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DESTINATION MOON: A History of the
Lunar Orbiter Program
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- CHAPTER VII: BUILDING THE
SPACECRAFT: PROBLEMS AND RESOLUTIONS
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- Testing Procedures and Program
Reviews
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- [156] One Important
feature of the Lunar Orbiter spacecraft was that its design did
not rely heavily upon...
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[157]
GRAPHIC
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- [158] redundant
subsystems or components. Moreover, although the subsystems were
integrated, they were not heavily interdependent and could
function more independently of each other than the subsystems
could in such spacecraft as Mariner. This design concept reflected
Boeing's long standing traditions in aircraft, and it paid off
handsomely.
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- The testing philosophy of the Lunar
Orbiter was one reason the design proved to be so successful.
Several kinds of tests and reviews were used in the program. First
was the Preliminary Design Review, conducted by NASA and Boeing.
This form of review was always held to check any specific
technical area or major subsystem before a final decision was made
to freeze the design. When agreement was reached, Langley gave
Boeing permission to fix the design, and then both parties met to
hold a Critical Design Review. In this review the item, whether a
component or a major subsystem, was picked apart or passed as
acceptable for fabrication and testing. If approved, the item was
procured or fabricated, and after approval Langley tried to hold
changes to an absolute minimum. During the fabrication stage,
various forms of reviews took place until the item was completed
and tested. At the completion point, a formal NASA
[159]
Acceptance Review was conducted.28
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- The Langley-Boeing testing procedure was
aimed at making the first mission a complete operational success.
The procedure played a vital part in the program and reflected the
positive attitudes throughout the entire Lunar Orbiter Program
team.
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- At the beginning of the whole testing
sequence, all components of the spacecraft system went through a
Flight Acceptance Test (PAT), which exposed them to "nominal"-or
expected -vibration, temperature, and vacuum conditions of
operational environments. Three sets of each component were then
divided into sets A. B. and C for more specific tests. Set A was
used for qualification tests simulating overstress conditions.
This kind of test was designed to push the component beyond
expected endurance limits to determine what punishment it could
actually withstand. Set B underwent reliability demonstration
tests that simulated two real-time missions at the FAT level.
Finally, Set C components made up subsystem assemblies that were
tested and then [160] integrated into a complete spacecraft (Spacecraft
"C").
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- This first complete spacecraft system,
minus the photographic subsystem, was subjected to compatibility
tests with the Atlas-Agena launch vehicle; with the tracking and
communications network at Goldstone, California; and with the
Eastern Test Range tracking and communications facilities at Cape
Kennedy.29 The idea to test the spacecraft for compatibility
with the DSIF facility at Goldstone had been suggested by JPL;
Langley accepted it, and testing proved to be very useful in
establishing biases between the Lunar Orbiter communications
subsystem and the DSIF receiving station.30 A test film was read out during dryrun exercises
there to check the accuracy in the transmitting and receiving
equipment.
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- Boeing built a total of eight Lunar
Orbiter spacecraft for the program, including Spacecraft C.
Following Spacecraft C came Spacecraft 1 and 2. Number 1 underwent
qualification tests at spacecraft level while Number 2 was
subjected to thermal vacuum tests for a period covering the
duration of two missions. The other five Lunar Orbiters (3, 4, 5,
6, and 7) were put through Flight Acceptance Tests...
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- [161] (CHART)
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- LUNAR ORBITER TEST PROGRAM
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- [162] ...and then sent
to the Eastern Test Range for their final checkout and launch. The
chart below clarifies the sequence:
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Spacecraft Number
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C
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1
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2
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3
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4
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5
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6
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7
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Lunar Orbiter
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Ground test
spacecraft
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V
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I
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II
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III
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IV
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Mission
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E/5
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A/1
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B/2
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C/3
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D/4
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- Clifford H. Nelson pointed out to the
participants of the XVIII International Astronautical Congress in
Belgrade, Yugoslavia, that no serious problems or failures were
experienced during all spacecraft-level tests in the program. This
testified to the standards and the thoroughness which Boeing and
Langley had used in testing at the component and subsystem level,
and it also testified to the excellence of the spacecraft's
design. Faulty equipment and poor designs had been effectively
rooted out during the testing phase of the program when potential
problems in subsystem integration had been
exposed.31
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- More interesting, however, was the fact
that Boeing and Langley had agreed early on testing in a parallel
mode rather than in a series mode. Tight schedules and a spartan
[163]
economy were largely responsible for this. Thus, for example, the
three sets of components (A, B, and C), Spacecraft 1 and 2, and
the five Flight Spacecraft (3, 4, 5, 6, and 7 ) were tested in
periods that substantially overlapped.32 Ira W. Ramsey headed a team of men in the LOPO
which was responsible for the entire Lunar Orbiter testing program
and for the success of the parallel mode despite its inherent
risk.33
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