To soar far away from Earth and even on to Mars, NASA has dreamed up the world's most powerful rocket, a behemoth that borrows from the workhorse liquid-fuel rockets that sent Apollo missions into space four decades ago.
NASA Administrator Charles Bolden and several members of Congress joined Wednesday in unveiling the Obama administration's much-delayed general plans for its rocket design, called the Space Launch System. It will begin unmanned test flights in six years, and carry astronauts in a capsule on top in a decade.
"This is a great day for NASA, I think, for NASA and the nation," NASA Administrator Charles Bolden said at a U.S. Senate news conference called to unveil the concept.
The rocket-building effort is projected to cost $18 billion through 2017, and about $35 billion by the time it carries astronauts beyond Earth orbit.
Two of the senators who worked with NASA and the White House on the plan, Florida Democrat Bill Nelson and Texas Republican Kay Bailey Hutchison, said they were pleased by the plan and signaled that Congress would give its assent.
"I believe we really are going forward now, all as one, with one goal," Hutchison told journalists. She said the plan was "a commitment that NASA — NASA — is going to lead the pack."
Closer to Apollo
The size, shape and potentially heavier reliance on liquid fuel as opposed to solid rocket boosters is much closer to Apollo than the recently retired space shuttles, which were winged, reusable ships that sat on top of a giant liquid-fuel tank, with twin solid rocket boosters providing most of the power. It's also a shift in emphasis from the moon-based, solid-rocket-oriented plans proposed by the George W. Bush administration.
"It's back to the future with a reliable liquid technology," said Stanford University professor Scott Hubbard, a former NASA senior manager who was on the board that investigated the space shuttle Columbia's loss in 2003.
NASA figures it will be building and launching about one rocket a year for about 15 years or more in the 2020s and 2030s, according to senior administration officials who spoke with The Associated Press on condition of anonymity in advance of Wednesday's announcement.
The idea is to launch its first unmanned test flight in 2017, with the first crew flying in 2021 and astronauts heading to a nearby asteroid in 2025, the officials said. From there, NASA hopes to send the rocket and astronauts to Mars — at first just to circle, but then later landing on the Red Planet — in the 2030s.
At first the rockets will be able to lift at least 70 metric tons (77 U.S. tons) of payload, which would include the six-person Orion multipurpose crew vehicle and more. Eventually it will be able to carry at least 130 metric tons (143 U.S. tons) into space, maybe even more. In comparison, the long-dormant Saturn V booster that sent humans to the moon was able to lift 120 metric tons (132 U.S. tons).
"It's fair to call this the most powerful rocket built," Bill Gerstenmaier, NASA's associate administrator for human exploration and operations, told journalists. He said potential contractors would gather with NASA officials to discuss the project at an "industry day" on Sept. 29.
The plans dwarf the rumbling liftoff power of the space shuttle, which could haul just 27 U.S. tons. The biggest current unmanned rocket can carry about 25 tons.
The size plans elicited an amazed "good grief" from Hubbard, who said it would limit how often they could be built or launched. Unlike the reusable shuttle, these rockets are mostly one-and-done, with new ones built for every launch.
Some of the design elements, the deadline and the requirement for such a rocket were dictated by Congress.
While the recently retired space shuttle's main engines were fueled by liquid hydrogen and liquid oxygen, it was primarily powered into orbit by solid rockets. Solid rocket boosters were designed to be cheaper, but a booster flaw caused the fatal space shuttle Challenger accident in 1986. The biggest drawback was that solid rockets can't be stopped once they are lit; liquid ones can.
The new plan is to use a giant rocket powered by liquid hydrogen and liquid oxygen. Apollo, Gemini and Mercury flew into space on liquid rockets, and liquids fuel most of the world's unmanned commercial rockets. Russia's Soyuz rocket is liquid-fueled, too.
During its initial test flights the rocket will use solid rocket boosters designed for the shuttle strapped on its outside, and will have three shuttle main engines powering it on the inside. But soon after that, the rocket would be built with five main engines, and the solid rocket boosters would be replaced with new-technology boosters that may be either liquid or solid.
"We can go compete that and get the best value" for the resulting launch system, Gerstenmaier said.
Big questions over cost
NASA figures it will spend about $3 billion a year on the plan, with development costs adding up to around $35 billion, officials said.
Nelson's office said the cost of getting the rocket ready for its first unmanned flight in 2017 would amount to $18 billion, with $10 billion of that going to the rocket, $6 billion to the Orion capsule and $2 billion to launch pad construction at Kennedy Space Center.
"What we have here now are the realistic costs," Nelson said in a statement.
Gerstenmaier said follow-on development and test flights after 2017 would add to the $18 billion figure — but he declined to be specific on the spending levels, other than to say that $3 billion a year was a rough estimate. Gerstenmaier told msnbc.com that the spending levels would be in line with the plan already in place for the coming years.
"This is accommodated in our current NASA budget," he said.
The key financial part of this arrangement is that NASA hopes to save money by turning over the launching of astronauts to the International Space Station, which orbits Earth, to private companies and just rent spaces for astronauts like a giant taxi service. NASA would then spend the money on leaving Earth's orbit and the Earth-moon system.
The project could give a powerful boost to the aerospace workforce employed by NASA and its contractors, which have ordered thousands of layoffs due to the end of the 30-year space shuttle program this summer.
But in his interview with AP, Hubbard worried that NASA has a history of spending way more than initially proposed — the space shuttle cost about twice what it was supposed to — and that the rocket development effort could drain money from other NASA missions. Additional money would have to be spent developing other hardware for human exploration, such as landers and habitats.
Sore point for Congress
Wednesday's unveiling of the new rocket concept came after weeks of criticism from members of Congress, who had accused the Obama administration of trying to sabotage U.S. human spaceflight by producing inflated cost estimates for the program and delaying the release of its plan.
Hutchison acknowledged that there were frictions between Capitol Hill and the White House but indicated that policymakers had smoothed over their differences.
"This is a day that we have been looking forward to for a long time," she said. "It's no secret that we had hoped it would be sooner."
Three leading House Republicans — Ralph Hall of Texas, Steven Palazzo of Mississippi and Frank Wolf of Virginia — issued a statement expressing irritation that it took so long for the White House to give its go-ahead to the rocket plan.
“It is our sincere hope that today’s announcement signals a breakthrough with this president that will help alleviate the uncertainty that has plagued our aerospace industrial base and wreaked havoc on its employees," they said. "We will not judge today’s announcement by the administration’s words, but by their deeds and actions in the coming months and years.”
This report includes information from The Associated Press' Seth Borenstein and msnbc.com's Alan Boyle.