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How a bomb built the space program

The Rover Program—Los Alamos’ solution to delivering an H-bomb around the world—was the United States’ first foray into nuclear rockets.
July 18, 2019
The earth above the moon's horizon.

What started with a 40,000-pound bomb and a question of transport launched the field of space exploration. Coming full circle from past to present, the technology that came out of Project Rover is now leading America’s way to Mars.CREDIT: Dreamstime


Rover’s mission was to build a new kind of rocket, one that was nuclear powered, to rapidly and safely deliver a heavy-weight hydrogen bomb to Moscow.

By Katharine Coggeshall

“America has a 40,000-pound hydrogen bomb that needs to be transported 5,700 miles to Moscow,” says Laboratory historian Alan Carr. “How do we do it?”

What sounds like a junior-high math problem is actually the question that spurred Los Alamos to delve into nuclear rockets in the 1950s. With national security as the catalyst, the Laboratory began a space program that continues to this day.

Hydrogen bombs were first built in the throes of the Cold War, when tensions were escalating between the United States and the Soviet Union, as each country developed increasingly powerful nuclear weapons. Although Los Alamos scientists constructed a new behemoth bomb—nearly four times heavier than the first wartime atomic bomb, “Little Boy”—they were unsure how to deliver it. Carr jokes that scientists “just hoped the plane would stay together,” but that’s not far from the truth. A bomb weighing nearly five tons needed a more reliable and efficient way to travel halfway around the world.

Enter Project Rover—Los Alamos’ first foray into space technology. As a part of the Nuclear Rocket Propulsion Division, Rover’s mission was to build a new kind of rocket, one that was nuclear powered, to rapidly and safely deliver a heavy-weight hydrogen bomb to Moscow.

A gray and yellow weapon on display outdoors.

In the 1950s, the most powerful nuclear weapons were too heavy for an airplane to carry halfway around the world. So Los Alamos began designing nuclear-powered rockets to do the job.

Before Project Rover, chemical rockets were the standard for space. But the speed, power, and fuel economy that a nuclear-powered thermal rocket could offer were undeniable—nuclear rockets are three times as efficient as chemical rockets, and they significantly cut travel time in space. With a nuclear rocket, a trip to Mars could be accomplished in as little as four months, and the delivery of a hydrogen bomb to Moscow could be accomplished in 30 minutes.

When it began in 1955, Project Rover was one element of Los Alamos research that acted as a metronome for keeping pace in the Cold War. Los Alamos scientists were simultaneously working to miniaturize atomic bombs, and by 1956, the problem was solved with a design for a lighter bomb. This second-generation hydrogen bomb was tested during Operation Redwing and offered a 5-megaton-yield nuclear explosion (equivalent to 5 million tons of TNT) at half the weapon weight. This newer, lighter bomb was transportable by conventional rockets, so building a nuclear rocket for bomb delivery was no longer necessary. It was time for Project Rover to abide by the rules of evolution—adapt or die.

Project Rover was on the brink of extinction when hysteria was unleashed by news of Sputnik, the first man-made satellite, which was launched by the Soviet Union. The pressure to beat the Soviets in both the arms race and the space race ballooned across America, and all eyes were back on Rover. Instantly reinvented as the solution to the Soviet’s sudden lead in space, Project Rover surged on, leaving behind its original mission of bomb delivery and focusing entirely on space travel. “Sputnik was a pivotal piece and the best thing that ever happened to space research at Los Alamos,” Carr reflects. Americans were thirsty for space research, and the Rover scientists intended to deliver.

President Kennedy rides by the Los Alamos post office in a car.

President Kennedy rides through downtown Los Alamos.

In 1962, President John F. Kennedy brought national attention to Project Rover when he visited the Laboratory. Dressed in suit and tie, Kennedy was hands-on with the cutting-edge technology that was changing the world. Kennedy’s visit culminated in a speech to the townspeople in which he praised Los Alamos' contributions to the nation. He said, “It’s not merely what was done during the days of the second war, but what has been done since then, not only in developing weapons of destruction which, by an irony of fate, help maintain the peace and freedom, but also in medicine and in space, and all the other related fields which can mean so much to mankind if we can maintain the peace and protect our freedom.”

