MIL-STD 810 is a Department of Defense Test Method Standard for environmental engineering considerations and laboratory tests. It is the most popular Military specification used to conduct environmental testing of military products. Given the fact that these products may be exposed to harsh or even extreme conditions, their reliability under stress is essential. It exists so as to ensure that products used for defense-related purposes meet very specific requirements with regard to ruggedness, durability, and performance.
MIL-STD-810 is a series of performance and manufacturing guidelines established by the US Department of Defense for military and commercial equipment and their applications. These guidelines specify allowable parts and environmental condition ranges in which a device such as a power supply, DC-DC converter or a DC-UPS must be able to operate in compliance, to the specification required. MIL-STD-810 is a generally accepted standard of ruggedization testing and compliance for most military equipment in ground mobile applications.
Operating Environment Stresses
The first hurdle for space electronics to overcome is the vibration imposed by the launch vehicle. The demands placed on a rocket and its payload during launch are severe. Rocket launchers generate extreme noise and vibration. There are literally thousands of things that can go wrong and result in a ball of flame. When a satellite separates from the rocket in space, large shocks occur in the satellite’s body structure. Pyrotechnic shock is the dynamic structural shock that occurs when an explosion occurs on a structure. Pyroshock is the response of the structure to high frequency, high magnitude stress waves that propagate throughout the structure as a result of an explosive charge, like the ones used in a satellite ejection or the separation of two stages of a multistage rocket.
Another obstacle is the very high-temperature fluctuations encountered by a spacecraft. A satellite orbiting around Earth can be divided into two phases; a sunlit phase and an eclipse phase. In the sunlit phase, the satellite is heated by the Sun and as the satellite moves around the back side or shadow side of the Earth, the temperature can change by as much as 300°C. Because it is closer to the Sun, the temperature fluctuations on a satellite in GEO stationary orbit will be much greater than the temperature variations on a satellite in LEO. Here again, ceramic packages can withstand repeated temperature fluctuations, provide a greater level of hermeticity, and remain functional at higher power levels and temperatures. Ceramic packages provide higher reliability in harsh environments.
Pyroshock exposure can damage circuit boards, short electrical components, or cause all sorts of other issues. Understanding the launch environment provides a greater appreciation for the shock and vibration requirements, and inspections imposed on electronic components designed for use in space level applications. High reliability and devices with space heritage are key factors in the selection of components for space-level applications. NASA generally specifies Level 1, qualified manufacturer list Class V (QMLV).
The space radiation environment can have damaging effects on spacecraft electronics. Outside the protective cover of the Earth’s atmosphere, the solar system is filled with radiation. The natural space radiation environment can damage electronic devices and the effects range from degradation in parametric performance to a complete functional failure. These effects can result in reduced mission lifetimes and major satellite system failures. The radiation environment close to Earth is divided into two categories: particles trapped in the Van Allen belts and transient radiation. The particles trapped in the Van Allen belts are composed of energetic protons, electrons, and heavy ions. The transient radiation consists of galactic cosmic ray particles and particles from solar events (coronal mass ejections and solar flares).
Missile environments generally cover these parameters: High and low temperature, Vacuum, Shock, Acceleration and Extreme vibration. Designers would generally agree that no one design will be optimum under all conditions for this kind of environment. Therefore, a design compromise must be achieved to reduce the extremes sufficiently and meet performance requirements reliably.
In general, fixed-ground military equipment resides in controlled environments and isn’t subjected to the harsher operating environments of mobile ground, ship, aircraft, missiles, and space equipment.
Low and high temperatures can affect the basic physical properties of semiconductor materials and junctions which, in turn, affect the device- and system-level performance parameters. Temperatures can also cause fatigue, distortion of assemblies, and rupturing of seals due to different coefficients of thermal expansions. The electric propulsion system of a main battle tank can reach temperatures of up to +200°C while aircraft operating temperatures can reach +300°C.
