The solid propellant called for in the original NAA proposal on the service module propulsion system was replaced by a storable, hypergolic propellant. Multitank configurations under study appeared to present offloading capabilities for alternative missions.

On the basis of a study by NAA, a single-engine configuration was chosen as the optimum approach for the service module propulsion subsystem. The results of the study were presented to MSC representatives and NAA was authorized to issue a work statement to begin procurement of an engine for this configuration. Agreement was also reached at this meeting on a vacuum thrust level of 20,000 pounds for the engine. This would maintain a thrust-to-weight ratio of 0.4 and allow a considerable increase in the lunar liftoff weight of the spacecraft.

A meeting to review the lunar orbit rendezvous (LOR) technique as a possible mission mode for Project Apollo was held at NASA Headquarters. Representatives from various NASA offices attended: Joseph F. Shea, Eldon W. Hall, William A. Lee, Douglas R. Lord, James E. O'Neill, James Turnock, Richard J. Hayes, Richard C. Henry, and Melvyn Savage of NASA Headquarters; Friedrich O. Vonbun of Goddard Space Flight Center (GSFC); Harris M. Schurmeier of Jet Propulsion Laboratory; Arthur V. Zimmeman of Lewis Research Center; Jack Funk, Charles W. Mathews, Owen E. Maynard, and William F. Rector of MSC; Paul J. DeFries, Ernst D. Geissler, and Helmut J. Horn of Marshall Space Flight Center (MSFC); Clinton E. Brown, John C. Houbolt, and William H. Michael, Jr., of Langley Research Center; and Merrill H. Mead of Ames Research Center. Each phase of the LOR mission was discussed separately.

The launch vehicle required was a single Saturn C-5, consisting of the S-IC, S-II, and S-IVB stages. To provide a maximum launch window, a low earth parking orbit was recommended. For greater reliability, the two-stage-to-orbit technique was recommended rather than requiring reignition of the S-IVB to escape from parking orbit.

The current concepts of the Apollo command and service modules would not be altered. The lunar excursion vehicle (LEV), under intensive study in 1961, would be aft of the service module and in front of the S-IVB stage. For crew safety, an escape tower would be used during launch. Access to the LEV would be provided while the entire vehicle was on the launch pad.

Both Apollo and Saturn guidance and control systems would be operating during the launch phase. The Saturn guidance and control system in the S-IVB would be "primary" for injection into the earth parking orbit and from earth orbit to escape. Provisions for takeover of the Saturn guidance and control system should be provided in the command module. Ground tracking was necessary during launch and establishment of the parking orbit, MSFC and GSFC would study the altitude and type of low earth orbit.

The LEV would be moved in front of the command module "early" in the translunar trajectory. After the S-IVB was staged off the spacecraft following injection into the translunar trajectory, the service module would be used for midcourse corrections. Current plans were for five such corrections. If possible, a symmetric configuration along the vertical center line of the vehicle would be considered for the LEV. Ingress to the LEV from the command module should be possible during the translunar phase. The LEV would have a pressurized cabin capability during the translunar phase. A "hard dock" mechanism was considered, possibly using the support structure needed for the launch escape tower. The mechanism for relocation of the LEV to the top of the command module required further study. Two possibilities were discussed: mechanical linkage and rotating the command module by use of the attitude control system. The S-IVB could be used to stabilize the LEV during this maneuver.

The service module propulsion would be used to decelerate the spacecraft into a lunar orbit. Selection of the altitude and type of lunar orbit needed more study, although a 100-nautical-mile orbit seemed desirable for abort considerations.

The LEV would have a "point" landing (±½ mile) capability. The landing site, selected before liftoff, would previously have been examined by unmanned instrumented spacecraft. It was agreed that the LEV would have redundant guidance and control capability for each phase of the lunar maneuvers. Two types of LEV guidance and control systems were recommended for further analysis. These were an automatic system employing an inertial platform plus radio aids and a manually controlled system which could be used if the automatic system failed or as a primary system.

The service module would provide the prime propulsion for establishing the entire spacecraft in lunar orbit and for escape from the lunar orbit to earth trajectory. The LEV propulsion system was discussed and the general consensus was that this area would require further study. It was agreed that the propulsion system should have a hover capability near the lunar surface but that this requirement also needed more study.

It was recommended that two men be in the LEV, which would descend to the lunar surface, and that both men should be able to leave the LEV at the same time. It was agreed that the LEV should have a pressurized cabin which would have the capability for one week's operation, even though a normal LOR mission would be 24 hours. The question of lunar stay time was discussed and it was agreed that Langley should continue to analyze the situation. Requirements for sterilization procedures were discussed and referred for further study. The time for lunar landing was not resolved.

