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Page Title:
Environmental service conditions |
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|  MIL-T-70521A(AR)
3.3 Environmental service conditions. Any telescope subjected
to any or all of the requirements of 3.3.1, 3.3.2, 3.3.3, and 3.3.4
shall subsequently meet the requirements of 3.3.5 through 3.3.9
unless otherwise specified.
3.3.1 Vibration. The telescope shall be positioned with the
line of sight through the eyepiece and objective tube in a
horizontal plane and the telescope supported at the 0.624 inch
diameter of the objective tube. The telescope shall then be
vibrated at a constant frequency of 30 cycles per second with an
amplitude of 1/16 inch (1/8 inch total excursion) for a period of
5 minutes + 15 seconds.
3.3.2 Shock. The telescope shall be shocked six (6) times in
each of two (2) positions. The applied shocks shall be inn a
vertical, up direction. In the first position, the telescope shall
be positioned with the line of sight through the eyepiece and
objective tube in a horizontal plane. In the second position, the
telescope shall be positioned with the line of sight through the
eyepiece and objective tube in a vertical plane. In both positions
the telescope shall be supported at the 0.624 inch diameter of the
objective tube. The shock, for all twelve (12), shall be 300 g's
for one (1) mini-second and have a 1/2 sine wave pulse.
3.3.3 Temperature.
3.3.3.1 Operating. The telescope shall meet the requirements
of 3.4 when stabilized thermally at any temperature between +60F
(+16C) and +90F (+32C).
3.3.3.2 Nonopererating (storage). The telescope shall not suffer
permanent damage when subjected to the constant temperature extremes
of -50F (-46c) for a period of 24 hours and +160F (+71C) for a
period of 4 hours (after temperature stabilization), and shall meet
the requirements of 3.4 when returned to room ambient.
3.3.4 Sealing and flushing. The telescope shall show no
evidence of leakage in excess of 0.2 psig when subjected to an
internal pressure of 5 + 0.10 psig for a period of two hours using
dry nitrogen having a dew point at least as low as -25F (-32C).
The telescope shall then be flushed with dry nitrogen until the
interior atmosphere of the telescope has a dew point at least as low
as -25F (-32c).
3.3.5 Condensation (low temperature). When viewed through the
eyepiece and objective ends of the telescope, there shall be no
evidence of condensation at room temperature immediately upon
thermal stabilization, subsequent to being subjected to the -50F
(-46C) and prior to the +160F (+71C) requirement of 3.3.3.2.
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