[easyazon-image align=”left” asin=”B000FUTQFU” locale=”us” height=”160″ src=”http://ecx.images-amazon.com/images/I/51TNQVM1YKL._SL160_.jpg” width=”107″]Explode something behind your spaceship and in league with Newton’s laws, your ship moves, it’s fundamental and there are hundreds of variations on the theme. One of the most fascinating was the Project Orion ship which used atomic bombs as fuel. It was a brilliant concept with a couple of crucial weaknesses (as I’ll explain). The magnificent Orion ship of the 1960s would have cruised the solar system with a crew of hundreds of scientists living and working in large and luxurious rooms. On the first tour there would be a two-year stop at Mars before reaching Saturn in 1970. It was all so close.

Orion was space travel as imagined in the expansive 1950s. A big ship, with a crew of hundreds, exploring the entire solar system. Weight and size were not particularly pressing issues, miniaturization was not needed. In all the crew compartment designs there was always room for a dedicated barber’s chair – it was the designers way of indicating luxury. No one was going to be bolted into a chair and have to urinate in their spacesuit. Orion had all the comforts. Instead the issues were heavy engineering and nuclear science.

In George Dyson’s excellent 2002 book “Project Orion” he quotes Brian Dunne, the team’s lead experimentalist: “It was a crazy era. All our values were tweaked because of the cold war. It was a closed society and all kinds of strange ideas were able to grow.” (The author, George Dyson, is the son of the team’s leader, Freeman Dyson).

The idea of the Orion ship was fundamentally simple: Explode an atomic bomb behind a spaceship and the force of the explosion will push the ship forward. The idea was first proposed by Los Alamos mathematician Stanislaw Ulam at the end of World War II. Small scale tests were carried out using regular explosives to prove the concept.

The Orion project was started by a young colleague of Ulam, Ted Taylor, who was also the designer of both the smallest and largest fission bombs in the US atomic arsenal. It was calculated that it would take about 600 detonations, totalling 100 megatonnes, to boost a generous 20-story spaceship into a 300-mile Earth orbit. Said Taylor: “I used to have a lot of dreams about watching the flight, the vertical flight. The first flight of that thing doing its full mission would be the most spectacular thing that humans had ever seen.”

The egg-shaped craft would feature an enormous 1000-tonne “pusher plate” at the rear attached by shock absorbing legs to the ship. As well as the store of atomic bombs, the Orion ship would use propellant – any propellant – from shipboard waste to ice, rocks, or anything collected during the mission. As Dyson explains: “The propellant is vaporized into a jet of plasma by the bomb. In contrast to a rocket, which pushes the propellant away from the ship, Orion pushes the ship away from the propellant – by ejecting slow-moving propellant, igniting the bomb and then bouncing some of the resulting fast-moving off the bottom of the ship.

“The bomb debris hits the pusher at roughly 100 times the speed of a rocket’s exhaust, producing temperatures that no rocket could withstand. The time is too short for heat to penetrate the pusher, so the ship is able to withstand an extended series of pulses, the way someone can run barefoot across a bed of coals without getting burned. Even on an ambitious interplanetary mission, involving several thousand explosions, the total plasma-pusher interaction time amounts to less than one second.”

Impressive statistics, yet to get the ship into orbit would still require detonating 100 megatonnes in Earth’s atmosphere. That was a drawback of course, although supporters pointed out that it was no more than was already been detonated every year in routine above-ground nuclear testing.

Specific impulse

From the Wikipedia page on specific impulse: http://en.wikipedia.org/wiki/Specific_impulse

The Orion concept was enthusiastically embraced in 1958, primarily due to its outstanding specific impulse (roughly defined as engine efficiency) figures. The best chemical rockets might achieve a specific impulse of 430; the Orion ship would deliver a specific impulse of 3000 in its first generation; 6000 in the second generation and perhaps as high as 60,000 with further research.

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“Whoever controls Orion will control the world”

Ted Taylor’s first designs called for a 4000-tonne ship carrying 2600 bombs, a crew of at least a hundred (possibly even a thousand or more), and lift a 1600 tonne payload to orbit. It would cost $500 million and be ready by 1964. The scientists imagined a new Darwin-like “Beagle voyage” through the solar system with a two-year stop on Mars and visits to the moons of Saturn in 1970. General Thomas Power, head of Strategic Air Command saw a slightly different mission, the ability to deliver massive bombs on any target from orbit: “Whoever controls Orion will control the world.”

