How SpaceVPX is Influencing the Design of Next Generation Spacecraft Avionics

Over the last decade, a government-industry effort to advance the use of modern computer processors and networks in spacecraft avionics systems has quietly been making its own gains in industry adoption and a re-thinking of the way next generation spacecraft electronic systems could be designed in a less costly and more interoperable way.

Spacecraft avionics systems are all of the electronic instruments, components, computers and subsystems that control primary spaceflight flight and data communications functionality.

This is an image from the NASA Engineering & Safety Center (NESC) Interoperability Assessment that describes the basic building blocks of a SpaceVPX-aligned embedded computing module. (Image: NESC)

Historically, spacecraft OEMs, systems integrators and designers have relied on avionics systems and embedded computer processing architectures that are singularly developed, power hungry and often sharing data over legacy networks between computers that use older processor technology.

Over the last decade, the advancement and revision of the SpaceVPX (VITA 78) standard has been the driving force behind removing bandwidth as a constraint for spacecraft avionics systems and establishing an ecosystem of suppliers and designers that develop systems based on re-usable card-sized processing modules.

What is SpaceVPX?

SpaceVPX is an embedded computing standard based on bridging the VMEBus International Trade Association (VITA) OpenVPX standards to space applications. OpenVPX is a set of embedded computing system standards that are widely used in safety critical aerospace and defense platforms such as vehicles and weapons. Its primary purpose is to provide a standardized architecture for the electrical, physical and mechanical specifications, form factors and characteristics of embedded computing modules, backplanes and chassis.

The SpaceVPX standard was first established in 2015, when it was officially recognized by the American National Standards Institute (ANSI) under VITA Standards Organization (VSO) guidance as ANSI/VITA 78.00-2015.

This table from NESC Interoperability Assessment features the individual use cases that were assessed. (Image: NESC)

Patrick Collier, who currently works as a consultant with Aspen Consulting Group and Michael Walmsley, a Product Manager at TE Connectivity, two of the original architects of the SpaceVPX standard, previously explained the development of SpaceVPX from its origins in their August 2022 SpaceNews article, “SpaceVPX (VITA 78) and the World of Interconnect.”

In the article, the two engineers describe SpaceVPX as a “standard for creating plug-in cards (PICs) from its slot profile and module (protocol) profiles. In turn, these building blocks create interconnected subsystems and systems.” They go on to state that the primary goal of SpaceVPX is to “cost-effectively remove bandwidth as a constraint for future space systems.”

SpaceVPX and Interoperability

Another image from the NESC Interoperability Assessment features a notional redundant SpaceVPX system using a switched topology for data plane interconnect. Note that although not illustrated in this figure, SpaceVPX supports a mesh topology. (Image: NESC)

SpaceVPX seeks to give next generation spacecraft the ability to perform flight control and other bandwidth intensive applications using smaller and lighter avionics boxes that are more interoperable, less expensive to develop and leverage modern processors and data networks and protocols. In September 2022, NASA Engineering & Safety Center (NESC) published an in-depth understanding of the goals of the use of the SpaceVPX standard, and what aspects of the standard still need to be revised.

NESC’s “SpaceVPX Interoperability Assessment,” is a 92-page assessment of SpaceVPX’s goals of incorporating fault tolerance features that are required by spaceflight systems as well as how it creates interoperability between spacecraft avionics. Leveraging use cases, embedded computing product surveys and SMEs and briefings to gauge industry and government interest internationally in the use of SpaceVPX-aligned systems, the assessment found that “VITA-78 allows so much flexibility that interoperability between modules cannot be assured.” The assessment also includes an overview of what a SpaceVPX embedded processing or computing module looks like, which at its most basic description is a radiation hardened processing module that can operate in the extreme temperatures and environment of space and includes payload inputs, processing cards, memory and power in a package that can be linked to other embedded spacecraft systems via SpaceWire, Ethernet or other data control networks.

