Well, really all three are due to insufficient launch capbility. We'll have to assemble the colony ship in orbit. Really, we need to build the Orion nuclear pu

Well, really all three are due to insufficient launch capbility. We'll have to assemble the colony ship in orbit. Really, we need to build the Orion nuclear pulse ship for heavy lift and intra-stellar transport. Without a reworking of modern physics, the Alcubierre Drive for example, transport is going to take a loooong time. Even if we didn't need a backup planet, this is the next phase is human exploration. It's inherently part of human nature to expand our prescense.