More than 30 stories tall, the Space Launch System will be the most powerful American rocket since the Saturn V that thundered aloft with Apollo astronauts destined for moon landings in the late 1960s and early 1970s.
NASA's Orion crew capsule is designed to ride atop it.
An initial unmanned test flight is slated for 2017. A first piloted shakedown cruise would follow in 2021.
U.S. astronauts then would make preparatory voyages about once a year before setting sail on an expedition to an asteroid in 2025.
Senior administration officials say the heavy-lift development program will cost $3 billion per year. That's about the same amount that NASA spent to run the space shuttle program in 2009.
"We are trying to make this as affordable and sustainable as possible," an administration official said. "That's a large part of what we've been doing over the last year."
NASA Administrator Charles Bolden will detail the plan in a morning news conference on Capitol Hill with U.S. Sens. Bill Nelson, D-Fl., and Kay Bailey Hutchison, R-Texas, two big backers of the project.
The heavy-lift rocket, which will launch from Kennedy Space Center, will be about 34 stories tall. Its development will leverage billions of dollars of investments already made in the shuttle program and the cancelled Project Constellation return-to-the-moon initiative.
The major components of the rocket:
• The vehicle's core stage will be a stretched version of the shuttle's bullet-shaped external tank. It will be powered at first by five space shuttle main engines; an upgraded version of the engine will be developed for use later on.
• The second stage of the rocket will be powered by a J2X engine, which already is in development. An advanced version of a Saturn V second-stage engine, the J2X would have been the second stage of Project Constellation's Ares I and Ares V rockets.
•The vehicle also will be equipped with either shuttle-derived solid rocket boosters or liquid-fueled boosters.
There will be a booster contract competition that will be based on cost and performance requirements. Administration officials envision potential cost savings and improved performance.
"We thought we could get both cost and performance savings by doing the competition," a senor administration official said.
The Obama White House considers the heavy-lift rocket and Orion crew capsule programs crucial parts of an affordable program that calls for:
• Extending International Space Station operations to at least 2020.
• Investing in the development of commercial spacecraft to ferry astronauts to and from the International Space Station and other low Earth orbit destinations.
"It really is critical that we pair this with the commercial crew program. That is the way that NASA is going to have sustainable resources in the long run to be able to focus on deep space," a senior administration official said.
"And so we really see this all as being linked. Commercial crew will be our transportation to and from the International Space Station and low Earth orbit, and then to go farther, we really need to focus on building the larger rocket and (Orion) crew vehicle."
The new initiative is important to Florida's Space Coast, where thousands of jobs have been lost in the wake of the completion of International Space Station assembly and shuttle fleet retirement.
A senior administration official said the heavy-lift development program would provide a "stable future" from KSC, Johnson Space Center in Houston, Marshall Space Flight Center in Huntsville, Ala., and Stennis Space Center in Bay St. Louis, Miss. --(AT) NASA's four major human space flight facilities.
"I think we're preserving high-tech jobs here that will be producing innovation over the coming decade that will be useful to the space program," the official said.
The plan for a heavy-lift rocket emerged in Congress last year with the bipartisan NASA Authorization Act of 2010. It called on NASA to develop a heavy-lift rocket that initially could carry at least 70 to 100 metric tons into orbit — about three to four times the capacity of the retired space shuttle.
The vehicle would evolve into a rocket that could haul 130 metric tons, roughly five times the capability of the shuttle and about the equivalent of the Saturn V moon rocket.
The legislation was signed by President Barack Obama last fall and required NASA to report back within 90 days on its design for the rocket.
The agency did so in January, sending a report that said the job could not be done with $11 billion by 2016, the funding limit and deadline date set by key congressional leaders.
At $3 billion per year, the new plan would cost $18 billion through an initial test flight in 2017, and about $30 billion through the first piloted mission in 2021.
The heavy-lift rocket and Orion spacecraft then would become the workhorses of inner solar system exploration, the vehicles enabling mankind once again to explore beyond the grasp of Earth's gravity.
So why did it take until September for NASA to nail down a design?
"We think the timetable is appropriate for the level of investment that we're asking the American taxpayers to make here," a senior administration official said.
"It's the most important (space program) decision we will make for at least the next decade. We wanted to take the time to get it right."