With the curtain coming down on the Space Shuttle Program, NASA has set its sights on the future with the announcement of a heavy-lift launch vehicle that is designed to take man beyond the moon to explore near-Earth asteroids, Mars and its moons, and beyond. Dubbed the Space Launch System (SLS) its configuration harks back to the Saturn V rocket-based systems employed to propel Apollo astronauts to the moon but also incorporates technology developed in the Shuttle Program.

The SLS will use a liquid hydrogen and liquid oxygen propulsion system, which will include the RS-25D/E from the Space Shuttle Program for the core stage and the Saturn V-derived J-2X rocket engine for the upper stage. However, initial development flights will also use solid rocket boosters. The SLS will have an initial lift capacity of 70 metric tons (154,324 lbs), which NASA points out is roughly the weight of 40 SUVs. An evolved SLS will then see lift capacity increased to 130 metric tons (286,600 lbs), which by NASA's logic would be roughly the weight of 75 SUVs.

The initial SLS will weigh 2,500 metric tons (5.5 million pounds) and stand taller than the Statue of Liberty, at 97.5 m (320 ft) high. At liftoff it will generate 8.4 million pounds of thrust, which is 10 percent more than the Saturn V. The subsequent evolved SLS will weigh 2,950 metric tons (6.5 million pounds) and stand 122 m (400 ft) high. At liftoff it will generate 9.2 million pounds of thrust, which is 20 percent more than the Saturn V at liftoff.

NASA says the SLS's architecture provides a launch vehicle that can be adapted to suit different missions through the use of different core stage, upper stage, and first-stage booster combinations. This flexibility is designed to allow it to more economically carry the Orion Multi-Purpose Crew Vehicle, as well as cargo, equipment and science experiments to as low as Earth's orbit and as far as Mars and beyond. While NASA is looking to save money by having private companies ferry astronauts to the International Space Station (ISS), the SLS will also serve as a backup for commercial and international partner transportation services to the ISS.

The SLS was unveiled by NASA Administrator Charles Bolden and several members of Congress on Wednesday, with Bolden saying, "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."

Dreaming big is fine, but with an estimated cost of US$18 billion just for the next five years and the U.S. Government constantly modifying NASA's budget, it remains to be seen whether NASA will be able to make its dream reality. NASA stresses that the SLS architecture benefits from significantly reduced development and operations costs as it leverages existing capabilities resulting from the Space Shuttle and Constellation Programs. NASA says the early developmental flights may take advantage of existing solid boosters and other existing hardware, while a competition will be held to develop the boosters.

"NASA has been making steady progress toward realizing the president's goal of deep space exploration, while doing so in a more affordable way," NASA Deputy Administrator Lori Garver said. "We have been driving down the costs on the Space Launch System and Orion contracts by adopting new ways of doing business and project hundreds of millions of dollars of savings each year."

The first SLS unmanned developmental flight is targeted for the end of 2017 with the first manned flight penciled in for 2021. NASA then aims to follow up with a manned mission to a nearby asteroid around 2025 and one to Mars in the 2030s.