SpaceVPX adds fault tolerance, cuts cost for space-bound HPEC systems

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June 09, 2015

In the rigors of space, fault tolerance is a prerequisite for high-performance embedded computing (HPEC) systems responsible for the transmission of mission-critical data. Faced with extreme temperatures and radiation levels, extended deployment, and the improbability of hardware maintenance, space-bound technology platforms must be designed to standards of reliability and resilience seldom matched by applications on Earth. Meanwhile, space agencies are being asked to do more with less since the effects of sequestration began to take hold in the earlier part of the decade, as are the agencies’ suppliers, who are perpetually tasked with delivering components that are smaller, more powerful, and more affordable.

Though certain off-the-shelf architectures have had successful flight heritages in space, their use beyond prototyping and development has been largely spotty. On the whole, commercial-off-the-shelf (COTS) technology has been viewed as incapable of offering the robustness required by an industry that has traditionally turned to custom solutions, but as the space sector becomes increasingly international and more commercialized, historical perceptions are beginning to change. This is evident through the recent ratification of VITA 78, or SpaceVPX.

SpaceVPX: Dual-redundant, fault-tolerant COTS

SpaceVPX began as part of an industry/government collaboration called the Next Generation Space Interconnect Standard (NGSIS), and is a retrofit of the VITA Standards Organization’s (VSO’s) OpenVPX specification that adds fault tolerance to meet the demands of space flight, says Patrick Collier, Senior Electrical Research Engineer, Space Communications Program at the Air Force Research Laboratory (AFRL) Space Vehicles Directorate and NGSIS and VITA 78 Working Group Chair. Looking to define a modular open systems architecture (MOSA) for space system interconnects that removed bandwidth constraints, the NGSIS working group selected OpenVPX as a physical baseline for SpaceVPX due to its broad ecosystem support, which helps reduce cost and promotes technology reuse, he says.

“Originally, the whole effort was under the NGSIS umbrella, which started close to three years ago,” Collier says. “It was an option from an effort that focused on protocols. When we started, NGSIS didn’t have SpaceVPX, and we were talking about which commercial protocol would be best for space systems. After about a year or so there was a discussion among people in the group because they started to see that all of the vendors were looking to use VPX to build their chassis, and they started to ponder whether it would be a good idea to see what we could do to OpenVPX to enhance it for space. So a separate study group was formed and it turned into a working group under the VSO. I proposed the effort to VITA at one of their face-to-face meetings, and they accepted it as a study group. Then it moved from there into a working group.

“Specifically, [SpaceVPX] provides for fault tolerance and dual redundancy, which you don’t get in OpenVPX,” he continues. “You have single-stream systems in OpenVPX, which is basically just one set of cards. With SpaceVPX, it provides for greater resiliency by having dual redundancy in the system, and one thing that we added to provide a greater degree of fault tolerance is a new board type called a Space Utility Management (SpaceUM) module that collocates all of the management and utility signals that you might have on a separate payload card or SBC, and then distributes those signals to all of the cards in the chassis and also distributes power. The idea here is that there are not meant to be single points of failure, so you have it such that if you see losses in signals or in certain sets of signals that it won’t bring down the whole system.”

In particular, the SpaceVPX SpaceUM receives utility and management signals from an independent management controller, which, along with power from an independent power supply, are then distributed to SpaceVPX modules in each of eight system slots to enable fault tolerance. An example SpaceVPX backplane topology can be seen in Figure 1.

 

Figure 1: The SpaceVPX specification includes a Space Utility Management (SpaceUM) module that provides dual redundancy for space systems.

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In addition, the SpaceVPX specification limits the number of OpenVPX slot profiles to a subset that accommodates the current and future needs of the space electronics community, Collier says. Of the 17 total backplane profiles, one of the payload slot profiles and one of the data switch profiles were directly mapped from OpenVPX, while several new, backward-compatible profiles and special slot definitions that enable the bridging of SpaceVPX modules to heritage CompactPCI (cPCI) modules were introduced. Table 1 includes a description of the backplane profiles contained in the SpaceVPX specification.

 

Table 1: Listed here are details of the slot profiles defined by SpaceVPX.

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Commercializing cost for space electronics

Rather than building custom development platforms, NGSIS and SpaceVPX also reduce the cost of designing, testing, and integrating system prototypes before they are ported to deployment-ready models, Collier says, which over the life of a program can yield significant savings.

“From a quantitative perspective it would be hard for me to gauge at this point how much savings, but what we’re hoping over the long term is that you would see a significant cost savings.

“Given what vendors might do today if they had to build their own custom systems to do development work before porting them over to a space system, we’re hoping that we’ll see a lot of people using OpenVPX systems that they then port over to a SpaceVPX system, mainly because there are restrictions on the types of slot profiles that are available from COTS vendors,” he says. “That’s why we tried to make sure we mimicked particular slot profiles so that they could be used in a SpaceVPX system.

“There are some slot profiles that we have that directly map to what OpenVPX uses; an example would be one of the payload slot profiles,” Collier continues. “There are others that you won’t find in OpenVPX, but it could still be used with a foreign OpenVPX system since it is backward-compatible, he adds.

“It’s over the lifetime of a project or a program that you’ll see significant savings, and hopefully as the market grows you’ll see more people building a subset of those slot profiles for different uses – maybe you’ll see some of these used for non-space systems, maybe for a high-reliability air platform or some other type of high-reliability application that could be non-aerospace or non-space,” Collier notes.

Future SpaceVPX applications

Currently, NASA is evaluating SpaceVPX, and Collier points to “significant interest” from the European Space Agency (ESA) and its suppliers as another area of potential growth.

“Over a year ago I approached Space Systems Loral (SSL) to discuss the space systems that we were using and the spec that we were developing, but at the time it may have been too soon,” Collier says. “For [commercial space] companies like SSL or Iridium, they already have their buses defined. Now whether or not they see it from a box level that this makes sense, I haven’t seen an indication that their interest is increasing.

“I’m hoping [the European interest] will take hold. In that way you might see the market grow with contractors in Europe starting to use SpaceVPX boards and chassis,” he continues. “The ESA would be the end user, but part of it would also be to get their end contractors, say, like Airbus or Thales. If they’re looking to design new architectures and they’re looking to save costs, this would be one way they could save.”

Current efforts

Currently, Collier cites BAE Systems and Honeywell as two companies that have already publicly started building and could ship SpaceVPX products as early as Q2 2016, though many of the organizations involved in VITA 78 are possible vendors as well (Table 2).

 

Table 2: Listed here are members of the original Next Generation Space Interconnect Standard (NGSIS) SpaceVPX Subcommittee.

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Moving forward, the VSO has begun work on a VITA 78 dot spec for 3U SpaceVPX systems, which Collier hopes will help drive the technology into smaller low size, weight, and power (SWaP) systems and applications.

For more information, visit the Air Force Research Laboratory (AFRL) Space Vehicles Directorate website at www.kirtland.af.mil/afrl_vs.