NASA's Exploration Chief to Step Down for Family

Scott "Doc" Horowitz, head of NASA's effort to replace the space shuttle and return astronauts to the Moon, is stepping down to spend more time with his family, he said Friday.

Horowitz said he will leave his post as NASA's associate administrator for the Exploration Systems Directorate, which he's held since 2005, on Oct. 1 to devote more time to his wife Lisa and three children.

"It's taken a tremendous toll on my family, and I really do need to put some energy and effort into that," Horowitz said of his wife, 11-year-old daughter and four-year-old fraternal twins during a teleconference with reporters. "To be able to do all the exciting and fun things I've gotten to do, they've taken kind of a back seat for quite a while, and the last two years are no exception."

Horowitz informed coworkers of his resignation plan on Wednesday, ?the same day that NASA associate administrator Rex Geveden -- the agency's third-highest ranking official -- announced his intent to leave his own post to serve as president of the Huntsville, Alabama firm Teledyne Engineering. NASA's current chief engineer Chris Scolese will succeed Geveden, though a successor has not yet been named to replace Horowitz.

Horowitz said the timing between both announcements is unrelated and should not be taken as a sign of internal restructuring.

"It truly is coincidence, so there is no major realignment," he added. "We don't plan to make any changes to the structure of what we're doing."

A retired U.S. Air Force colonel, Horowitz first joined NASA as an astronaut in 1992 and flew on three space shuttle missions as pilot, as well as a fourth as commander. He left NASA in 2004 for the aerospace firm Alliant Techsystems, where he served as the director of exploration and space transportation. It was while there that Horowitz vigorously supported using the reusable space shuttle solid rocket booster (SRB) as the basis for the first stage of NASA's next crewed launch vehicle, the Ares I rocket.

"The Ares I crew launch vehicle concept is Doc's brainchild, a fact that crews launching safely a generation from now will remember with gratitude," NASA administrator Michael Griffin said in a statement released today. "[He] has been the key person for NASA's exploration effort during the critical period immediately following definition of the architecture for shuttle replacement and lunar return."

The Ares I booster will launch the Orion Crew Exploration Vehicle, NASA's capsule-based shuttle successor, with an SRB-derived first stage to be built by Alliant Techsystems. NASA chose the design over competing boosters, such as the Atlas 5 or Delta 4 expendable launch vehicles (ELVs), before Horowitz rejoined the space agency as its exploration chief in September 2005.

"The physics are [that] the ELV is not the right answer for this problem," Horowitz said, adding that the SRB-derived design is on track. "Every study and every single analysis shows that it's the right answer and I have no doubt that that's where we'll continue to be headed."

A new heavy-lift booster, the Ares V rocket, is also under development for future Moon missions. NASA plans to retire its three-shuttle fleet by September 2010, launch its first crewed Orion mission by March of 2015 and aims for a manned Moon mission by no later than 2020.

"That is fully within our grasp, given everything that we know today," Horowitz said of the Moon plan.

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