The director of NASA’s main rocket development center urged aerospace contractors to get with the program and stop second-guessing the decision to use space shuttle-heritage hardware to launch future astronaut crews to Earth orbit and beyond.

Speaking Feb. 20 at a Capitol Hill breakfast

sponsored by the Space Transportation Association, Marshall Space Flight Center Director David King warned that abandoning the Ares 1 crew launch vehicle and Ares 5 heavy-lift rocket designs being developed as the cornerstones of NASA’s

human space exploration program is not a realistic option.

“If we change the approach in architecture of Constellation – and there are people who would like to do that very thing – we simply won’t ever get off the ground,” King said.

Constellation is the program under which NASA is developing the hardware it needs to replace the space shuttle in the near term and return astronauts to the Moon by 2020.

King said NASA gave careful consideration to using the Atlas 5 and Delta 4 rockets developed under the U.S. Air Force’s Evolved Expendable Launch Vehicle (EELV) program as the foundation for the nation’s next human spaceflight system, but decided by mid-2005 that the so-called shuttle-derived approach involved less development risk, would be about a fifth cheaper, and twice as safe for the astronauts on board.

NASA awarded the final major Ares 1 contract in December

, selecting Boeing Space Exploration of Houston to build the instrumented avionics ring that will guide the 36-story-tall rocket in flight. The rocket’s main stage is a longer, five-segment version of the solid-rocket boosters NASA

uses in pairs to launch the space shuttle. This booster will be built by AlliantTechsystems of Edina, Minn.

The Ares 1 upper stage,

to be built by Boeing, will be powered by a single J-2X engine that traces its roots to NASA’s

Apollo Moon program.

NASA also plans to use the five-segment boosters and J-2X engine for its proposed Ares 5 heavy-lifter, which is still in the very preliminary design stage at

Marshall in Huntsville, Ala.

The first Ares 1 test flight – a suborbital mission

featuring a dummy upper stage boosted by a four-segment solid-rocket booster – is scheduled

for April 2009. The rocket’s first crewed launch to the international space station, however, is not expected to occur until March 2015. U.S. voters will have gone to the polls twice by then to elect a new president, a point

King referenced in his talk.

“We live in an uncertain world. Political leaders change

, budgets fluctuate, and the winds of public opinion can sometimes be tenuous. If we continue to argue over how to accomplish this mission, we run the risk of losing the opportunity to do the work,” he said.

Taking questions following his prepared remarks, King said a potentially dangerous

vibration issue –

thrust oscillation in technical parlance – discovered

during computer-simulated Ares 1 launches last year does not appear to be anything engineers cannot solve.

“Yes, we have our technical challenges,” King said. “This is a development program of a pretty large nature and in any development program of a new vehicle you are going to have issues like thrust oscillation and other issues that you have got to

go deal with.”

King said engineers have identified multiple options for mitigating the thrust oscillation problem, which if left unchecked could produce unacceptable levels of vibration

at the top of the rocket, threatening the safety of the Orion crew capsule and its onboard astronauts


“I am pretty confident we will find a way of doing this [without] impacting the schedule and/or budget by too large a measure, quite frankly,” King said.

Immediately following King’s presentation, about two dozen of the space professionals in attendance gathered in front of the restaurant’s television to watch

Space Shuttle Atlantis return from its 13-day mission to the international space station, toasting with mimosas once the orbiter had

touched down safely.