In addition, as equipment such as communications and radar devices, and their sub-systems including switched-mode power supplies, evolve to operate at higher frequencies, EMC protection measures must also improve to be effective at the higher frequencies. This can require significant changes in the techniques employed.

Tougher specifications

Experienced defence contractors are now dealing with demands to take EMC protection in new systems to an unprecedented level. A recent project completed by Tekdata Interconnections, to develop wiring harnesses for communication equipment used in homeland security applications, specified EMC criteria that are more severe than any applied in previous projects. The team was able to satisfy the requirements using proprietary best-practice techniques; however, improved design techniques are now being developed in anticipation of further increases in EMC specifications.

At the same time, the new harnesses were able to meet requirements for low overall weight, as well as compact physical dimensions; such demands are also growing in importance as modern forces seek to become more nimble and capable of extremely rapid tactical response against increasingly unpredictable and improvised enemy action. In this latest harness development project it was possible to halve the physical space requirement to fulfil the complete system wiring requirements, compared to previous similar projects.

Design challenges

Building instruments for space observation has much to teach engineers about lightness in the design of flight harnesses. There are strict limitations on payload, particularly with smaller launch vehicles such as Ariane 5, which was used in May 2009 to transport  the Herschel Space Observatory and a sister vehicle, the Planck Satellite, 1.5 million kilometres into space to observe minuscule thermal and microwave signals originating from the birth of stars. Moreover, bespoke design is necessary to minimise the thermal mass of the harness so as not to overload the vehicle’s cooling system. The detector plates of instruments such as Herschel’s Spectral and Photometric Imaging Receiver (SPIRE) and the High-Frequency Instrument (HFI) aboard the Planck Satellite operate at temperatures close to absolute zero; as low as 0.1 Kelvin in the case of HFI.

To minimise the weight and power of the cryogenic cooling system, all components including the electrical interconnects to the detectors must impose the lowest possible heat burden. Among numerous custom interconnects created specifically for SPIRE, some highlights developed by Tekdata include nano-density terminations and a micro-miniature 12-core shielded cable having a very small outside diameter of 1.6mm.

Obsolescence management

Successful space projects such as Herschel and Planck result from many years – sometimes decades – of planning, funding and technical effort. Indeed, the aerospace, defence and, increasingly, automotive spaces are characterised by the demand for technical support throughout far longer periods than normally required for consumer or industrial equipment. To operate effectively in these markets, companies must have well developed systems and expertise to manage issues such as the need to keep accurate records of designs, to be able to retrieve archived drawings and tooling quickly, and to deal with obsolescence among bought-in components. Other valuable capabilities include designing-in improvements where desirable while maintaining form-, fit- and function-compatibility with the original system.

Resolving obsolescence issues: engine control system for which replacement parts are made

Computer aided engineering can help companies meet these ideals. However, some customers have been known to request support for equipment originally designed before computerisation. This can be more challenging, but may benefit from access to staff who were involved with the project originally. These may be design engineers or component engineers with detailed technical knowledge or supply-chain contacts, or production staff such as equipment operators. Their knowledge can be valuable to help train new operators, or to inform of any build issues encountered and the solutions employed.

As far as bought-in components are concerned, there are a number of established mechanisms to protect against obsolescence. These can include last-time-buys, as well as links with specialist stockists who maintain suitable long-term storage and testing facilities for obsolete components. Commercial or industrial-grade equivalents can also be up-screened to permit use in military or aerospace projects.

Long-term support for older, analogue equipment is usually more straightforward than for more recent, digital equipment. Component manufacturers tend to support analogue products for longer, and later equivalents may be available even if the exact original part is not. Digital ICs, on the other hand, have a far more transitory existence as manufacturers move on quickly to later and better product generations.

It is also worth mentioning that connector manufacturers often retain tooling for obsolete connectors, which may be used as-is for making a special batch of obsolete product. Failing that they can make replica tooling, although this may entail significant one-off costs. Either way, careful estimates of quantities for last-time buys usually help ensure costs don’t spiral out of control.

In all situations, the ability to assess accurately the costs involved in providing the support required is vitally important. Factors such as the expense of re-qualifying a product if modifications have been made, or the impact of a high Minimum Order Quantity for an obsolete component must be considered and carefully calculated to ensure that the support required can be delivered at a cost-effective price.

Overall, there is no effective standardised approach to providing long-term support and managing obsolescence; it depends on the total commitment of those involved, to deliver the best possible solution to customers’ requirements.

Continuous investment in knowledge, equipment and facilities, however, is central to delivering the high-quality products and services expected by customers; including achieving the highest applicable quality assessments and approvals, acquiring new design techniques to meet increasingly tough specifications, building up in-house engineering skills, and investing continuously in equipment and properly organised premises to manufacture and test the latest technologies. Without proper attention to these issues, it is simply not possible to continue to meet the highest standards, going forwards.

Mark Howitt, Business Development Manager, Tekdata Interconnections

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