Orbital Sciences Corp. said it "likely" will no longer use Aerojet Rocketdyne's AJ-26 rocket motors on its missions to supply the International Space Station. Investigators are still searching for the cause of a spectacular explosion of an Orbital launch on Oct. 28. Orbital Sciences Corp. said Wednesday it "likely" will no longer use Aerojet Rocketdyne's AJ-26 rocket motors on its missions to supply the International Space Station.