NASA announced Wednesday the design plans for the largest rocket yet that will carry its next generation spacecraft for carrying astronauts into deep space, dpa reported. The heavy-lift Space Launch System (SPL) rocket will be even more powerful than the Saturn V rocket that carried astronauts to the moon and is part of US plans to focus on travelling beyond low-Earth orbit to an asteroid and, eventually, Mars. The initial development is projected to cost some 18 billion dollars, with further development costs later as details about the craft's mission become clearer. The first version of the rocket will be able to lift 70 metric tons into space, some 10 per cent more than the Saturn V moon rocket, and a later, more powerful version would carry 130 metric tons, NASA officials said. The rocket will carry a six-person crew capsule called the Orion Multi-Purpose Crew Vehicle, which is already being developed. The first unmanned test flight is slated for 2017 and the craft is expected to fly about once or twice a year through the 2020s, NASA said. NASA hopes to fly a manned mission to an asteroid by 2025, but exact plans for when and where the new craft's first mission will be are not yet set. The rocket will combine elements of the space shuttle engines and a rocket that had begun to be designed for an earlier programme and was later scrapped by the agency. Unlike the shuttle, it will use liquid rocket fuel, which is safer but more expensive than the shuttle's solid rocket fuel. "This launch system will create good-paying American jobs, ensure continued US leadership in space, and inspire millions around the world," NASA Administrator Charles Bolden said. "President Obama challenged us to be bold and dream big, and that's exactly what we are doing at NASA. While I was proud to fly on the space shuttle, tomorrow's explorers will now dream of one day walking on Mars." NASA retired its ageing space shuttle fleet earlier this year and is shifting attention to working with commercial companies to fly astronauts to the International Space Station and other destinations in low-Earth orbit. Meanwhile, the space agency will turn its attention to developing its own spacecraft capable of travelling to more distant destinations. These new plans replace an effort announced by former president George W Bush that focussed on developing a different spacecraft primarily designed to return to the moon.