Second stage

The new second stage will be developed specifically for the Ares-I launch vehicle and will be powered by a single J-2X rocket motor burning liquid oxygen and liquid hydrogen to produce 1,300 kN of thrust. The second stage will lift its payload to an altitude of 116km before shutting down and being jettisoned. The Orion spacecraft’s service module propulsion system will complete the climb into a circular orbit at an altitude of 340 km. Boeing has been awarded a $515 million contract to support the NASA-led development of the Ares-I second stage and then produce the stage once definition is complete. Under the contract, Boeing will produce a single Ground Test Article, three Flight Fest Articles, and six production stages.

The second stage will be manufactured in the standard pattern, with the pro­pellant tanks positioned one on top of the other and joined by an aluminium skirt. The main stir-welded aluminium stage structure and propellant tanks will be covered by insulating foam similar to that currently employed on the Shuttle’s External Tank. The Shuttle’s ever-present risk of damage from insulation foam falling off of the External Tank is negated by the fact that at launch the Orion spacecraft will sit at the top of the Ares-I launch vehicle. As a result any insulation foam shed from the exterior of the second stage during launch will already be beneath the spacecraft and should therefore be carried away by the launch vehicle’s slipstream and not impact on the Orion spacecraft.

The J-2X is derived from the original J-2 re-startable rocket motor used on the Saturn-V’s S-IVB third stage. The original motor could not be used because the aluminium alloy employed in its construction is no longer available, and some com­ponents used in the J-2 motor have since been banned for environmental reasons. The J-2X was originally part of a dual study with the J-2XD. The J-2X was to have served on the Ares-V launch vehicle and the J-2XD on the second stage of the Ares-I. The decision to use the J-2X on both vehicles was made in July 2007. On July 17, 2007, NASA awarded Pratt & Whitney Rocketdyne (P&WR) a $1.2 billion design and development contract to develop, produce, and test the first eight J-2X rocket motors. Only one will be a flight engine, with another serving as the motor for the Ares-I second-stage Propulsion Test Article, and six ground test articles. The contract runs through the end of December 2012.

In June 2007, NASA announced a contractor competition for the Ares-1 guidance avionics package, with bids to be submitted by July 30, and the contract expected to be awarded in November. The guidance package would prove inflight guidance to both Ares-I stages during the power flight phase. The package would be mounted on the second stage at Boeing’s Michoud facility, where that stage will be manufactured.