Nukes are absolutely needed for any deep space missions beyond Mars. Unless you're going with laser propulsion or solar sails. Moreover, if you can fit a compa

Nukes are absolutely needed for any deep space missions beyond Mars. Unless you're going with laser propulsion or solar sails. Moreover, if you can fit a compact reactor (fission or fusion) on a space ship, then you can run nuclear thermal (ISP >800), or nuclear ion engines with extreme efficiency. (>15,000 ISP!) Considering NASA's Kilowatt reactor weights 2tons, assume a dry mass of 10t and a payload of 2%, you end up with a 500t ship (wow, do we even have 498 metric tons of xenon in the world?), but with a delta-v of 500,000 m/s. That gets you to Pluto flyby in 99 days. (I didn't count the Kilowatt reactor fuel weight, I'm not sure how much uranium is needed for a 15,000 Isp burn, I was just interested how much delta-v 15,000 Isp buys you.) SpaceX starship, if it works, could launch this in about 4 refuelings. (>100-125t to LEO)