The Chinese mission to Neptune

China believed in 2020 it could insert a probe into Neptune's orbit:

the escape velocity of Neptune is 23.53 km/s, which is about twice the Earth’s 11.18 km/s. Unlike the exploration missions of low-mass celestial bodies such as Mars and the moon, the propellant consumed in order to realize the gravitational capture of Neptune is greatly reduced.

No, I do not claim to know any hànyǔ (nor 韩语 for that matter). I'm trusting Google.

The main constraint was how to power the thing, since solar's out (faaaar out, 30 AU). Also they need to keep some comms on whilst it's going out there, and to beam signals HARD back to Earth. They figured: 10 kWe. Per ToughSF: Heat pipe fast reactor, Uranium Nitride.

The Long-March rocket might actually be able to do this, if they don't mind spending the cash. I'd prefer Uranus as closer UPDATE 7/11 especially if they forget about throwing away a Falcon Heavy and use the SuperHeavy.

ALSO UPDATE 7/11 China is still working on it.