Nuclear-Powered Rockets Might One Day Carry Astronauts to Mars

NASA and DARPA are building a nuclear thermal rocket engine that could slash the time it would take to reach the Red Planet

Artist's concept of a spacecraft flying away from Earth
Artist's concept of a spacecraft that will test a nuclear thermal rocket engine. DARPA

Astronauts might one day travel to Mars with a rocket fueled by nuclear power: NASA and the Department of Defense’s Defense Advanced Research Projects Agency (DARPA) are teaming up to develop a nuclear thermal rocket engine, which would dramatically improve a trip to the Red Planet, NASA said in late January.

The space agency aims to send its first crewed mission to Mars in the 2030s. But one major challenge is the amount of time it takes to get there. Long journeys in space can expose astronauts to harmful levels of radiation, and lots of time in microgravity can cause loss of bone density, loss of muscle mass and vision problems.

Nuclear thermal propulsion could cut the length of a trip to Mars from nine months to two, reports Mashable’s Elisha Sauers.

“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,” NASA administrator Bill Nelson says in a statement. NASA and DARPA aim to test the engine in space as soon as 2027.

The U.S. military and NASA first conducted experiments on nuclear rockets in the 1950s, but they never launched to space, writes Bob McDonald of CBC Radio. The new project—dubbed DRACO, short for Demonstration Rocket for Agile Cislunar Operations—“will build on those lessons learned” from earlier experiments, says Tabitha Dodson, DARPA’s program manager for DRACO, to Spectrum News Anthony Leone.

The new rocket would harness the power of nuclear fission, in which a rapidly moving neutron crashes into an atom, splitting it into two smaller atoms and releasing large amounts of energy. A fission reactor in the rocket would generate heat to expand a liquid propellant, which would shoot out of a nozzle to propel the spacecraft. Nuclear thermal rockets can be three times as efficient as chemical propulsion, per NASA’s statement.

Officials said that the rocket would be safe for both people on Earth and astronauts in space. It would not be used to propel the rocket off the ground; chemical rockets would be used for the launch, and the nuclear-powered engines would kick in once the spacecraft had traveled between 400 and 1,300 miles into space, according to Mashable. That helps ensure the material isn’t still radioactive when it re-enters Earth’s atmosphere, Pam Melroy, NASA’s deputy administrator, tells the publication.

“As long as the reactor is not turned on, it will not generate any … fission products,” Dodson says to Spectrum News. That means that before launch, “people are free to work around and near it safely.” And, since the nuclear reactor wouldn’t operate until well after the launch, “if there is some kind of first-stage launch vehicle failure that breaks the reactor and exposes the core, the materials in the core will be safe to those around the launch site,” she tells the publication.

Astronauts aboard a spacecraft with a nuclear-powered rocket would be separated from the engine by the hydrogen fuel tank, which would absorb some of the engine’s radiation, Dale Thomas, deputy director of the University of Alabama in Huntsville’s Propulsion Research Center, tells Mashable.

The nuclear-powered rocket would have other benefits beyond decreasing the length of the trip. For one, Mars and Earth only align on the same side of the sun every 26 months, writes the Washington Post’s Christian Davenport. These alignments allow the most energy-efficient trips to Mars, per NASA. With a nuclear-powered rocket, “you don’t have to wait for the planets to align. You’ll have launch opportunities every year,” Thomas tells Mashable.