Directlauncher.com team member and AIAA paper co-author Chuck Longton has responded to the NASA criticism of the DIRECT concept in this Hyperbola blog post and pointed out what his team considers are Constellation's failures with its architecture
See Chuck's main points in the extended entry portion of this post. He also says in his original comment that "there will be an upcoming response that will be placed, at the very least, on the www.directlauncher.com website"
* As of today's date, July 4th, 2008, the Ares-I/V is still incapable of even a minimal lunar mission, still being a minimum of 8 metric tonnes short of what's required to go thru trans lunar injection.
*The 2xJupiter-232 profile not only meets the ESAS minimum, it exceeds it.
* The AIAA paper was published in September 2007 and the NASA critique was completed the following month, October 2007. NASA then sat on it for almost 10 months...then they released their analysis of the house of cards.
*There are many, many things in NASA's analysis that are very wrong, misleading and completely misstated. I will name just one...the critique faults the DIRECT architecture for reusing the STS infrastructure [but reusing the STS infrastructure] is specificically what the Congress directed NASA to do
*The latest Ares-V design is so massive that even the Crawlerway will need to be replaced; it cannot handle the weight.
*[Ares V]...next iteration, which is baselined internally, is so tall that it no longer fits inside the VAB.