Choosing connectors to address the challenges facing NewSpace satellite designers.
Recent years have seen the emergence and the rapid growth of the so-called ‘NewSpace’ sector as private enterprise continues to expand its presence in the potentially lucrative businesses of everything from space tourism to commercial communications and asset tracking. According to market intelligence firm Euroconsult this market grew by 8% last year and is expected to reach over $737B within a decade. Much of that growth will come from developing the satellites needed to deploy many of the new and emerging space-based services.
Thanks to the unique environment in which they operate, electronic systems for satellites present engineers with additional challenges over and above those they face when developing applications for use on Earth. Among these are operation in a vacuum and at extreme temperatures, protecting against radiation, and delivering rugged solutions that must function reliably for many years.
While several standards have been created to certify the reliable operation of space-grade components, qualification to these standards is typically a lengthy and expensive process. This is out of step with the pressures that today’s NewSpace satellite designers face to optimize performance and minimize time-to-market to maintain competitive advantage and ensure commercial viability. Of course, these designers still need to pick products that are tested to the relevant standards for space, but they do not necessarily want to be restricted to choosing only those with official certification as this can lead to prohibitive cost models at the same time as limiting access to the latest technologies.
Connector selection
The challenge of creating robust system architectures in satellite applications is particularly acute when it comes to connectors and cable assemblies, which are some of the bulkier individual elements of an electronic circuit (and, therefore are expected to meet stringent size and weight criteria). With engineers increasingly seeking ‘off-the-shelf’ interconnect technologies for satellite design, it’s important to understand what criteria need to be considered when reviewing datasheets or talking to the connector manufacturer.
Potential applications
The absence of atmosphere and operation in a vacuum presents satellite designers with problems that their counterparts working on earth-based designs often don’t have to consider. Consider the high-energy charged X-rays and gamma rays that are produced in space. Because these particles can cause degradation or failure of electronic systems, it becomes essential to choose or develop solutions for shielding against cosmic radiation. This is likely to mean conductive enclosures that prevent the reception of radiation, as well as shielded cables that minimize the impact of radiation on the system.
Cosmic rays are not the only radiation of concern. The effect of thermal radiation when a satellite is in direct sunlight should also be considered, as should thermal cycling that occurs when satellites rotate, placing any electronics on or near the outside in alternating conditions of extreme heat and extreme cold. Indeed, moving between facing the sun and facing the earth, a satellite can experience temperature variations of more than 400°C. This makes assessment of maximum and minimum temperature ratings of the chosen connectors and cabling vital and, in some cases, may mean speaking to suppliers to specify additional testing that anticipates operational life in temperature extremes.
Another issue of concern is outgassing. Also known as offgassing, this is a situation in which the absence of an atmosphere causes plastics and other materials used in connectors and cable assemblies to slowly release volatile compounds as a gas or vapor that can subsequently impact equipment operation. In the past, this problem has led to degraded performance of charge-coupled-device (CCD) sensors in space probes and impacted camera performance when the released gases condense on other system components such as camera lenses, impacting their performance or making them unusable. Thus, it is important to check maximum levels of outgassing when choosing connectors and cables.
One fundamental aspect to consider when selecting a connector for satellite applications is that of reliability, ensuring that the technology can not only withstand the rigors of lift-off but will also operate as expected for many years without any possibility of ‘in-field’ repair. This means carefully reviewing connector specifications with respect to their ability to withstand acceleration, shock, and vibration, and adding additional mounts or latches as appropriate.
Finally, so-called SWaP-C pressures mean minimizing size and weight is a challenge for designers of both earth-bound and space-based applications. SWaP-C’s significance is particularly important when it comes to satellite applications in which every extra portion of board space and every extra ounce has direct impact on cost. This means it can pay dividends to spend time identifying the smallest and lightest connector solutions for a given performance and reliability rating.
Commercial solutions
The good news is that there is a growing market of commercial interconnect technologies that are not just suitable for many aspects of satellite deployment but, increasingly, have been specifically designed with that target market in mind, being optimized in terms of performance and cost while meeting all the criteria necessary for successful operation in space.
It is now possible, for instance, to find COTS (commercial off-the-shelf) high-reliability 2A and 3A, 2mm and 1.25mm pitch connectors in single- and double-row configurations that are rated for vibration up to 20G and shock up to 100G, and that can withstand temperatures as low as –65°C and as high as +150°C.
Available with jackscrews, stainless steel mate-before-lock screw fixings, or miniature latching for full vibration resistance and maximum strain relief, these connectors conform to rigorous NASA specifications for outgassing and provide a low-profile, low-weight solution for all variations of satellite cable-to-board, board-to-board, and cable-to-cable interconnect requirements. As a result, they are being deployed in applications such as field emission electric propulsion (FEEP) thruster modules that require precise, low-noise handling over the full throttle range as well as attitude control systems, tracking and telemetry, and on-board computing.
Similarly, when it comes to high-power applications such as power control systems and servos, there are a growing number of robust options for satellite designers to choose from. State-of-the-art solutions include compact, high-reliability 8.5mm pitch connectors designed to operate at temperatures from –65°C to +150°C that are provided in shrouded housings, are capable of handling currents up to 60A and voltages as high as 3,000V, and withstanding vibrations and shock of 20G and 100G, respectively.