Project Orion

[An epidiascope was probably used for the illustrations]


   Tonight I shall not be talking about the famous constellation, but rocket science.

   Solid fuel rockets were invented by the Chinese thousands of years ago, but for serious flight they were limited by the poor power/weight ratio of the fuel and the fact that once started they could not be controlled or stopped.

   Liquid fuel rockets were built and tested on a small scale in Europe in the 1930’s, at which time science fiction and comics featured ‘atomic drives’ to take astronauts anywhere in space, along with ‘death rays’, robots, and ships that could not only fly but swim below oceans on planets where alien populations were never friendly.

   Come World War II, and while Vernon von Braun and his team were perfecting the ‘conventional’ liquid oxygen and kerosene V2, in 1944 American scientists successfully exploded the first atom bomb in the Nevada desert, completing the Manhattan Project. Veteran scientists on this project included Theodore Taylor, Stanislaw Ulam, and Frederick Hoffman, led by Robert Openheimer. Seeing the power of atomic energy in 1944 made Ulam and Hoffman seriously consider the possibilities of nuclear propulsion.

   After the war the US Atomic Energy Commission worked with various agencies on a series of nuclear engine projects with weird names like Dumbo, Kiwi, and Pluto, culminating in Nerva - Nuclear Engine Rocket Vehicle Application - and was close to producing a flight prototype in 1972, when the project was cancelled.


   The basic idea with all such engines was to heat a working fluid by pumping it through a nuclear reactor and let the now very hot gas expand through a nozzle to create thrust. It sounds simple but the engineering problems were immense. As well as the weight of the engine, this system required a very high constant temperature to be efficient, well over 3000 degrees C., but this would melt and vaporise any material, so a much less efficient, lower temperature would have to be used. Then came the idea of having a chemical rockets propel a combustion chamber and payload to 150 miles up. Once clear of the atmosphere the chamber, 130 feet across, would continue by having ‘small’ atomic bombs which would drop and explode within, propelling the vehicle into space.  In 1955, a classified paper by Stanislaw Ulam and Cornelius Everett modified the design to eliminate the combustion chamber altogether. Bigger nuclear bombs would be ejected from the back along with solid propellant discs. The initial explosion would vapourise the discs, and the resulting exploding plasma would hit a pusher plate at the base of the rocket.

   Could this theory survive, let alone fly ? In the mid to late 50’s everyone seemed to be testing nuclear bombs near the surface of our planet. Then, in 1957, the Soviet Union put up Sputnik1, a basketball size satellite, followed by the larger Sputnik 2 later in the year, much to the surprise and dismay of the USA.

   At the time, Frederick Hoffman had been the head of General Atomic, a research facility studying the peaceful uses of atomic energy including civilian nuclear reactors. A result of the shock of the Russian satellites was that Project Orion was conceived. Hoffman was able to woo the best nuclear scientists from the weapons laboratories of the Rand Corporation and General Dynamics to the well appointed,well paid, and easier on the conscience work at General Atomic, fully funded for Project Orion. Among the 50 or so scientists who gathered there were Theodore Taylor, the leader of the project, and the brilliant British physicist, Freeman Dyson, from Princeton University in 1958.

    America was already improving conventional rockets, aided by von Braun’s team, but were barely competitive with the USSR. In the spring of 1958 the USA finally launched a ‘grapefruit’ into orbit with radio transmissions, but rather small beer.

    Orion promised to be different, so many people would write off the whole idea of nuclear propulsion as ridiculous. A clue that it could be possible had arisen out of the first ever nuclear test in 1944. The bomb was raised onto a 200 foot metal pylon tower and detonated. One would expect the fireball to instantly vaporise the tower but when Theodore Taylor visited the site later the metal pieces had been thrown a considerable distance but were in themselves complete - the explosion could push material without destroying it.

   Experiments with small Orion prototypes began by using conventional explosives but designers and scientists wasted no time calculating, designing, but not quite building the real thing. One prototype, 3 ft. by 2 ft. did manage a 100 metre flight.

   The proper rocket envisaged was as follows:-   [diagram slide]

   A vehicle in the shape of a squat shell ( similar to Jules Verne’s projectile fired from a gun ). Measuring 160 ft. X 100 ft. it would stand on several giant shock absorbers, rather like those of a car , but huge. The base of the shocks would be rooted in an  upper base plate, below which there would be a layer of further shock absorbing bags or springs. And below this the essential pusher plate, against which the force of nuclear bombs would hit and push. This pusher plate would be about 130 feet across, 6 to 12 inches thick, and weigh 1000 to 2000 tons on its own.

   A nuclear bomb every half second or so would be delivered down a pipe and through a small hole in the pusher plate, and detonated 100 to 200 feet below it, with yields of 0.1 to 20 kilotons.

