Asteroid Redirect Vehicle bus
The Asteroid Redirect Vehicle was a robotic, high performance solar electric spacecraft for the Asteroid Redirect Mission (ARM). The mission was to send the spacecraft to a near-Earth asteroid and capture a multi-ton boulder from the surface with a grappling device. It would then transport the asteroid into orbit around the Moon where crewed missions to study it could be conducted more easily.[7][12] The mission was cancelled in early 2017 and the spacecraft's propulsion segment became the Power and Propulsion Element (PPE) for the Deep Space Gateway, now known as the Gateway.[6]
Reusable Space Tug missions
During the Asteroid Redirect Mission, space tug missions were proposed to separate Mars logistics that can spend a longer time in space than the crew into a separate mission, which could have reduced the costs by as much as 60% (if using advanced solar electric propulsion (ion engines) [13]). They would also reduce the overall mission risk by enabling check-out of critical systems at Mars before the crew departs Earth. This way if something goes wrong in those logistics, the crew is not in danger and the hardware can simply be fixed or relaunched.[14][15][16][17][18][19]
Not only would the solar electric propulsion (SEP) technologies and designs be applied to future missions, but the ARM spacecraft would be left in a stable orbit for reuse.[14][16][15] The project had baselined any of multiple refueling capabilities. The asteroid-specific payload was at one end of the spacecraft bus, either for possible removal and replacement via future servicing, or as a separable, reusable spacecraft, leaving a qualified space tug in cislunar space. This made adaption for Gateway easy, as the propulsion system was already designed to be multi-mission reusable.[20][21][22][23][24]
Power and Propulsion Element
In 2017, a year after the Artemis program came into existence, the ARM space tug/propulsion bus was repurposed as the main propulsion system for the Gateway space station. It officially became known as the Power and Propulsion Element or PPE.[6] The PPE will be a smaller version of the Asteroid Redirect bus.[6][25] In 2018, the Gateway was split off from Artemis as a separate program to allow a Moon landing by 2024 without having to wait for the Gateway to be completed.
Commercial company studies
On 1 November 2017, NASA commissioned 5 studies lasting four months into affordable ways to develop the Power and Propulsion Element (PPE), hopefully leveraging private companies' plans. These studies had a combined budget of US$2.4 million. The companies performing the PPE studies were Boeing, Lockheed Martin, Orbital ATK, Sierra Nevada and Space Systems/Loral.[26][4] These awards are in addition to the ongoing set of NextSTEP-2 awards made in 2016 to study development and make ground prototypes of habitat modules that could be used on the Gateway as well as other commercial applications,[27] so the Gateway is likely to incorporate components developed under NextSTEP as well.[4][28]
Contract awarded
In May 2019, Lanteris Space Systems (as Maxar Technologies) was contracted by NASA to manufacture this module, which will also supply the station with electrical power and is based on Lanteris's Lanteris 1300 series satellite bus.[29] The PPE will use Redwire's roll-out solar arrays for power generation, Busek 6 kW Hall-effect thrusters and NASA Advanced Electric Propulsion System (AEPS) Hall-effect thrusters.[30][31][32] Maxar was awarded a firm-fixed price contract of US$375 million to build the PPE. Maxar's SSL business unit, previously known as Space Systems/Loral, will lead the project. Maxar stated they will receive help from Blue Origin and Draper Laboratory on the project, with Blue Origin assisting in human-rating and safety aspect while Draper will work with trajectory and navigation development.[9] NASA is supplying the PPE with a S-band communications system to provide a radio link with nearby vehicles and a passive docking adapter to receive the Gateway's future Utilization Module.
Integration with HALO
As originally planned, PPE would implement the passive mode International Docking System Standard (IDSS) docking port.[35] This meant that any spacecraft implememting active IDSS could theoretically dock to the PPE, such as Orion, Dragon 2, Dream Chaser, and Boeing Starliner. Maxar completed a system requirements review of this design in 2019.[36]
In 2020 NASA introduced new requirements, including integration of PPE and HALO before launch.[36] PPE thus does not need to dock with HALO in space, and its docking port was eliminated. Thus it will no longer be able to undock from HALO.[37] In February 2021 NASA contracted with SpaceX
SR-1 Freedom
In March 2026, NASA announced the indefinite suspension of the Gateway program. PPE was repurposed as the propulsion element of the nuclear-powered Space Reactor‑1 Freedom spacecraft.[1]
PPE construction
- In 2025, the solar array which provides power to the module successfully passed testing.[40]
- On November 4, 2025, Intuitive Machines announced that it would buy Lanteris Space Systems.[41]
- In early 2026, the power systems of PPE were turned on successfully for the first time at the Lanteris Space Systems facility.[42]