To stay within MIL-STD-883 upper limit of +125°C, these systems must employ cooling measures—which add weight and costs—and consume power. Recent research has found that these limits may be unduly restrictive and that many systems can perform adequately up to +200°C without changes. However, high-temperature electronics above +220°C is an important area of research for the military.
Low temperatures are also of concern. Currently, systems requiring operation at -40°C and lower use military-grade, hermetically sealed ceramic packaged microelectronic circuits. The limited availability and high cost of these devices make commercial plastic encapsulated microcircuit (PEMs) an attractive alternative.
The accuracy and life expectancy of electronic devices can be degraded by sustained high temperatures. There are three ways of dissipating the heat generated by the electronics: convective, diffusive, and radiative. In the vacuum of space there is no thermal convection or conduction taking place. Radiative heat transfer is the primary method of transferring heat in a vacuum, so satellites are cooled by radiating heat out into space.
Shock and Vibration
Shock and vibration are considerations for missiles, high-thrust jets, and rocket engines during operation. Much of the shock and vibration research is concerned with developing models to assess these stresses for PoF analysis.
Moisture or contaminants can cause corrosion failures. Moisture is a special consideration for shipboard military products: combined with the corrosive effects of salt, it can have a devastating effect on electronics. Humidity can also promote the growth of fungi and mold which also cause corrosion. Missiles, in particular, experience heavy exposure to bacteria and fungus. Because they aren’t hermetic, plastic packages are at risk from humidity, although the last decade has seen many reliability improvements in PEMs in this regard.
Contaminants such as sand, snow, and salt can erode surfaces and penetrate into or between components that appear sealed. They are a particular problem in desert or arctic environments. As with moisture, a product’s hermeticity will determine the amount of contaminants that enter the product. Conformal coatings are used to protect printed wiring boards from humidity, corrosive gases, solvents, dust, and sand. Worldwide solvent restriction legislation is causing a transition from solvent-based urethanes, acrylics, and paraxylene to solid silicone coatings. Moreover, silicone coatings have been shown to outperform solvent-based coatings. In the 1980s, the automotive
industry’s usage of conformal coatings surpassed that of defense for the first time. While the automotive industry has switched to silicones, defense continues to use the older coatings partly because their lower production volumes and longer product life cycles do not economically justify switching at this time.
Radiation-hardness assurance (RHA) is critical for components used in satellites and avionics systems as well as in military systems designed to survive radiation from the explosion of nuclear weapons. Hermetic devices are currently preferred for RHA. However, there is some evidence that PEMs can withstand the effects of radiation. Moreover, commercial applications, such as nuclear power plants and therapeutic radiation equipment, also require RHA. This should spur the development of commercial-grade RHA devices.
Electricity can also cause electronics failures. Electromigration and electrical failure mechanisms from high temperatures are of particular concern to the military.
Non-Operating Environment Stresses
The two main non-operating environments are storage and dormancy. Storage is where the electronics are totally inactivated and residing in a storage area. Dormancy is the state in which the equipment is in its normal operational configuration and connected, but not operating. Temperature, shock and/or vibration, and corrosion account for most non-operation failures.
For example, low-temperature non-operating requirements can exceed operating requirements. During nonoperation, not only are the electronics themselves not generating heat but environmental control systems aren’t operational. This is true for missiles which are often stored for long periods in cold climates.
During shipping, handling, and transportation, electronics are subjected to substantial shock and vibration. Because shock and vibration cause cracking, PEMs, which are mechanically more rugged, are preferred to ceramic packaging. What isn’t known (yet) is the long-term storage life of PEMs, an important consideration for missiles that have a storage requirement of 20 years. A study of PEMs stored and operated for 10 to 15 years didn’t show any appreciable degradation due to storage.
