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 demonstrate nuclear thermal propulsion in orbit by 2027. DRACO was expected to be the first in-orbit test of a nuclear thermal rocket engine using low-enriched uranium, and its reusability and performance were projected to significantly outpace current chemical propulsion systems. Launch operations were to be supported by the U.S. Space Force, with the Vulcan Centaur rocket identified as the planned launch vehicle. In 2023, NASA formally joined the DRACO program, seeking to leverage nuclear propulsion to drastically reduce travel time to deep-space destinations such as Mars. Nuclear thermal propulsion was expected to yield two to three times the efficiency of chemical propulsion, with mission durations to Mars potentially cut in half. DARPA program manager Tabitha Dodson remarked that nuclear propulsion could form the foundation for evolving systems such as fusion-based spacecraft, enabling more ambitious human exploration missions with greater safety margins. According to Lockheed Martin and BWXT, there were considerable efficiency and time gains from the nuclear thermal propulsion. NASA believed the much higher efficiency will be two to three times more than chemical propulsion, and the nuclear thermal rocket is to cut the journey time to Mars in half.