The Ares was a proposed intercontinental ballistic missile (ICBM) derived from the Titan II missile. It was a single-stage rocket with a high-performance engine to increase the rocket's specific impulse. Both Aerojet and Rocketdyne carried out engine design studies for the project, but Ares was ultimately cancelled in favour of solid-fuel ICBMs, which were safer to store and could be launched with much less notice.