NASA is preparing to send a nuclear-powered rocket to Mars. Not in some distant, aspirational future. The agency has committed to launching a demonstration mission by 2030, a timeline that would have seemed reckless a decade ago but now reflects a growing consensus that chemical propulsion simply can’t get humans to Mars fast enough to keep them alive and healthy.
The program is called DRACO — Demonstration Rocket for Agile Cislunar Operations — and it represents the most serious effort in more than 50 years to fly a nuclear thermal propulsion (NTP) system in space. Developed jointly by NASA and the Defense Advanced Research Projects Agency (DARPA), DRACO aims to prove that a nuclear fission reactor can heat hydrogen propellant to extreme temperatures and expel it at velocities far exceeding what any chemical engine can achieve. The result: roughly twice the fuel efficiency of conventional rockets, as measured by specific impulse, and transit times to Mars potentially cut from seven or eight months to as little as three or four, according to Futurism.
That difference isn’t academic. It’s existential for any crew making the trip.
Every additional month in deep space exposes astronauts to punishing levels of cosmic radiation, muscle atrophy, bone density loss, and psychological strain. NASA’s own research has documented the toll that extended microgravity takes on the human body — Scott Kelly’s year aboard the International Space Station produced measurable changes in gene expression, vision, and cardiovascular function. A Mars transit lasting seven months each way, plus surface time, could stretch a mission to nearly three years. Cutting the cruise phase in half would dramatically reduce cumulative radiation exposure and the volume of consumables — food, water, oxygen — that must be launched from Earth.
So the physics argument for nuclear propulsion is overwhelming. The engineering argument is harder.
Nuclear thermal propulsion isn’t a new idea. The United States tested NTP engines extensively during Project NERVA (Nuclear Engine for Rocket Vehicle Application) between 1955 and 1973. Those ground-based tests demonstrated that reactors could heat hydrogen propellant to over 2,000 degrees Celsius and produce thrust with a specific impulse around 900 seconds — roughly double the 450 seconds typical of the best liquid hydrogen/liquid oxygen chemical engines. But NERVA was canceled amid budget cuts and shifting priorities after Apollo. No nuclear thermal engine has ever flown in space. Not once.
DRACO is designed to change that. The program’s architecture centers on a flight demonstration using a smaller-scale NTP engine integrated onto an upper stage. Lockheed Martin is building the spacecraft, while BWX Technologies is responsible for the reactor and fuel elements. The engine will use high-assay low-enriched uranium (HALEU) fuel, a deliberate choice to reduce proliferation concerns compared to the highly enriched uranium used in NERVA-era designs. The reactor won’t be activated until the vehicle reaches a safe orbit, minimizing any risk of radioactive contamination during launch.
DARPA’s involvement signals something beyond pure science. The defense agency has its own strategic interests in rapid maneuvering capabilities in cislunar space — the volume between Earth and the Moon — where military planners increasingly see competition emerging. A nuclear thermal engine’s superior thrust-to-weight ratio and fuel efficiency would allow spacecraft to change orbits quickly and unpredictably, a capability with obvious defense implications.
But for NASA, the prize is Mars.
Administrator Bill Nelson and other agency leaders have repeatedly framed DRACO as a critical stepping stone toward crewed Mars missions in the late 2030s or 2040s. The logic is straightforward: without a faster propulsion method, the consumables and shielding mass required for a long-duration Mars transit would make the mission architecture prohibitively expensive and dangerous. Nuclear thermal propulsion offers a way to shrink the problem.
The technical challenges remain formidable. Operating a nuclear reactor in the vacuum of space introduces thermal management problems that don’t exist on the ground. The reactor must cycle from cold startup to full power reliably, and the hydrogen propellant — stored as a cryogenic liquid — must be kept from boiling off during the weeks or months before engine ignition. Materials science is a persistent concern: the uranium fuel elements must withstand extreme temperatures and corrosive hydrogen flow without cracking or degrading. During NERVA testing, fuel element erosion was a recurring issue that engineers never fully resolved before the program ended.
