Nearly three years ago, the US Defense Advanced Research Projects Agency announced its intent to develop a flyable nuclear thermal propulsion system.

The military agency called this program a Demonstration Rocket for Agile Cislunar Operations, or DRACO for short.

At the same time, NASA was coming to realize that if it were really serious about sending humans to Mars one day, it would be good to have a faster and more fuel-efficient means of getting there.

An influential report published in 2021 concluded that the space agency's only realistic path to putting humans on Mars in the coming decades was using nuclear propulsion.

"With the help of this new technology, astronauts could journey to and from deep space faster than ever, a major capability to prepare for crewed missions to Mars."

Nuclear thermal propulsion has long been a goal of spaceflight advocates, dating back to the days of German rocket scientist Wernher von Braun and NASA's Project NERVA.