Why not use comets as spacecraft?

Well, there are a few advantages to using a comet as a spacecraft. They contain lots of water ice, which you could break down to provide oxygen and hydrogen. They contain organic compounds that could be used for various purposes. read more

While normally landing on a comet does not make sense, because it requires the same energy / delta_v as making the spacecraft enter the same trajectory without a comet, NASA is investigating the "Comet Hitchhiker" idea - a new space travel concept, where spacecraft grabs the nearby comet or asteroid using its harpoon, gaining kinetic energy (similar to gravity assist). read more

Spacecraft have proven very effective at spotting comets as well, so the names of many comets incorporate the names of missions such as SOHO or WISE. History In antiquity, comets inspired both awe and alarm, "hairy stars" resembling fiery swords that appeared unpredictably in the sky. read more