Project Constellation is a plan for the United States Government, via the space agency NASA, to land a man on the Moon, establish a permanent base there, and set the stage for a possible Mars mission. As currently envisioned, Project Constellation consists of the design, construction, testing, and use of heavy boosters (Ares I, Ares IV, Ares V), two new spacecraft (Orion Crew Vehicle and Altair Lunar Lander), and a lunar booster (Earth Departure Stage).
Project Constellation may be considered a modernized version of the Apollo Project of the 1960s, with more of an eye towards a permanent moon base and a future Mars mission. Project Constellation is expected to cost $20 billion US Dollars over twenty years (2004 – 2024), with the cost of spacecraft orders not to exceed $3.5 billion USD. By comparison, the Apollo Project cost $28 billion USD (2006 dollars), while the Shuttle program cost $145 billion (2006 dollars).
The main goal of Project Constellation is to put a man on the Moon by 2020. This is a more relaxed timeline than the Apollo program, which was announced in 1961 and reached the Moon by 1969.
For reaching the Moon, the Apollo missions used a Lunar Orbit Rendezvous (LOR) approach, firing a two-part craft into lunar orbit. One part of the craft (Lunar Module) detached from the other (Command Module), descended to the Moon, then made a rendezvous with the Command Module in lunar orbit. These craft then returned to Earth together. Project Constellation will put a greater emphasis on Earth Orbit Rendezvous (EOR). In EOR, the supplies and fuel are launched separately from the astronauts. These spacecraft then link up in Earth orbit prior to their trip to the Moon. Upon arrival at the Moon, the Orion Crew Vehicle is left in orbit unmanned, while the four-person crew boards the Altair Lunar Lander for a visit to the Moon. Upon conclusion of their stay, Altair again hooks up with Orion, and they return to Earth. This mission approach combines EOR and LOR.
NASA has been testing an inflatable habitat in Antarctica for use by the astronauts of Project Constellation. This could form the nucleus of a future lunar base.