps by as much as 454 kilograms (1000 pounds).

1963 December 21 - .
  • MSC defined the Apollo LEM terminal rendezvous maneuvers - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM RCS; LM Ascent Propulsion; LM RCS. 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.

1964 January 8 - .
  • Apollo LEM translation and descent engine thrust controllers - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Descent Propulsion; LM RCS. 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.

1964 January 27 - .
  • Attitude control of docked vehicles using the Apollo LEM's RCS - . Nation: USA. Related Persons: Hohmann, Bernhard. Program: Apollo. Spacecraft: Apollo LM; LM RCS. ASPO asked Grumman to study whether attitude control of the docked vehicles was practicable using the LEM's stabilization and control system (RCS). Grumman also was to evaluate the RCS fuel requirements for a five-minute alignment period to permit two star sightings. ASPO further directed the contractor to determine RCS fuel requirements for a second alignment of the LEM's inertial measurement unit during descent coast. This second alignment was needed for the required landing accuracy from a Hohmann descent.

1964 February 20-26 - .
  • Apollo LEM's reaction control system propellant tank contract - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Summary: Grumman completed negotiations with Bell Aerosystems Company for the LEM's reaction control system propellant tanks..

1964 March 12 - .
  • Apollo LEM propulsion as backup to the SM engine - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. North American was directed by NASA to study feasibility of using the LEM propulsion system as backup to the SM propulsion system. The most important item in the contractor's analysis was strength of the docking structure and its ability to withstand LEM main-engine and reaction control system thrusting.

1964 October 8 - .
  • Contract for the Apollo LEM attitude translation control assembly - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Communications; LM Guidance; LM RCS. Radio Corporation of America's (RCA) Aerospace Systems Division received a 9 million contract from Grumman for the LEM attitude translation control assembly (ATCA). The ATCA, a device to maintain the spacecraft's attitude, would fire the reaction control system motors in response to signals from the primary guidance system.

1964 October 8-15 - .
  • Configuration established of the reaction control system engines - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM Block I; LM RCS. MSC established the configuration of the reaction control system engines for both the service module (SM) and the LEM, and informed North American and Grumman accordingly. The Center also directed North American to propose a design for an electric heater that would provide thermal control in lunar orbit and during contingency operations. The design would be evaluated for use in Block I spacecraft as well.

1964 October 12 - .
  • Apollo CSM-LM active docking interfaces discussed - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM RCS; LM RCS. At a North American-Grumman interface meeting on September 23-24, two possible relative role alignments for CSM-active docking were agreed upon. The major item blocking final selection was the effect of the SM's reaction control system engines upon the LEM antennas. ASPO requested Grumman to investigate the problem, to analyze the design penalties of the two-attitude docking mode, and to report any other factors that would influence the final attitude selection.

1964 December 7 - .
  • Apollo LEM to be the active vehicle during lunar rendezvous - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM RCS; LM RCS. Summary: MSC advised Grumman that, normally, the LEM would be the active vehicle during lunar rendezvous. This would conserve reaction control system propellants aboard the CSM..

1964 December 9 - .
  • Criteria for firing times of the SM RCS - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Grumman received from Houston criteria for firing times of the SM reaction control system (RCS). These served as a basis for the design of the LEM's steerable antenna. The thermal design proposed by Dalmo-Victor, the vendor, appeared feasible to watchdogs in MSC's Instrumentation and Electronic Systems Division. On the other hand, the unbalanced wind torque produced by the RCS engines was still a problem. RCA and Dalmo-Victor's estimates of the amount of torque varied considerably, and Grumman consequently undertook a study of this problem.

1964 December 11 - .
  • Updated criteria for the Apollo LEM's landing gear - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Descent Propulsion; LM Landing Gear; LM RCS. 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."


