Solar Radiation (Sunshine), MIL-STD-810 Method 505 is used to evaluate thermal and actinic effects on equipment caused by exposure to the sun. This testing is performed in specially designed environmental chambers. This test methodology can be tailored to simulate spectral exposures at high altitudes where increased levels of Ultraviolet (UV) light are present.
This method has two procedures, Procedure 1 – Cycling and Procedure 2 – Steady State. Procedure 1 is used to evaluate response temperatures caused by simulated solar exposure. Procedure 2 investigates the actinic effects on test items to simulated long term exposure to sunlight.
While both procedures use artificial lighting to simulate solar exposures, different levels of radiation are used in testing. While cycling uses expected levels of exposure, steady state uses levels of approximately 2.5 times normal exposure.
Thermal Solar Radiation Effects and Testing
Equipment can experience numerous effects from solar induced temperatures. These include changes in strength or elasticity, degradation of elastomers and polymers, delamination of coatings and adhesives, and loss of seal integrity.
Equipment that is exposed to solar radiation in induced conditions, such as a vehicle crew compartment, may experience extreme differential heating. In such cases it preferred that Solar Radiation (Sunshine) testing be performed as opposed to solely relying on Method 501 High Temperature testing. This testing can be performed using mocked up enclosures that simulate the expected exposures.
Normal test duration for this procedure is at least three 24-hour cycles. If the maximum of the previous 24-hour during three cycles, then the cycles are repeated until the peak temperatures are reached or seven cycles have been performed.
Actinic Effects of Solar Radiation and Testing
Actinism is a property of solar radiation that causes photochemical and photobiological reactions to occur. Materials exposed to the sun can be degraded by Ultraviolet radiation. This can result in chalking and fading of coatings, deterioration of elastomers and polymers, and fading of colors in plastics and fabrics. Natural exposures of UV rays vary according with altitude as there is less atmospheric interference at higher altitudes.
Testing for actinic effects with Procedure 2 requires a 4-hour lights off period for each 24-hour cycle to allow for thermal cycling. For equipment that is continuously in an outdoor environment a minimum of 56 cycles is recommended.
Special Considerations for Testing
There are a number of items that should receive special consideration when planning solar radiation testing:
- Tailoring is required to determine which method and level of testing is required. This is of great importance as this testing is costly and can require significant time. Guidance for irradiance and spectral distribution at high altitudes can be found in Annex A of the standard.
- The use of arc type lights presents significant dangers to humans and can cause sunburn and blindness. Care should be taken to ensure that exposure to high UV levels is prevented.
- Arc lamps can cause a buildup of ozone. Care should be taken in adequately monitoring ozone and removing concentrations of the gas from enclosed areas.
- Care should be taken to ensure that temperatures do not exceed desired levels as ignition of materials may occur.
- The combined effects of temperature and solar radiation can cause outgassing of VOCs, Carbon monoxide, and Phthalates. Care should be taken to monitor for these gasses with sensors to protect personnel.
- Xenon lamps ignition pulses can exceed 60 kV. Additionally, these bulbs can explode violently.
- Finally, spectral power distribution must be monitored and maintained. This involves the use of pyranometers and spectroradiometers. Significant guidance is provided in the standard in Annexes B and C to address these concerns.
Detailed Environmental Test Plan Templates
CVG Strategy offers EZ-Test Plan Templates for MIL-STD environmental (climatic/dynamic) and EMI/EMC testing documentation. Our Detailed Environmental Test Plans (DETP)s are written as specified in MIL-STD-810 Task 405. They are available for specific applications such as Ground Mobile, Ground Stationary, and Shipboard Controlled, Shipboard Uncontrolled, and Aircraft Military.
These DETPs include appropriate test methods, (such as MIL-STD-810 Solar Radiation (Sunshine) addendums for product specific information, test labels for photo identification and data sheets for collection of required data. Profile (LCEP).
Our Electromagnetic Interference Test Plans are written as specified by the Department of Defense. They contain the test methodology, addendums for product specific information, test labels for photo identification and data sheets. These plans are available for procedures listed in MIL-STD-461 and are also available for MIL-STD-1275, MIL-STD-704, and MIL-STD-1399-300.
Custom Test Plans are also available for applications not covered in the EZ-Test Plan offerings. These plans can be written for any number of applications and their relevant standards.
Put CVG Strategy’s Experience to Work for You
Companies of all sizes, from start up to established product developers, face challenges in product test and evaluation. This can particularly be the case when a product is developed for a new market sector or expanding sales internationally.
Properly tested products prevent costly product recalls, product redesign, and product liability. They maintain customer satisfaction and keep your company’s reputation in good standing. Contact CVG Strategy to see how our testing services can assist your engineering team with Solar Radiation (Sunshine) MIL-STD-810 Method 505, or any other test and evaluation concern.