   The explosion would create plasma, briefly reaching 100,000 degrees C. with a speed of 300,000 mph when it hit the outside surface of the pusher plate. The plate is briefly accelerated to 1000 G, but the combined shock absorbing makes the upward thrust in the main body of the rocket survivable (at some 10 - 20 metres/sec squared). The whole assembly, weighing around 10,000 tons, would get pushed into orbit by 1000 bombs exploding in quick 0.5 second pulses. As the entire thing (minus the bombs) reaches Earth orbit and beyond, and only a small part of the rocket’s weight is ‘fuel’, it means that the payload can be huge. In the conventional rocket 85% of the weight is fuel.

    But with 1000 bombs exploding 100 to 200 feet from the pusher plate, how long would it last ? This was Freeman Dyson’s problem. His calculations involved radiation, the speed and extreme temperatures of the plasma, and the densities and evaporation rate of steel. All very complex but he confidently predicted that less than one inch of the plate would vaporise, and this aspect of the Orion launch was viable. A car, after all is driven by a series of more conventional explosions.

    Small test runs continued, while the USA, UK, USSR, China and France went ahead with full scale surface nuclear tests.

    Long distance solar system travel necessitated many more bombs than those required for take-off. A trip to Mars needed acceleration to 50,000 miles per hour, deceleration at Mars, and then to make the return journey.

   The living accommodation would require ‘shipyard heavy’ technology for, perhaps 8 astronauts, plus 100 tons of equipment and supplies. In the 1950’s Freeman Dyson  calculated, with orbits and trajectories, that such a mission could go to Mars sometime between 1965 and 1970.

   Now, NASA, created in January,1958 as a civilian administration to race Russia to the Moon, was committed to using only chemical rockets, and was not to be secret.

Orion, being secret, was transferred to the Air Force, even though it was supposed to be a nuclear power for peace, and not a military weapon. It was a way of getting the Air Force into space tactics, with a huge payload to boot ! A flying model and a film presentation was used to sell the project to the Air Force and keep the funding going. The presentation was a success, and the Air Force took it ‘under their wing’ as it were, but it sowed the seeds of its demise.

   The potential for a large payload fired the minds of the military with any number of strictly non peaceful uses, and even crackpot ideas, turning the ploughshare back into a sword.

   It could take 250 marines to any trouble spot in the world inside half an hour, though there might be problems making an emergency nuclear bomb powered landing in, say, the USSR, with the thing packed with troops. Another crazy idea was the Domesday Bomb. Basically this was the biggest hydrogen bomb the payload would allow, and it would be sent into high geosynchronous orbit over Russia. Meanwhile in Washington there would be the big red button someone could push if all else failed and it would be the end of the Soviet Union. Of course, neighbours, and the climate of the Northern hemisphere would suffer grievously, the price to be paid for freedom, democracy, and the American way of life.

   Almost no one considered it a good idea, although the physics and feasibility studies were completed, yet it was acknowledged that it could evolve into a ‘death star’, a weapon to enforce peace. One person, General Thomas Powers, Second in Command, Strategic Air Command, wanted to pursue the idea. He ordered a model be made of an Orion weapon system for space. The orbiting battleship had to be equipped with a nuclear armoury and, once expended, it could protect itself from retaliation by hiding behind its own pusher plate.

   The model, the size of a car, was put on show at the Strategic Air Command air base at Vandenburg to impress President Kennedy on his presidential visit to the base in March,1962. But it backfired!  The world of the 1950’s was changing.

   The radiation effects of surface nuclear testing were causing public alarm and outcry, with strontium 90 appearing in milk and bones. Dyson himself calculated that an Orion launch would produce radiation that could cause 1 to 10 deaths, unacceptable until bombs were drastically cleaned up to produce less than one 1/100th of a death per launch. Kennedy had dealt with the so called ‘Cuban Missile Crisis, in 1962 and was horrified when he saw the model Orion. This was the last thing the world needed - a nuclear arms race in space.

   By 1963 Dyson’s concerns about fallout had become conviction. As a technical consultant with the International Disarmament Agency he had to choose between Orion and recommending the end of atmospheric tests, and felt that the Test Ban Treaty was the correct path. In 1963 the funding for Project Orion was stopped and the project terminated. Freeman Dyson returned to Princeton University.         

   More than 30 years later, a brilliant British academic working in mathematics  at Princeton, achieved world fame. Andrew Wiles solved Fermat’s ‘Last Theorem’, a puzzle that had defeated the world’s best mathematicians for 350 years.

  Looking to the future, such a ship could still be built, but nuclear bombs confined to deep space. The heavy craft would have to remain in orbit of Earth on return, and crew, supplies, etc. taken up or down by conventional shuttle or rocket.

                               Any Questions ?