April 21, 2021
A brain, a body and courage — but it’s not the Wizard of Oz
By Peter Lord (Maxar), David Oh (JPL), and Steven Scott (Maxar) as told to Danya Gainor
As the Psyche spacecraft transitions into its ATLO (assembly, test, launch, and operations) phase, the recent arrival of the solar electric propulsion (SEP) chassis to JPL brings to mind a novel (and somewhat radical) choice we made early on to have a commercial company, Maxar Technologies, build the SEP chassis, but have JPL build the main computer and software that control the spacecraft. The choice of spacecraft provider is an important and high stakes decision made in the early phases of mission development. The choice to split the spacecraft between two partners was deliberate, unusual, and driven by the needs to the mission. This is the story of how that decision was made.
Getting into orbit around Psyche requires the use of advanced propulsion systems – electric thrusters that ionize propellant to turn electricity into thrust. In 2013, we found that the government-designed legacy ion propulsion system used on missions like Dawn was no longer available, and that building a new system from scratch was impractical from a time and cost perspective. We instead looked to take advantage of the fact that commercial companies had built and operated hundreds of electric propulsion spacecraft. We needed to find an experienced industrial partner that could provide the electric propulsion thrusters and big, 20kW, power system needed to take us to Psyche.
Maxar has built over 300 geosynchronous satellites, and importantly, over 35 of those satellites operate on Maxar’s own electric propulsion system. While Maxar’s SEP hasn’t yet flown beyond lunar orbit, Maxar understands how to build SEP for big power systems – it is currently designing the Power and Propulsion Element for NASA’s Lunar Gateway, which will include three 12.5kW and four 6kW individual electric propulsion thrusters powered by a 60kW solar array. That’s big power.
In contrast, JPL has experience flying deep-space spacecraft, doing fault protection, and operating completely autonomous spacecraft that explore the solar system. But JPL has never built a power system in-house of the size necessary to meet the needs of a billion-mile journey to Psyche.
Working together as a team, we proposed combining the strengths of both Maxar and JPL, with the aim of reducing time, risk, and cost: Maxar would build the solar electric propulsion chassis which includes the power system, the propulsion system, and the basic structure (including the high gain antenna, thermal control and avionics systems) and JPL would build the main flight computer and all spacecraft software—the “smarts” that allow it to operate in deep space. This proposed solution was unique for JPL because, historically, JPL either builds an entire spacecraft in-house (with smaller subsystems provided by outside contractors) or the entire spacecraft is built by an industrial partner. With Psyche’s proposed combination, however, the team could efficiently develop a deep space spacecraft with the requisite power system and electric propulsion.
Of course, the success of a new approach like this doesn’t just rely on integrating the parts of the spacecraft; it requires the integration of different teams with different institutional cultures and processes. From the beginning, we made a concerted effort to have frequent collaboration meetings with each other, a habit and commitment that remains intact despite the challenges from COVID-19. This teamwork has, and will, allow us to overcome the numerous technical and engineering challenges that are expected for such a complex mission.
We continue to rely heavily on the shared team culture we’ve developed as we work together to integrate JPL’s spacecraft “brains” with Maxar’s spacecraft “body.” Teams from both institutions are working together side by side at JPL now that Maxar has delivered the SEP chassis to Pasadena. We know that there is a lot that is going to be tricky. When we take Maxar’s test computer out of the SEP chassis and replace it with JPL’s flight computer and software, there are guaranteed to be challenges. Even though the team has run countless tests and mitigation efforts, until we really see how the spacecraft components operate together, we don’t know exactly what the challenges will be–the devil is always in the details. But we are also confident that we’ll be able to work through it all. Psyche Principal Investigator, Dr. Lindy Elkins-Tanton, strategically drove this shared team culture since day one and that, as much as the technology itself, will be what gets Psyche over the finish line.