The U.S. plans to launch the world's first nuclear-powered spacecraft into orbit as early as 2025, NASA and the Defense Advanced Research Projects Agency (DARPA) have announced.
The $499 million mission, named Demonstration Rocket for Agile Cislunar Operations (DRACO), will be the first test for a new type of rocket propulsion system that the agencies claim could send astronauts to Mars in just 45 days.
The agencies, which have partnered to develop the rocket, announced on July 26 that they had reached an agreement with the U.S. defense contractor Lockheed Martin to design, build and test the prototype.
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"We're going to put this together, we're going to fly this demonstration, gather a bunch of great data and really, we believe, usher in a new age for the United States [and] for humankind, to support our space exploration mission," Kirk Shireman, vice president of Lockheed Martin Lunar Exploration Campaigns, said during a press conference.
NASA's current rocket systems — including the Space Launch System that last year sent the Artemis 1 rocket on a historic round-trip to the moon — are based on the century-old method of chemical propulsion, in which flammable rocket fuel is mixed with an oxidizer to create a flaming jet of thrust.
The proposed nuclear system, on the other hand, will harness the chain reaction from ripping apart atoms to power the spacecraft. The nuclear fission reactor will be "three or more times more efficient" and could reduce Mars flight times to a fraction of the current seven months, NASA said.
Nuclear engines generate less maximum thrust than their chemical counterparts but can fire more efficiently for extended periods of time — propelling rockets at much higher speeds and for significantly longer portions of their journey.
NASA began its research into nuclear thermal engines in 1959, eventually leading to the design and construction of the Nuclear Engine for Rocket Vehicle Application (NERVA), a solid-core nuclear reactor that was successfully tested on Earth. Plans to fire the engine in space, however, were scrapped following the end of the Apollo missions in 1973 and a sharp reduction in the program's funding.
DRACO's reactor will work by splitting uranium atoms inside a nuclear reactor — a process that will superheat hydrogen before blasting it out of the spacecraft's thruster to push it forward.
Before it is heated to a searing 4,400 degrees Fahrenheit (2,427 degrees Celsius), DRACO's hydrogen propellant will need to be kept at an ultra-cold minus 420 F (minus 251 C) — a major challenge for the spacecraft's developers.
"Our life-limiting factor is how long we can keep the hydrogen cryogenic," Tabitha Dodson, the DRACO program manager at DARPA, said during the press briefing. "This is just as much a demonstration of on-orbit storage of cryogenic liquid hydrogen as it is a demo of the nuclear thermal rocket engine."
Once the spacecraft is assembled, it will be sent into a high orbit between 435 miles and 1,240 miles (700 to 2,000 kilometers) above Earth, allowing it to last roughly 300 years in orbit — long enough for its dangerously radioactive fuel to decay to safe levels, Dodson said.
