WASHINGTON — As NASA nails down requirements for the Ares 1 Crew Launch Vehicle, the man in charge of building the U.S. space agency’s first human launcher since the space shuttle says the rocket is neither too skinny nor to tall to fly despite rumors to the contrary.

Steve Cook, director of the Exploration Launch Projects Office at NASA’s Marshall Space Flight Center, Huntsville, Ala., said the analysis done to date shows that the Ares 1 will work. And for those who remain unconvinced by reams of data and thousands of computer simulations, he said, an April 2009 launch of the Ares 1’s five-segment solid-rocket booster topped with an inert upper stage should allay all doubts.

With the Ares 1 systems requirement review getting under way this month and due to wrap up by early December, Cook does not have much time for the second guessing going on in some corners of the aerospace community and even within NASA itself.

“I don’t want to speculate on where rumors are flying from,” Cook said in a recent interview. “You hear rumors coming around and all I can say is we think we’ve picked an architecture that is robust.”

Cook is headlining a Space Transportation Association breakfast here Oct. 24 billed as a discussion of “the role of the Exploration Launch Projects Office in the Vision for Space Exploration.”

NASA officials familiar with the preparations going on behind the scenes said Cook’s speech is intended to counter those who contend that NASA’s space shuttle-derived launch architecture is rife with pitfalls and to quash the sentiment among those people inside and outside NASA that the agency would have been better off using the Atlas 5 or Delta 4 Evolved Expendable Launcher Vehicles as the starting point for its new crew and cargo launch systems.

NASA announced just over a year ago that it intended to go back to the Moon using new rockets built from space shuttle-derived hardware. The Ares 1 Crew Launch Vehicle that the agency is under the gun to field by 2014 at the latest is a five-segment-version of the shuttle’s solid-rocket booster topped with an upper stage powered by an updated version of the Saturn 5’s J-2 engine. Standing over 300 feet tall, the Ares 1’s primary job will be to lift the 25-ton Orion Crew Exploration Vehicle into orbit.

Cook said a year of hardcore engineering has bolstered NASA’s confidence that the Ares 1 is “doable.”

“Everything we’ve done in the last year in terms of analysis has validated the decisions we made in [the Exploration Systems Architecture Study (ESAS)] and post-ESAS in terms of the doability of this vehicle,” Cook said. “We think we are on the right track to get this vehicle flying in the time frame and the schedule and meet the performance requirements. The work we’ve done has helped validate the decisions that have been made to date.”

Over the past year, NASA engineers and their contractor counterparts have wrestled with questions concerning the structural integrity of the five-segment solid-rocket booster and the tall launcher’s stability in flight. A recent report by the Congressional Budget Office highlighted structural integrity and stability control among the top development risks cited by NASA engineers.

Cook said the more analysis NASA does on the controllability question, the more confidence it gains that Ares 1’s control systems have more than enough capability to counter the torque and roll the rocket will see as it slices through the atmosphere on its way to orbit. “It’s one of our key risk items that we track and manage,” he said. “It’s actually one that we have seen reduced in risk level because we put a lot of analysis talent on it here at Marshall and through the NASA Engineering Safety Center.”

As NASA digs into the structural integrity question, Cook said he is reassured by what engineers are concluding about the strength of the solid-rocket booster.

“While it’s true that the shuttle [solid-rocket booster] was not designed to have as second stage ride on top, it is a very robust stage, ” h e said. “Even with the way it is designed today and given the loads we think we are going to see with the Ares, based on all the analysis we have done to date, it is within the design limits of the boosters.”

Cook said NASA also is being hyper-vigilant about ensuring that changes made to Ares 1 along the way do no t erode its lift performance. “We’ve got more margin on this vehicle at this stage in the game than any other vehicle we have [designed in the past],” he said. “That’s a lesson we’ve learned.”

Cook and his team also are expected to deliver a launcher that i s much less prone to weather-related launch scrubs than the space shuttle.

“Our requirement right now is 95 percent launch availability,” Cook said. “W e’re designing for worst case wind loads and we add a factor on top of that and our intent is to be able to design for seasonal wind loads so we can make this vehicle robust so you dial in what month or what part of the season you’re in and you can fly. As we get further into the design, if we decide that’s too conservative, we can use approaches that are used today on the Altas 5 and Delta 4 where they actually measure the winds before they fly and adjust the controls to be able to account for that just hours before the launch.”

With NASA determined to minimize the gap between shuttle’s 2010 retirement and the introduction of Ares 1, Cook and his team have limited time and a $5 billion budget to get the job done.

“From budget standpoint right now we’re on a 2014 track to fly the first human flight vehicle,” Cook said. “From a technical perspective, the earliest we believe we could have a launch vehicle ready for the first human flight would be 2012.”

Cook said the Ares 1 development schedule is driven primarily by the time needed to get an updated version of the J-2S engine flight ready. The J-2S was developed at the end of the Apollo program but never flew.

“The critical path item right now on CLV is the J-2X and right behind that is the upper stage – it’s just barely behind it.”

Cook said the J-2X and upper stage are the so-called long poles in the tent because of a number of “mundane things … like valves, actuators, [and] requalifying vendors to build large cryogenic lines.”

Requalifying the vendors NASA needs to build a new rocket is no small consideration. Cook said it is a big part of NASA’s early focus. “We’re going out with some early advanced development to try to get vendors qualified, and up and running and soon as we can so we can get these tests done.”

NASA so far has approved sole source awards for Promontory, Utah-based ATK Thiokol and De Soto, Calif.-based Pratt & Whitney Rocketdyne for the Ares 1 main stage and J2-X upper-stage engine respectively and is in the process of finalizing contracts, Cook said. In the year ahead, NASA expects to solicit proposals and select a contractor to build the Ares 1 upper stage.

Cook does not minimize the scope of the task at hand and the many challenges, both technical and political, that lie ahead.

“Building a launch vehicle is hard,” he said. “We haven’t done a new launch vehicle that can carry crew in over 30 years. And that’s a big deal. But we think we’ve taken a measured approach where we’re going to bite off a piece at a time.”