I Downloaded from https://www.everyspec.com MIL-STD-81OD . 19July 1983 which unfairly penalizes the test item. However, there should not be enough cooling air to produce unrealistic coolirig. Since the actinio effects’’are highly dependentupon the solar radiation spectrum.(as well aa intensity and duration), the spectrum must be as close as possible to that of natural sunlight:” -- ... ,... ., The 4-ho&r ‘flightsoffot‘periodof each 24-hour cycle allows for ‘testitem conditions (physical and chemical) to return toward riormaland pFovides’some degree of thermal stress exercising. .. I-3.2 QQiCe of related test CQ51WSUW After choosing the test procedure,. !
choose the diurnal cycle, test duration’,test item configuration, and any additional appropriate conditions. a. ~nal CVCI.Q. For procedure,I“,two high-temperature diurnal cycles are provided in table 505.2-I, with the saoiasolar radiation conditions for both. The first cycle’(Hot Dry) has a peak temperature of 49° C (120° F) and 1120’W/m2 (355 Btu/ft2/h) and represents’the hottest cOnditio~s, exceedid nOt more than.1 percent of,the hours in extreme month at the most severe locationa under consideration.
This cycle ia used when there”is a requirement for the test item to perform aatisfactorily worldwide.’.The second cycle (Basic Hot Dry) ia less severe and peaka at an air temperature of 44° C (111‘F) and a solar radiation intensity of 1120 W/m2. This cycle is used when there is a Y requirement for the teat item to perform without degradation in many , geographical areaa of the world that extend outward from the Hot Dry regions Of the United Statea, Mexico, Africa, Asia, Australia, South Africa; South f America, southern Spain, and eouthwest Aafa.
(See method 501.2 for area descriptions.) This cycle ia also used when special precautions are taken to provide protection against the aun in hot, dry areas (such as with munitions). !. b. ~ ,. ,, (1) (See figure“505.2-1.) The test item‘shall be exposed to continuous 24-hour cycles of controlled simulated solar radiation” and dry-bulb temperature aa indicated in table 505.2-I or as specified in the requirements documents. The number of cycles performed shall be the minimum neceaaary to produce the peak reaponae temperature caused by the stacking :
effect of the test item (within 2° C (3.60F) of the peak ‘responsetemperature achieved during the previous 24-hour cycle) or three continuous cycles, whichever is longer. For most applications, the maximum teat duration should be aeven cycles. (.2) uQcsuLu. (See figure 505.2-2.) Procadure II will give an. acceleration factor of approximately 2.5 aa far as the total energy received by the test itei is concerned. Eight ‘hoursof exposure to 1120 W/m2 (355 Btu/ft2/h), as in the steady-state teat, is equal tO 24 hours Of the cY@lins test (20 hours of light and 4 hours of no light per cycle).
A duration of ten 24-hour cycles la suggested for equipment which is occasionally used outdoors, such as portable test items, etc. For equipment centinuously exposed to outdoor conditions, a test duration of 56 cycles or longer is suggested. Increasing the Irradiance above the specified level is not recommended, because of the danger of overheating, and there is presently no indication that attempting to accelerate the test in this way gives results that correlate with equipment response under natural solar radiation conditions. MSTHOD 505;2 - 19 July 505.2-4“J