Alliant Techsystem's development work on the first stage of NASA's Ares I crew launch vehicle is progressing, with segments for the ground vibration test article already fabricated.

Preparations are under way to ship hardware for the analog test flight Ares I-X to NASA's Kennedy Space Center by July.

Ares I's first stage is a five-segment solid rocket boster (SRB). For ground vibration testing, ATK is to supply two five-segment stacks: one empty of the solid fuel, the other an inert version of a fuelled stack.

These will be tested at NASA's Marshall Spaceflight Center in 2010. ATK has produced three of the inert stack's five segments, using them as manufacturing process pathfinders.

The Ares I-X test flight, which uses a four-segment SRB first stage with a dummy fifth segment, upper stage and Orion crew exploration vehicle payload, is scheduled for 15 April 2009. ATK expects the last of its hardware for that launch to be at Kennedy by October.

But almost two weeks before that analog flight will be the 2 April 2009 test-firing of the first five-segment development motor, DM-1. This will take place at the company's T-97 test stand, used for Shuttle SRB testing and to be modified for the five-segment booster's extra power.

DM-1 will be followed by three more tests, DM-2, -3 and -4, taking place in September 2009, August 2010 and February 2011, respectively. The segment casings for DM-1 have already flown "six or seven" times on Space Shuttle missions, says ATK Ares I programme manager Fred Brassfield.

A five-segment SRB has been fired previously - in 2003, under development work for the Shuttle programme, when the fleet was still expected to last until 2020. But beyond having five segments, the stack was no different to the Shuttle booster.

During Ares' first-stage development, ATK will be qualifying a number of changes, including: new insulation, work on which began under the Shuttle programme an altered solid fuel with reduced oxidiser levels placing of all the separation motors on the aft skirt, with one or two perpendicular to it, to kick the stage into a tumbling re-entry mode and larger parachutes for the faster descent speeds from its higher separation. Also, says Brassfield: "We need to build a larger bearing for gimballing the larger nozzle."

ATK space launch systems vice-president Michael Kahn says that, as the requirement for Ares I nozzle gimballing is "slightly less" than on the Shuttle, the thrust vector control (TVC) system does not have to be changed.

But a TVC system that uses helium to drive the actuator hydraulics, instead of hydrazine, is being examined as a potential life-cycle cost-reduction effort because it removes the expensive controls and precautions required when dealing with a hazardous chemical such as hydrazine.

One element of the first-stage design that will not change is the segment's metal casings, says Kahn. The loading on them from the combined mass of the upper stage and CEV will be no higher than that experienced during Shuttle launches, he adds.