Electrical failure, electrolytic corrosion, and radiation failure are generally not problems in non-operating environments. Likewise, high-temperature failures do not occur in non-operating environments where—even in full solar radiation—products do not generally reach temperatures above the MIL-STD-883 limit of +125°C
MIL STD 810
Thankfully, properly designed rugged military servers and workstations, certified to Military Standards, are prepared for this. In other words: designed, manufactured, and tested to battle harsh conditions with ease. In the United States, the Military Standard (also written as MIL-STD) is enforced by the Department of Defense and maintained by the U.S. Air Force, Army, and Navy. It exists to ensure products meet specific requirements for various defense-related purposes. There are over 40 Military Standards and a profusion of Test Methods encompassing a myriad of use cases. Some of the most popular MIL-STDs that Ruggedized Computers test for are: MIL-STD-810; MIL-STD-461; MIL-S-901 and MIL-STD-167
The MIL-STD-810 test method is used to generate confidence in the environmental worthiness and overall durability of the ‘material system’ design. The testing process follows guidelines, which include program documentation, program roles, test standards, and laboratory test method guidelines for all categories. The standard describes environmental management and engineering processes that can be of enormous value to generate confidence in the environmental worthiness and overall durability of a system design. The standard contains military acquisition program planning and engineering direction to consider the influences that environmental stresses have on equipment throughout all phases of its service life. The document does not impose design or test specifications.
Rather, it describes the environmental tailoring process that results in realistic materiel designs and test methods based on materiel system performance requirements. MIL-STD-810, emphasizes tailoring an equipment’s environmental design and test limits to the conditions that it will experience throughout its service life, and establishing chamber test methods that replicate the effects of environments on the equipment rather than imitating the environments themselves. Although prepared specifically for military applications, the standard is often used for commercial products as well.
MIL-STD-810 addresses a broad range of environmental conditions that include: low pressure for altitude testing; exposure to high and low temperatures plus temperature shock (both operating and in storage); rain (including wind blown and freezing rain); humidity, fungus, salt fog for rust testing; sand and dust exposure; explosive atmosphere; leakage; acceleration; shock and transport shock; gunfire vibration; and random vibration.
The standard, 804 total pages, is broken up into three parts:
- Part One: Environmental Engineering Program Guidelines
- Part Two: Laboratory Test Methods
- Part Three: World Climatic Regions – Guidance
The standard’s guidance and test methods are intended to:
- Define environmental stress sequences, durations, and levels of equipment life cycles;
- Be used to develop analysis and test criteria tailored to the equipment and its environmental life cycle;
- Valuate equipment’s performance when exposed to a life cycle of environmental stresses
- Identify deficiencies, shortcomings, and defects in equipment design, materials, manufacturing processes, packaging techniques, and maintenance methods; and demonstrate compliance with contractual requirements.
The laboratory test methods are broken down into 24 categories and thereafter procedures (specific tests or levels) appropriate to the environment in which theequipment is expected to be used. The actual tests are carried out according to pre-defined test plans and criteria. The testscan be laboratory or natural environment field tests, or a combination, whichever applies. The test procedure is dependent on the environment tested. The procedure(s) and its execution provide the basis for collecting the necessary information. After completion of each environmental test, the test data is examined and recorded in accordance with material specifications and program guidelines. A final test report will be created for each test, which includes an analysis of the test results. This report will then be available to the customer.
Some products will carry a MIL-STD 810E rating and some may state they are MIL-STD810F compliant. The Latest MIL-STD-810G is a revision of MIL-STD 810F and 810E. Thetests and methods are basically the same but much of the standard has been rewritten toprovide clearer direction.
Example tests and procedures
Test Method 500.2 – Altitude
To observe low air pressure effects on either operational or non-operational design parameters.Standard: MIL-STD-810F, Method 500.2, Procedure I & II• Environment: 40,000 ft. and 70,000 ft. operational
Test Method 500.5 – Low Pressure (Altitude)
The purpose of this method is to determine if a product can operate in a low pressure setting or withstand swift pressure changes. It does not cover products that are to be installed or operated in space.
Test Method 501.5 – High Temperature
This test is used to determine the effects on the material as well as performance of the rugged computer under high temperature conditions. Not for long-term exposure to high temps or if you’re trying to determine the effects of degradation on a rugged server.
