Reduced SWaP, COTS in space, and budget constraints in the rad-hard world

Story

June 15, 2015

Radiation-hardened electronics designers, facing the heat of reduced SWaP requirements in satellite programs and customer budget constraints, find they need to be even more innovative and open-minded to deliver commercial-level capability to space systems in low-cost packages.

The government segments of the space market look to be flat or slow growing for the foreseeable future, even as the development of megaconstellation small satellites begins to heat up. Meeting the needs of one doesn’t necessarily meet the needs of the other; as a result, companies are diversifying their rad-hard product lines and even considering the use of commercial-off-the-shelf (COTS) technology.

“Military space customers want smaller and lighter components with higher levels of overall performance while also reducing cost,” says Monty Pyle, Vice President of Sales and Marketing at VPT in Blacksburg, Virginia. “This can definitely be an engineering challenge. The budget constraints many integrators in the military space market face forces them to take a hard look at what exactly is needed in terms of radiation resistance within individual programs and try to strike a balance to help reduce the costs. In other words, for areas that require only minimum rad-tolerance, they are moving away from using devices with maximum rad-tolerance and more toward components that fit the exact need. It’s too expensive to make every component with maximum radiation resistance in modern space systems and it’s not necessary.”

“A big trend right now is to reduce size and weight, a demand which will only increase with the rise of CubeSats, where weight is critical especially when using a ‘pound for launch’ cost metric,” says Philip Chesley, Senior Vice President, Precision Products at Intersil in Palm Bay, Florida. Regarding reduced size and weight, Intersil offers a rad-hard temperature sensor called the ISL71590SEH, he adds. The device is a two-terminal temperature-to-current transducer that is accurate over time, temperature, and radiation exposure – specifically with a ±1.7 °C accuracy over temperature and less than –1 °C change in accuracy over low-dose-rate radiation. “Developers of the most advanced next-generation satellite systems require temperature sensors that provide accuracy over the mission life of a satellite, eliminating the need for expensive radiation lot acceptance testing or spot shielding,” Chesley notes. The Intersil device is qualified over the full military temperature range and to over 50 krad (Si) low-dose-rate and 300 krad (Si) high-dose-rate irradiation.

COTS in space

Budget constraints and the growth of the CubeSat market is also giving commercial electronic suppliers confidence that they can succeed in the space markets, although some have their doubts.

[For more on COTS in space see Executive Interview on page 20.]

“Folks are trying to bring COTS technology to space,” Chesley says. “This industry is cyclical in that way. Every ten to 15 years the pendulum swings to trying a COTS approach to meet budget constraint challenges, which is true today as the pressure to use more COTS is actually coming from government programs rather than commercial satellite systems as government outlets are facing pressure to slash costs.”

“The barrier of entry in this market is huge and to be successful companies need to build up a heritage of product success as the customer base is very conservative,” says Danny Gleeson, Business Development Manager for Space Market at Curtiss-Wright in Dublin, Ireland. “Our move into space began with SpaceX using our modular avionics data acquisition device – the KAM-500 – in the flight test phase and then it was retained for the production vehicle and we found that it met all the necessary requirements.” The product also has a Microsemi ProAsic FPGA that is inherently rad-tolerant.

“We have integrated our COTS modules in a smart backplane that we call a radiation safety net,” Gleeson says. “It enables the use of those modules in a radiation environment and protects them from latchups and other destructive events. Due to competitive reasons I cannot say more about the COTS backplane except that the radiation protection is at the board module level. Total ionizing dose (TID) resistance of commercial components varies depending on the technology, but typically is between five and 20 krad TID and this is compatible with a range of space missions.”

The Curtiss-Wright backplane has just gone through radiation testing at NASA and the next phase will be to create a rad-hard ASIC that will contain the company’s data acquisition, Gleeson continues. “The new ASIC will form the building block for creating a family of rad-hard modules for remote terminal units onboard satellites. The Intermediate eXperimental Vehicle (IXV) spacecraft, the European Space Agency’s experimental re-entry vehicle, is using Curtiss-Wright’s data acquisition, networking, and recording subsystems (Figure 1).

 

Figure 1: Pictured is the Intermediate eXperimental Vehicle (IXV) spacecraft, the European Space Agency’s experimental re-entry vehicle that is using Curtiss-Wright’s data acquisition, networking, and recording subsystems.

