NASA's five possible alternatives to the Ares rockets

Though NASA had a successful test flight of the Ares I-X (which by the way has been selected by TIME as the invention of the year), it's still not certain whether the rocket will be approved as is or whether a different model will be instated in its place due to budgetary and engineering reasons. An article here has a nice overview of the five possible models for a new rocket that could take its place (slightly enlarged image here).

#2 is the most famous of the five as it's a way to transfer current knowledge and technology from the Shuttle program into something fairly easy and cheap to make, but I'm also partial towards #5 which is actually the cheapest in spite of its size, and also has an interesting feature in using some Russian technology. Plus it's based on the Saturn V, which is a bit of a legendary rocket.


Also on a slightly related note (propulsion), here is an article today on a  new method to make ion engines more efficient by using electrified carbon nanotubes instead of xenon gas, though it likely won't be seen in practice until 2015.