the same rocket, the plans for Project Constellation outlined having two separate launch vehicles, the Ares I and the Ares V, for crew and cargo, respectively. Having two separate launch vehicles allows for more specialized designs for the crew and heavy cargo launch rockets. The Ares I rocket was specifically being designed to launch the Orion Multi-Purpose Crew Vehicle. Orion was intended as a crew capsule, similar in design to the Apollo program capsule, to transport astronauts to the International Space Station, the Moon, and eventually Mars. Ares I might have also delivered some (limited) resources to orbit, including supplies for the International Space Station or subsequent delivery to the planned lunar base. Contractor selection NASA selected Alliant Techsystems, the builder of the Space Shuttle Solid Rocket Boosters, as the prime contractor for the Ares I first stage. NASA announced that Rocketdyne would be the main subcontractor for the J-2X rocket engine on July 16, 2007. NASA selected Boeing to provide and install the avionics for the Ares I rocket on December 12, 2007. On August 28, 2007, NASA awarded the Ares I Upper Stage manufacturing contract to Boeing. Boeing built the S-IC stage of the Saturn V rocket at Michoud Aerospace Factory in the 1960s. The upper stage of Ares I was to have been built at the same rocket factory (Michoud) used for the Space Shuttle's External Tank and the Saturn V's S-IC first stage. J-2X engines At approximately US$20–25 million per engine, the Rocketdyne-designed and produced J-2X would have cost less than half as much as the more complex RS-25 engine (around $55 million). Unlike the Space Shuttle Main Engine, which was designed to start on the ground, the J-2X was designed from inception to be started in both mid-air and in near-vacuum. This air-start capability was critical, especially in the original J-2 engine used on the Saturn V's S-IVB stage, to propel the Apollo spacecraft to the Moon. The Space Shuttle Main Engine, on the other hand, would have required extensive modifications to add an air-start capability System requirements review On January 4, 2007, NASA announced that the Ares I had completed its system requirements review, the first such review completed for any crewed spacecraft design since the Space Shuttle. This review was the first major milestone in the design process, and was intended to ensure that the Ares I launch system met all the requirements