An image of Alpha Data’s ADM-VA601 Versal AI Core Radiation Tolerant Reference Design & Development Kit for Space 2.0. The kit features a SpaceVPX Slot Profile, and AMD’s Versal AI Core System-on-Chip configuration. (Image: Alpha Data)

The NESC report states that in evaluating the use of OpenVPX for potential space usage, several shortcomings were observed. “The biggest deficiency was the lack of features that could support a full single fault tolerant and highly reliable configuration. Utility signals were bussed and, in most cases, only supported one set of signals, via signal pins to a module. Therefore, a pure OpenVPX system has opportunities for multiple failures,” the report states. “As the typical OpenVPX control planes are PCI Express or Ethernet, this was a concern since their usage in space applications was minimal, at the time, and SpaceWire was the dominant medium speed data and control plane interface for most spacecraft. This has evolved since the inception of SpaceVPX and the use of Ethernet and PCIe in space applications has grown. The SpaceVPX Working Group is reviewing a 2022 content proposal for the inclusion of high-rate Ethernet.”

The NESC report also highlights NASA and government/industry adoption of SpaceVPX, while outlining how it could be used in a variety of space missions. The first spaceflight application of a SpaceVPX module occurred on the Earth Surface Mineral Dust Source Investigation (EMIT), which is an Earth Ventures-Instrument (EVI)-4 mission to map the mineral composition of arid dust source regions of Earth via imaging spectroscopy in the visible and short-wave infrared. EMIT was developed at JPL and launched in 2022, and installed on the underside of the International Space Station. EMIT was enabled by a 3U SpaceVPX solid state drive module, and integrated into a non-SpaceVPX avionics architecture.

Wesley Powell, NASA STMD Principal Technologist for Advanced Avionics, was one of the lead authors of the interoperability assessment. In an August 2023 interview, Powell told Aerospace & Defense Technology (A&DT) that the key feature of SpaceVPX that benefits space computing applications is the support for fault tolerance. The standard ensures that the power, control signals and clock functions are distributed radially to each of the modules within a chassis, according to Powell. This can prevent an anomaly on one module from taking down the entire chassis, he said.

“SpaceVPX is not envisioned to be a NASA-centric standard. We rely on commercial industry partners to accomplish many of our most ambitious missions. We want to foster a SpaceVPX ecosystem where any integrator — be it NASA, industry or another organization — can take best of breed modules for their particular application from a variety of vendors and have them work together. That’s the goal we’re trying to achieve,” Powell further explained. “We want system integrators and spacecraft avionics developers to be able to utilize boards from a variety of vendors with a variety of functions and have them work together.”

One of the challenges with space missions according to Powell is that sensor data bandwidth often exceeds the available downlink bandwidth for a spacecraft over the course of its mission. When this is the case, either data compression or some other means of onboard data reduction is needed. Typically, the onboard processing that is needed for this data reduction requires high-bandwidth interaction between different modules, for example an I/O board, a data storage board, and a single board computer. These are the types of applications that SpaceVPX could enable, he said.

“Additionally, increasingly ambitious missions to the outer reaches of our solar system are driving the need for increased onboard autonomy. SpaceVPX can enable the high-performance onboard computing systems needed to implement this autonomy,” Powell said.

NASA’s Interoperability Assessment further outlines specific use case applications for spacecraft that could leverage SpaceVPX. These include crewed mission avionics, a robotic landing rover, and the use of avionics in a communications relay spacecraft, spectroscopy, an advanced earth observing hyperspectral instrument and a high bandwidth synthetic aperture radar.

The Future of SpaceVPX

Mercury’s SCFE6933 is a radiation-tolerant 6U SpaceVPX FPGA processing board enabled by AMD’s Xilinx Versal AI core. The company claims that it “performs in a single board what previously required three boards, simplifying mission architectures, and reducing costs.” (Image: Mercury Systems, Inc.)

In November 2023, Powell gave the presentation, “NASA’s Future Avionics Vision,” at the 2023 Radiation Hardened Electronics Technology (RHET) Conference. That presentation provided updates on the work still being done to increase the interoperability between SpaceVPX modules enabled by the standard for the space avionics community. In the presentation, Powell notes that NASA and the broader industry and other government agencies are following through on a key recommendation from the Interoperability Assessment that advises NESC to engage with industry and the SOSA Consortium on revision to VITA-78 and “refine the module definition and interoperability and daughtercard use.”

