The Deep Space GATEWAY (now simply GATEWAY)
The Deep Space GATEWAY
is lead by the
Multilateral Coordination Board
(MCB). It has its roots as the Cis-lunar base envisioned back in the 2010's. The GATEWAY is currently intended as a stepping stone to Mars and support the
Global Exploration Roadmap
. It may also be used for lunar surface operations.
Photograph courtesy of NASA
In 2016 the MCB had determined the ORION would be used for deep space operations. The 21st Workshop on Radiation Monitoring for the ISS, session 11 presented Orion Exploration Mission 1: Proposed Radiation Measurements in Cislunar Space. Note that ORIONs free space starts to shrink due to radiation concerns.
Progress in defining the Deep Space Gateway and Transport Plan, March 28, 2017 provides an outline of GATEWAY. Additional information can be found at russianspaceweb.
From February 27 through March 1, 2018 a Deep Space Gateway Concept science workshop was held in Denver, Colorado. Jason Crusan, Advanced Exploration Systems at NASA HQ released Future Human Exploration Planning: Lunar Orbital Platform-Gateway and Science Workshop Findings.
May 2, 2018 NASA posted NASA's Lunar Outpost will Extend Human Presence in Deep Space.
October 18, 2018 NASA posted NASA Calls for Instruments, Technologies for Delivery to the Moon.
The GATEWAY will have a habitat module to home astronauts in upcoming exploration missions. Nasaspaceflight shows one habitat being furnished by international partners and a second habitat fron the U.S. which may include "expandable" technology. On September 8, 2018 Nola Taylor Redd contributed to space.com with Take a Look Inside Lockheed Martin's proposed Lunar "Gateway" Habitat for Astronauts. The habitat is reportedly 15' wide and nearly 22' long with astronauts occupying the space for up to 90 days. Another possible habitat configuration is presented at Marshall Space Flight Center consisting of a hab, a Multi-Mission Space Exploration Vehicle (MMSEV) docking tunnel and MPLM. It is intended that ORION would be docked with GATEWAY for these durations.
When you consider the hab would require "life-support systems, sleep stations, exerecise machines, science lab space and robotic workstations" habitable space starts to shrink as shown at this nasaspaceflight post for a 4-astronaut 500 days configuration.
The size of the habitat is dependent on what can fit on the SLS launch system. So why not use and expandable such as the Bigelow Aerospace B-300? There is another plan in progress for the B-300 - the "Lunar Depot".