1964 December 15-16 - .
  • Thermal-demanded weight increases for the Apollo LEM's steerable antenna - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM RCS; LM RCS; LM Weight. Dalmo-Victor studied thermal-demanded weight increases for the LEM's steerable antenna. Investigators reported to Grumman and RCA that, in the plume of the CSM's reaction control engines, 1.18 kg (2.5 lbs) was necessary merely for the survival of the antenna; another 1.18 kg would be required for tracking during this impingement.

1964 December 21 - .
  • Thermal status of antennas for the Apollo CSM and LEM spacecraft - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM Heat Shield; CSM SPS; LM RCS; LM Weight. The Structures and Mechanics Division (SMD) summarized the thermal status of antennas for the Apollo spacecraft (both CSM and LEM). Generally, most troubles stemmed from plume impingement by the reaction control or radiation from the service propulsion engines. These problems, SMD reported, were being solved by increasing the weight of an antenna either its structural weight or its insulation; by shielding it from the engines' exhaust; by isolating its more critical components; or by a combination of these methods.

1965 January 18 - .
  • Low-burst factor for the gaseous helium tanks on the Apollo LEM approved - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. The Structures and Mechanics Division approved a low-burst factor for the gaseous helium tanks on the LEM (as recommended by Grumman). This change permitted a substantial lightening of the spacecraft's propulsion systems: descent 45 kg (99 lbs); ascent, 13 kg (29 lbs); reaction control, 2.3 kg (5 lbs).

1965 January 28-February 4 - .
  • Device to detect failures in the reaction control system (RCS) for Block I Apollo CSMs cancelled - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM Block II; LM RCS; LM Weight. MSC canceled plans (originally proposed by North American) for a device to detect failures in the reaction control system (RCS) for Block I CSMs. This was done partly because of impending weight, cost, and schedule penalties, but also because, given an RCS failure during earth orbit, the crew could detect it in time to return to earth safely even without the proposed device. This action in no way affected the effort to devise such a detection system for the Block II CSM or the LEM, however.

1965 March 15 - .
  • Descent engine cutoff light during the Apollo LEM lunar touchdown - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM Descent Propulsion; LM Landing Gear; LM RCS. 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).
    It was concluded that a 0.9-m (3-ft) probe would be adequate to ensure pilot cutoff of the descent engine before touchdown provided the pilot reaction time could be reduced to 0.4 sec or less by improving the location of the cutoff switch.

1965 April 7 - .
  • A LEM/Apollo CSM interface meeting uncovered a number of design problems - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM RCS; LM Communications; LM RCS. A LEM/CSM interface meeting uncovered a number of design problems and referred them to the Systems Engineering Division (SED) for evaluation: the requirement for ground verification of panel deployment prior to LEM withdrawal; the requirement for panel deployment in earth orbit during the SA-206 flight; the absence of a backup to the command sequencer for jettisoning the CSM (Flight Projects Division (FPD) urged such a backup signal); and Grumman's opposition to a communications link with the LEM during withdrawal of the spacecraft (FPD felt that such a link was needed through verification of reaction control system ignition). SED's recommendations on these issues were anticipated by April 22.

1965 April 15-22 - .
  • Program for the Apollo LEM's reaction control system - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. MSC and Grumman reviewed the program for the LEM's reaction control system. The only issue outstanding was Grumman's in-house effort: MSC felt that that effort was "overestimated" and that the manufacturer alone should not handle support from subcontractors.

1965 April 22 - .
  • Common Apollo reaction control system propellant tanks - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM RCS; LM RCS. Grumman was requested to attend a meeting at MSC and to present their reasons as to why the LEM reaction control system (RCS) propellant tanks could not be of common technology with the CSM RCS propellant tanks. Grumman was to also say why an additional development program was required for the LEM tanks.