Test Method 502.5 – Low Temperature
Much like the previous test method, it ensures proper material reliability during low temps but it also focuses on performance during storage, operation, and manipulation. Don’t use this test method if you plan on having the product in an unpressurized environment.
Test Method 503.5 – Temperature Shock
This would be a great test for our Aviation & Aerospace Scenario. It is used to determine sudden changes in temperature and its effect on the physical rugged server as well as performance.
Test Method 504.1 – Contamination by Fluids
If you are expecting exposure to liquids during the life cycle of the program or application, whether that’s temporarily, intermittently, or for long periods of time, this test method will ensure proper performance as well as the physical effects on the computer as a whole.
Test Method 505.5 – Solar Radiation (Sunshine)
Use this test method if you are expecting your rugged computer to be exposed to solar radiation, such as direct exposure to sunlight.
Method 506.5 – Rain
This test, even though it states “rain”, is not only for environments that experience a lot of rainfall but it deals with other factors such as water spray or dripping water during storage, transport, or operation. The rugged chassis plays a major role here as it helps prevent any water intrusion to the internal system components.
Test Method 507.4 – Humidity
HumidityA humidity test simulates the moisture-laden air found in tropical regions. Standard: MIL-STD-810F, Method 507.4 Procedure I, Cycle I• Environment: 240 hours, 95% RH
Test Method 507.4 – Temperature Humidity Bias
An operational test that evaluates the reliability of the device package in humid environments.Standard: MIL-STD-810F, Method 507.3• Environment: 85°C, 85°/s RH, high line input voltage
Test Method 507.5 – Humidity
This test methods combines heat and water and measures the effects on the rugged server when exposed to warm, humid atmospheres.
Test Method 508.4 – Fungus
To determine if a material (or materials) will support the growth of specific fungi.Standard: MIL-STD-S1OF, Method 508.4 Section U• Environment: Severe climate conditions
Test Method 508.6 – Fungus
A computer system can have fungal growth, and it may impact the metal and/or performance. This Test Method tests how the system would work under those rare circumstances if fungal growths were a problem.
Test Method 509.5 – Salt Fog
If there’s a protective coating on a rugged computer, it needs to get tested as well for its effectiveness. Not only that, this Test Method ensures that even if salt deposits make it onto the physical or electrical components of the rugged computer, it will work just fine.
To determine the resistance of the equ~ornent to the effects of a salt atmosphere, primarilyStandard: MIL-STD-810F, Method 509.1 Procedure• Environment: Salt fog harsh environment
Test Method 510.5 – Sand and Dust
Covering two actual tests in one, this is quite a popular Test Methods for programs or applications that will put rugged computers in environments where dust or sand particles are a concern. It tests the openings and crevices of the rugged computer and measures the effectiveness of filters. The test does span into performance parameters as well, meaning how is the rugged server doing if under these conditions and if particles do penetrate the exterior enclosure.
Test Method 511.4 – Explosive Atmosphere
To determine the ability of equipment to operate in the presence of an explosive atmosphere.Standard: MIL-STD-810F, Method 511.4, Procedure I, operational* Environment: Fuel-Air Explosive Atmospheres
Test Method 511.5 – Explosive Atmosphere
This test does not measure the ruggedness of the computer around explosive material rather it measures if the computer can operate in a fuel-air atmosphere without causing an explosion or if an explosive or burning reaction occurs, will it be contained within the rugged server. A popular test method for the Oil & Gas industry.
Test Method 512.5 – Immersion
Yes. Exactly what it sounds like. This is a test method that measures how well a rugged computer can perform while immersed or partially immersed in water. It measures performance before, during, and after the procedure to arrive at a conclusion.
Test Method 513.6 – Acceleration
Perfect for aircraft-dependent programs or applications. This test method ensures that a rugged computer can function properly when exposed to the high accelerations an aircraft may pose.
