WASHINGTON — Boeing announced Nov. 5 that it has submitted a proposal to NASA to develop a lunar lander that could be launched in a single piece on a Space Launch System rocket.

The company said its “Fewest Steps to the Moon” proposal, submitted for NASA’s Human Landing Services program, minimized the number of launches and other “mission critical events” needed to get astronauts to the surface of the moon.

“Using the lift capability of NASA’s Space Launch System Block 1B, we have developed a ‘Fewest Steps to the Moon’ approach that minimizes mission complexity, while offering the safest and most direct path to the lunar surface,” Jim Chilton, senior vice president for space and launch at Boeing Defense, Space and Security, said in a company statement.

The two-stage launched would launch on the enhanced Block 1B version of the rocket, which uses the more powerful Exploration Upper Stage (EUS), and go into lunar orbit. It would either rendezvous with the lunar Gateway or directly with an Orion spacecraft, where astronauts would board it for a trip to the lunar surface.

The lander is designed to be launched as a single unit, rather than in separate modules that would be aggregated at the Gateway. The lander also doesn’t require a separate transfer stage to maneuver from a near-rectilinear halo orbit to low lunar orbit, as some other designs have proposed.

This approach, the company said in a statement, reduces the number of mission critical events, such as launches and dockings, to as few as five. Alternative approaches, Boeing claims, require 11 or more such events.

That argument mirrors one made by Doug Cooke, a former NASA associate administrator for exploration who now consults for several companies, including Boeing, at a House hearing in September. “The fewer launches and critical operations per mission, the higher the probability of mission success,” he said, identifying “17 critical mission operations” required for a successful mission under NASA’s baseline approach.

He argued that NASA should focus on SLS, including the Block 1B version, and Orion spacecraft, as well as a payload shroud for the SLS that could accommodate a lunar lander. “I believe a crew and a less constrained lander can be launched to the moon with two SLS launches,” he said.

Under NASA’s current plans, though, the Block 1B version of SLS won’t be ready in time for a 2024 landing. NASA announced Oct. 16 that it was in talks with Boeing to award a long-term production contract for the SLS, but that the Block 1B would not enter service until the Artemis 4 mission in 2025.

Boeing joins a Blue Origin-led “national team” that includes Draper, Lockheed Martin and Northrop Grumman in pursuing a NASA lunar lander contract. Blue Origin confirmed that its team, announced by company founder Jeff Bezos Oct. 22, had submitted a proposal to NASA by the Nov. 5 deadline. Boeing, by contrast, does not have major partners in a similar teaming arrangement, company spokesman Steve Siceloff said.

SpaceX is also expected to submit a proposal, one likely based on its Starship reusable launch vehicle under development. A SpaceX spokesperson said Nov. 5 the company wasn’t disclosing details about any proposal it may have submitted, but did refer comments made by SpaceX President Gwynne Shotwell at a media roundtable last month during the International Astronautical Congress where she said the company was “aiming to be part of Artemis for sure.”

NASA expects to award initial study contracts to several companies as soon as the end of the year, and eventually select two companies to proceed into full-scale development of landers, one which would be used for the initial 2024 landing and the other for a 2025 mission. Those plans, though, are pending funding for fiscal year 2020 yet to be appropriated by Congress.