Work on the Ares 1 booster, which will launch the new Orion Crew Exploration Vehicle, is moving right along with the completion of the first design analysis cycle. Several changes were made resulting in a shorter, lighter stage.
NASA has switched from an intertank structure between the upper-stage liquid oxygen and liquid hydrogen tanks to a common bulkhead with a resulting mass saving, including residual propellant, of around 635kg (1,400lb). At 79.4m long, the Ares I is now about 1.83m shorter with the common bulkhead.
"Anything we can do to increase controllability [by shortening the booster] is welcome. All of our cryogenic upper stages for manned spaceflight historically have used a common bulkhead," says Steve Cook, director of NASA Marshall Space Flight Center's exploration launch projects office.
NASA has also agreed on a composite interstage to connect the first and upper stages and a star-like, 12-lobe geometry has been selected for the solid propellant in the first stage, to make the burn rate faster than in the Space Shuttle SRB on which it is based.
The same polybutadiene acrylonitrile (PBAN) propellent used in the Shuttle SRB has also been selected, with reduced iron oxide content for burn rate amelioration.