WASHINGTON-Companies have until Nov. 1 to submit proposals to NASA for a human-rated lander that could be ready in time to carry astronauts to the moon’s surface by the end of 2024, and the agency is leaving open the option for contractors to develop a descent craft that would bypass the planned Gateway mini-space station in lunar orbit, at least for the first landing attempt.

The lunar lander, or Human Landing System, is critical to the Trump administration’s goal of returning humans to the moon’s surface by the end of 2024. NASA named effort after Artemis, the twin sister of Apollo in Greek mythology, after Vice President Mike Pence announced the 2024 goal in a speech March 26.

In the interest of speed, NASA has also relaxed requirements for the early human-rated lunar landers to be reusable. NASA eventually wants to reuse landers on missions ferrying astronauts between the moon’s surface and the Gateway space station in lunar orbit, where the spacecraft could be refueled for multiple landings. And NASA has limited the time for companies to submit their proposals to one month.

“Thirty days,” said Marshall Smith, NASA’s director of human lunar exploration programs. “We know it’s crazy, but so is 2024, I suppose. So we’re all working very fast. I will tell that what we’ve done between March 26 to now probably would have taken the old NASA two years to do.

“For HLS, every action we have worked has been streamlined in order to achieve to the surface of the moon by 2024,” said Lisa Watson-Morgan, the lander program manager at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

There’s little time to spare, and NASA is not planning to conduct an unpiloted demonstration of the lander without astronauts on-board before committing a human crew to a landing attempt.

NASA’s Aerospace Safety Advisory Panel has warned against that strategy. During a September public meeting, the panel suggested that NASA and its contractors “consider the merits of including an uncrewed test of the Human Landing System prior to the first crewed mission as a major risk reduction exercise.”

NASA’s approach to the Artemis program’s first lunar landing mission, which would target a landing near the moon’s south pole, includes several elements. First, at least two components of a new mini-space station lunar orbit, named the Gateway, would launch in 2022 and 2023 to generate electricity, provide propulsion and offer a limited habitat for astronauts.

Components of a human-rated lunar lander would next launch, possibly on multiple rockets, to dock with the Gateway, where the pieces would be robotically assembled into a complete spacecraft. The lander will likely include two or three elements, such as a transfer vehicle to travel from the Gateway’s elliptical orbit around the moon to a closer distance, a descent module for landing, and an ascent vehicle to travel back to the Gateway.

After a checkout of the lander, the Space Launch System heavy-lift rocket would then launch an Orion crew capsule toward the Gateway station with four astronauts on-board in 2024. After Orion docks with the Gateway, two of the astronauts would transfer into the lander for descent to the moon.

Two test flights of the SLS/Orion vehicle to vicinity of the moon and back are planned before the 2024 landing attempt — one without a crew and one with astronauts on-board.

It’s an aggressive schedule, and some senior NASA leaders have demurred when asked about the likelihood of a crewed moon landing occurring by the end 2024.

NASA released a final solicitation, or broad agency announcement, to industry Sept. 30, seeking bids for a contract to design, develop and a lunar lander capable of carrying astronauts. Companies have until Nov. 1 to submit their proposals, and NASA aims to select up to four companies by January to begin 10-month design studies under firm fixed-price contracts.

The request for bids released Sept. 30 came after two draft solicitations, after which industry officials offered comments and proposed changes before the final announcement.

“We have a goal of awarding the contracts in January of 2020, and all this is really needed in order for us to make the schedule of 2024,” Watson-Morgan said an a Human Landing System industry day meeting Oct. 3.