DARPA has canceled the Demonstration Rocket for Agile Cislunar Operations (DRACO) project announced in 2020 by DARPA to develop a nuclear-powered rocket engine. According to DARPA, advances in current rocket technology such as that used in SpaceX's Starship rocket make it unnecessary to continue developing this nuclear-powered rocket. DRACO's cancellation comes at the same time that DARPA also canceled the Liberty Lifter ekranoplan project.
With this nuclear thermal propulsion (NTP) engine, a mission to Mars could be shortened to three months compared to seven months using a chemical rocket engine. The fuel burned by the heat of a nuclear reactor offers a specific impulse twice as good as a chemical rocket system. Specific impulse is a measure used to calculate the efficiency of a rocket engine.
In 2023, Lockheed Martin was awarded the contract to build the DRACO engine with the goal of testing it in space as early as 2027. It will not be used to launch a rocket from Earth. Instead, it will only be turned on immediately after it enters space to continue its journey to Mars. Apart from the United States, the UK is also developing a similar project but so far only the Sunbird concept by Pulsar Fusion has been shown.