Of all the dreams of the golden years of the 20th century, in which flying cars would be be crossing the skies of technologic utopias, one of them actually had serious chances of becoming reality exactly as imagined in cheap sci-fi comics. Shortly after stepping on the Moon, we would be colonizing Mars, visiting Saturn and the satellites of Jupiter, all in gigantic spaceships hundreds of meters long, with thousands of tons and hundreds of astrounauts. Huge permanent colonies would be established in other planets and even Alpha Centauri would be at our reach.
It would all be possible through one project: Orion.
In a sort of poetic beauty, this project full of hopes for humankind was born on the mind of the first man to create the most destructive weapon ever conceived. Stanislaw Ulam, who along with Edward Teller created the key concept behind the hydrogen fusion bomb, had a few years earlier thought about using the power of nuclear explosions for a peaceful end. At the end of his life, he would consider the concept of nuclear pulse propulsion his greatest invention.
Since the beggining of the century, physicists had realized that the energies involved in nuclear reactions were many orders of magnitude greater than those in meager chemical reactions to which we are more used to, from a burning match to even TNT. And they spent the next decades trying to control it, first through nuclear reactors and then unleashing this power in an instant with the atom bomb.
On thinking about how to use this huge power to send humans to space, Ulam realized that it was not feasible to contain those explosions in chambers, like we do with our chemical rockets. His alternative concept for nuclear pulse propulsion was more feasible, and essentially very simple, though his original written note about it remains classified to this day.
Ulam proposed to simply detonate a small nuclear bomb at the rear of a vehicle and catch the blast with a simple and strong pusher plate, coupled to a shock aborption system to avoid having the whole vehicle tearing apart from the sudden acceleration. Repeat the process one or more times per second, and you would be going to the stars, pogo-stick style.
But would such a simple method actually work? The video below demonstrates the exotic concept just may be possible:
The experiments used common, chemical, high explosives though. Wouldn’t the pusher plate be pulverized if it caught any significant thrust from the nuclear explosions?
In 1954, an experiment proved that engineered objects could survive a nuclear fireball, where two graphite-covered steel spheres placed near the center of an explosion were later found at a distance, almost intact.
In 1958, a project was created to develop the concept. Project Orion was born. Contrary to almost everything in the history of the space race, all semed to conspire for Orion to succeed.
At around the same time, the military had already mastered the techniques to create small and resilient nuclear bombs, including some that could be fired from cannons. On Project Orion, the spaceship would be loaded with a few thousand small nuclear bombs, stored and deployed one at a time by a mechanical system based on those used on Coca-Cola bottling factories (!).
The explosions would not pulverize the pusher plate. In fact, they would only take a fraction of its thickness, and even that could be dealt with if the plate was first sprayed with an oil, in which case the plate itself would not lose any material in thousands of explosions.
The thrust would be huge. Even though it seems very wasteful at first, and it actually is, since you don’t need to contain the explosion it can be very powerful. It would work in the space vacuum too: the chemical explosives that first ignite the nuclear components turn into the propellant after the nuclear explosion.
Also, the huge thrust produced by the explosions could only mean one kind of vehicle: a hugely massive one. Contrary to the rockets we know, built for minimum possible mass, the more mass the Orion vehicles had the better, as they would translate the thrust into accelerations safe for the fragile human beings inside it.
Project Orion spaceships were designed based on submarines, not aircrafts. Being made of strong steel, their mass was always counted in thousands of tons. Such mass would also be useful as a shield for cosmic radiation, as well as the radiation produced by the constant nuclear explosions at the rear of the vehicle.
Suddenly, huge spaceships were not an issue, but an engineering solution.
The high efficiency of the nuclear pulse propulsion would also allow the vehicle to reach speeds almost impossible for chemical rockets, making round trips to Pluto and even close stars, at fractions of the speed of light, became plausible objectives. The Orion scientists actually made the calculations for such trips.
One by one, all the technical difficulties of the project were being solved, at least in the paper, and the military sponsors were willing to spend almost unlimited resources for it to become a reality. Which, ironically, ended up being one of the main reasons for its demise. Initiated in 1958, when the project was starting to reach maturity as a concrete idea, real world politics got to Orion.
Not everything was a comic book dream. Detonating nuclear bombs in the atmosphere, even small ones, inevitably generates radioactive fallout. Calculations suggested that, statistically, one Orion rocket launch could cause up to ten deaths by cancer provoked by the added radiation in the atmosphere.
The nuclear explosions would also generate electromagnetic pulses (EMPs) which would affect and probably destroy all electronic equipment on a huge area below the rocket, as well as nearby satellites in orbit.
That the military men were also enthusiastically dreaming of great nuclear battleships in space and showed a model of one such monster to John Kennedy also didn’t help. Kennedy had just been through the Cuban missile crisis, and a space race with nuclear battleships over our heads was the last thing we needed.
The Partial Test Ban Treaty of 1963, prohibiting nuclear explosions in the atmosphere, effectively put an end to the project. It survived a few more years, being even supported by figures like Wernher von Braun, but NASA was already on its chemical rocket path to the Moon.
Even today, the nuclear pulse propulsion remains the best technology ever conceived for space travel. It’s not the only way to apply the power of the atom to travel in the skies, but it’s the only one that combines both high thrust and high specific impulse. Ionic and even other kinds of nuclear engines can generate high specific impulse, but only with a very small thrust. Our chemical rockets generate huge thrust, but with such bad performance that it’s impossible to escape Earth without multiple stages. With an Orion vehicle, a rocket could go from the ground to other planets with just a single stage.
It may seem paradoxical that nuclear bombs may mean both the end of our species through an Armageddon caused by intercontinental nuclear bombs, or the guarantee of our future through interplanetary nuclear spaceships.
But it just illustrates how science is just a way of gathering knowledge about the world. Technology is a way of applying this knowledge. But if and how we will apply it, is something for us to decide through other means, unfortunately not as clear cut.
Up until now, we didn’t explode ourselves, but we also didn’t take the leap that could get us “where no man has gone before”.
Above: excerpt from BBC’s “To Mars by A-Bomb“. The reference about project Orion is the book “Project Orion: The True Story of the Atomic Spaceship“, by George Dyson, son of Freeman Dyson.
Wikipedia has a nice summary on the subject, and a more detailed article freely available is “Project Orion: Its Life, Death, and Possible Rebirth“, with a long list of links and further references.
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