What is the Artemis program?
Humans have not left Earth orbit since Apollo 17 returned from the Moon in 1972. NASA has been trying to change that since 2004, when then-president George W. Bush announced the Vision for Space Exploration, an initiative to send humans back to the Moon and eventually to land on Mars. Since then, NASA's deep space efforts have had a number of names: Constellation (2004-2010, targeted lunar surface and Mars), Journey to Mars (2015-2018, targeted cislunar space, asteroid and Mars), and Moon to Mars (2018 to present, targeting lunar surface and Mars).
Through its current Artemis program, NASA envisions sending astronauts to the lunar south pole by 2024 and eventually establishing a permanent presence on the Moon. The program is a result of the Trump administration's Space Policy Directive 1 and a 26 March 2019 speech by Vice President Mike Pence directing NASA to reach the Moon by 2024, 4 years earlier than its previous goal.
Artemis is designed to land humans on the Moon quickly, by 2024, and focus on Mars as a long-term human spaceflight goal after that. The preliminary short-term plan involves using both commercial rockets and NASA's Space Launch System, the Orion crew capsule, and a lunar landing system. A small space station in lunar orbit called the Gateway would serve future surface missions.
The Planetary Society's principles for human spaceflight lay out how we evaluate, support, and critique proposed plans for human spaceflight.
What is the Space Launch System?
The Space Launch System, or SLS, is a massive rocket based on Space Shuttle-derived technology. It is essentially a larger version of the Shuttle stack that trades out the winged orbiter for either cargo or the Orion crew capsule on top. The vehicle's core stage is a stretched Shuttle external fuel tank powered by 4 Space Shuttle (RS-25) main engines. (During the Shuttle program these engines were refurbished and reused; for SLS they will be ditched in the ocean.) Assisting the core stage during the initial phase of flight is a pair of 5-segment Space Shuttle solid rocket boosters.
Orion is a crew vehicle capable of supporting up to 4 astronauts on deep-space journeys, similar in concept but having a larger interior than the gumdrop-shaped Apollo capsules. Unlike capsules designed solely for transportation to low-Earth orbit, Orion’s heat shield can withstand the high-velocity reentry necessary when returning from deep space. The Orion spacecraft consists of three major components: a pressurized crew capsule, a service module, and a launch abort tower, which is nominally jettisoned during ascent.
The Lunar Gateway is a small space station in lunar orbit that would function as a fuel and supply depot, a science outpost, and a waypoint for missions to and from the lunar surface. The Gateway is currently not required to be operational for the initial 2024 Moon landing. NASA is asking commercial companies to provide Gateway cargo transportation services, similar to the way it does for the International Space Station.
NASA will send a small spacecraft called CAPSTONE (Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment) to the same lunar orbit Gateway will occupy. The microwave oven-sized CubeSat will test out a number of key technologies critical for Artemis, including spacecraft-to-spacecraft communication using the Lunar Reconnaissance Orbiter.
NASA is asking commercial companies to build lunar lander systems that would eventually dock with the Gateway. A visiting Orion crew would board the lander, take it to the surface, and return in either an ascent module or the entire vehicle. Early landers would only be capable of short surface stays, while future vehicles would be able to house crews through the lunar night.