Clark Lindsey has a little roundup of links relating to the “Direct Launch” concept. Short answer, Doug Stanley believes that it can’t provide the necessary performance. Having read his argument, I have no reasons to disagree, or think him less than sincere.

Of course, it doesn’t matter to me, since I’ve never been a big fan of it anyway. The fundamental problems with NASA’s approach to achieving the president’s Vision for Space Exploration go far beyond critiques of specific vehicle designs.