WASHINGTON — NASA now expects to release a draft request for proposals for the first element of the proposed Lunar Orbital Platform-Gateway this summer, several months later that previously planned.

In an update posted on the Federal Business Opportunities website May 31, NASA said it expects to release the draft solicitation for the Power and Propulsion Element (PPE) of the Gateway in June or July, followed by an industry day at the Glenn Research Center. The update didn’t state when a final solicitation would be released, but said NASA expected final proposals to be due in November.

In the previous formal update about the PPE program, posted to the same website in February, NASA said it was expecting to release a draft solicitation in April, with proposals due in late July. The agency didn’t explain the delayed schedule for the PPE program in its statement.

The PPE is the first element of the Gateway, providing power for later elements as well as electric propulsion. NASA plans to later add to the Gateway modules for habitation and logistics, as well as an airlock and docking ports for visiting Orion spacecraft. The Gateway is intended to support future robotic and crewed missions to the lunar surface as well as build up experience for future human missions to Mars.

PPE itself is based on work NASA performed on the Asteroid Redirect Mission (ARM), whose robotic element planned to use a spacecraft with a power and electric propulsion system similar to PPE to travel to a near Earth asteroid and collect a boulder from it for return to cislunar space.

“We have a head start on the Power and Propulsion Element based on work we did with the previous mission, the Asteroid Redirect Mission,” said Ron Ticker, deputy director of the PPE program at NASA Headquarters, during a May 25 presentation at the International Space Development Conference in Los Angeles. “Many of the technologies developed under ARM are also applicable to PPE.”

PPE’s baseline capabilities include the generation of 50 kilowatts of electrical power as well as hosting a 40-kilowatt electric propulsion system, with storage of up to two tons of xenon propellant and the ability to be refueled. In addition, he said the unit would be responsible for communications with Earth, visiting spacecraft and spacecraft on the lunar surface. The spacecraft will be able to support science and technology demonstration hosted payloads on its exterior, and have a service life of 15 years.

NASA plans to procure the PPE through a public-private partnership. Ticker, echoing comments from other NASA officials earlier this year, left open the possibility of acquiring more than one PPE unit from industry. “NASA intends to release a [Broad Agency Announcement] to award one or more contracts for a NASA-industry partnership for development and demonstration of a PPE,” he said.

NASA still plans to complete the PPE in 2022, he said, launching it on a commercial launch vehicle. The agency hasn’t released formal plans for how it will procure other Gateway elements, including the roles international partners may play in providing those components, other than a May 2 memo that states that by the summer “the goal is to have the distribution of functions across all partners (domestic and International) sufficient to begin design and acquisition work on [the] gateway for the remaining elements beyond the PPE.”