Method 514.3, category C -Mechanical Shock
To determine the ability to withstand mechanical shocks from suddenly applied forces or an abrupt change in motion produced by handling, transportation or fieldoperation. Standard: MIL-STD-810F Method 514.3, category C .• Environment: 75 g 11 ms saw tooth shock, 3± shock/axis, 3 axis, 18 total.
Test Method 514.6 – Random Mechanical Vibration
To evaluate the construction, materials and mounting of the device for ruggedness.Standard: MIL-STD-810F Method 514.5 and MIL-HDBK-344A• Environment: Vibration step from 21 — 41 g.
Test Method 514.6 – Vibration
A very popular method! When vendors state ‘shock & vibe certified’, this is one of the methods that they are referring to. It ensures the rugged components function appropriately through vibration levels.
Test Method 515.6 – Acoustic Noise
Think noise test. If there are acoustics that could potentially affect the performance of the computer, this test makes sure to identify said problem.
Test Method 516.6 – Shock
If you want to remember one Test Method, this would be it. The infamous Shock testing method, most searched for test method: MIL-STD-810G 516.6. It measures how effective a rugged computer is in withstanding shock during transportation, handling, and service. Passing this Test Method is the equivalent of being able to call your computer rugged by military standards.
Test Method 517.1 – Pyroshock
Tests how well a rugged server performs when a nearby explosive shock goes off. It looks at how structurally sound the rugged chassis is during and after the explosion and how well the overall system maintains stability.
Test Method 518.1 – Acidic Atmosphere
This test determines how a rugged computer and its coating withstand corrosive atmospheres and at times even during operation.
Test Method 519.6 – Gunfire Shock
Another popular test method that measures how well a rugged server can withstand the short bursts of gunfire shock and if it will have a negative impact on the performance of the system.
Test Method 520.3 – Temperature, Humidity, Vibration, and Altitude
It measures how well a rugged computer system squares up to all of the environmental factors combined. This does not only apply to aircraft but can also be used on ground vehicles, obviously at that point the Altitude portion of the test is omitted.
Test Method 521.3 – Icing/Freezing Rain
A test that validates a rugged computer under freezing conditions that may cause a system to freeze or ice over. This method also covers the way in which operators can administer to defrost the system without harm.
Test Method 522.1 – Ballistic Shock
This is another variation of a shock test where a rugged computer is tested against infrequent shock effects caused by elevated levels of momentum. Think of a moving object where the computer sits and a sudden stop occurs. Think like a crash test from high speed to zero or vice versa. Simply put, abrupt momentum shift.
Test Method 523.3 – Vibro-Acoustic/Temperature
Another mixed test method where multiple environmental factors are tested at once. This method, however, focuses on externally carried aircraft stores during flight.
Test Method 524 – Freeze / Thaw
All about the changes of going from a solid to a liquid or vice versa state. If a computer froze over and it is currently thawing, what are the effects on the overall system structure and performance.
Test Method 525 – Time Waveform Replication
Ever heard the expression “to withstand the test of time”? This is the method for that. If a rugged computer is known to be exposed to certain harsh conditions, this test method ensures how long it can withstand its own environment before changes start to occur.
Test Method 526 – Rail Impact
During transport, a lot of things can happen. This test ensures that the rugged server will survive likely scenarios of car impact during transport.
Test Method 527 – Multi-Exciter
All about replication of an entire environment. Whether derived from actual reports or replicated at best ability of the test lab, this test method applies multiple stress factors at once to see how well the rugged computer system will battle until it starts to show signs of weakness.
Test Method 528.1 – Mechanical Vibrations of Shipboard Equipment (Type I – Environmental and Type II – Internally Excited
Strictly for shipboard equipment installed on ships, the test method measures environmental or internal vibrations and its effects on the computer.
