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

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that a part operatesbefore!te limiting condition sets in or before
write-off.
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Identical motors during operation will have different longevity
since damage and breakdowns are possible in various elements of the'
motor and at different times and occur as a'resuit of scarcely
noticeable differences in'material, manufacturing;procedures, ptc.
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The life (service) is established'by. the supplier plant as
the time of guaranteed faultless operationof the engine. After
working its full life the engine is removed- l'om operation.
Longevity is
different for engines-of different purposes-.
For example, for liquid and solid propellant rocket engines (LPRE and
SPRE) it is less than 5 h, for aviation turbojet'(TJE) 100-1500 h,'
and. for extraterrestrial electrical rocket engines (ERE) 5-l0,000 h.
Life pf ordinary rocket. engines (LPRE and SPRE) for one-shot
use is made up of the useful operating time, the' plant inspection time, 1
and the acceptance testing time. I I
The life of engines for repeated l use is
easily established,
based on the trouble-free service time of the most stressed critical
part of the engine. Such engines have the concept of full or
amortized life, which is established from several intermediate liv4s.
After operating for a period corresponding to an intermediate lifetime
the motor undergoes complete dismantling, replacement, of stressed
parts which are dangerous in
operation on the following lifetime.
an emergency, and then the second
There can be several such
* lifetimes. Amortized or full life can consist of two or three
intermediate lifetimes after overhauls. Only after working out the
amortized or full lifetime does an engine go for remelting.
The longevity of ERE can be different depending upon their
purpose.,
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