1965 June 16-23 - .
  • Two thermal problems with the Apollo LEM identified - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM ECS; LM RCS. Structures and Mechanics Division (SMD) reported that Grumman had found two thermal problems with the LEM:

    1. On the basis of current predictions, the spacecraft's skin and several antennas would overheat during the boost phase of the mission. SMD engineers, after analyzing the problem, believed that an "acceptable LEM environment" could be achieved by lessening the heat transferred from the inner panels of the adapter and by increasing that emitted by the outer panels.
    2. Also, Grumman had reported that, when exposed to exhaust plumes from the SM's reaction control engines, the LEM's skin would overheat in about five seconds. "Since the LEM withdrawal . . . requires 20 to 26 sec RCS firing," SMD understated, "it is apparent that a problem exists." One suggested solution involved improved insulation.

1965 July 23 - .
1965 August 29-September 4 - .
  • Several important activities were noted during Apollo reporting period - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Several important activities were noted during the reporting period: (1) Qualification of the new reefing line cutters was progressing satisfactorily and scheduled for completion in October 1965. (The cutter had been used successfully on the last two earth landing system tests conducted at El Centro); (2) the helium storage tank for the LEM reaction control subsystem successfully passed qualification tests; and (3) the Aero Spacelines' new aircraft, "Super Guppy," made its maiden flight from Van Nuys, Calif., to Mojave Airfield, Calif. The new aircraft had the capability of airlifting the spacecraft-LEM-adapter as well as providing vital backup for the "Pregnant Guppy" aircraft.

1965 August - .
  • Explosion damaged Apollo LEM reaction control system - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Summary: An explosion damaged a LEM reaction control system thruster being fired in an up attitude in altitude tests at MSC..

1965 September 27 - .
  • Problem of Apollo back contamination of earth discussed - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. Officials from the U.S. Public Health Service (PHS) and the Department of Agriculture met at MSC to discuss informally the problem of back contamination. They listened to briefings on the mission profile for Apollo; reentry heating rates; present thinking at the Center on the design of the Lunar Sample Receiving Station (LSRS); and MSC's plans (none) for quarantining the astronauts.

    James Goddard, Assistant Surgeon General in PHS, presented three broad areas of concern:

    1. quarantine procedures and accommodations inside the LSRS for both astronauts and technicians;
    2. quarantine facilities aboard the recovery ships; and
    3. the need to gather samples before the moon's surface was contaminated by the astronauts or the LEM's atmosphere.
    These matters were discussed in some detail. MSC's failure to plan for the astronauts' return, and Goddard's ideas on what procedures were needed, provoked "very extended and somewhat heated" discussions. It was generally agreed that Apollo astronauts could not entirely avoid lunar contaminants: the level of contamination inside the spacecraft's cabin, although low, nonetheless would be "significant." MSC then asked, hypothetically, what PHS's reaction would be if Apollo astronauts were recovered and returned in much the same manner that Gemini crews were. The representative from PHS's Foreign Quarantine Division replied "emphatically" that, in such a case, those crews would not be allowed back in the country.

    On October 15, Lawrence B. Hall, Planetary Quarantine Officer in NASA's Office of Space Science and Applications, summarized for Deputy Administrator Hugh L. Dryden the September 27 meeting, and recommended that such informal discussions continue. "I believe," he told Dryden, "that . . . the Manned Spacecraft Center is more fully aware of the point of view of the regulatory agencies on this matter. Unfortunately, the regulatory agencies still do not understand the reasons for the Manned Spacecraft Center's reluctance to face this problem."


1965 November 15 - .
  • MSC instructed North American to study Apollo CSM thermal situation - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM ECS; LM RCS. MSC instructed North American to:

    • Submit a preliminary design of Block II CSM jettisonable covers to protect the radiator and CM heatshield thermal coatings from degradation by the boost environment.
    • Furnish preliminary design of nonablative reaction control system (RCS) plume heat protection to prevent SM coating degradation on Block II CSMs.
    • Determine the effect on the overall SM and LEM adapter thermal design of coating degradation to a level specified by MSC and to propose design changes or mission constraints for Block I and Block II CSMs.
    • Determine the effect on the SM RCS thermal design of coating degradation to the level specified by MSC and to propose design changes or mission constraints for Block I and II CSMs.

