In addition to SWaP, four additional trends influence modern military connector design.
In the high-intensity world of military operations, the technologies that support the troops are essential to deliver performance and safety when it matters most. Even the smallest components—like connectors—can play a pivotal role in ensuring the equipment operates at its peak performance.
Two well-known standards describing military interconnector size, weight, and power (SWaP) specifications help to standardize the designs to simplify the system connection. They are MIL-DTL-83513 (micro-D connectors) and MIL-DTL-32139 (nano-miniature connectors). The exact SWaP parameters vary based on the number and arrangement of pin connections and the housing in a manufacturer’s specific design. The standard also calls out the orientation of the connector, such as straight, 90° angle, PCB mount, or other styles.
The standards limit the current load to ~3A max per contact and can have up to 100 pins per configuration, though exact guidance considers these standards in concert with connector design guidance. And, while SWaP values are the more well-known, four additional advanced trends influence modern military connector design.
Enhanced Durability
Military applications present engineers with a durability challenge. Existing connectors can withstand harsh environments such as subsea and high salt spray concentrations (to comply with the appropriate MIL Specs). However, customers developing new aerospace applications assume total reliability and require durability beyond the existing levels covered in the standard.
An example of the increased durability requirements could come from a manufacturer looking for high-impact connectors that can withstand ten shuttle launches. The company also expects the connectors to be repurposed if supporting components can be reused, which is increasingly common for expensive spacecraft launches. In addition, connectors that do not require replacement at each launch offer substantial cost savings (with a quick payback of any additional capital cost) while improving durability.
Ruggedness: The term “rugged” is related to durability by conveying an item’s resistance to increasingly harsh environments. A current trend is to design sealed connectors into flight controls and landing gear systems. The connectors are easier to install and can endure the stresses of flight to add ruggedness to the assemblies.
Other design conditions for new military connectors include:
- Temperature exposure from –150°C to +150°C
- Environments containing dust, dirt, water, chemicals, corrosion from atomic oxygen exposure
- A range of ambient pressures
- Thermal cycling
- Thermal shock
- Shock exposures up to 300g/load
Signal integrity and EMI/RFI protection
Signal integrity is essential for high-speed military applications operating in rugged environments. Electromagnetic interference (EMI) and radio frequency interference (RFI) can introduce noise and other disturbances into the signal path. These inefficiencies erode the signal strength, compromising the signal and reducing the connectors’ reliability and response time. In addition, EMI and RFI can also have the secondary effect of radiation emissions, which further compromises component performance.
Fortunately, engineers can design in several control measures to address these interference types. The first two control levers are MIL-STD-461 standard compliance and proper signal integrity design. The standard ensures that the connectors should work in their appropriate conditions, while the design practices limit signal crosstalk and reflection that degrade the signal.
Designers can also add shielding, filtering, and grounding to control and direct harmful interference away from the signal to preserve its quality.
Reduced package size and miniaturization
Miniaturization is an enduring trend in nearly all electronics (historically following Moore’s Law, which describes a continual increase in computing density). Along with transistor dimensions decreasing from millimeters in the 1940s to tens of nanometers in the 2020s, thereby enabling miniaturized components, the shift from analog to digital has had compounded positive effects on military connectors.
Increased processing density enables a smaller packaging envelope for the connectors. This advantage releases critical design space for additional design flexibility, saving materials and costs. In addition, smaller sizes can be lighter weight and may have fewer losses due to shorter run paths.
High-speed and high-bandwidth
Modern military operations need technology to respond in real time. As a result, many applications require speeds up to 10Gb/s, with the requirement (either stated or implied) of maintaining reliability. As a result, engineers are adding networking connectors into commercial and military/aerospace avionics designs. These connectors will enable the technology to realize the advantages of 5G for rapid, high-quality, high-volume data transmission.
Fiber Optics: A recent design engineering interest in delivering high-speed and bandwidth military connectors uses fiber optics. These fibers enable efficient, safe, and accurate missile firing from air, land, or sea launch points. Following standards MIL-DTL-38999, 28876, and others, these cables can transmit large amounts of data over long distances with minimal loss of reliability and consistent, high-accuracy performance.
Fiber optics are ideal in several areas. First, they are spatially efficient, enabling smaller package sizes than traditional copper wire, thereby creating redundancy opportunities for increased system resiliency or retrofitting into existing systems to avoid capital expense.
Takeaways
Military applications expose connectors to some of the harshest environments on Earth. Protecting and ensuring connector performance is vital to the success, safety, security, and outcomes of military operations. Engineers are prepared for these challenges, augmenting the current size, weight, and power guidance with enhanced design features.
Boosting durability, signal integrity through interference mitigation, miniaturization to reduce package size, and fiber optics for high-speed and high bandwidth are four approaches that can address rugged environment challenges head-on. Adding these features to connector designs ensures that critical military applications will perform at peak levels when they are needed the most.