The possibility of landing a human on Mars is one step closer to reality now. A boost to the attempts to carry out deep-space exploration happened when NASA finalized a $2.8 billion contract with the Boeing Co. to build the Space Launch System rocket, or SLS.

The deal was finalized after NASA completed a critical design review (CDR) of the core stage of SLS. This is the first time since the heyday of the Saturn V that a launch vehicle has passed the CDR stage. The Saturn V was operational from 1966 to 1973 and was used in a number of moon missions.

The US space agency has all plans to use the SLS to eventually send astronauts beyond low Earth orbit (LEO) using the spacecraft Orion which was built by the Lockheed Martin Corp. The aim is to explore the deep reaches of space but is not limited to near-Earth objects like asteroids and Mars. Orion can carry as many as four astronauts on long duration missions.

The avionics team of Boeing would start work on two different versions of the rocket. One version would be 321 feet tall and be capable of lifting 154,000 pounds to LEO whereas the other version would be 384 feet tall and will be capable of lifting 286,000 pounds to LEO.

The initial test flight is scheduled to launch at Cape Canaveral in 2017. If the first mission carrying an empty Orion capsule is successful, then a second, manned mission is expected in the year 2021.

The announcement of the contract comes at a time when the plan of NASA to launch a mission to a near-Earth asteroid by mid-2020s failed to garner much support or even funding.

The SLS program also has a fair share of detractors. The Space Frontier Foundation which is a NASA critic told the LA Times that the SLS was "built from the rotting remnants of leftover congressional pork".