In the discussion of rendezvous requirements, it was agreed that two systems be studied, one automatic and one providing for a degree of manual capability. A line of sight between the LEV and the orbiting spacecraft should exist before lunar takeoff. A question about hard-docking or soft-docking technique brought up the possibility of keeping the LEV attached to the spacecraft during the transearth phase. This procedure would provide some command module subsystem redundancy.

Direct link communications from earth to the LEV and from earth to the spacecraft, except when it was in the shadow of the moon, was recommended. Voice communications should be provided from the earth to the lunar surface and the possibility of television coverage would be considered.

A number of problems associated with the proposed mission plan were outlined for NASA Center investigation. Work on most of the problems was already under way and the needed information was expected to be compiled in about one month.

(This meeting, like the one held February 13-15, was part of a continuing effort to select the lunar mission mode).

Wernher von Braun, Director, Marshall Space Flight Center, recommended to the NASA Office of Manned Space Flight that the lunar orbit rendezvous mode be adopted for the lunar landing mission. He also recommended the development of an unmanned, fully automatic, one-way Saturn C-5 logistics vehicle in support of the lunar expedition; the acceleration of the Saturn C-1B program; the development of high-energy propulsion systems as a backup for the service module and possibly the lunar excursion module; and further development of the F-1 and J-2 engines to increase thrust or specific impulse.

J. Thomas Markley, command and service module Project Officer at MSC, announced details of the space facility to be established by NASA at White Sands Missile Range (WSMR). To be used in testing the Apollo spacecraft's propulsion and abort systems, the WSMR site facilities would include two static-test-firing stands, a control center blockhouse, various storage and other utility buildings, and an administrative services area.

MSC reported that Arnold Engineering Development Center facilities at Tullahoma, Tenn., were being scheduled for use in the development of the Apollo reaction control and propulsion systems. The use of the Mark I altitude chamber for environmental tests of the command and service modules was also planned.

The Aerojet-General Corporation reported completion of successful firings of the prototype service propulsion engine. The restartable engine, with an ablative thrust chamber, reached thrusts up to 21,500 pounds. (Normal thrust rating for the service propulsion engine is 20,500.)

North American chose Simmonds Precision Products, Inc., to design and build an electronic measurement and display system to gauge the service propulsion system propellants. Both a primary and a backup system were required by the contract, which was expected to cost about 2 million.

NASA Headquarters, MSC, Jet Propulsion Laboratory, MSFC, North American, and Grumman agreed that the LEM and CSM would incorporate phase-coherent S-band transponders. (The S-band system provides a variety of communications services. Being phase-coherent meant that it could also provide Mission Control Center with information about the vehicle's velocity and position, and thus was a means of tracking the spacecraft.) Each would have its own allocated frequencies and would be compatible with Deep Space Instrumentation Facilities.

North American asked MSC if Grumman was designing the LEM to have a thrusting capability with the CSM attached and, if not, did NASA intend to require the additional effort by Grumman to provide this capability. North American had been proceeding on the assumption that, should the service propulsion system (SPS) fail during translunar flight, the LEM would make any course corrections needed to ensure a safe return trajectory. Additional Details: here....

Qualification testing began on fuel tanks for the service propulsion system (SPS). The first article tested developed a small crack below the bottom weld, which was being investigated, but pressurization caused no expansion of the tank. During mid-October, several tanks underwent proof testing. And, on November 1, the first SPS helium tank was burst-tested.

Firings at the Arnold Engineering Development Center (AEDC) and at Aerojet-General Corporation's Sacramento test site completed Phase I development tests of the SM propulsion engine. The last simulated altitude test at AEDC was a sustained burn of 635 seconds, which demonstrated the engine's capability for long-duration firing. Preliminary data indicated that performance was about three percent below specification, but analysis was in progress to see if it could be improved.

The Air Force Eastern Test Command concurred in the elimination of propellant dispersal systems for the SM and the LEM. Costs, schedules, and spacecraft designs, NASA felt, would all benefit from this action. ASPO thus notified the appropriate module contractors.

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.

Test Series I on spacecraft 001 was completed at WSTF Propulsion Systems Development Facility. Vehicle and facility updating in progress consisted of activating the gimbal subsystem and installing a baffled injector and pneumatic engine propellant valve. The individual test operations were conducted satisfactorily, and data indicated that all subsystems operated normally. Total engine firing time was 765 seconds.

North American reported two service propulsion engine failures at AEDC and a third at WSMR. At the first location, both failures were attributed to separation of the thrust chamber from the injector assembly; in the latter instance, weld deficiencies were the culprit. Analysis of all these failures was continuing.

