MIL-STD-810G – METHOD 505.5

Purpose

This method has two objectives:

To determine the heating effects of direct solar radiation on equipment.
To assist in identifying the actinic (photo-degradation) effects of direct sunlight.

Application

Use this method to evaluate equipment that may be exposed to solar radiation during its lifecycle in open hot climates, where heating or actinic effects are a concern. This method is valuable for assessing the effects of direct sunlight exposure (solar spectrum and energy levels at sea level).

Procedure I is useful for determining the temperature rise (above ambient) of materials caused by solar loading.
Procedure II, while not specifically designed for this purpose, can be used to simulate the ultraviolet effects of solar radiation in different locations and altitudes using various radiation sources that reasonably compare to measurements of these natural radiation conditions.
The heating effects of solar radiation differ from those caused by high ambient air temperatures alone, as solar radiation produces directional heating and thermal color variations. In a solar radiation test, the amount of heat absorbed or reflected depends primarily on the absorption or reflective properties of the surface (e.g., roughness, color, etc.) where the radiation is applied. If a glazing system (glass, transparent plastic, or other transparent media, such as a windshield) is part of the test item’s configuration, and the component of concern is exposed to solar energy that has passed through the glazing system, a full-spectrum source should be used.

In addition to amplifying the differential heating of different materials, variations in solar radiation intensity can cause components to expand or contract at different rates, leading to severe stresses and loss of structural integrity. In addition to the issues identified in Method 501.5, consider the following common problems to determine whether this method is applicable to the test item.

Partial List of Possible Effects:

• Obstruction or release of moving parts.
• Weakening of solder joints and bonded parts.
• Changes in strength and flexibility.
• Loss of calibration or malfunction of mechanical couplings.
• Loss of sealing integrity.
• Changes in electrical or electronic components.
• Premature actuation of electrical contacts.
• Changes in the properties of elastomers and polymers.
• Peeling or delamination of paints, composites, surface laminations, and radar-absorbing materials.
• Softening of filling compounds.
• Pressure changes.
• Sweating of composite materials and explosives.