When you compare SpaceX to the world’s other space enterprises, it’s probably easier to list the things SpaceX hasn’t done instead of reciting all of the company’s achievements.

One of these is the launch of nuclear materials. SpaceX has launched a handful of planetary science missions for NASA, but these spacecraft have all used solar arrays to generate electricity. In this century, NASA’s probes relying on nuclear power have all flown on rockets built by United Launch Alliance (ULA), a 50-50 joint venture between Boeing and Lockheed Martin.

This is about to change with a $256.6 million contract NASA awarded to SpaceX on Monday. The contract covers launch services and related costs for SpaceX to launch Dragonfly, a rotorcraft designed to explore the alien environment of Saturn’s largest moon, Titan.

Dragonfly’s power source is a radioisotope thermoelectric generator (RTG), which generates electricity from the heat put out by the radioactive decay of plutonium-238. These plutonium-fueled generators have flown on many previous space missions, including NASA’s Perseverance and Curiosity rovers on Mars, the New Horizons spacecraft that beamed back the first up-close views of Pluto, and the long-lived Voyager probes exploring interstellar space.

All of these missions were launched on rockets that have either retired or are nearing retirement: the Atlas V, the Titan, and the space shuttle, to name a few.