Last year, NASA awarded Maxar Technologies the contract for the Power and Propulsion Element, the very first Lunar Gateway contract and, at the time, the first module scheduled to be launched.
The Power and Propulsion Element (PPE) acts as Gateway’s service module, providing solar electric propulsion for orbital adjustments, and electricity with its solar arrays. It is an essential piece of the early Artemis puzzle as it will be the only power generating element for the Gateway in Phase 1.
In a recent interview with Maxar’s Vice President of Space Infrastructure and Civil Space, Al Tadros provided greater insight into Maxar’s progress on the PPE to Toufiq Tahmid for NASASpaceflight.com.
PPE is the major power generation element for the Gateway. Arrays known as Roll Out Solar Arrays (or ROSAs) will be used and are proportioned in a way that allows them to produce up to 60kW of electrical power that will then be distributed between other Gateway locations such as the habitation module, elements that will support scientific experiments and human astronauts, and the grapple fixtures for Canadarm3.
The arrays will also provide power for the Electrical Propulsion System, Gateway’s main way of performing large maneuvers in space.
We are excited to team up with @Dynetics on the power and propulsion element for the Gateway – an essential component of @NASA’s #Artemis lunar exploration program and future expeditions to Mars. https://t.co/KFA2OVZlaw pic.twitter.com/lvQmD0V940
— Maxar Technologies (@Maxar) July 9, 2019
If there was a power emergency, the PPE could revert to backup batteries that can be used for limited periods when the solar arrays are not generating the required amount of power.
The PPE is to launch with enough propellant to serve a 15 year mission, as Gateway’s design life is 15 years. But Maxar plans on using orbital refuelling to extend the Gateway’s lifespan.
Maxar completed a study of orbital refuelling for the HLS (Human Landing System) studies NASA commissioned last year. This kind of technology will be needed as NASA pursues the goal of having a sustainable human presence on and around the Moon as part of their Artemis Program and also for future human missions to Mars.
The Preliminary Design Review on the PPE is expected to occur sometime late this year. Maxar received the NASA contract last year and have since completed a System Requirements Review and have already ordered all the flight-proven parts for the PPE.
Many of these parts will go through a Critical Design Review by the end of 2020 as well.
“We have placed over 90% of our key subsystem hardware orders with our suppliers, including long-lead orders for exotic materials required for the solar electric propulsion thrusters,” said Mr. Tadros. “Also, NASA has delivered early computer-based Gateway emulators to Maxar to support early PPE software prototyping.”
The PPE’s design has evolved since the initial contract from May 2019, with the most recent and most notable change being the switch to a dual-module launch configuration.
Originally, PPE was supposed to launch separately as the first Gateway module in late 2022 and perform a demo in lunar orbit before the second module, known as HALO (Hab and Logistics Outpost), arrived in 2023.
To reduce mission complexity, risk and cost, NASA made the choice to integrate the PPE with the HALO module on the ground and then launch the combined stack on a single commercial launch vehicle.
This now means the PPE has to transport a large portion of Gateway to its lunar orbit rather than just itself. So there have been some design adjustments, and Maxar is working closely with NASA as mission requirements evolve.
Nonetheless, the PPE is progressing both in design and in hardware, although former Associate Administrator of the Human Exploration and Operations Mission Directorate, Doug Loverro, raised concerns on Gateway’s readiness for the Artemis 3 mission, specifically citing the PPE’s method of propulsion.
Addressing that, Mr. Tadros noted, “To reduce the schedule risks associated with the Advanced Electric Propulsion System, Maxar is leveraging its extensive experience in electric propulsion to develop alternate solutions that meet the PPE’s mission requirements.”
A Human Landing System docked to the Gateway. (Credit: NASA)
“NASA has asked us to begin designing an alternate power processing unit to provide power to the electric propulsion thrusters. This approach takes advantage of our proven electric propulsion architecture, which is successfully operating on more than 35 spacecraft today.”
Mr. Tadros added, “PPE is not a standalone program. It’s part of Gateway, which in turn is part of NASA’s Artemis program. There are a lot of pieces in motion. We continue to work closely with NASA as its mission requirements evolve, and we are confident that we will deliver an innovative, cost-effective solution that meets or exceeds the program’s performance and schedule requirements.”
In this way, Maxar is not starting from scratch. They’re leveraging their experience with satellite busses and space hardware on many geostationary communication satellites over the decades in their design.
“PPE is based on our highly reliable and scalable 1300-class spacecraft platform, of which there are more than 90 currently on-orbit,” said Mr. Tadros. “Our 1300-class platform is also the basis of NASA’s OSAM-1 satellite servicing mission and Psyche metallic asteroid exploration mission.”
But even with that experience, the PPE will still push Maxar into new territory. “Our PPE design will stretch its capabilities to 60kW of solar array power generation and electric propulsion thrusters operating at 12kW — an unprecedented level.”
And it will have to debut these new capabilities while ferrying not just itself but HALO out to its intended lunar orbit.
The PPE and HALO after launching together toward lunar orbit. (Credit: NASA)
Under the original contract, Maxar was responsible for soliciting and choosing a commercial launch vehicle for the PPE’s launch in 2022. But since PPE is no longer launching alone, who is responsible for procuring that launch vehicle?
“Since the PPE will be assembled with the Habitation and Logistics Outpost on the ground, Maxar is no longer responsible for the launch,” stated Mr. Tadros. “NASA’s Launch Services Program has taken the lead on arranging for the launch of the combined spacecraft in 2023.”
While NASA’s Launch Services Program have not yet chosen a launch vehicle, Falcon Heavy is largely understood to be not just the front runner but the only real contender at this point given comments at the latest public HEO meeting hinting at Falcon Heavy and in which NASA officials stated they expect only one launch vehicle to be ready and certified for a 2023 launch.
The comment did leave some wiggle room for the potential of Vulcan as an option given the fact that ULA vehicles can usually precede through NASA certification processes quickly and that ULA has likely already started that certification process with NASA.
However, the same comment almost certainly precludes Blue Origin’s New Glenn from being a viable option for this launch given that the rocket has no verifiable target date for its maiden voyage and the fact that NASA would not just be certifying a brand new rocket but a brand new company as well, two elements that usually result in longer certification periods.