Why is NASA using its precious, and shrinking, funding to construct a massive, Saturn V (which took Apollo astronauts to the moon) type rocket, the Space Launch System (SLS), when private companies, such as SpaceX and Orbital Sciences Corporation already or soon will have rockets that will accomplish all the functions sooner and cheaper?
SpaceX's Falcon 9 rocket is already delivering cargo regularly to the ISS (International Space System) and even to Geosynchronous orbit (22,000 miles high). It is easily already man-rated in terms of safety, and will be carrying astronauts into orbit within a couple of years. A more powerful version of the Falcon, the Falcon Heavy, is due for testing in 2014 and will also be ready for missions within the same time span. While not as powerful as the SLS, the combination of a Falcon Heavy (to carry the needed equipment) and Falcon 9 (to carry a crew) will already have the capacity to send men to the moon or beyond -- even to Mars perhaps -- before the end of this decade, ahead of SLS' schedule. SpaceX is also working on recoverable rocket stages and other advanced technologies.
NASA awarded to Orbital a Commercial Orbital Transportation Services (COTS) Space Act Agreement (SAA) in 2008 to demonstrate delivery of cargo to the International Space Station. For these COTS missions Orbital intends to use Antares to launch its Cygnus spacecraft. In addition, Antares will compete for small-to-medium missions. On December 12, 2011 Orbital Sciences renamed the launch vehicle "Antares" from the previous designation of Taurus II, after the star of the same name.
I cannot see how, between SpaceX and COTS, the two companies and their rockets alone don't invalidate the need for the SLS. If it were scrubbed (it is an Obama Administration project), large amounts of money could be freed up for more unmanned planetary missions, such as to Europa, Uranus, and Neptune, and to asteroids for mining possibilities.