Ares I-X stacking set to start today

Editor's note: updated at 4 p.m.

The first prototype of the rocket NASA is designing to replace the space shuttle reaches an important milestone today, though its launch date remains uncertain.

Workers at Kennedy Space Center will begin stacking the 321-foot Ares I-X rocket on a mobile launcher platform inside the Vehicle Assembly Building.

This morning, the rocket's aft skirt and first solid rocket motor segment were transferred to the 52-story VAB from the nearby Rotation Processing and Surge Facility.

The attached components will be hoisted over a transom into high bay No. 3 and lowered on to the launcher platform tonight, starting at 9:30 p.m.

"We are very excited," said Jon Cowart, deputy Ares I-X mission manager.

The official launch date for the $360-million test flight remains no earlier than Aug. 30.

But Cowart said a more realistic working target is mid-September, and "it is not unrealistic to think that we could go into October."

NASA will likely set a new launch date later this month.

The test flight from launch pad 39B will test the rocket's first-stage flight control system and parachute recovery system, the system that separates the first and second stages, and launch-induced vibrations.

Cowart said "tiger teams" of engineers were analyzing those vibrations to ensure they would not disable the system that allows the rocket to be blown up if it veers off course.

Stacking of the first stage's four shuttle solid rocket booster segments is expected to be completed by July 20.

Then stacking of a simulated fifth solid motor and the mock-ups of a liquid-fueled upper stage could start within days.

Before proceeeding with the upper stage, managers will decide if modifications to the rocket are needed.

Meanwhile, a panel established by the Obama administration is reviewing whether NASA should proceed with development of Ares I rockets at all. Recommendations are expected next month.

NASA's current plan is to have an Ares I rocket and Orion crew capsule ready to carry astronauts back to the International Space Station by 2015.

The shuttle is scheduled for retirement late next year after eight more flights, including one by Endeavour that is scheduled to launch from KSC at 7:39 p.m. Saturday.

All the remaining missions are to the International Space Station.

IMAGE NOTE: On Wednesday morning, the Ares I-X aft assembly moved inside the Vehicle Assembly Building at NASA's Kennedy Space Center. It will be stacked with other segments to complete the Ares I-X test vehicle. The aft assembly will be the first segment to be stacked on the mobile launch platform in the VAB. Part of the Constellation Program, the Ares I-X is the test vehicle for the Ares I. Photo credit: NASA/Jim Grossmann.