Making it rad-hard takes time

Nov. 1, 2008
Designers of radiation-hardened military and aerospace electronics and electro-optics systems are continually looking for ways to keep power down, cut the long development cycles, and still maintain performance.

By John McHale

Designers of radiation-hardened military and aerospace electronics and electro-optics systems are continually looking for ways to keep power down, cut the long development cycles, and still maintain performance.

“The development time for traditional rad-hard processors is still long and results in processors that have less performance than their commercial equivalents,” says Larry Longden, senior director of marketing and technology at Maxwell Technologies in San Diego. “Systems required to withstand military nuclear weapons require this type of rad-hard design.”

It takes time to screen all components to ensure survivability in extreme radiation environments.

“The latest method is an improvement of previous screening efforts based on 100 percent upscreening to meet NASA EEE specifications, such as EEE-INST-002,” says Doug Patterson, vice president of sales and marketing at Aitech in Chatsworth, Calif. “In our previous methodology, every batch of processor components in a single lot/date code required 100 percent upscreening in addition to the destructive qualification [including destructive parts analysis] of a fixed sample size of those components regardless of the lot size.

“Aitech found with actual qual test data that there are high variations of power consumption to the processor components, including thermal runaway that could become an issue at high temperature operation in rugged and conduction-cooled environments,” Patterson says. “Aitech has enhanced its upscreening method to screen out processor components with abnormally high power consumption.”

It comes down to understanding how commercial parts will behave when radiation constantly bombards them; systems must not fail because they are mission- and life-critical.

“Today, commercial processors have good ionizing total-dose performance and, because they are built using SOI [silicon on insulator] technology, are single-event latchup immune,” Maxwell’s Longden says. “Our job is then to characterize the commercial processor, understand its upset performance in a single-event environment and then provide a system-level architecture that mitigates upsets.

“Maxwell’s product is based on commercial processors and memories,” Longden continues. “This gives us the ability to capitalize on products developed by the commercial market and allows us to provide higher performance than traditional rad-hard designs.”

Patterson says Aitech’s S950 product “embodies and typifies the true nature of the use of COTS in space where our customers are leveraging the availability of existing, off-the-shelf products rather than re-inventing the wheel for every project and for every program, thus saving development funding and fielding systems sometimes years sooner than ever before.”

When it comes down to it, rad-hard customers want what everyone else wants–high-performance and low-power. Aitech’s radiation-hardened COTS processor boards “have software features to allow the throttling of CPU clock frequency during operations to adjust the performance and power consumptions of the processor board dynamically in orbit, or in space.”

Maxwell has implemented a strategy to enhance total-dose hardness and latch-up immunity, and to mitigate upset errors. The SCS750 has one board upset every 3,000 years in geosynchronous or low Earth orbits.

Traditionally, the market for rad-hard processors and boards was dominated by the Manassas, Va., operation of BAE Systems and Honeywell in Plymouth, Minn. Both companies provide a single-board computer qualified for the most extreme radiation environments of space, also know as mega-rad environments. BAE Systems produces the 32-bit RAD 6000 and the 64-bit RAD750. Honeywell produces the rad-hard 1750A microprocessor. Companies such as Aitech and Maxwell have provided a cost-alternative.

“Mega-rad-hardened devices have their place in mission-critical applications where continuous operation during long-duration space flights to the outer planets, comets, and other severe radiation environments is a requirement,” Patterson says. In some cases, Aitech’s SBCs are being used by our customers together with the BAE or Honeywell SBCs in a single system, where Aitech’s SBCs are typically used in high-performance, short-duration data processing, robotic arm control, and complex DSP (digital signal processor)-like computations.

Longden says that Maxwell’s boards compete “very well” against the mega-rad boards due to business and performance factors. “We compete on total value, which includes performance, price, support, and future product path that will be compatible with current products. The most important drivers are performance and the design margin that the system designer achieves by using an SBC that provides more processing power than required as well as more memory than required.”

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