Yahoo News has a short video on the progress NASA is making developing the Space Launch System (SLS), which would be the world’s largest rocket when operational. Unfortunately, what NASA has produced to date is mostly scale models and animated movies, with the first test launch of a working booster scheduled more than three years from now.
SpaceX, meanwhile, has a working rocket that has already delivered cargo to the International Space Station. Admittedly, the current Space X rocket is significantly smaller, but it looks to be several times cheaper than existing launch systems per kg of cargo. Primarily, this is because the SpaceX main booster is designed to land itself and be re-used. Overall, SpaceX looks like the disruptive innovator in this matchup. It will be interesting to see if its platform — currently inferior to the SLS — eventually outpaces the capabilities of NASA’s system.
Image source: http://science.howstuffworks.com/space-launch-system.htm