Kennedy’s support of space research at Los Alamos was echoed by his successor, President Lyndon Johnson, but budgets fell short with President Nixon in 1973, and the project was canceled.

Though the history of why the Laboratory’s science turned skyward is unexpected, the resulting technical contributions that came out of Los Alamos space research are invaluable.

Counterproliferation technology

One of the most important contributions to space research was the Los Alamos–developed suite of satellites called Vela, which launched in 1963 and could detect nuclear detonations in space (even at clandestine test sites, such as behind the moon) as well as on the Earth’s surface and under water. The Velas used special sensors for x-rays, gamma rays, neutrons, and the natural background of radiation in space.

A man laying on the floor reaches for a satellite as he inspects it.

The Vela series of satellites carried Los Alamos-designed-and-built sensors for detecting x-rays, gamma rays, neutrons, and the natural background of radiation in space. They functioned as "watchdogs" for possible clandestine nuclear testing and more.

Before Vela (meaning “the watchman” in Spanish), the United States lacked the technology to know whether a nuclear treaty was being followed, so we had to resort to informal agreements that relied on trust. But trust is fleeting in times of war, even in cold war, and the security Vela offered calmed the nation. “Vela changed history,” Carr notes as he explains that this new counterproliferation technology played a role in securing the 1963 Limited Nuclear Test Ban Treaty with the Soviets.

The development of Vela sensors and satellites required extreme engineering, and it was accomplished at a breakneck pace. “We built the sensors in about one year,” says Los Alamos Intelligence and Space Research Division Leader
Herb Funsten. But quality was not compromised for speed: the sensor technology deployed on Vela satellites as the eyes and ears of the nation is still in use today.

In the 56 years since Vela launched, Los Alamos has flown 400 instruments carrying more than 1,400 sensors on more than 200 total launches. These five decades of space research built upon Vela’s foundation, adding monumental advances in satellites—GPS, broader nuclear weapon detection, multispectral thermal imaging, and miniaturization (see “Electronic license plates for space,” below). While Vela could detect a nuclear explosion, current satellites can detect facilities on Earth that conceal nuclear weapons (preventing an explosion in the first place).

Nuclear-powered space travel

The other important Los Alamos contribution to space research evolved on the ground through Project Rover. Three nuclear rocket designs, done in series—Kiwi (1955 to 1964), Phoebus (1964 to 1969), and Peewee (1969 to 1972)—brought about the knowledge required to achieve space travel powered by a nuclear rocket. All of these designs rely on nuclear fission (the splitting of a nucleus into smaller particles) to heat a propellant gas, in this case, hydrogen. The hydrogen expands as it reaches higher and higher temperatures, causing pressure to build inside the rocket. The pressurized gas can be funneled through a rocket nozzle to create thrust.

Kiwi (named for the flightless bird) was the first nuclear rocket series built at Los Alamos. Tested at the Nevada Test Site, it was never intended for flight; instead, Kiwi was a practice design that defined basic nuclear rocket technology.

A success in its own right, the Kiwi series led to the development of the Phoebus series. Phoebus focused on copious power, with the goal of an interplanetary voyage—such as a voyage to put a man on Mars, which was one of Kennedy’s intentions. Phoebus led to the Peewee series, which focused on a more compact nuclear rocket design, ideal for unmanned missions to space.

A large piece of equipment at the side of a building; three people stand next to it.


This science was novel and incredibly complex—literally rocket science. It demanded numerous inventions in materials and engineering to overcome the extraterrestrial challenges these rockets would face. For example, special uranium-loaded graphite fuel and stable internal engine components were designed at the Laboratory’s Sigma Complex; heat pipes were created as a cooling system solution (because nuclear cores get incredibly hot); and new techniques for advanced understanding of graphite and carbon were developed. With every barrier to rocket science success came an even greater scientific invention. More than 100 technical papers were published as a result of Project Rover.

