More Bounce to the Ounce! - by Maciej Cegłowski

Mars For The Rest of Us

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More Bounce to the Ounce!<br>A love letter to the rocket that everyone is too chicken to build

Maciej Cegłowski<br>Jul 17, 2026<br>∙ Paid

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My purpose, and my belief, is that the bombs that killed and maimed at Hiroshima and Nagasaki shall one day open the skies to man.<br>—Freeman Dyson, A Space Traveler’s Manifesto, 1958

The nuclear pulse rocket is what you’d get if you hired a 12 year old to get you to Jupiter. It works by farting a continuous string of nuclear bombs (at the rate of about one per second) out its back end and riding the ensuing blast waves on a giant shock absorber, like a pogo stick. A series of hundreds or thousands of nuclear detonations accelerates the spacecraft to pretty much any speed you want, and when it’s time to slow down, you just turn around and start nuking in the forward direction.<br>Simple, easy, and fun!<br>The performance on this thing is sensational. Rocket engineers have always been stuck having to choose between thrust and efficiency. Chemical rockets that are powerful enough to get things off the ground (like Saturn V or Starship) are hopelessly inefficient, while the efficient ion motors we put on probes and satellites have only a few ounces of thrust. It’s like forever being forced to choose between an electric tricycle and a top fuel dragster, with no middle ground.<br>Like an El Camino rolling coal, nuclear pulse rockets occupy that missing middle. The energy density of nuclear fuel gives them incredible miles to the mushroom cloud, while thrust is only limited by how much the hammering the spaceship can take before shaking apart. Where the Apollo rockets had six stages and a mass ratio of about 540:1 (for every kilo of astronaut or spacecraft that landed back on Earth, you needed more than half a ton of fully-fueled rocket on the launch pad), a nuclear pulse rocket has a mass ratio closer to 1.5. It can take off from Earth, land 4,000 tons of scientists and equipment on Mars, and come back in one piece to refuel, as many times as you want.<br>That kind a mass budget is what Mars mission planners call ‘ample’. Consider that the International Space Station, the biggest object ever assembled in space, weighs 400 tons. Nuclear pulse propulsion means no more worrying about life support or radiation. You can stock the inside with all the oxygen and frozen steaks a crew can eat, encase the whole thing in radiation-blocking plastic, cap it with a glass-domed rotating casino for the view, and still have room for the thousands of fission bombs (dispensed like coke cans) you will need to detonate to get the thing moving. A crew on such a rocket would travel to Mars in comfort and style and arrive refreshed.<br>For that matter, they could travel to Saturn and arrive refreshed. An early 1958 design envisioned sending a crew of 20 to Enceladus and back within a span of three years, or about as long as it would take to fly astronauts to Mars and back on a conventional mission using chemical rockets. And they could do it in a fully reusable vehicle on a single launch from Earth.<br>In short, the nuclear pulse rocket solves all of the problems that plague chemical rockets, albeit at the cost of replacing them with much bigger, scarier problems.<br>Here are some other representative missions enabled by nuclear thunder:<br>Soft-land 5,700 tons on the Moon (compare to 17 tons for Apollo)

Land a 1300 ton payload (three times the mass of the International Space Station!) on Enceladus and return it to Earth on a 3 year round trip.

Send a crew of 20 on a two year round trip to Callisto or Europa (with enough shielding to make Europa survivable)

Send a crew of 50 on a 200 day round-trip to Mars, with 30 day surface stay

Send 10,000 tons to medium Earth orbit.

Orion capabilities. Table adapted from George Dyson’s book Project Orion<br>Unlike every other kind of spacecraft, the only size constraint on a nuclear pulse rocket is that it can’t be too small. A practical nuclear pulse rocket—and just typing the adjective ‘practical’ here kind of sets my heart racing—weighs around 4,000 tons, about the size of a decemt apartment building. But you get much better performance if you build one the size of a cruise ship, or a city.<br>Like so many good ideas, nuclear pulse propulsion started with a Polish guy living in New Mexico. While working at Los Alamos in the 1940s, the mathematician Stanisław Ulam sketched out an idea for a spacecraft that could be accelerated by small nuclear explosions behind it. Freeman Dyson and Ted Taylor (the Rembrandt of American nuclear weapons design) later fleshed out the idea at General Atomic and got it modestly funded in the wake of the 1957 Sputnik panic.<br>Even in the 1950s, it was hard to get anyone with budget authority to stop screaming long enough to appreciate the benefits of the design. And so the budgets for Project Orion were always stingy; no one wanted to take the responsibility of...