Exploring the Unknown: Selected Documents in ... - The Black Vault

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First Steps into Space: Projects Mercury and Gemini
subsequent cursory analysis of the systems showed that there are several such. For
example, three retro-rockets are provided to decelerate the capsule out of orbit.
The entire package is held on by a single explosive bolt. There is a possibility that a
stray current in the circuit beyond the main switch could fire the bolt prematurely
and jettison the rocket package before it had performed its function and thus
make it impossible to get out of orbit. Just such unexplained currents have plagued
two of the Little Joe shots. Another possible difficulty centers around the necessity
for releasing both the main and the emergency parachutes from the capsule upon
impact with the water. There is a possibility that a premature spurious signal may
make the release at high altitude and drop the capsule with catastrophic results.
The panel is concerned that steps may not have been taken to specifically
tabulate the operations or functions in which a signal failure would lead to
catastrophe. When such possibilities have been defined, then special testing,
inspection, and check out procedures should be adopted in order to obtain the
maximum possible reliability for the associated components.
6. Status of the Quantitative Reliability Studies
The recommendation of the preceding section that the single failure
possibilities be critically analyzed serves to emphasize the value which a
reliability analysis has in a program of this magnitude and complexity. From
the presentations, it was learned that the McDonnell Aircraft Corporation had
performed an extensive failure mode analysis and that a separate reliability study
had been initiated at NASA Headquarters and, subsequently, had been transferred
to the Space Task Group.
Through a misunderstanding, the questions which were asked by the
panel about the McDonnell study were deferred until later in the briefing when
the reliability studies would be presented in detail. The later presentation proved
to be on the NASA study, and consequently, very little was learned about the
failure mode analysis studies of McDonnell. Hence, no evaluation of their impact
on the program can be made. [12]
When the NASA reliability studies were presented, it became apparent
that as yet they had not played an important role in the design. The mean time to
failure of each component which was the basic parameter in the analysis did not
reflect the changes which had been made to correct obvious early difficulties. The
results which are available from a reliability analysis for the Atlas orbiting mission
in which the man is assumed to play no role. The analysis was in the process of
being revised and results would not be available until approximately July 1,1961.
In view of this situation, the panel was left in doubt as to how comprehensive has
been the analysis of the possibilities of single mode failures, of simple correlated
multiple failures, and of subtle failures in redundant subsystems which might
preclude the use of either subsystem for the Atlas shots.
In view of this uncertainty, the panel wishes to express an opinion that an
emphasis be placed on having the results of such a systematic analysis available
prior to the first launchings of the manned Atlas vehicles. Further, the panel