The first stage of NASA's Ares I crew launch vehicle is facing further change as the agency has decided to study a different solid propellant oxidiser in response to US Environmental Protection Agency concerns over perchlorate in drinking water.

Originally to be a Space Shuttle solid rocket booster motor, this CLV first stage has already had its propellant - with polybutadiene acrylonitrile for the fuel and ammonium perchlorate for the oxidiser - changed once to alter its burn rate.

Now, after the CLV's preliminary design review, NASA's Ohio based-Glenn Research Centre is to study the oxidiser ammonium dinitramide (ADN). The Swedish Defence Research Agency will be involved because of its ADN expertise.

Glenn Research Center says: "The research is investigating [the] replacement of ammonium perchlorate in future solid rocket boosters. Since the Space Shuttle is to be retired, the research would apply to only new space launch vehicles."

NASA's exploration systems mission directorate, which oversees the CLV's development, was not available for comment. The agency has announced that technology challenges has forced it to delay its Mars Science Laboratory rover mission from 2009 to 2011.

Source: Flight International