DESTINATION MOON: A History of the Lunar Orbiter Program
 
 
CHAPTER VII: BUILDING THE SPACECRAFT: PROBLEMS AND RESOLUTIONS
 
Preliminary Mission Planning Activities
 
 
 
[147] A third area of the Lunar Orbiter Program was mission design, and success in planning the missions to be flown depended heavily upon coordination among the various NASA and industry participants. Implementation of the planning activities depended upon the establishment of schedules for the program's various task groups; in turn these had to be integrated with one another to effect the timeliest utilization of information within each specific area of the Lunar Orbiter Program.
 
Although detailed consideration had been given to ways and means of utilizing NASA's capabilities to facilitate Boeing's work during the period of contract negotiation, the first major meeting to discuss actual schedules and working relationships convened on April 15, 1964,at the Langley Research Center. The meeting's purpose was twofold. First the participants from Headquarters, Langley, Lewis, JPL, and Boeing had to work out a basic agreement about the delegation of responsibilities which had not yet been assigned through any earlier agreements. This included, tentative declarations by each party of its capabilities and limitations and what tasks each believed it could best perform to contribute to the success of the program. Secondly, the representatives of the various [148] centers and the prime contractor had to agree upon the implementation of the decisions in the first area of agreement.13
 
Thomas Yamauchi of the Boeing Company began the talks with a presentation of a condensed project schedule and noted the time intervals in which Boeing would require trajectory information from the Lewis Research Center and JPL concerning the launch vehicle and tracking and data-acquisition needs. He outlined the kind of information which Boeing would require from each.14
 
Dr. Karl A. Faymon of Lewis responded by specifying approximately the times before each launch when Lewis could deliver various preliminary and final data on launch vehicle checkout and performance. He also explained the times at which Boeing would have to supply data to Lewis on launch constraints, detailed mission profiles, and updated weight estimates. The flow of information between Lewis and Boeing appeared not to present any serious problems at the time of the Langley meeting.15
 
While the job which Lewis would perform for Boeing [149] and the Lunar Orbiter Program concerned hardware, the role which the Jet Propulsion Laboratory and the Deep Space Network would perform was much more complex. The services which JPL and the DSN would render fell into two categories: flight programs and tracking and data acquisition. Both required different kinds of organization. JPL had already committed the Deep Space Network facilities which the Lunar Orbiter Program would require, and these and their operation came under the auspices of the NASA Office of Tracking and Data Acquisition (OTDA). There was little trouble here between Langley and JPL.
 
The work which JPL flight programs manpower could reasonably render the Lunar Orbiter Program was another matter. Before JPL could do anything, it had to know the amount and kind of resources which Langley desired that JPL commit to Lunar Orbiter. In this case JPL's ability to commit the resources depended upon its commitments to other flight programs: Ranger, Surveyor, and Mariner. These programs were all funded through the Office of Space Science and Applications, and any decision about an increased work load for JPL would have to take them into consideration.16
 
[150] When Langley had requested additional support from JPL on April 2, the request was not for work to be done by the DSN. It fell instead within the realm of flight programs, and JPL manpower was already spread thinly. On April 2 Langley had requested of NASA Headquarters that JPL take on the responsibility "for the programming of all operational computer programs, including reviewing the physical and engineering problems they represent, their mathematical formulation, and the formal requests for programming." This was not all. Langley wanted JPL to "make a definitive study of Lunar Orbiter tracking data requirements, including the accuracy of real-time trajectory determination, considering tracking sites, data types, sampling rates, data noise biases, site errors, etc."17
 
The Lunar Orbiter Project Office at Langley also wanted JPL to "check the Space Flight Maneuver Specifications Tables; i.e., the guidance philosophy for midcourse, deboost, and retro firing, including numerical firing tables which will be used in DSN operations."18 Boeing, at the same time, was to conduct a similar study of tracking and [151] data-acquisition requirements and was to review all JPL support work. When Floyd L. Thompson had presented these expanded requests to Marshall Johnson, the Tracking and Data Systems Manager at the DSN, and Victor Clarke, also of JPL, they had reacted favorably but had stipulated that the Systems Analysis Section and the Computer Applications and Data Systems Section at JPL would require more manpower to perform the Lunar Orbiter work.19 However, Johnson and Clarke were part of the DSN, not the JPL flight programs operation, and they were not in a position to commit non-DSN resources.20
 
At the April 15 Langley meeting JPL representatives proposed a multi-staged program to educate Boeing and Langley personnel about the capabilities of the DSIF and SFOF so that they, in turn, could use their manpower to perform the flight operation tasks necessary to the preparation and execution of each mission. JPL also suggested that Boeing set up a computer facility to "resemble" the Space Flight Operations Facility and run its own programming while having a private contractor check it independently.21
 
[152] Langley and JPL proceeded to work out a compromise agreement to facilitate the timeliest integration of schedules. The actual problems of mission design and orbit determination remained in the hands of the Lunar Orbiter Project Office, specifically under the direction of William J. Boyer, the LOPO Operations Manager and John B. Graham, in charge of operations integration.
 
