NASA is confident that its first test flight of the new Ares I-X rocket will go well next week. But if it ends in an explosive failure, the agency affirmed that the nearby space shuttle Atlantis atop its own launch pad will be safe.

Space shuttle program manager John Shannon said it was his call to move Atlantis to Launch Pad 39A for its planned Nov. 16 liftoff from the Kennedy Space Center in Florida, even as NASA prepares for the Ares I-X test launch on Oct. 27 from nearby Pad 39B.

The risk of a disaster at the Ares I-X launch pad has been assessed, Shannon said, but should not endanger Atlantis. Much of the shuttle is protected by a Rotating Service Structure, a shell-like covering that guards against weather, he added.

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About 40 percent of all new rockets end in failure, NASA has said, and Ares I-X is not exempt from those chances.

"The impact zone for an explosion [at Ares I-X's launch pad] would just barely clip Pad A," Shannon said.

Launch test legacy

The $445 million Ares I-X rocket is a suborbital prototype of NASA's two-stage Ares I booster designed to replace the shuttle fleet by launching astronauts on Orion capsules for trips to orbit and, ultimately, the moon. The rocket concept and NASA's overall human spaceflight plans are in the midst of a major review by President Barack Obama's administration.

"Any time you launch something new there's always the possibility of an accident. This is still rocket engineering," said John Logsdon, a space policy expert and professor emeritus at George Washington University in Washington, D.C.

The shuttle program is still waiting on definitive numbers for a potential disaster from NASA's Constellation program, which oversees the development of the Ares I rockets and Orion spacecraft. But all tests to date point toward a successful launch test next week, Shannon said.

"If we really thought that [Ares] I-X was going to have a problem, then we're not ready to go launch, even on a test flight," he added.

A full Ares I rocket would use a five-segment solid rocket booster a bit larger than the four-segment ones used on NASA space shuttles. Ares I-X, however, will use the four-segment rocket motor and a dummy fifth segment. It is capped with a mock-up of the Ares I second stage, Orion capsule and launch abort system.

Logsdon said the relative simplicity of Ares I-X, when compared to the Ares I design, may make success more likely.

"The stage itself – the four segment solid stage - has been launched how many times now? 250 or more times with one problem — because it's the strap-on for the shuttle," he said. "It's the most reliable rocket stage in the world."

Tale of two launch pads

The Ares I-X towers 327 feet (100 meters) above Launch Pad 39B, a launching site that until recently was used to fly space shuttles, and has been converted for the new booster.

Pad 39A, which NASA is using for its remaining shuttle missions, is about 1.6 miles (2.5 km) away with Atlantis. The Launch Control Center, NASA Press Site and other structures are outside a 3-mile (4.8-km) safety perimeter from the launching pads.

"Generally speaking we don't put two vehicles out [at once]," Jon Cowart, Ares I-X deputy mission manager, told SPACE.com. But in this case it was deemed to be an acceptable risk, he said.

Unlike shuttle launches, which take nearly nine minutes to reach orbit, the Ares I-X test flight will take just over 2 1/2 minutes. The rocket is expected to fly 28 miles (45 km) high, experience stage separation 43 miles (69 km) down range and end 147 miles (236 km) over the Atlantic Ocean when the dummy upper stage crashes into the sea.

"While this is the rocket business and you can't make anything one hundred percent safe," Cowart said he was confident the rocket was in good shape and would fly safely. "I really, really do" feel confident that it will take off on time and safely, he said.