Alliant Techsystems has begun modifications to components of a retired Shuttle solid rocket booster in preparation for the first test flight of a prototype Ares launch vehicle in April.

Dubbed Ares 1-X, the launch will test a four-segment ATK-built solid rocket booster with a dummy fifth segment, components that together make up the planned first stage of the Ares booster. A second stage, also a mass simulator without propellant topped with the Orion crew exploration crew vehicle, will fall to the ocean after the suborbital test flight. On burnout, ATK will test the three-parachute recovery system for its first stage.

Modifications under way on the 9,979kg (22,000lb) aft skirt of the first stage include adding twin ATK-built separation motors to each side of the skirt, aligned perpendicular to the flightpath. The rockets will be used to tumble the first stage after it separates from the upper stage, a necessary action to slow the booster to subsonic speed for parachute deployment, says ATK. The company is also installing a series of small solid rockets on each side of the first stage to decelerate the booster after separation with the second stage at first stage burnout.

The solid rocket booster steering mechanism will remain largely unchanged, with hydrazine-powered auxiliary power units running dual redundant linear actuators that steer the solid motor's nozzle as much as 6° from centre position for rocket control.

Other changes on tap include removing the Shuttle external tank attach points and adding a linear charge to the bottom solid motor segment to be used if the first stage must be destructed during launch, a safety mechanism already included in the upper three segments. The company anticipates installing active and passive dampers to the stage to reduce oscillations considered problematic in analyses.

Ares 1-X first stage components will largely come from a solid rocket booster that had exceeded its five-year storage life after the Shuttle grounding following the Columbia accident in 2003, says ATK. The company says solid rocket booster segments dormant for more than seven years have been test fired with no detrimental performance effects.

Source: Flight International