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“Our space COTS products are equipment that was never intended for space that we retasked for use in space radiation environments on a mission-by-mission basis,” he continues. “As we started entering the market, we did performance characterizations and qualifications for different radiation conditions in space and mapped our products to match mission profiles. It comes down to the risk versus cost analysis or what some call the eighty percent solution. In other words, if the environment in space does not call for components that meet extreme radiation requirements, then why procure them? This mindset is helping drive the use of COTS in space environments. Even though it may be COTS, if it meets the requirements, why not use it?”

 

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Not everyone in the rad-hard industry agrees with that analysis. “Maybe COTS will take over the rad-hard business and prove me wrong, but the physics don’t back up that theory,” Chesley says. “I’m skeptical of any radical change, as commercial parts – designed for the automotive world or similar consumer markets – do not work in space. I’ve tested thousands of them and they simply do not have the reliability necessary for rad-hard environments.

“If the government looks at what SpaceX is doing – just launching things into space – they realize they can’t do the same as they have to keep things in space, which is a big difference,” he continues. “To keep it in space, the parts must not fail. A distributed architecture works great for an Iridium-type program but can be problematic in strategic military space programs. It’s not worth the risk of the parts failing. Many people in the strategic satellite business struggle to see how distributed architectures solve that problem.”

Rad-hard Intersil integrated circuits (ICs) such as voltage regulators, multiplexers, dual analog switches, MOSFET drivers, quad differential receivers, and microprocessor supervisory circuits flew on the crew module on the first flight of NASA’s Orion spacecraft, the uncrewed Exploration Flight Test 1.

Product trends: SpaceVPX, FPGAs, power ICs

Engineers at Cobham are now offering their Gen6 single board computer (SBC), which is based on the LEON microprocessor, says Anthony Jordan, Vice President, Product Marketing and Applications Engineering, at Cobham Semiconductor in Colorado Springs, Colorado. “It has a Technology Readiness Level (TRL) of 6, which we believe allows us to offer an off-the-shelf onboard SBC or for use as a payload or instrument controller. The SBC leverages Cobham’s standard product portfolio including LVDS, SpaceWire, logic, volatile, and nonvolatile memory solutions. Based on the 3U CompactPCI form factor, the Gen6 SBC is designed for fault-tolerant, mission-critical applications.”

Cobham’s entrance into the space SBC market puts them up against companies such as Aitech in Chatsworth, California, and Maxwell Technologies in San Diego. Aitech produces the SP0 3U CompactPCI SBC that is used by Boeing on the Commercial Crew Transportation System (CCTS) and Crew Space Transportation (CST)-100 spacecraft. Maxwell also offers a 3U CompactPCI SBC for space called the SCS750 (Figure 2).

 

Figure 2: Aitech’s SP0 3U CompactPCI SBC is used by Boeing on the Commercial Crew Transportation System (CCTS) and Crew Space Transportation (CST)-100 spacecraft.

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All these designers are keeping an eye on the development of the SpaceVPX standard out of VITA. “We look forward to low-cost and SpaceVPX board-level solutions, as we are very interested in extending this base capability,” Jordan says. “Weather instrumentation, remote sensing, and data-intensive applications will drive the use of RapidIO and SpaceVPX in the space market.”

[For more on SpaceVPX see article on page 34.]

Crane Aerospace & Electronics in Redmond, Washington, saw its Interpoint MFP0507S POL DC-DC converter fly onboard NASA’s Orion spacecraft. The company has delivered more than 90 MFPs to the Orion program. The MFP0507S converters reside on network interface cards that are used throughout the spacecraft. The converter can be used with a 3.3 VDC input bus or 5.0 VDC input bus, has the flexibility to be set for any output voltage from 0.8 VDC to 3.5 VDC, and requires no external components to achieve all specified performance levels.

A new product line for VPT that is just completing DLA (Defense Logistics Agency) qualification is the SVLD (Low Dropout) family, which is designed to work the Xilinx 5 and other FPGAs for space applications that require extremely tight bus regulation with very low noise. “The Xilinx 5 has really set the standard for space FPGAs in my personal opinion as it is re-programmable after launch,” VPT’s Pyle says. “Many of our customers have been asking about interfacing with the Xilinx 5 and we see it as being there for the long haul. Previously they had to provide their own interface from our traditional isolated DC-DC converters to their sensitive FPGA applications. With VPT’s upcoming SVLD Series, a VPT space customer can address all their power requirements from the main power bus, through our EMI filter, isolated DC-DC converter, point-of-load non-isolated DC-DC converters, and SVLD to their Xilinx 5 or other FPGAs.”