Demonstration Rocket for Agile Cislunar Operations

The Demonstration Rocket for Agile Cislunar Operations (DRACO) was a planned spaceflight demonstration mission under the joint auspices of DARPA, NASA, Lockheed Martin, and BWX Technologies, aiming to carry out the first in-orbit test of a nuclear thermal rocket by 2027. Fueled by low-enriched uranium, its reusability and performance were projected to significantly outpace current chemical propulsion systems.

Source: Wikipedia — Demonstration Rocket for Agile Cislunar Operations (CC BY-SA 4.0)