Downloaded from https://www.everyspec.com MIL-STD-81OC 10 March 1975 METHOD 505.1 SOLAR RADIATION (SUNSHINE) 1. PURPOSE. The sunshine test is conducted to determine the effect of solar radi-nergy on equipment in the Earth’s atmosphere. For the purpose of this test, only the terrestrial portion of the solar spectrum is considered. The limits and energy levels specified herein provide the simulated effects of natural sunshine. The ultraviolet portion simulates natural sunshine in a general way and is considered to be representativeof irradiation in most geographical locations.
The sunshine tests are applicable to equipment which may be exposed to solar radiation during service or unsheltered storage at the Earth’s surface or in the lower atmosphere. 1.1 General effects. Heating effects may cause bending, differential expan- sion, bulging, cracking, crazing, softening and melting, overheating,binding, permanent set of gaskets, etc. Degradation from spectral energy input is manifested as fading of fabric colors, checking of paints and deterioration of natural rubber and plastics. 1.2 Procedure I. Accelerated steady state, solar radiation test; equipment nonoperating. 1.3 Procedure II. Accelerated cycling temperature and solar radiation test.
This procedure is intended to simulate natural cycling temperature and solar radiation conditions. It is used either for evaluating heating effects on a real time basis, or for determining the temperature equipment reaches under the severest required conditions. 2. APPARATUS. Solar radiation chamber. 2.1 Chamber. The test chamber volume shall be a minimum of ten times that of the volume of the envelope volume of the test item. The chamber’s simulated solar radiation source area shall be a minimum of 125 percent of the horizontal area projection of the test item. 2.2 Solar radiation source. For the purposes of this test, the following spectral distribution of solar radiation is acceptable:
50 to 72 watts/ft2 of infrared (of wavelengths above 7,800 angstrom units), 4 to 7 watts/ft2 of ultraviolet (of wavelengths below 3,800 angstrom units), and the balance visible. The radiation source shall be located at least 30 inches away from any outer surface of the test item. (Lamp vendor’s spectral distribution curves may be used in establishing the spectral distribution within the above specified limits. U. S. Bureau of Standards traceability of this vendor data is waived). 505.1-1 METHOD 505.1 10 March 1975