Fans of Fred Hoyle’s classic sci-fi book “The Black Cloud” might imagine Orion’s scientific crew hijacking the mission, commanding the world be good until their return, then detonating their way on the grand tour of the solar system after all. Then you’d have to wonder about their return, the stock of atomic bombs depleted and possibly faced with a second Orion in orbit…

Radioactive junkyard

As good as it all seemed on paper there was still the issue of all that fallout. In 1959 the Orion team travelled to the mooted launch site in the Nevada desert. Freeman Dyson recalled: “There in the white, flat silence I began for the first time to feel a slight sense of shame for what we were proposing to do. Did we really intend to invade this silence with our trucks and bulldozers, and after a few years leave it a radioactive junkyard? The first shadow of a doubt about the rightness of Orion came into my mind.”

The problem was more clinically portrayed in the original contract with ARPA. In “Task 5: Overall Design Integration” was subheading number 10: “World-wide contamination and contamination of launch site.” Even plans to use regular explosives for the initial launch phase failed since it was shown that the use of atomic bombs anywhere in the magnetosphere would eventually bring the radioactive material back to Earth along the magnetic field lines.

A detailed study was made into the fallout effects from an Orion spaceship. That study, by Freeman Dyson, is still classified, but the essentials of it are available. The study calculated that current atmospheric testing killed about 1000 people worldwide every year. Each launch of an Orion ship would kill another 10. Freeman says that for him 10 deaths was a showstopper.

Solving the fallout problem

Dyson needed a cleaner bomb so he went to Livermore for an answer. “Unless the bombs were cleaned up drastically the thing really made no sense,” said Dyson. What they offered was the neutron bomb. “That would have meant killing one person per mission – on the edge of being acceptable considering that all these big projects kill people one way or another.” Yet even Livermore’s promised “clean” neutron bombs failed to materialize, which Dyson later reflected was just as well.

The team then began talking with Von Braun about putting a very small Orion atop a Saturn V rocket. The new plan would mean a 125-tonne Orion spaceship would be used only when lifted to orbit by the Saturn V. A crew of eight astronauts could reach the Moon in 1964. Never daunted by issues of scale, the team then calculated that a much larger conventional booster, such as a 4000-tonne “Super Nova”, might still get their beloved original 4000-tonne Orion into orbit as originally planned.

It was all getting too big and too challenging for the newly created NASA. Officials were daunted by its scale and worried how the system could ever be tested. NASA declined to fund the project. Only the Air Force remained in support. Their representative to NASA, Don Prickett, told the review committee: “There are always two philosophies encountered during the research phase of new concepts. One which says that if the concept has potential for a significant step forward it is worth a considerable effort to solve the problems even if this effort involves high risks. There is the other philosophy which approves only of research in which there are no real fundamental problems to be solved but rather improvement of established technology. What we need is more people working on novel ideas to solve some of the problems rather than viewing the problems as unsolvable.”

The outstanding engineering problems included the issue of how to get a bomb behind the pusher plate at exactly the right place, then a moment later another, and another, and another. While it might seem simple to send them straight out the back of the ship, that means creating a hole in the massive pusher plate which in turn leads to obvious safety concerns if the hatch was open when a bomb detonated on the plate. The there was the question of the pusher plate itself and whether the proposed ablative coatings would survive repeated atomic detonations.

Despite all this it was generally recognized that only the Orion program had the needed specifications for crewed missions in the solar system. The project was finally terminated in 1965 because, according Orion’s James Nance, NASA had “…no requirement for manned planetary missions.”

[easyazon-image align=”left” asin=”B003L784LG” locale=”us” height=”160″ src=”http://ecx.images-amazon.com/images/I/51zr1S-LmoL._SL160_.jpg” width=”104″]Science fiction author Stephen Baxter includes the Orion concept in his book “Ark” as a solution to the desperate problem of getting a large ship off the Earth with a payload and sending it into the deep solar system. sadly he didn’t reimagine the project at all, address any of its problems, and in the end teamed it with a far sillier engineering scheme around Jupiter. I’ll save that rave for another day.

Freeman Dyson wrote the final report wrapping up the Orion Project in 1965. In it he wrote: “The men who began the project in 1958 aimed to create a propulsion system commensurate with the real size of the task of exploring the solar system, at a cost which would be politically acceptable, and they believe they have demonstrated the way to do it.” he went on to note that: “there was no more brave talk of Mars by 1965 and of sampling the rings of Saturn by 1970. What would have happened to us if the government had given full support to us in 1959, as it did to a similar bunch of amateurs in Los Alamos in 1943?”

Finally, Dyson told Ulam (Orion’s founder) that: “My concern is to make sure that the public knows what has happened, so that they will be ready to come back to these ideas when the time is ripe.”

[easyazon-link asin=”B000FUTQFU” locale=”us”]Project Orion – The Atomic Spaceship 1957 – 1965 by George Dyson[/easyazon-link]

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