Fifty years later, the technology from Project Rover has evolved at the Lab into the development of highly compact nuclear reactors. “These compact reactors can be safely deployed in space, providing unprecedented power—both heat and electricity,” Funsten explains.

From Rover to rover

Each of the Project Rover nuclear rocket series proved successful, but none has launched explorers on long-range space missions—yet. Space travel is expensive, but no one is questioning whether Americans will eventually land on Mars. “By the mid-2030s, I believe we can send humans to orbit Mars and return them safely to Earth,” said President Barack Obama in 2010. “And a landing on Mars will follow. And I expect to be around to see it.”

On March 11, 2019, NASA Administrator Jim Bridenstine formally announced the “Moon to Mars” initiative, financially backed by the Trump administration. Bridenstine explained, “We will go to the Moon in the next decade with innovative, new technologies and systems to explore more locations across the lunar surface than ever before. This time, when we go to the Moon, we will stay. We will use what we learn as we move forward to the Moon to take the next giant leap—sending astronauts to Mars.” The NASA timeline has the manned Mars mission slated for the 2030s, just as Obama predicted.

But before Americans can set foot on Mars, exploratory missions offering look-before-you-leap information about the planet must take place. Once again, Los Alamos is taking center stage. Laboratory space researchers are developing the power supply and two new space instruments—SuperCam and SHERLOC—for NASA’s 2020 Mars rover. “The goal is to better understand Mars, our sister planet,” explains Laboratory Fellow Roger Wiens. Wiens is not only the principal investigator for the two new instruments, he was also the mind behind the successful ChemCam instrument currently aboard NASA’s Curiosity Mars rover.

Powered by 10 pounds of non-fissionable plutonium fabricated by Los Alamos, Curiosity’s goal is to study Mars’ past habitability and characterize the planet’s hazards to humans: Can we have a sustained human presence on Mars? ChemCam is the Los Alamos–developed instrument aboard Curiosity that is currently helping to answer that question. This instrument uses a laser to identify molecules such as water and organics on Mars. Thus far, the data from ChemCam and the other rover instruments are promising; NASA will land another rover on Mars in 2020 to gather even more data.

The new rover will boast a souped-up version of ChemCam, called SuperCam, which is a suite of instrumentation: laser-induced breakdown spectroscopy, Raman and time-resolved fluorescence, color micro-imaging, and VISIR spectroscopy. Another fascinating addition is a microphone. “For the first time,” Wiens explains, “we will be able to listen to Mars!”

A man inspects a piece of equipment.

Laboratory Fellow Roger Wiens, principal investigator for SuperCam.

SuperCam’s job is to blast Martian rocks with its laser to investigate chemical and mineral compositions from a distance. In addition to SuperCam, there will be six other new instruments on the 2020 rover. SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) is the second Los Alamos contribution, which will reside on the rover’s robotic arm. SHERLOC is equipped with an ultraviolet spectrometer and camera for studying organics. The 2020 rover will answer the question: Which resources will humans be able to use on Mars?

But one remaining concern about sending Americans to Mars is radiation. As Funsten explains, “Traveling beyond the protective magnetic cocoon of Earth’s space environment and into interplanetary space, where cosmic rays continuously bathe spacecraft and solar storms can unleash high-energy particles, is our biggest challenge. Radiation from these sources can cause permanent damage to our bodies.” The current solution to this problem is the same solution we turned to for fast, efficient bomb delivery in the 1950s—nuclear rockets.

Given that total radiation exposure is a function of radiation flux and time, getting humans to Mars faster will be one way to minimize exposure. To that end, NASA is once again looking to Project Rover’s nuclear rocket technology. A nuclear rocket is expected to cut travel time to Mars in half, making a human journey to Mars feasible and certainly in our near future.

What started with a 40,000-pound bomb and a question of transport launched the field of space exploration. Coming full circle from past to present, the technology that came out of Project Rover is now leading America’s way to Mars.H

A digitally created image of a rover on Mars.

The Mars 2020 rover will carry SuperCam, designed at Los Alamos.