Why NASA should go all-in on nuclear propulsion

Viewed from orbit, Jackass Flats — situated in southern Nevada about 65 miles northwest of Las Vegas — could easily be confused for Mars. The alluvial basin is full of tan and gray regolith, hued slightly red, and almost completely surrounded by carved, rocky hills. It was here, a half-century ago, that NASA engineers tested nuclear rockets intended to get us to the Red Planet by 1978.

Officials had even grander hopes for the descendants of those rockets. They were planned to be mules for a permanent lunar base by 1981, propulsion systems for deep space probes to Jupiter, Saturn, and the outer planets, and engines for “space tugs” and shuttles ferrying payloads and people from low Earth orbit (LEO) to space stations around the Earth and the Moon. NASA even envisioned a “Grand Tour” of the Solar System propelled by nuclear rockets, taking advantage of a planetary alignment that happens every 174 years to visit Jupiter, Saturn, Uranus, and Neptune with one sweeping mission between 1976 and 1980.

Why didn’t this glorious space future come to pass? What went wrong? Well, nothing. Testing these rockets went astoundingly well, in fact.

“The Rover/NERVA program conducted through the decade of the 1960’s was a highly successful technology program,” a NASA contractor report praised in 1991. “Its goals and objectives were to demonstrate the feasibility of a nuclear rocket engine system for space application. This ‘Proof of Concept’ program was mission oriented and culminated in the successful demonstration of a ground test engine system.”

Nuclear rockets were nearly ready to launch into Earth orbit for the next phase of testing. Then everything changed.

Why don’t we have nuclear propulsion now?

The short story: America won the lunar space race. Afterward, public attention soon turned back to earthly affairs: ending the Vietnam War, record inflation, an oil crisis. Politicians preferred cost-cutting to pricey space adventures. In January 1973, the Nixon Administration abruptly canceled NERVA, the Nuclear Engine for Rocket Vehicle Application program, after 17 years of research and development and roughly $10 billion spent in 2025 dollars. The Space Shuttle program became NASA’s primary focus. It turned out to be a successful, but decidedly more local, venture.

Nuclear propulsion received piecemeal federal funding and attention over the ensuing decades, but nothing close to what it enjoyed in the 1960s. There was Project Timberwind in the 1980s, the Space Nuclear Thermal Propulsion program in the 1980s and 1990s, Project Prometheus between 2003 and 2006, and most recently, the DRACO program between 2023 and May of this year. All projects were ultimately canceled.

Bhavya Lal — a Professor of Policy Analysis with RAND School of Public Policy and a former NASA associate administrator for technology, policy, and strategy — recently co-authored a report that tallied government spending on nuclear propulsion and explored why the programs failed.

“The US didn’t fail to deploy space nuclear systems because we lacked the physics or the funding or the people,” she said at a Washington Space Business Roundtable event in July. “What we didn’t have was mission pull, institutional coherence, and a sense of scale.”

In other words, every single government program focused on developing nuclear propulsion has been a side project. These missions are susceptible to cuts when politicians look to reduce spending. But despite decades of false starts, the case for nuclear remains strong.

The case for going nuclear

Nuclear space propulsion comes in two flavors: nuclear thermal rockets and nuclear electric propulsion (NEP). In nuclear thermal rockets, a small nuclear reactor heats up a propellant — often liquid hydrogen — to blazing temperatures in the thousands of degrees. Then, just like a conventional chemical rocket, this propellant is transformed into a hot gas and expelled out of a nozzle, blasting the rocket forward. Nuclear thermal rockets are roughly twice as fuel-efficient as chemical rockets while also packing a decent amount of thrust. Not as much as chemical rockets, but more than enough to propel a spacecraft out into the Solar System once a vehicle is in space.

NEP, on the other hand, utilizes a nuclear reactor to electrify thrusters that provide propulsive force. These thrusters put out minuscule amounts of thrust compared to chemical or nuclear thermal rockets, but they are up to 20 times more efficient than conventional rockets. This means they can accelerate spacecraft for much longer durations, trading slower starts for greater efficiency and range, making transit times comparable to other options. A spacecraft equipped with nuclear electric propulsion could also utilize its nuclear reactor to power the entire mission. In space, where mass-efficiency is everything, this could be a game-changer. Bhavya Lal, a Professor of Policy Analysis with RAND School of Public Policy and a former NASA associate administrator for technology, policy, and strategy, explained in an interview with SpaceNews.

