Mark your calendar for 2017. That's the year NASA says it plans to launch the most powerful rocket that humans have ever sent into space.

With up to 20 percent more thrust than the Apollo-era Saturn V and standing up to 40 feet taller, the new NASA rocket is the hardware portion of the answer to a question Washington has been wrestling with in earnest since the space shuttle Columbia broke up on reentry in 2003: What comes after the shuttle program?

The new design, formally unveiled Wednesday, looks a bit like a stubby version of the Saturn V rocket. It draws heavily on key systems from the space shuttle and now-defunct Ares programs.

The broad-brush blueprint: Stretch the shuttle's external fuel tank, bolt three to five shuttle main engines to the bottom, and add a second stage topped with a crew capsule. Or configure the second stage for cargo only. Then strap two or more outboard boosters to the side of the first stage to ensure the rocket eventually can carry up to 130 metric tons to orbit.

By 2017, the National Aeronautics and Space Administration anticipates launching the first demonstration version of the rocket, the forerunner of a version capable of launching 70 metric tons. The agency pegs the cost of developing the initial version of the rocket and preparing its launch facilities at the Kennedy Space Center in Florida at $18 billion.

The cost is in line with funding levels set in a bipartisan NASA authorization bill that cleared Congress last fall, NASA officials say.

Beyond 2017, NASA officials are unwilling to speculate on costs. Although President Obama and NASA officials have spoken of missions to an asteroid, the moon, and eventually Mars during the 2020s and beyond, those go, no-go decisions ultimately will be made by future administrations.

NASA still aims to rely on private companies to transport astronauts and supplies to and from the International Space Station. At the end of November, Space Exploration Technologies Corp., based in Hawthorne, Calif., is scheduled to launch a Falcon 9 rocket, topped with the company's Dragon capsule, on a demonstration flight to the space station. If all goes well, the company anticipates the start of regular resupply flights soon thereafter.

The approach and the next-decade destinations grow out of options developed by a commission that Mr. Obama appointed in 2009 to review the US human spaceflight program and offer suggestions for putting it on a financially sustainable path, one that could be expected to span several administrations.

Although the committee, headed by former aerospace executive Norman Augustine, took pains to describe its results as "options," it clearly favored the approach the White House ultimately adopted. That approach, the so-called flexible path, included a shuttle-derived heavy-lift rocket as one possible design that NASA could use to loft astronauts beyond low-Earth orbit.

Such a design is what was unveiled Wednesday.

The goal of the space launch system (SLS) program, officials say, is to ensure that if and when Washington commits to sending astronauts beyond low-Earth orbit, NASA has a flexible launch system that will be able to support such trips.

"We have a really sound configuration here," one that enjoys "pretty good support overall" from the White House and key lawmakers on Capitol Hill, said William Gerstenmaier, NASA's associate administrator for human exploration and operations mission directorate, during a briefing Wednesday.

As if to underscore the point, Sen. Kay Bailey Hutchison (R) of Texas noted during an earlier press conference that "as ranking member of the committee that is writing the budget, I see very strong bipartisan support of NASA and its key roles," including space exploration.

GOP budget hawks in the Senate are offering up proposals for deep cuts in federal spending, she notes. "But they have not cut the core mission of NASA," she said.

NASA has long had a reputation for low-balling initial budget estimates for new rockets. The space shuttle remains the classic example. Initially billed as a system that would cost some $43 billion in 2011 dollars and after adjusting for inflation, the final bill has come in at just under $200 billion.

A never-been-done-before, complex system like the shuttle is always vulnerable to rising costs as experience forces design changes, point out aerospace engineers. Moreover, the programs are subject to the ups and downs of the federal budget process, which can force agencies to stretch a project's development time and so boost its cost.

This time around, NASA is basing its design – and hence cost estimates – on flight-tested hardware with production facilities and experienced workers to build it.

Still, the 2017 date won't be easy to meet, Mr. Gerstenmaier cautions.

"We've minimized the amount of development" by incorporating off-the-shelf shuttle main engines, as well as outboard solid-rocket boosters that have been flight-tested, he says. "But there's still a lot of work to do" to design the first and second stages.