Design and Stress Analysis of Extraterrestrial ... - The Black Vault

consists of kerosene (RP-l fuel) and liquid oxygen. It was developed
during the period 1960-1965 with 1545 bench starts and an overall
average operating time of %'8200 s for each engine.
Fifty-eight
motor samples were spent on the first thousand starts. In use on
a rocket this motor should work reliably for %l50-s,,.jIf we assume 1
that at the moment of the beginning of motor operation its
P was equal to zero (in
operation of this type engine with the first
lower than 0.2) and then it
reliability
actuality, probability of breakdown-free
start can scarcely be
built up according to exponential law
P=1I -- e-a (1.4)
where N is the number of tests, a is a certain coefficient which
characterizes the rate of reliability rise (see example at the end of
section), then after conducting 310 tests the reliability calculated
thus was 0.7-0.75, and after conducting 1545 tests it became no
less than 0.9975. By reliability we meap the lower confidence limit
of the probability of breakdown-free operation during a preset
period of time under given conditions with a confidence coefficient
of 0.95.2
As concerns ERE, because of their extremely high cost they
can only be manufactured in single samples. However, the quantitative
forecast of reliability and its experimental confirmation are
necessary; special items are not isolated for confirmation of
reliability, but everything necessary for this is obtained
simultaneously with operation and acceptance tests of working
samples.
" 1 Barlow P., Proshan F., Mathematic reliability theory, translated
from English, izd-vo "Sovetskoye radio," 1969, str. 334.
2 Confidence range is the interval limited by the confidence
boundaries in which, with a given confidence coefficient, lie the
parameter being evaluated. Confidence parameter is the probability
of the fact that the parameter being evaluated lies within a given
confidence interval (GOST 13216-67).
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