1966 August 22 - .
  • Surveyor vernier engine to be fired after landing - . Nation: USA. Related Persons: Pickering. Program: Apollo. Spacecraft: Surveyor; LM Descent Propulsion; LM RCS. 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.

1966 December 26 - .
  • Extravehicular activity on the Apollo AS-503 mission - . Nation: USA. Program: Apollo. Flight: Apollo 8. Spacecraft: Apollo LM; LM Descent Propulsion; LM ECS; LM Hatch; LM Landing Gear; LM RCS. 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. Additional Details: here....

1967 May 29 - .
  • Bare copper wires exposed to glycol/water found to ignite in Apollo oxygen cabin environement - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; CSM Block II; LM RCS. W. R. Downs, Special Assistant for Advanced Systems, MSC Structures and Mechanics Division, discovered that bare or defectively insulated silver-covered copper wires exposed to glycol/water solutions would ignite spontaneously and burn in oxygen. Copper wire or nickel-covered copper wire under identical conditions did not ignite. The laboratory results were confirmed in work at the Illinois Institute of Technology. In a June 13 memorandum, the Chief of the Structures and Mechanics Division recommended that if additional testing verified that nickel-coated wires were free of the hazard, consideration should be given to an in-line substitution of nickel-coated wires for silver-coated wires in the LM. It was understood that the Block II CSM already had nickel-coated wires. In a June 20 memo to the ASPO Manager, the Director of Engineering and Development pointed out that silver-plated pins and sockets in connectors would offer the same hazards. He added that Downs had also identified a chelating agent that would capture the silver ion and apparently prevent the reaction chain. In a July 24 memorandum, ASPO Manager George Low said that, in view of recent spills of ethylene glycol and water mixtures, spacecraft contractors North American Aviation and Grumman Aircraft Engineering had been directed to begin actions immediately to ensure that a fire hazard did not exist for the next manned spacecraft. Actions were to include identification of the location of silver or silver-covered wires and pins and of glycol spills.

1968 February 20 - .
  • Apollo RCS engine ruptured during test - . Nation: USA. Program: Apollo. Spacecraft: Apollo LM; LM RCS. MSC informed NASA Hq. that a reaction control system (RCS) engine ruptured at Marquardt Corp. the previous night during a heater integration test within a normal duty cycle run. This was a development test; the cause of the rupture was unknown at the time of the report. A second RCS failure occurred at Marquardt March 6 during a rerun of the LM heater integration tests. The rerun series started March 2. No facility damage or personnel injuries were reported from either incident. Investigation was under way at Marquardt by both NASA and Marquardt engineers to determine the cause of the failures and the effect on the program.

1968 June 10 - .
  • Important Apollo events - . Nation: USA. Program: Apollo. Flight: Apollo 9. Spacecraft: Apollo LM; LM RCS. Summary: In his weekly progress report to the NASA Administrator, Deputy Administrator for Manned Space Flight George E. Mueller cited several important Apollo events during the first week of June.. Additional Details: here....

1968 August 7 - . LV Family: Saturn V. Launch Vehicle: Saturn V.
  • George Low promotes idea of flying Apollo 8 as a lunar orbit mission without the Lunar Module - . Nation: USA. Related Persons: von Braun. Program: Apollo. Flight: Apollo 7; Apollo 8; Apollo 9. Spacecraft: Apollo LM; Apollo CSM; CSM Block II; LM Guidance; LM RCS. On August 7, Low asked MSC's Director of Flight Operations Christopher C. Kraft, Jr., to look into the feasibility of a lunar orbit mission for Apollo 8 without carrying the LM. A mission with the LM looked as if it might slip until February or March 1969. The following day Low traveled to KSC for an AS-503 review, and from the work schedule it looked like a January 1969 launch. Additional Details: here....

1971 October 6-7 - .
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