Ares V
NASA planned to use two separate boosters for the Constellation Program missions – the Ares I for crew and the Ares V for cargo. This would have allowed the two launch vehicles to be optimized for their respective missions, and allowed a much higher total lift for the Ares V without being cost-prohibitive. The Constellation Program thus combined the Lunar Orbit Rendezvous method adopted by the Apollo program's lunar missions with the Earth Orbit Rendezvous method which had also been considered.