In order to use the LEM as a backup for the service propulsion system (SPS) to abort the mission during the 15-hour period following translunar injection, Grumman informed North American that some redesign of the spacecraft's helium system would likely be required. This information prompted North American designers to undertake their own analysis of the situation. On the basis of their own findings, this latter group disagreed with the LEM manufacturer. Additional Details: here....

Resident ASPO quality assurance officers at North American began investigating recent failures of titanium tanks at Bell Aerosystems. Concern about this problem had been expressed by the Apollo Test Directorate at NASA Hq in July and MSC started an investigation at that time. The eventual solution (a change in the nitrogen tetroxide specification) was contributed to by North American, Bell Aero Systems, the Boeing Company, MSFC, MSC, Langley Research Center, and a committee chaired by John Scheller of NASA Hq. The penstripe method to find cracks on the interior of the vessels was used to solve the problem. The quality assurance people viewed the failures as quite serious since Bell had already fabricated about 180 such tanks.

North American reported that ground testing of the service propulsion engine had been concluded. Also, changing the propellant ratio of the service propulsion system had improved the engine's performance and gimbal angles and had reduced the weight of the Block II SM.

As a result of discussions with North American and Aerojet-General, MSC ordered several changes to the service propulsion engine:

1. redesign of the ablation chamber seals and the flange mountings
2. modifications to permit ground purging
3. redesign of the injection hub
4. doubling of the nominal valve opening time (from 0.3 to 0.6 sec).

ASPO Manager Joseph F. Shea decided that no device to indicate a failure of the secondary gimbal motor in the service propulsion system (SPS) was necessary on Block I spacecraft. Two factors shaped Shea's decision:

1. procedures for inflight checkout of the vehicle called for gimbaling the service propulsion engine with both primary and secondary drive motors prior to SPS burns;
2. furthermore, all Block I (i.e., earth orbital) spacecraft would be capable of returning to earth by means of the SM's reaction control system.

Engine testing at the Arnold Engineering Development Center (AEDC) had been the subject of discussions during recent months with representatives from MSC, Apollo Program Quality and Test groups, AEDC, Air Force Systems Command and ARO, Inc., participating. While AEDC had not been able to implement formal NASA requirements, the situation had improved and MSC was receiving acceptable data.

In a letter to ASPO Manager Joseph F. Shea, Apollo Program Director Samuel C. Phillips said, ". . . I do not think further pressure is in order. However, in a separate letter to Lee Gossick, I have asked that he give his personal attention to the strict adherence to test procedures, up-to-date certification of instrumentation, and care and cleanliness in handling of test hardware."

Design Certification Reviews of CSM 101 and LM-3 were held at MSC. Significant program-level agreements reached included validation of a 60-percent-oxygen and 40-percent-nitrogen cabin atmosphere during launch; reaffirmation of the February 6 Management Council decision that a second unmanned LM flight was not required; and the conclusion that, in light of successful static firing of the 102 service propulsion system and subsequent analysis, a static-firing of the 101 system was not required.

Eberhard F. M. Rees, Director of the Apollo Special Task Team at North American Rockwell, wrote to the company's CSM Program Manager Dale D. Myers to express his concern over persistent problems with leaks in the ball valves for the service propulsion system. Rees doubted that any real progress was being made, stating that the problem persisted despite relaxations in leakage criteria and that qualification failures continued to occur. Rees described a review of the program on March 18 at Aerojet-General Corp. as lacking in factual depth. Also, the company did not appear to be pursuing developmental testing of configurational changes with any degree of vigor. Rees suggested to Myers that his people were on the right track and with management attention the vendor's efforts could be channeled to get some genuine results.

In a Mission Preparation Directive sent to the three manned space flight Centers, NASA Apollo Program Director Samuel C. Phillips stated that the following changes would be effected in planning and preparation for Apollo flights:

Apollo-Saturn 503

• Assignment of Saturn V 503, CSM 103, and LM-3 to Mission D was canceled.

• Saturn V 503 would be prepared to carry CSM 103 and LTA (LM test article)-B on a manned CSM-only mission to be designated the C prime mission.

• The objectives and profile of the C prime mission would be developed to provide maximum gain consistent with standing flight safety requirements. Studies would be carried out and plans prepared so as to provide reasonable flexibility in establishing final mission objectives.

• All planning and preparations for the C prime mission would proceed toward launch readiness on December 6, 1968.

Apollo-Saturn 504

Saturn V 504, CSM 104, and LM-3 were assigned to the D mission, scheduled for launch readiness no earlier than February 20, 1969. The crew assigned to the D mission would remain assigned to that mission. The crew assigned to the E mission (Frank Borman, James A. Lovell, Jr., and William Anders) would be reassigned to the C prime mission. Training and equipping the C prime crews and operational preparations would proceed as required to meet mission requirements and to meet the newly established flight readiness date.