The Test Methods of MIL-STD-810G
Test Method 500 – Low Pressure (Altitude)
Test Method 501 – High Temperature
Test Method 502 – Low Temperature
Test Method 503 – Temperature Shock
Test Method 504 – Contamination by Fluids
Test Method 505 – Solar Radiation (Sunshine)
Test Method 506 – Rain
Test Method 507 – Humidity
Test Method 508 – Fungus
Test Method 509 – Salt Fog
Test Method 510 – Sand and Dust
Test Method 511 – Explosive Atmosphere
Test Method 512 – Immersion
Test Method 513 – Acceleration
Test Method 514 – Vibration
Test Method 515 – Acoustic Noise
Test Method 516 – Shock
Test Method 517 – Pyroshock
Test Method 518 – Acidic Atmosphere
Test Method 519 – Gunfire Shock
Test Method 520 – Temperature, Humidity, Vibration, and Altitude
Test Method 521 – Icing/Freezing Rain
Test Method 522 – Ballistic Shock
Test Method 523 – Vibro-Acoustic/Temperature
Test Method 524 – Freeze / Thaw
Test Method 525 – Time Waveform Replication
Test Method 526 – Rail Impact.
Test Method 527 – Multi-Exciter
Test Method 528 – Mechanical Vibrations of Shipboard Equipment (Type I – Environmental and Type II – Internally Excited)
Malfunctions and failures
Test data shall include complete identification of all test equipment and accessories. The data shall include the actual test sequence used and ambient test conditions recorded periodically during the test period. The test record shall contain a signature and data block for certification of the test data by the test engineer.
Failure criteria is an important factor in MIL-810-C testing. This military test standard states that the item shall have failed the test when any of the following occur.
The monitored functional parameters deviate beyond the established acceptable limits. There is a catastrophic or structural failure of the unit under test. Mechanical binding or loose parts result in component failure or a hazard to personnel safety. These can include items such as screws, clamps, bolts and nuts.
A malfunction of the unit under test is considered a failure. The term malfunction should ideally be defined prior to the test starting. Finally, degradation of performance beyond pretest record or equipment specification requirements.
It is important to note that certain types of equipment are often expected to demonstrate lesser performance at an environmental extreme, partially low temperature. A failure would occur only if degradation is more than expected. Examples of these equipment types are propellants and electrically driven devices. This degradation includes any additional deviations from acceptable criteria established before the test and recorded. Also, deterioration, corrosion or change in tolerance limits of any internal or external parts which could in any manner prevent the test item from meeting operational service or maintenance requirements
Compliance to MIL-STD-810
MIL-STD-810 is a flexible standard that allows users to tailor test methods to fit the application. As a result, a vendor’s claims of “…compliance to MIL-STD-810…” can be misleading, because no commercial organization or agency certifies compliance, commercial vendors can create the test methods or approaches to fit their product. Suppliers can—and some do—take significant latitude with how they test their products, and how they report the test results. When queried, many[quantify] manufacturers will admit no testing has actually been done and that the product is only designed/engineered/built-to comply with the standard. This is because many of the tests described can be expensive to perform and usually require special facilities.
When selecting a rugged product, it is essential to check whether it is ‘designed to meet’, tested or compliant with MIL-STD-810 and that the actual tests to which the product is compliant reflect the environment in which the item is to operate. For instance, a product may have been tested to 501.5 III A2 (High temperature, Tactical standby to operational, Basic Hot) but has it been tested to 510.5 I (Sand and Dust, blown dust, 24 hour test) which may highlight problems with ventilation and heat management when operating in the real world?
Consumers who require rugged products should verify which test methods that compliance is claimed against and which parameter limits were selected for testing. Also, if some testing was actually done they would have to specify: (i) against which test methods of the standard the compliance is claimed; (ii) to which parameter limits the items were actually tested; and (iii) whether the testing was done internally or externally by an independent testing facility.
Finally, there are limitations inherent in laboratory testing that make it imperative to use proper engineering judgment to extrapolate laboratory results to results that may be obtained under actual service conditions. In many cases, real-world environmental stresses (singularly or in combination) cannot be duplicated in test laboratories. Therefore, users should not assume that an item that passes laboratory testing also will pass field/fleet verification tests.