The launch of the Phoenix spacecraft on a Delta II rocket in 2007. NASA is looking for alternatives to hydrazine monopropellant, used en route by Phoenix's navigational thrusters (Photo: NASA/Sandra Joseph and John Kechele)
NASA has put out the call for greener propellant fuel for use on the spacecraft of the future. Though it does not appear that NASA has stipulated that alternative propellants must match the performance of current mainstay hydrazine, it's clear that only high-performance substances need apply. Environmental credentials are where the new fuel must demonstrate an edge over hydrazine, which is a corrosive, toxic pollutant. As well as the environmental benefits, use of greener propellants should prove more economical, reducing the need for involved safety procedures that can lengthen launch times.