Hypersonic Missiles Demand Unique Coaxial Cable Assemblies

Hypersonic missiles represent the most significant advancement in defense weaponry since the 1960s. However, they also present substantial challenges. The term “hypersonic” describes any speed faster than five times the speed of sound. In fact, these missiles are so fast that, as they travel, their speed can alter the adjacent air molecules. Compared to ballistic missiles, which are fast but travel along a predictable trajectory, and cruise missiles, which are accurate but slower, hypersonic weapons combine speed and accuracy. In addition, they are low-flying and maneuverable, designed to be too quick and nimble for traditional missile defense systems to detect in time to launch.

RF technology is key to powering many advanced electronics applications found in hypersonic missiles. However, designing a crucial RF interconnect system that will perform well and withstand the extraordinary environmental and technical conditions presented by hypersonic missiles requires unique, highly customized coaxial cable solutions to prevent failure.

For example, a hypersonic missile utilizes multiple antennas and sensors with phase-matched or time-matched cables. These elements must survive at speeds that can exceed Mach 5, at times topping 5,000 miles an hour. At such speeds, the temperature on the surface and in the boundary layer of the missile may exceed 1,800°F (1,000°C)

During its journey, hypersonic missile guidance will reach temperatures ranging from 200-250°C, or even as high as 600-1,000°C. This creates a unique material challenge as extreme temperatures will melt the plastics and polymers typically used in coaxial cables.

High-performance dielectrics and phase-matched systems are essential to meet phase versus temperature requirements. A hypersonic missile will go through the top of the atmosphere, generating vast amounts of heat, similar to a space shuttle during re-entry. As the cable moves from cold to very hot temperatures, the phase matching between cables needs to track.

Hence, phase is a crucial parameter for detection and measurement in RF systems that rely on high accuracy continuous transmission and reception of RF signals. RF signals must travel through coaxial cables at consistent speeds regardless of environmental factors. Temperature variations degrade the electrical match between coaxial cable assemblies. That small amount of degradation, known as its phase tracking characteristic, can adversely affect system performance.

For example, the electronically steered antennas used in many RF applications employ an array of radiating elements to steer antenna beams rather than physically moving an antenna. Beam steering for transmission or reception is performed by adjusting the phase of the individual antenna elements in the array. High-frequency transmission lines feed each antenna array element. The accuracy of the signal phases presented to each array element depends on the phase accuracy and stability of the cable assemblies. Therefore, cable assemblies optimized for phase performance usually exhibit minimal changes in phase with temperature, or at least very predictable ones.

Modern missile systems also combine extensive communications equipment packed within a highly confined space. This creates a demand for novel solutions that combine a small form factor to reduce weight, with a rugged construction to withstand the high-impact and vibration conditions from deployment to target.

Silicon Dioxide Coaxial Cables Answer the Call

Times Microwave Systems developed a proprietary silicon dioxide dielectric (SiO2™) to address these unique challenges. Silicon dioxide is well known and used in the microelectronics industry for its excellent insulating properties.

The SiO2™ construction starts with a solid oxygen-free copper center conductor, a silicon dioxide insulating dielectric, and a stainless-steel jacket with copper cladding to act as the outer conductor.

Low loss, high-velocity silicon dioxide dielectrics excel in extreme environments as they provide excellent phase stability and can perform at extreme temperatures ranging from just above absolute zero to  well over1,000°C. In addition, compared to other cable types, SiO2™ cables provide exceptionally low hysteresis, with phase and loss returning to the same values at a given temperature even after extreme excursions.

The metal and silicon dioxide dielectric construction make the cable resist radiation naturally, up to 100 MRads. All connectors for Times’ SiO2 cable assemblies use a crack-free, fired glass seal to provide the optimum microwave performance. The stainless-steel jacket is welded to the connectors with laser beam technology to create a hermetic seal.

5 Steps to Find the Best RF interconnect Supplier

 To ensure the best possible performance for demanding hypersonic missile applications, as expediently and cost-effectively as possible, consider the following when choosing the optimal RF interconnect supplier:

Qualifications and heritage: Many suppliers offer a good list of standard capabilities, but hypersonic missile requirements are unique. Look for partners that have experience in military and defense.

Dedicated technical experts: Always ask to speak with technical experts. The complexity of hypersonic missile applications requires an effective partnership; choose a supplier that will work collaboratively as an extension of your design team. Hypersonic missiles do not use a standard solution, so it’s vital that the RF supplier’s technical team asks questions and listens to understand the application’s unique needs. Don’t work with a supplier committed to selling the same product they are selling everyone else. The supplier should also help you understand your application’s electrical and mechanical trade-offs.

Breadth of products:  A provider that offers a broad range of products is better equipped to sell the right system for your application. To select the right materials, choose from multiple cable constructions, various connector designs (low power, high power, etc.), and assembly techniques, all from the same supplier. Many technical standards must be met for products deployed in hypersonic missiles, such as using only acceptable materials or mil-spec cable constructions. There is, however, no standard for how to apply these materials to construct an RF solution that is reliable time after time. That is where your supplier’s expertise and access to a full range of product options are needed.

Manufacturing execution: Ideally, an RF supplier has all the technology and products and understands how to put them together into a final product. The next qualification to consider is the supplier’s manufacturing operations. Does the company have robust facilities and processes to support execution? Cleanroom manufacturing capabilities are essential. Traceability is also vital in managing all the parts that make complicated assemblies. What quality standards does the supplier follow? What about extended services?

Agility: Be sure to choose an RF partner that is strong enough, both financially and operationally, to deliver and survive through turbulent times.