By
NASA is developing ways to use nuclear energy to send spacecraft to their destinations. Nuclear propulsion could significantly reduce travel time to Mars, perhaps shortening it from more than 6 months to 3 or 4 months.
The idea of nuclear propulsion in space dates back to the Cold War. But NASA has been pursuing this technology more aggressively since billionaire and commercial astronaut Jared Isaacman took over as director of the agency in December 2025. Isaacman is a well-known advocate for the technology and “truly unleash Humanity’s ability to explore the stars.”
In March 2026, the American space agency launched an unmanned, nuclear-powered mission to the Red Planet, scheduled for late 2028.
Every spacecraft begins its journey by fighting Earth’s gravity by burning chemical fuel. Rockets mix fuel with an oxidizer, ignite everything, and force the expanding gas out through a nozzle. According to , when the gas pushes downward, the rocket receives an equal upward thrust.
Chemical propulsion is powerful, reliable, and quite simply the only practical way to escape Earth’s gravity. But it brings a serious limitation. Rockets must carry both the fuel and, in most cases, the oxidizer needed to burn it.
This means that much of a rocket’s mass at liftoff is propellant, not payload. The longer and more ambitious the trip, the more propellant is needed and the heavier the rocket becomes.
Mars is far enough away that the long travel time, the threat of cosmic radiation to astronauts, the mass required to transport life support systems, and restrictions on return travel pose serious problems for mission planning.
That’s why engineers continue to look for more sustainable alternatives to chemical rockets.
Two technologies
NASA’s distinguishes two main approaches: thermal propulsion and electric propulsion.
follows a 3-step process. First, the nuclear reactor inside the engine splits uranium atoms to generate enormous amounts of heat. Second, liquid hydrogen is pumped through the reactor core, where it instantly boils and expands, turning into a high-pressure gas. 3rd, this superheated gas is ejected through a nozzle at high speed to propel the spacecraft forward.
According to the US Department of Energy, nuclear thermal propulsion to Mars by up to 25% and, more importantly, limiting crew exposure to cosmic radiation. This would also expand the launch windows in which spacecraft could fly to Mars.
These windows depend on the alignments between Earth and Mars, which occur every 2 years. Greater flexibility in launch windows would allow astronauts to abort missions and return to Earth if necessary.
A, on the other hand, uses a nuclear reactor to generate electricity. This powers a type of engine called an ion thruster, which accelerates charged atoms (like xenon) out of a nozzle. If nuclear thermal propulsion is the sprint approach, nuclear electric propulsion is the marathon option. Nuclear electric propulsion produces very low thrust but can run continuously for years.
This is perfect for sending exploring robots or heavy payloads (such as habitats and food supplies) to Mars months before humans arrive. In deep space, a small boost applied over a long time can make a huge difference.
A chemical rocket is like a powerful kick. Nuclear electric propulsion is more like a persistent hand on the shoulder.
This could facilitate the transport of heavy payloads through deep space, provide abundant onboard power, and remain effective far from the Sun, where the power available for solar panels is weakest.
This is the main idea behind NASA’s mission. SR-1 Freedom is a nuclear electric propulsion mission, whose launch NASA currently plans for December 2028.
It would be the first nuclear-powered interplanetary spacecraft. It will travel to Mars to prove that nuclear energy can provide the sustainable, high-efficiency power needed for deep space travel.
Upon arrival at Mars, approximately 1 year after its launch, SR-1 Freedom is expected to release the Skyfall payload. It is a set of small drones that will explore the Martian surface.
NASA says the mission will establish whether nuclear equipment can be used on other flights. It could also create a regulatory precedent and activate an industrial base for future space systems based on nuclear fission.
For human exploration, the combination of nuclear electric propulsion and nuclear thermal propulsion is very attractive. Because nuclear electric propulsion is incredibly fuel efficient, it can move large amounts of weight (habitats, food for years, rovers, and life support equipment) using very little propellant.
In these cases, it may not matter so much that the payload takes more than nine months to reach Mars. But for our fragile human bodies, longer stays in space increase the risk of cancer due to cosmic radiation and cause bone and muscle loss.
Another issue is the fact that bones and muscles are not being exercised in microgravity. Nuclear thermal propulsion provides the high thrust needed to reach Mars in 3 to 4 months, drastically reducing these health risks to astronauts.
Steep path
Despite the clear benefits, the road to the launch pad is steep, with the SR-1 Freedom launching in 2028. A nuclear electric spacecraft needs a reactor, shielding, heat management, power conversion, radiators, electrical thrusters, control systems, and fault tolerance. Each of these mission components requires careful testing and integration to make them work together.
The reactor heat must be controlled without damaging other components. The thrusters must operate reliably for months. Other factors may interact in ways that only reveal themselves when the spacecraft’s subsystems are assembled. For SR-1 Freedom to meet its December 2028 launch window, NASA has very little time to put together a mission that would normally require years of design, integration and review.
Nuclear propulsion in space has spent more than 60 years somewhere between engineering reality and technological myth — although the physics have always been sound.
What proved most difficult was making the technology safe, affordable, licensable (able to meet regulatory safety standards), and ready to fly on a real mission schedule. So far, the US has only launched one fission reactor into orbit, .
The SR-1 Freedom could pave the way for more capable systems to follow. Nuclear electric propulsion won’t make traveling to Mars easy. But it could start to break down the barriers to traveling to Mars, and that’s a prospect we should be excited about.
is a professor of Intelligent Systems and Data Science at .
This text was published [inserir o link original] originally by The Conversation, on May 15, 2026. The content is free for republication, the source is cited, and has been adapted to the standard of Poder360.
