Nasa has revealed plans for a new giant rocket to spearhead its space programme.
It harkens back to the giant Saturn V workhorses that propelled men to the moon. But this time the destinations will be much farther and the rocket even more powerful.
The Space Launch System is a multibillion-dollar programme will carry astronauts in a capsule on top and start test launching from Cape Canaveral, Florida, in six years.
Senator Bill Nelson, a Florida Democrat, called it "a monster rocket."
"Will it be tough times going forward? Of course it is," he said. "We are in an era in which we have to do more with less - all across the board - and the competition for the available dollars will be fierce. But what we have here now are the realistic costs that have been scrubbed by an outside, independent third party."
Mr Nelson put the cost of the programme at about 18 billion dollars over the next five years.
The size, shape and heavier reliance on liquid fuel as opposed to solid rocket boosters is much closer to the moon rockets than the recently retired space shuttles, which were winged, reusable ships that sat on top of a giant liquid fuel tank, with twin solid boosters providing most of the power. It is also a shift in emphasis from the moon-based, solid-rocket-oriented plans proposed by the George Bush administration.
Nasa estimates it will be building and launching about one rocket a year for about 15 years or more in the 2020s and 2030s.
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. 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 carry into space 77 tons to 110 tons of payload, which would include the six-person Orion Multi-Purpose Crew Vehicle capsule and more. Eventually it will be able to carry 143 tons, maybe even 165 tons. By comparison, the long-dormant Saturn V booster was able to lift 130 tons.
The plans dwarf the rumbling lift-off power of the space shuttle, which could haul just 27 tons. The biggest current unmanned rocket can carry about 25 tons.