NASA has 'firmly committed' to launching the new Space Launch System rocket by 2018 - and one day using it to take humans to Mars.
The new rocket launcher is the largest and most complex ever devised, and will finally give NASA a way to send its own astronauts into space - a task for which it currently relies on Russia.
The SLS will also take explorers to asteroids and possibly to the Moon, as it looks set to be NASA's main ticket to space for the next 30-40 years.
Parts of the rocket - many of which are based on existing tech - are already undergoing testing
Now NASA has said the rocket has completed a "rigorous review" of the system, and have approved it for full development -- the first craft to be approved in this way since the Space Shuttle.
"We are on a journey of scientific and human exploration that leads to Mars," said NASA Administrator Charles Bolden. "And we�re firmly committed to building the launch vehicle and other supporting systems that will take us on that journey."
SLS will be able to fly in a number of different configurations, from a relatively light 70-metric-tons to more than 130.
NASA said the first test will take $7 billion and about four years from this point to complete, but said it will not rush since it "owes it to the American taxpayers to get it right".
"The Space Launch System Program has done exemplary work during the past three years to get us to this point," said William Gerstenmaier, associate administrator for the Human Explorations and Operations Mission Directorate at NASA Headquarters in Washington. "We will keep the teams working toward a more ambitious readiness date, but will be ready no later than November 2018.�
The SLS will eventually be used to launch NASA's new manned Orion space capsule, which is also undergoing development.
Meanwhile commercial space companies like SpaceX are developing their own rockets and space flight systems to help NASA complete more missions, more cheaply in the decades to come.