Robert J. Helberg at Boeing assigned Thomas Yamauchi to coordinate mission planning with the LOPO at Langley. On June 10, 1964,a major meeting convened at NASA Headquarters to review the status of Yamauchi's work, the proposed first mission, and the technical problems which placed constraints on the design of that mission. It had become apparent to Scherer, Kosofsky and Swetnick of the Headquarters Program Office that a dichotomy existed between the requirements of the short-term photographic mission and the extended selenodetic mission of the spacecraft. This dichotomy affected design of the attitude control system, since its performance could determine the orbital parameters of the spacecraft during the long-life mission which was to last about one year after termination of photography and readout.22
 
Scherer outlined the first tentative Lunar Orbiter [153] mission to the participants of the meeting as an introduction to the areas of difficulty. Mission A, as it was later called, would inject an Orbiter into a nearly circular orbit approximately 925 kilometers above the Moon with an inclination of 210 to the lunar equator. The orbit was then to be changed to an ellipse ranging from 925 kilometers at apolune to 46 kilometers at perilune, because this would be most satisfactory for high- and medium-resolution photography.23
 
Dr. Gordon MacDonald of UCLA, a member of the OSSA Planetology Subcommittee, expressed some doubt about the safety of the spacecraft at such a low perilune over a period of one year. His reasoning was based upon the fact that the attitude control system, as it was then designed, would cause periodic perturbations in the orbit by repeated firing of its thrusters. (At this time the Orbiter had one-pound thrusters located at the tips of the solar panels. When fired they would change the spacecraft's attitude, but they would also cause some oscillations in the solar panels and would affect the spacecraft's thrust vector.) This could cause a three-meter change in the perilune per orbit, according to MacDonald. A Boeing study that Yamauchi had directed substantiated his conclusion. The change would be [154] too great for the spacecraft's velocity control subsystem to handle over the long run and could jeopardize the extended mission. MacDonald suggested that Boeing make a detailed analysis of the attitude control subsystem and its effects on the velocity and thrust vector control.
 
The members of the meeting agreed that Boeing should examine the following questions:
 
1. What dead zone can the Lunar Orbiter attitude control system accept on an extended mission?
 
2. What will be the effects of the control jets on the motion of the Lunar Orbiter?
 
3. Can the impulses on each control jet be measured and counted, even during the time the spacecraft is not within line of sight telecommunications to earth?
 
4. What possible effects can an imbalance, such as the high gain antenna on the end of a boom, have on the attitude of the Lunar Orbiter over an extended lifetime mission?
 
5. Is it possible to modify the design of the attitude control system to operate coupled pitch and yaw jets?24
 

Following the meeting, the Boeing Company went to work on the design of the attitude control subsystem, and by the First Quarterly Review at the end of August, the spacecraft design was beginning a three-stage metamorphosis which would result in its final configuration in the spring of [155] 1965.25 The metamorphosis through April 1965 can be briefly summarized.

 
Initially the spacecraft had a photographic subsystem housed in a barrel-shaped "bathtub." The attitude control thrusters were located at the periphery of the solar panels with requisite plumbing to feed gas to them from storage tanks in the engine module. At stage two the spacecraft had a more efficiently shaped "bath tub" with a flat bottom for better thermal control. An arch from the equipment deck to the middle deck had been placed over the photographic subsystem to add strength, and the structure of the velocity control subsystem had been changed. However, the attitude control thrusters still remained at the tips of the solar panels.
 
In the third stage stage of the metamorphosis the velocity control engine had been gimbaled, the change reducing its fuel requirement and allowing more room for the nitrogen tank to fit down into the center of the engine module. The attitude control thrusters had been reduced from one-pound to one-half-pound thrusters, and they had been relocated on the periphery of the upper-most deck of the engine module. They had also been coupled, and the need for the plumbing to carry gas to the tips of [156] the solar panels had been eliminated. The omni-antenna boom had been strengthened, and the micrometeoroid detectors had been placed around the middle deck.26
 
These changes raised technical design problems, but they also affected preliminary mission planning activities-as did the working arrangement established between Langley and JPL. At the beginning of July 1964 officials from the two centers worked out the details for educating selected Langley and Boeing personnel in mission analysis, programming standards, and the review of existing programs that might benefit Lunar Orbiter. Training began on July 15 and afforded the Lunar Orbiter Program the opportunity to solve its own problems of analysis without unduly taxing JPL manpower.27 Boeing was very willing to learn from JPL, a fact which facilitated the implementation of the Langley-JPL working agreement and, indeed, overall mission success in the program.
 

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LUNAR ORBITER SPACECRAFT

 
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