The Trump Administration is proposing to formally start a cislunar space station program and begin assembly early in the next decade with launch of the first element. The Power and Propulsion Element (PPE) is the core module of the station, now named the “Lunar Orbital Platform – Gateway” (LOP-G).



As a part of commercial space industry initiatives for human exploration, the Fiscal Year (FY) 2019 NASA budget request submitted by the President to Congress in February also proposed an accelerated, dedicated commercial launch of the PPE in 2022.

The PPE was previously scheduled to launch as a secondary payload on Exploration Mission-2 (EM-2), which is currently planned to be the first crewed Orion spacecraft mission launch on NASA’s Space Launch System (SLS) rocket. With the PPE no longer on the EM-2 manifest, NASA is evaluating changes to that mission, including aspirations of flying the Habitation module on a more ambitious flight for Orion’s first crew.

Administration green light for “Lunar Orbital Platform – Gateway”

Formerly known as the Deep Space Gateway (DSG), the NASA FY 2019 budget request submitted to Congress in February proposes a formal start to the Lunar Orbital Platform – Gateway program. “While some aspects of the LOP-G program, such as PPE, had been previously funded in Advanced Exploration Systems (AES), this is a new funding line established in the FY 2019 Budget,” the budget submission notes.

The administration is requesting LOP-G funding of US $504.2 million in FY 2019, along with a projected “out-year” funding profile of $662.2 million in FY 2020, $540 million in FY 2021, $558.9 million in FY 2022, and $459.1 million in FY 2023. New government programs like LOP-G need to be approved by both the President and Congress, but negotiations on funding and especially amounts of funding are usually slow and contentious.

The President’s budget request is the beginning of the appropriations process for the fiscal year that begins in October; more frequently, the process is ending without a full resolution. So far, this is the case with the current fiscal year of 2018. Both houses of Congress will draft appropriations bills, which will include funding for NASA, but in recent years few of those bills have been approved. Often, a series of Continuing Resolutions are passed which fund only programs previously authorized.

This is the case for FY 2018, which is almost half over. The last appropriations bill enacted was for FY 2017, and then not until May. If FY 2019 is partially or fully funded through Continuing Resolutions, the status of the LOP-G as a whole and the PPE more specifically would remain uncertain.

Under the administration’s budget request, the cislunar platform retains its basic composition. In contrast to the giant International Space Station (ISS) which has been continuously crewed since 2000, LOP-G would be a smaller, compact station, at least at the beginning.

“Current analysis suggests that the initial functionality will include four main elements: a Power and Propulsion Element (PPE), habitation element, airlock element to enable docking and Extra-Vehicular Activities (EVA), and a logistics element for cargo delivery, science utilization, exploration technology demonstrations, and potential commercial utilization,” the budget submission said.

Another contrast with the ISS is that the LOP-G is not planned to support a permanent human presence. It is expected that the gateway will allow Orion to extend its own space endurance beyond the standalone capability of 21 days with a crew of four. A Deep Space Transport concept outlined in previous studies is not mentioned in the budget request.

The PPE is the core element of the LOP-G. “It will provide transportation for the LOP-G between cislunar orbits with the option to perform any needed orbital maintenance,” the budget request stated.

“It will provide attitude control for the LOP-G in multiple configurations, communication to and from Earth, space-to-space communication, space-to-lunar communication, and in support of astronaut EVA. PPE will also deliver systems necessary for deep space navigation, docking, and refueling. At the end of the LOP-G operational life, PPE will move the integrated LOP-G stack to a disposal orbit.”

NASA is currently funding concurrent four-month studies by five U.S. companies of detailed PPE concepts. A total amount of approximately $2.4 million was divided up in awards to Boeing, Lockheed Martin, Orbital ATK, Sierra Nevada Corporation, and Space Systems/Loral. The studies are expected to conclude by the early Spring and the budget request proposes a launch readiness date for the PPE of August, 2022.

Plan to launch PPE as soon as possible in 2022

The Glenn Research Center in Cleveland is the lead NASA center for the PPE and the current plan is for the agency to award funding to a commercial developer to independently build the PPE and fly the spacecraft in cislunar space for a year-long demonstration mission. Titled “Spaceflight Demonstration of a Power and Propulsion Element (PPE),” the Sources Sought synopsis was originally posted by Glenn at the end of November and subsequently amended following the FY 2019 budget request submission.

Shortly after the existing commercial PPE studies are completed and received, the plan now is to release the solicitation for the PPE and its demonstration mission. “NASA is preparing to build in partnership the in-space infrastructure for long-term exploration and development of the Moon by accelerating its plans to launch the power and propulsion element of the Lunar Orbital Platform-Gateway into 2022,” Dr. Michael Barrett, Power and Propulsion Element Manager at NASA Glenn, wrote in an email.

“As the industry studies on affordable ways to develop the power and propulsion element are winding down, the agency published a synopsis February 20, 2018, outlining a forthcoming solicitation that may lead to the acquisition of the element. In the coming months, NASA intends to seek proposals for the development and spaceflight demonstration of the power and propulsion element.”

“NASA currently envisions the PPE will be fully owned and operated by the PPE developer through completion of an industry partner/NASA spaceflight demonstration, the duration of which would be up to 1 year (TBD),” the synopsis explains. “At the completion of the demonstration, and if NASA determines that the PPE meets its future needs, NASA intends to have the option to acquire the end item PPE for NASA use, specifically as the first element of the cis-lunar gateway concept.”

