Construction of the Lunar Orbital Platform-Gateway,as the ISS successor is now being called,is projected to begin in the first half of the 2020s.The LOP-G is the main destination for the Orion Program in the 2020s,building up enough experience for missions beyond the Moon and possibly to Mars and even a Venus flyby in the 2030s.The LOP-G is being designed by the five space agencies of the ISS Partnership to succeed the aging Low Earth Orbit station:NASA,ESA,Roscosmos,the Canadian Space Agency and the Japanese Space Agency.The second meeting for LOP-G planning was held in August 2017 at the European Space Centre,ESTEC,in Noordwijk,the Netherlands.*
An outline of the LOP-G initiative has been drawn up.It lays out establishing a cislunar presence as Phase 1 of the project,the core of which is the new space station.The LOP-G is not meant to be continually staffed,unlike the ISS;instead,with the Orion spacecraft docked,a crew of four would work in space for 42 day periods.The LOP-G would consist of a power/propulsion module;a habitation module;a possible airlock for space walks,similar to the Space Shuttle setup;likely an updated Canadarm robot arm;and possibly an advanced glass cupola for a 360-degree view of the Moon and Earth.
The core LOP-G would be assembled by 2025 over three SLS flights,each with a crewed Orion capsule.This could possibly be changed to two SLS flights plus a less expensive SpaceX Falcon 9 Heavy flight for the power/propulsion module deployment,given the President's 2019 NASA budget proposal.
Commercial or international partners could provide the resupply flights.The final construction mission,to bring up the airlock,is projected for 2026.*
With the LOP-G,NASA will practice complex deep space rendezvous,while learning to live and work where a quick return to Earth is not possible.The 40kw solar-electric propulsion system,more powerful than any SEP currently operating,will allow LOP-G to transition between an always-sunlight halo lunar orbit to other orbits that could be used for other applications,including lunar landings.Anyone can come and use the LOP-G,both the commercial and international partners.*
In Phase 2,the Deep Space Transport,depicted as a cylindrical vehicle in concept artwork,will be developed.The LOP-G will be a lunar port of call for a large crew vehicle,the DST.Between each trip,the DST will be resupplied,refurbished and maintained at the LOP-G.Each DST will be good for a total of three roundtrips to Mars.One SLS cargo flight will carry a DST to lunar orbit in 2027.No other launch vehicle but the SLS can carry the 41 metric tonnes of the DST to the Moon in one piece,the minimum size for a Mars-class transport.*
In 2029,a crew would board the DST for a one-year shakedown mission.In 2033,there will be the first crewed flight to a Mars orbit.If a Venus assist,or slingshot,is used to reach Mars,the astronauts could observe the clouds of Venus and the volcanoes of Mars on one mission.*
This is the basic outline sketched by the ISS partners in Holland last summer.Details may be altered,but President Donald Trump and the National Space Council under Vice President Mike Pence are committed to the Orion Program and its commercial and international partnerships.The President's 2019 NASA Budget proposal funds both EM-1 and EM-2,which are the first two Orion missions;the ISS through 2024;as well as the Parker Solar Probe,James Webb Space Telescope and other important missions such as New Horizons.