BWX Technologies has been working on advanced fuel forms that address these historical weaknesses. The company’s HALEU-based fuel elements use coated particle designs intended to contain fission products and resist hydrogen corrosion at high temperatures. Whether these perform as expected under actual spaceflight conditions is precisely what DRACO’s demonstration mission is meant to determine.
There’s also the regulatory dimension. Launching a nuclear reactor — even one that won’t be activated until orbit — requires navigating a thicket of interagency approvals involving NASA, the Department of Energy, the Nuclear Regulatory Commission, and the White House Office of Science and Technology Policy. The National Environmental Policy Act mandates environmental review. Public perception, shaped by decades of anti-nuclear sentiment, adds a political variable that technical performance alone can’t resolve.
Still, momentum is building. The fiscal year 2024 budget allocated significant funding to DRACO, and both DARPA and NASA have described the program as on track for its planned demonstration. Industry interest extends well beyond the prime contractors. Aerojet Rocketdyne, now part of L3Harris Technologies, has studied nuclear thermal engine designs for years. General Atomics and Ultra Safe Nuclear Technologies have also pursued NTP-related work, suggesting a broader industrial base is forming around the technology.
Private sector ambitions add urgency. SpaceX’s Starship, if it achieves its promised performance, could theoretically carry crews to Mars using chemical propulsion alone — but with long transit times and enormous propellant requirements, including in-orbit refueling. Elon Musk has spoken openly about Mars colonization timelines that many in the aerospace community view as aggressive to the point of fantasy. Nuclear thermal propulsion wouldn’t replace Starship; it could complement it, potentially serving as an upper stage or transit vehicle that takes over after Starship delivers payload to Earth orbit.
China’s space program is watching closely. Beijing has published research on nuclear thermal and nuclear electric propulsion concepts, and its rapid cadence of lunar and deep-space missions suggests it won’t cede the technology to the United States without competition. Russia, which has its own legacy of space nuclear power systems dating to the Soviet-era TOPAZ reactors, has discussed nuclear electric propulsion for interplanetary missions, though its current geopolitical and economic constraints limit near-term progress.
The distinction between nuclear thermal propulsion and nuclear electric propulsion matters. NTP uses the reactor’s heat directly to expel propellant at high velocity — high thrust, moderate efficiency. Nuclear electric propulsion (NEP) uses the reactor to generate electricity that powers ion thrusters — very high efficiency but very low thrust, meaning slow acceleration over long periods. For crewed missions where transit time is a health and safety constraint, NTP’s higher thrust profile is generally preferred. Some mission architects have proposed hybrid systems that combine both approaches, using NTP for the high-thrust phases and NEP for efficient cruising.
NASA has studied these hybrid architectures under its Space Nuclear Propulsion project, housed at Marshall Space Flight Center in Huntsville, Alabama. The agency’s long-term roadmap envisions DRACO as a proof of concept, followed by scaled-up NTP engines with thrust levels sufficient for crewed Mars vehicles. That scaling process — from a demonstration engine to a human-rated propulsion system — will take years of additional development, testing, and certification.
The timeline is tight. If DRACO flies by 2030 and performs as hoped, a crewed Mars mission using nuclear thermal propulsion might be feasible by the early 2040s. Slip the DRACO schedule, and that window slides further out. Budget uncertainty, always the silent killer of ambitious space programs, looms over every milestone. Congress has historically supported nuclear propulsion research in fits and starts — enthusiastic one cycle, indifferent the next.
And yet the fundamental calculus hasn’t changed since Wernher von Braun first championed nuclear rockets in the 1960s. Chemical propulsion got us to the Moon. Getting to Mars — and getting crews there alive and functional — almost certainly requires something more. DRACO is the first real attempt in half a century to prove that nuclear thermal propulsion can work in the environment where it actually matters: space.
Whether the political will and funding discipline hold long enough to see it through is the question that no reactor test can answer.
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