The commercial marketplace, driven by consumer demand for increasingly smart gadgets and lifestyle applications, has created an environment where funding for innovation within this sector vastly outstrips budgets available to all but the most well-funded military research programmes. There are therefore obvious technological and cost benefits from integrating COTS components and final products into military systems.
Operationally, there are many commercial product developments which can create a significant advantage to military systems, be that by utilising the latest wireless technologies, increased high speed data transfer, better power consumption, smaller more portable devices, and even compatibility with other systems, the possible benefits are clear.
This pace of technological development creates substantial opportunities for the smart acquisition of capability, when military and civilian requirements are found to be compatible. This approach has great potential to reduce the time needed for the transfer of leading edge technologies into useful military products which provide substantial benefits to the end-user.
In the commercial world, there are some 25 European directives that require CE marking, with some specifying exclusions for military equipment and some not. For example, the Electromagnetic Compatibility (EMC) Directive (2014/30/EU) has no exclusions for military equipment.
In the military domain, EMC compliance is critical since electromagnetic interference may severely impair radio-communications and the functioning of other devices. As commercial products develop with more and more wireless technology, these wireless aspects need also to be considered when being used in a military environment, both in terms of how they may impact, or enhance, operations.
Therefore, the use of commercial equipment in the military domain often requires additional electromagnetic considerations, beyond those normally experienced in the commercial environment, in order to enhance compatibility with potentially sensitive military systems. For example, these may be barriers such as shielded racks and filters, to reduce equipment susceptibility to harsher electromagnetic environments.
In order to assess if any electromagnetic protection is required when developing military equipment, the risk assessment process of Def Stan 59-411 can be used. Def Stan 59-411 Issue 3 was issued on 14 June 2019 and provides the foundation for ensuring EMC in defence procurement. TÜV SÜD was an editor within the original Def-Stan 59-411 EMC Working Group and has carried out development work in support of the Issue 3 update.
Using the guidance in Def Stan 59-411 Part 1, a ‘gap analysis’ process can be used to determine whether the compliance evidence is more or less stringent than the Def Stan 59-411 test limit. Any shortfalls identified will help to specify the degree of additional protection that is required, such as shielding or filter attenuation.
In cases where commercial compliance has yet to be addressed, it can also define a testing strategy that satisfies both commercial and military specifications. This gap analysis strategy can therefore be used to ensure that specifically designed military products can easily be used in a commercial environment, and still comply with relevant equipment directives. This may of course introduce a cost saving for testing a newly developed product.
As this is a common issue, many manufacturers now offer suitable RF shielded racks and enclosures, within which the equipment can be housed without modification so that the validity of the CE marking for the commercial equipment can be preserved.
Ensuring that a power supply is safe and appropriate for a particular product is a complicated process, with typically at least fifteen separate testing considerations to be taken into account. Also, as the military typically operates at 50, 60 or 400 Hz, while domestic supplies operate at 50 Hz, this will affect the power components selected when developing a product.
Power quality tests for military equipment are harsher than those that would be applied for a commercial product to meet CE marking requirements, as equipment upset by power surges is not acceptable for mission-critical defence equipment. The electrical power environment can also be very different in naval vessels, military vehicles and where soldiers rely on batteries or generators in field operations, rather than the consistency of electrical supplies normally experienced in the commercial world.
The ability of military products to operate and survive against physical stresses such as extreme climate, changes in temperature, vibration and shock, is paramount and therefore requires a rigorous testing regime, such as in accordance with Def-Stan 00-35. These military standards help define the testing reequipments for equipment depending on the environment that the equipment will be used in. For example, land or sea environments, the platforms with which equipment may be combined, or the regions of the world in which equipment may be deployed. Understanding and testing to correct operation in the right environments is therefore key to ensuring successful operational deployment, and these requirements significantly exceed normal commercial equipment operation.
As there are so many variables, extra unknown factors may come into play in the real world. For example, while you may have tested for a humid environment, you may not have anticipated that one particular user would leave the product in the sun for long periods of time, before rain rapidly cools it. It is therefore possible to develop tests that combine environments to simulate such “real life” scenarios, reproducing these physical environments in the laboratory under repeatable conditions to simulate the actual environment.
BS EN 60068-2 is a general standard which gives guidance on how to conduct environmental testing. Meanwhile, the defence sector has its own specific requirements which sit alongside this, such as the USA military environmental testing standard, MIL-STD-810. However, as BS EN 60068 is not market or product specific, it is a useful tool to tailor environmental tests specific to each individual product need.
Manufacturers of commercial equipment, that want to take a step into the military market, may assume that this is a complex and costly issue. Indeed, some may over complicate the test process, resulting in unnecessary duplication of compliance-testing. However, testing can be minimised by using gap analysis between Defence Standards and the commercial standards, such as those for CE marking.
About The Author
Pete Dorey is a Principal Consultant at TÜV SÜD a global product testing and certification organisation and has been working with aerospace and defence manufacturers for 50 years.