“The energy density is so high, you can have a Mars mission with uranium the size of a marble,” she said. “But beyond that, there is no way to do a whole lot of science without nuclear. A few years ago, we went to Pluto with the [New Horizons] mission. The probes whisked past Pluto. Why? Because we didn’t have the delta V to go into orbit… All we have is basically 24 hours worth of data. So we just get so much more value for our money if we have nuclear.”

Almost all spacecraft sent to deep space — including the Voyager probes, Juno, Cassini-Huygens, and Galileo — must execute gravity assist maneuvers, slingshotting around planets to gain velocity for their vast treks. These circuitous routes greatly lengthen mission durations and limit launches to tight windows. Nuclear propulsion can free spacecraft from these constraints.

A NASA all-in on nuclear

So why not make nuclear propulsion a central focus at NASA rather than a side project? Before his nomination to lead the space agency was unceremoniously axed earlier this year as collateral damage of President Donald Trump’s break-up with Elon Musk, Jared Isaacman intended to do exactly that. The entrepreneur, pilot, and commercial astronaut, who was widely viewed as an excellent choice to lead NASA, planned to make nuclear electric propulsion one of his signature issues.

“I think the best way to boost morale and inspire the next generation is to ‘get the big missions done!’: Return American astronauts to the Moon, establish an architecture for routine and affordable missions, and lay out a credible path to Mars,” Isaacman told Big Think in an email. “NEP has an important role to play in that. It also properly calibrates NASA to focus on the “near-impossible”—the kind of work that other agencies or companies aren’t capable of doing or don’t have a business case to underwrite.”

In an op-ed published in August in RealClearScience, Isaacman teamed up with 2012 presidential candidate and former Speaker of the House Newt Gingrich to argue that NASA should build a fleet of NEP-powered spaceships, writing that it is “something no other agency, organization, or company is capable of accomplishing.”

“If America wants to lead, NASA must take on the hard problems again and do the near-impossible. It must urgently deliver the systems only it can build—leaving routine operations such as Earth-to-orbit delivery to the healthy commercial launch industry,” Isaacman and Gingrich wrote.

To make budgetary room for this bold endeavor, the duo advocated cutting the behind-schedule and over-budget Space Launch System (SLS), the super-heavy lift rocket intended to take astronauts back to the Moon with the Artemis program. After 14 years of development and roughly $30 billion spent, the rocket has had just one successful launch, in 2022. Isaacman clarified to Big Think that NASA should only pivot from SLS after the initial lunar objectives have been met.

“At some point we will need to move on from a $4 billion disposable rocket to something more sustainable for frequent lunar missions.”

In an email interview, Gingrich did not mince words in expressing his negative view of SLS.

“The Space Launch System is hopeless but survives by porkbarrel pressure,” he said.

Opening up the Solar System

NASA’s pioneering work in chemical rocketry paved the road for the now-thriving private industry in the U.S., opening up Earth orbit for business. A new focus on nuclear propulsion could open up the Solar System itself.

“The commercial launch industry is healthy and will continue driving down the cost to put mass in LEO,” Isaacman said. “We can then leverage NEP to efficiently transport mass to the Moon, Mars, and beyond. Think of it like a transcontinental railroad – not the fastest way to move a lot of mass, but certainly the most efficient.” 

“In the future, NEP could be the enabling technology for keeping cryogenic propellants cool on deep space missions,” he added, “providing power in regions where solar is less useful, enabling surface propellant manufacturing on Mars for return missions, and even supporting commercial applications like asteroid mining.”

For Gingrich, this nuclear propulsion is not just aspirational; it is an existential necessity. For well over a half-century, it’s been a given that the U.S. and democracy dominate space. A growing number of experts are now warning that China and authoritarianism could take over that leadership within the next decade. 

“We are on the edge of having freedom or communist totalitarianism lead the way into space,” Gingrich told Big Think. “It is historically vital that freedom leads the way and defines the rules.”

According to recent reports, Trump may be reconsidering his decision to rescind Isaacman’s nomination to lead NASA, so a huge nuclear propulsion advocate may soon lead the world’s premier space agency.

Isaacman told Big Think that he wants to see the routine at NASA shaken up.

“The status quo at the agency is not working — that is evident in every Inspector General report. This is not the time for stagnation as China looks to overtake America’s lead in the high ground of space. We need to challenge the status quo, recalibrate around NASA’s true mission and get back to making history. The country needs NASA and the world needs NASA. And I want to see the agency return to delivering world-changing discoveries.”