Specifying Components for Space Applications

October 1, 2010

Recently, NASA renewed a decades-old request for grant proposals that call for “faster, better, cheaper” projects. The ultimate agenda is to expedite developments in aerospace capabilities while yielding higher profits. While this controversial push for new, innovative methods is unusual for the institutionalized industry, it generates creative solutions to issues faced in the aerospace market. However, manufacturers are still required to meet a lengthy list of qualifications as detailed by NASA and the European Space Agency (ESA) to be specified for military/aerospace applications.

Comprehensive Testing

Employed in satellites and launchers, the D-sub-miniature connectors meet ESA qualifications and quality levels.

A connector that is introduced into a satellite or space application cannot be easily repaired or replaced once the application has been launched. Because of this, connectors are subjected to a battery of tests to meet zero-defect requirements. High shock and vibration are some conditions that impact connector alignment, and connector manufacturers test connectors with random or sinusoidal shock and vibration up to 20G in each of three simultaneously occurring directions, applying the motion for 90 minutes to guarantee that misalignment or mis-mating will not occur.

To achieve the zero-defect specifications, connector manufacturers must be aware of everything in their supply chain and manage all of the raw materials and component parts that will go into assembling each connector. This ensures each part is within the defined acceptance limits of the particular application for which it will be implemented. All parts are viewed with magnification up to 50x, further eliminating any possible defects. High-reliability connectors are also subjected to corrosion tests by emerging them in a salt bath to make certain there is no infiltration of particles that could cause materials on the connector to corrode. Finally, at the end of the assembly process, all parts are tested individually to ensure they meet defined specifications, such as the contact resistance, insulation resistance, and impedance value.

Connector manufacturers with ESA-qualified manufacturing facilities have zero-defect manufacturing standards in place, and often meet other qualifications and certifications as well, such as ISO and EN90001 standards.

Highly reliable, zero-defect, fully qualified connectors are paramount for space applications. ESA QPL-qualified connectors meet stringent reliability, outgassing, and residual magnetism requirements, as well as employ the necessary materials and configurations to withstand the extreme conditions found in aerospace applications. In the future, some connector manufacturers are looking to develop custom designs based on wire bonding systems — such as those used now with semiconductor chips — in order to allow the wiring of connector pins to the PC board to construct any configuration, providing even greater flexibility and further meeting application-specific needs.

Connector Materials

ESA-qualified microstrip single inline microminiature connectors employ nickel and gold plating, and are operational to -270 °C

Certain raw materials that are used in connectors are magnetic and outgassing, which can negatively affect the performance of the device and produce false readings. In order to circumvent those adverse affects, the use of non-outgassing and non-magnetic metal materials is imperative. Space and satellite applications call for connectors that are constructed from materials with no outgassing and low residual magnetism elements. Special copper alloys provide this solution, so no RF and magnetic interference occurs. Copper alloy materials are also capable of withstanding extremely high temperatures that the connector must endure in these applications.

Temperatures in atmospheric applications can range from below -200 °C to above 200 °C, forcing connector manufacturers to employ materials capable of withstanding extreme temperature variations. While many connector designs incorporate silver plating, silver typically exhibits contact resistance instability when the temperature exceeds 85 °C. Because of this, high-reliability components are often equipped with a combination of plating materials, such as an underlayer of nickel followed by a layer of gold, which is suitable for operation in higher temperatures that can range up to approximately 200 °C. Gold is also used in extremely low temperatures, as it does not lose connectivity due to the contact resistance of the material.

The use of specialized plating materials also allows connector manufacturers to design and manufacture devices to custom specifications, such as a completely terminated connector family, custom-designed insulators, shielded and unshielded designs, and the addition of outside molded strain to protect contact termination of connector wires. This allows the connector manufacturer to precisely meet customers’ application-specific needs.

Contact Configurations

The MDMA Series rectangular microminiature connectors employ a star clip contact system along with removable contacts.

Relays, modules, and PCBs in satellite and space applications require highly reliable connectors that provide cutting-edge technology with creative mounting. Contact configurations must provide a secure base for the contact and exhibit superior electrical and mechanical characteristics, as compared to an alternative traditional machined or stamped contact system. A micro twistpin contact system consists of beryllium copper wire wound around stranded cores. The wire bundle is crimped into a sleeve at one end, while the other end is terminated with a hemisphere-shaped weld. The flexible twist-pin is recessed into the insulator and the rigid socket is exposed, reversing the traditional positions of pin and socket. When the connector mates, the socket is guided into the pin insulator by the lead-in chamfer. The pin is kept from flexing beyond the socket capture radius by the walls of the cavity. The hemispherical weld of the controlled radius at the tip of the pin combines with the lead-in chamfers of the socket contact and the pin insulator to cam the pin into alignment. These contact designs provide multiple points of electrical contact, highly reliable crimps, high current-handling capabilities, and extended lifecycles, and such designs will mate even under severe misalignment conditions, such as high shock and vibration.

Variations in contact configurations also play a significant role in space applications. Removable contacts provide the end user with a number of benefits in terms of flexibility, as the customer can maintain and utilize contact and cable configurations. For example, removable contacts allow the user to adjust the length of the cable or crimp the cable in the contact before installation in the event of deviations during integration. This further shortens assembly time.

Star clip systems replace traditional screw lock technology, eliminating the need for screws, washers, and clips, and replacing them with a snap-in system. This type of technology not only provides a highly reliable solution, but also significantly shortens assembly time, particularly when it comes to costly satellite integration, saving the customer both time and money.

Size also factors into contact configurations, as micro and nano satellites weigh in kilograms, as opposed to traditional telecommunication satellites that weigh in tons, requiring all components to weigh much less as well. Micro and nano miniature connectors with star clip systems and removable contacts are ideally suited as they provide the utmost reliability and flexibility while meeting size constraints, and are thus finding greater prominence in micro and nano satellite applications.

The “faster, better, cheaper” projects that NASA has called for may impact the commercialization of space travel, but the factors considered in electronic components for aerospace must be kept stringent. Certification testing, materials used, and configuration are subjected to scrutiny in order to maintain standards for safety and efficiency. Manufacturers that continue to provide efficient, high-quality, low-cost components are paramount in answering NASA’s call.

This article was written by Gilles Parguey, Senior Product Manager at C&K Components, Newton, MA. For more information, Click Here