Mission Critical Components

In its ongoing quest to expand scientific knowledge about Mars, the NASA Jet Propulsion Laboratory (JPL) in Pasadena, CA, will launch the Mars Science Laboratory (MSL) in October 2011. Originally scheduled for launch in 2009, the MSL was recently delayed and has to wait 26 months for the next opportunity to reach Mars. The new Mars Science Laboratory is the largest rover sent to Mars to date, with the most advanced scientific payload ever assembled. Its mission will be to ascertain whether or not the environment was, or might still be, habitable for microbial life.

The MSL will rely on robust spacegrade connectors with a unique basket of wires technology to guarantee signal reliability throughout the mission. Hypertronics CompactPCI (cPCI) connectors were selected by JPL and are integral to the avionic assemblies that will provide signal interface during all stages of the Mars mission including lift-off, entry, descent, and landing and instrument surface controls. The connectors provide interfaces with all of the instruments and functions of the MSL.

The connectors were proven successful during testing done for the Solar Dynamics Observatory (SDO) satellite. NASA had to identify an interconnect solution with a corresponding contact system to satisfy the rigid signal reliability demands for space and worked closely with Hypertronics in developing and testing the Hypertronics cPCI connector family of connectors using the most severe testing protocol ever developed.

This successful testing resulted in NASA issuing Specification S-311-P-822, which details the utilization of the Hypertac system in all space flight cPCI architectures, as well as an addendum to EEE-INST-002 that prohibits the use of all COTS Commercial off-the-shelf cPCI connectors for space flight use, and mandates the use of S- 311-P-822 connectors. Hypertronics cPCI connectors are designed into several future space missions and recommended for critical space, military and aerospace systems.

Surviving Harsh Environments

Within the area in which Mars Science Laboratory is capable of landing, temperatures can range from 86°F to -197°F. Technologies for severe environments must create systems that are robust enough to handle conditions in space flight and on the Mars surface. Signal reliability is ensured by electrical connectors that join the single-board computers to a cPCI backplane bus architecture, which functions as the central nervous system for the rover. Given its extreme complexity, the MSL will rely on leadingedge computing technology with functionality, power and capabilities of the highest order. Signal transmission integrity under the harshest of conditions is of paramount importance during all mission phases. The Hypertronics connectors chosen for this task are designed to meet strict outgassing requirements and maintain their integrity in the extreme thermal conditions found on Mars and other space applications.

NASA Specification

In 2004, while researching for the Solar Dynamics Observatory (SDO) satellite, NASA had to identify an interconnect solution with a corresponding contact system to satisfy the rigid signal reliability demands for space flight. NASA was reasonably assured that the Hypertronics connectors would solve their issues and could handle even Hypermore.

Hypertronics Hypertac contact design was applied to 2mm cPCI connectors and put to the test, which resulted in NASA Goddard specification S-311-P-822.

Commercial-Off-The-Shelf (COTS) cPCI connectors can offer reliable service when used in office environments without severe thermal excursions, corrosive atmosphere, and excessive shock and vibration.

But for NASA, the problem was that these COTS connectors were not specifically designed to be utilized in severe conditions for extended multi-year space missions, and their performance is not capable of reliably meeting those demands. NASA required a robust high-density interconnect system with low contact resistance capable of withstanding the rigors of the shock and vibration of satellite launch and deployment but needed to conduct tests to ensure success.

The Mars Science Lab rover. Photo credit: NASA.

Basket of Wires Technology

Hypertronics Hypertac advanced wire basket socket contact system is distinguished by its unique design. The shape of the contact sleeve is formed by wires strung at an angle to the socket axis. When the pin is inserted into this sleeve, the wires stretch around it, providing a number of linear contact paths, extending the contact area around the pin to 360°. The low mass and resultant low inertia of the wires enable them to withstand the most abrupt or extreme excursions of the pin without loss of contact - a critical factor for ensuring electrical integrity in harsh environments and demanding applications.

The NASA team conducted its processor board connector comparison testing in order to determine if available connectors were susceptible surface deterioration and atmosphere-driven corrosion of the contacts, which can compromise connection integrity.

The testing protocol calls for qualification testing at the flight chassis and the individual connector levels, as well as materials analyses. The test regimen concentrated on strenuous shock and vibration testing that would identify potential causes of signal degradation and interruption. Previous testing of other products showed that shock and vibration causes contact fretting: rapid microscopic movement of connector mating components back and forth against each other ultimately leading to excess wear, which in turn can lead to signal deterioration or interruption and potential catastrophic failure. The connector must withstand micro movement of the male to female contact surfaces in relation to each other in order to maintain the electrical connection required for space flight. For electrical components terminated into space grade flight boards, solder is the preferred method of installation and has known reliability. There were concerns that for the COTS cPCI connectors, the press fit compliant pin tterminations could introduce damage to the plated thru-holes in the printed circuit board from installation or allow contaminants to enter the terminations, resulting in the potential for latent increases in resistance and subsequent signal deterioration within the processor.

Partnership Delivers Solution

When existing COTS cPCI connector technology was tested for space flight and found to provide unacceptable results, NASA contacted Hypertronics and expressed its interest in Hypertronics 2mm cPCI connector.

The 2mm cPCI connector features Hypertronics patented Hypertac configuration, which has proven to perform better under the toughest situations.

The Hypertronics 2mm cPCI connectors were subjected to more severe testing requirements than those used to test other suppliers cPCI connectors. One of the tests was a mixed flowing gas test, during which the 2mm cPCI was exposed to several severely corrosive gasses. Another was extended contact engagement and separation cycling. The new testing also included high magnification up to 200x, plating analysis, additional post-test micro-section visual inspections. The testing demonstrated that the Hypertronics 2mm cPCI connector outperformed and exceeded the established test criteria. Typical mate-demate testing requires that a connector withstand a minimum of 500 cycles. The Hypertronics 2mm cPCI was successfully taken to 4,400 cycles. The connector also held up through vibration testing better than any other because of its inherent design, which allows for multiple points of contact in each axis.

The Hypertac technology applied to the 2mm cPCI design proved to resist contact fretting and ensured a consistent connection. The mixed flowing gas test demonstrated that the internal contact engagement surface continuity remained intact and did not suffer signal degradation. The connector terminations also accommodate the NASA preferred solder termination method.

For full information on the Mars Science Laboratory project, please visit http://marsprogram.jpl.nasa.gov/msl/.

Hypertronics Corp.
Hudson, MA
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