In addition to starting and funding the LOP-G program, the FY 2019 budget request also proposes a dedicated, commercial launch for the PPE. Previously, plans were for the PPE to launch “co-manifested” on the SLS launch of the first crewed Orion spacecraft on EM-2. A week after the budget request was submitted to Congress in mid-February, the Sources Sought synopsis was amended to reflect this change, in which the winner of the award would have the authority to choose the launch provider for the PPE.

“The PPE is envisioned to be launched in 2022. Proposals are to include an Offeror provided commercial launch vehicle for the launch of the PPE,” the updated synopsis says.

The EM-2 launch is currently shown scheduled for FY 2023, but the new proposal allows the PPE to launch and begin its demonstration mission sooner, perhaps as soon as the August 2022 launch readiness date forecast in the budget request. In the meantime, the plan is for NASA to issue a request for proposals for the PPE and its demo mission in the next few months, with proposals due by mid-Summer.

“The targeted release of the draft solicitation will be in the April 2018 timeframe with final proposals anticipated to be due in the late July 2018 timeframe,” the synopsis added. “An Industry Day is planned to be held within two weeks following the release of the draft.”

The initial set of requirements for the PPE that went into the on-going commercial study were based on the original co-manifested SLS launch. This included constraints on compatibility with the SLS launch environment and a maximum mass of 7500 kilograms imposed by flying as an SLS co-manifest payload and the unique EM-2 mission profile.

It is currently unknown whether those SLS compatibility requirements for the PPE will remain.

Re-evaluating EM-2

With the PPE removed from the EM-2 manifest, NASA is now evaluating how this impacts the mission objectives and profile. EM-2 remains the first crewed flight of the Orion spacecraft, and the mission as baselined would keep Orion and crew close to Earth for the first 24 hours of the flight.

After launch into an initial low Earth orbit, SLS would place Orion and crew in a high Earth orbit that would take almost a full day to complete. This would allow a test flight checkout close to home of the new life support systems on Orion . If there were any serious problems early in the mission, staying in Earth orbit would permit a faster return. If everything checked out, then Orion would fire its engines to proceed on a flight around the Moon.

EM-2 is also planned to be the first flight of the Exploration Upper Stage (EUS), which provides enough performance to send both Orion and a large, secondary payload on a translunar trajectory. Given the desire to reduce risks on the first crewed flight of Orion, when the PPE was also on-board, the EM-2 mission profile had EUS doing double-duty. After dropping Orion off in high Earth orbit, EUS was to then send the PPE by itself to the Moon.

This was possible because the PPE is a fully-independent spacecraft, with its own maneuvering and attitude control capabilities. It is expected that on its dedicated commercial launch, the PPE will be placed on a similar lunar flyby trajectory that safely disposes of the launcher’s upper stage while allowing the spacecraft to maneuver itself into lunar orbit.

With the proposal for the PPE to launch ahead of EM-2, NASA is now thinking about moving the LOP-G Habitation module up to fly on the mission. Tucked away in a corner of a FY 2019 budget overview chart, the mission is now shown as “EM-2 (EUS, LOP-G Hab).”

Recent testimony by Acting NASA Administrator Robert Lightfoot to a House oversight subcommittee also hints at the ambition to fly the Habitation module on EM-2. Mr. Lightfoot’s written statement submitted to the Space Subcommittee of the House Committee on Science, Space and Technology for a March 7 hearing noted launch of two LOP-G pieces by the end of the budget’s five year outlook. “NASA plans to achieve uncrewed and crewed test launches of the SLS and Orion system; launched two of the initial elements of the Lunar Orbital Platform – Gateway (to be complete with two additional launches by 2025),” the statement said.

Prior to the budget request, the notional plan for the gateway assembly sequence was for the Hab module to be delivered by Orion to the gateway on the EM-3 mission.

EM-3 is a typical SLS/Orion mission, but also a more ambitious one. Rather than the current EM-2 plan for Orion and her crew to perform a flyby of the Moon, the notional EM-3 mission profile has the EUS place both Orion and the Hab module on a direct translunar injection (TLI) trajectory.

Orion would dock to the Hab module and fire its engines to enter into the same lunar halo orbit as the PPE. The spacecraft and crew would then rendezvous and dock with the PPE, leaving the Hab at the station as its second element. After staying there for some time, Orion and crew would leave lunar orbit and return to Earth.

If this mission profile were to be moved up and replace the current EM-2 test flight, development of Rendezvous, Proximity Operations and Docking (RPOD) capabilities for Orion would also need to be moved up.

There are also questions whether the risk-reduction objectives of the current EM-2 Orion mission are compatible with the objective of Orion taking the Hab module to rendezvous with the Gateway. First, it may not be possible for the EUS to first take the Orion-Hab duo to high Earth orbit, loiter there with them for 24 hours, and then finish a full translunar injection with another long burn.

Second, the other initial LOP-G elements have no built-in navigation or maneuvering capabilities and so could not support the same “multi translunar injection” (MTLI) profile as the PPE. The Hab relies on Orion for transportation from where SLS drops them off into lunar orbit and finally to the Gateway.

For now, without approval of the commercial initiatives in the budget request, EM-2 remains officially as baselined.

“The mission objective for EM-2 (a crewed flight test of SLS and Orion systems) and the EM-2 mission profile (with a one-time 24 hour high orbit checkout of Orion prior to insertion into a free-return lunar trajectory) are currently unchanged,” Cheryl Warner, Public Affairs Officer at NASA Headquarters, wrote in an email.

“[The] assessment is correct that the EM-2 mission profile would need to be changed to accommodate the change from a power propulsion element to a habitat on EM-2. NASA is looking at options for EM-2, with the expectation of making a mission planning decision by early next year.”