“Consistent with this recommendation, a follow-on NESC activity has been initiated to collaborate with industry and other agencies on the development of an interoperable variant of SpaceVPX (currently specified in the VITA-78 standard) within the Sensor Open System Architecture (SOSA) standards organization,” Powell notes in the presentation.

Over the last year, more embedded computing module designers and vendors have been introducing new SpaceVPX-aligned products. In September 2023 for example, Mercury Systems, Inc., published a press release introducing their first “space-qualified FPGA processing board to use AMD’s Xilinx Versal® AI core. The SCFE6933 is a radiation-tolerant, 6U SpaceVPX board that will make high-performance computing more accessible for a broad range of space applications and customers,” according to the release. The first customer for the SCFE6933 is Ball Aerospace, with whom the board is being co-developed. Mercury has also noted plans to make “flight unit” versions of SCFE6933 available this year.

Another example of some of the new SpaceVPX-aligned embedded computing becoming available recently came from Waterloo, Ontario-based electronic packaging supplier Pixus Technologies. In an August 2023 press release, Pixus announced their new “OpenVPX chassis platform that supports both 160 mm deep and 220 mm deep SpaceVPX and OpenVPX 3U boards.”

“The open frame chassis features up to four slots at 1.0” pitch of each board depth. The modular enclosure has card guide options to support both air-cooled boards and conduction-cooled boards. There are also 220 mm deep card guides that are wider to support extra thick SpaceVPX conduction-cooled boards per VITA 78,” the company notes in the release.

During the 2024 Embedded Tech Trends event hosted by VITA, Alpha Data, a supplier of embedded computing systems and modules with offices in Colorado as well as Edinburgh, gave a presentation about its own experience with SpaceVPX. Alpha Data Principal Engineer Kevin Roth highlighted the company’s development of new embedded computing modules aligned to the SpaceVPX standard. This includes the introduction of a reference design and development kit for “Space 2.0,” developed in partnership with AMD, Texas Instruments and Teledyne E2V. Known as the “ADM-VA601.”

In August 2023, Pixus Technologies introduced an OpenVPX chassis platform that supports both SpaceVPX and OpenVPX 3U processing boards. (Image: Pixus Technologies)

Roth’s presentation also notes that “VITA 78.0 tailors OpenVPX to Space applications,” and goes on to mention that “SpaceVPX is not as expansive as OpenVPX, but still unmanageable from a board vendor perspective.” In a follow up interview with Alpha Data CEO Adam Smith, he expanded on this perspective.

“SpaceVPX becomes unmanageable due to the wide range of communication and signaling standards supported across the power, data, expansion, and control planes. While this adds flexibility, it makes interoperability challenging. Especially the “user defined” options, which pretty much guarantee incompatibility. This is typical of VPX standards. You can see similar efforts in the embedded defense markets with organizations like SOSA consolidating OpenVPX,” Smith said.

Further, Smith describes the AMD XQR Versal AI Core VC1902 and Versal AI Edge VE2302 ACAP devices as enabling a step-increase in processing capability for SWAP-constrained platforms. “This technology is enabling the next generation of adaptable data processing in space. Versal is designed to enhance on-board processing for payload applications, boasting a significant boost in compute density for vector-based algorithms, and significant data throughput increase compared to earlier space devices. These devices feature a processing sub-system, hard-wired peripherals, and a platform controller that enable seamless on-orbit reconfiguration and mitigate single-event upsets (SEU) effectively,” Smith adds.

As NASA and other space agencies, OEMs and systems integrators continue to design next generation spacecraft avionics systems, the ongoing revision of SpaceVPX and government/industry adoption will continue to be a design trend to watch across the embedded computing world.

This article was written by Woodrow Bellamy III, Senior Editor, SAE Media Group (New York, NY).