WASHINGTON - NASA briefed senior White House officials Wednesday on its plan to spend $100 billion and the next 12 years building the spacecraft and rockets it needs to put humans back on the Moon by 2018.

The U.S. space agency now expects to roll out its lunar exploration plan to key Congressional committees on Friday and to the broader public through a news conference on Monday, Washington sources tell SPACE.com.

U.S. President George W. Bush called in January 2004 for the United States to return to the Moon by 2020 as the first major step in a broader space exploration vision aimed at extending the human presence throughout the solar system.

NASA has been working intensely since April on an exploration plan that entails building an 18-foot (5.5-meter) blunt body crew capsule and launchers built from major space shuttle components including the main engines, solid rocket boosters and massive external fuel tanks.

That plan, called the Exploration Systems Architecture Study, was presented by NASA Administrator Mike Griffin, his space operations chief Bill Gerstenmaier and several other senior agency officials Wednesday afternoon to senior White House policy officials, including an advisor to U.S. Vice President Richard Cheney and the president's Deputy National Security Advisor J.D. Crouch.

NASA's plan, according to briefing charts obtained by SPACE.com, envisions beginning a sustained lunar exploration campaign in 2018 by landing four astronauts on the Moon for a seven-day stay.

The expedition would begin, these charts show, by launching the lunar lander and Earth departure stage (essentially a giant propulsion module) on a heavy-lift launch vehicle that would be lifted into orbit by five space shuttle main engines and a pair of five-segment shuttle solid rocket boosters.

Once the Earth departure stage and lunar lander are safely in orbit, NASA would launch the Crew Exploration Vehicle capsule atop a new launcher built from a four-segment shuttle solid rocket booster and an upper stage powered by a single space shuttle main engine.

The CEV would then dock with the lunar lander and Earth departure stage and begin its several day journey to the Moon.

NASA's plan envisions being able to land four-person human crews anywhere on the Moon's surface and to eventually use the system to transport crew members to and from a lunar outpost that it would consider building on the lunar south pole, according to the charts, because of the regions elevated quantities of hydrogen and possibly water ice.

One of NASA's reasons for going back to the Moon is to demonstrate that astronauts can essentially "live off the land" by using lunar resources to produce potable water, fuel and other valuable commodities. Such capabilities are considered extremely important to human expeditions to Mars which, because of the distances involved, would be much longer missions entailing a minimum of 500 days spent on the planet's surface.

NASA's Crew Exploration Vehicle is expected to cost $5.5 billion to develop, according to government and industry sources, and the Crew Launch Vehicle another $4.5 billion. The heavy-lift launcher, which would be capable of lofting 125 metric tons of payload, is expected to cost more than $5 billion but less than $10 billion to develop, according to these sources.

NASA's plan also calls for using the Crew Exploration Vehicle, equipped with as many as six seats, to transport astronauts to and from the international space station. An unmanned version of the Crew Exploration Vehicle could be used to deliver a limited amount of cargo to the space station.

NASA would like to field the Crew Exploration Vehicle by 2011, or within a year of when it plans to fly the space shuttle for the last time. Development of the heavy lift launcher, lunar lander and Earth departure stage would begin in 2011. By that time, according to NASA's charts, the space agency would expect to be spending $7 billion a year on its exploration efforts, a figure projected to grow to more than $15 billion a year by 2018, that date NASA has targeted for its first human lunar landing since Apollo 17 in 1972.

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