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Orion

Two Mars exploration vehicles in convoy, designed by General Atomic for NASA in 1963–1964.

Fifty years ago tail fins, not seat belts, were standard equipment on American cars. Russia was ahead in space, but America was ahead on the road. Sputnik I, weighing 184 pounds, was launched on Oct. 4, 1957, and circled the Earth every 90 minutes for the next three months. Sputnik II, weighing 1,120 pounds, followed on Nov. 3 and included Laika, the pioneer of spacefaring dogs. Earth’s third artificial satellite was launched by a 32-ton Jupiter-C rocket built by the Chrysler Corporation, on Jan. 31, 1958. Explorer I weighed 31 pounds.

The race for space had begun. In Washington, D.C., the Advanced Research Projects Agency (now DARPA) was given a small office in the Pentagon and assigned the task of catching up. NASA would not exist until July of 1958. All three armed services had competing designs on space. “If it flies, that’s our department,” claimed the Air Force. “But they’re called spaceships,” replied the Navy. “OK, but the Moon is high ground,” answered the Army, who had already enlisted rocket pioneer Wernher von Braun.

ARPA’s mission was to consider all alternatives, however far-fetched. One of the alternatives, code-named Project Orion, was an interplanetary spaceship powered by nuclear bombs. Orion was the offspring of an idea first proposed, as an unmanned vehicle, by Los Alamos mathematician Stanislaw Ulam shortly after the Trinity atomic bomb test at Alamogordo, N.M., on July 16, 1945. It was typical of Ulam to be thinking about using bombs to deliver missiles, while everyone else was thinking about using missiles to deliver bombs.

With Sputnik circling overhead, Los Alamos bomb designer Theodore B. Taylor (see MAKE, Volume 07, page 188), who had recently moved to the General Atomic Division of General Dynamics, decided Ulam’s deserved another shot. “I was up all night and then I got alarmed that things were getting big,” he recalls. “Energy divided by volume is giving pressure, so the pressures were out of sight, unless it was very big. It got easier as it got bigger.”

According to Taylor, it was Charles Loomis, a former Los Alamos colleague working in the adjacent office, who said, “Well, think big! If it isn’t big, it’s the wrong concept.” Taylor’s perspective shifted. On Nov. 3, 1957, the day that Sputnik II (with Laika aboard) was launched, General Atomic issued T.B. Taylor’s Note on the Possibility of Nuclear Propulsion of a Very Large Vehicle at Greater than Earth Escape Velocities.

His proposal, submitted to ARPA in early 1958, envisioned a 4,000-ton vehicle, carrying 2,600 5-kiloton bombs. ARPA wrote a check for $999,750 to start things off. Suggested missions ranged from the ability to deliver “a hydrogen warhead so large that it would devastate a country one-third the size of the United States” to a grand tour of the solar system that Orion’s chief scientists envisioned as an extension of Darwin’s voyage of the Beagle: a four-year expedition to the moons of Saturn, including a two-year stay on Mars.

“Saturn by 1970,” projected the physicists. “Whoever controls Orion will control the world,” claimed General Thomas Power, commander in chief of the Strategic Air Command. An Air Force review of the project concluded: “The uses for Orion appear as limitless as space itself.”

At the center of General Atomic’s new 300-acre campus in La Jolla, Calif., near Torrey Pines, was a circular technical library, two stories high and 135 feet in diameter — exactly the diameter of the 4,000-ton Orion design. The library provided a sense of scale. Ted Taylor would point to a car or a delivery truck, the size of existing space vehicles, and say, “This is the one for looking through the keyhole.” Then he would point to the library and say, “And this is the one for opening the door.”

Orion was to be a one-cylinder external combustion engine: a single piston reciprocating within the combustion chamber of empty space. The ship, egg-shaped and the height of a 20-story building, is the piston, armored by a 1,000-ton pusher plate attached by shock-absorbing legs. The first 200 explosions, fired at half-second intervals with a total yield equivalent to some 100,000 tons of TNT, would lift the ship from sea level to 125,000 feet. Six hundred more explosions, gradually increasing in yield to 5 kilotons each, would loft the ship into a 300-mile orbit around the Earth.

“I used to have a lot of dreams about watching the flight, the vertical flight,” remembers Taylor, who planned to be on board for the initial trip to Mars. “The first flight of that thing doing its full mission would be the most spectacular thing that humans had ever seen.”

The 4,000-ton, single-stage Orion vehicle proposed in 1958 was intended to deliver 1,600 tons to a 300-mile orbit, 1,200 tons to a soft lunar landing, or 800 tons to a Mars orbit and return to a 300-mile orbit around the Earth. An “Advanced Interplanetary Ship,” powered by 15-kiloton bombs, with a takeoff weight of 10,000 tons, was envisioned as 185 feet in diameter and 280 feet in height. Payload to a 300-mile orbit was 6,100 tons, to a soft lunar landing 5,700 tons, or to a landing on an inner satellite of Saturn and return to a 300-mile Earth orbit — a three-year round-trip — 1,300 tons.

Nuclear fission releases a million times the energy of burning chemicals, but if you want to drive a spaceship, energy alone is not enough. Orion depended on whether translating the energy of a bomb to the momentum of a ship was feasible or not. Could you blow something up without blowing it up? The answer appeared to be yes.

Internal-combustion nuclear rockets are limited by the temperature at which the ship begins to melt. Orion escapes this restriction, because burning the fuel in discrete pulses and at a distance avoids high temperatures within the ship. In a chemical rocket, the burning fuel becomes the propellant. Orion’s propellant can be almost any cheap, inert material that’s placed between the pusher and the bomb. It might be as light as polyethylene or as heavy as uranium, and, on a long voyage, might include shipboard waste in addition to ice, frozen methane, or other material obtained along the way.

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 propellant 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 nozzle could withstand.

For about 1/3,000th of a second, the plasma stagnates against the pusher plate at a temperature of about 120,000°F — hotter than the surface of the sun, but cooler than a bomb. The time is too short for heat to penetrate the pusher, so the ship is able to survive an extended series of pulses, the way someone can run barefoot across a bed of coals.

Even on an ambitious interplanetary mission involving several thousand explosions, the total plasma-pusher interaction time amounts to less than one second. The high temperatures are safely isolated, in both time and distance, from the ship.

For seven years, the Orion team worked on a series of increasingly detailed designs, but never received the green light to move forward to actual nuclear tests. “Over this entire time span, no technical reason has been found that would render the concept not practicable,” they concluded in the project’s final report.

It was impossible to separate the development of Orion from the development of bombs. In 1958, the U.S. was testing some 100 megatons of nuclear weapons in the atmosphere each year — and not getting any closer to Mars as a result. A full-fledged Orion mission would have added about 1% to the fallout from existing weapons tests. Orion’s physicists believed this could be reduced by a factor of between 10 and 100 by designing cleaner — and highly directional — bombs. Still-classified evidence suggests they were at least partly right.

Orion remains the answer to a question we were never able to ask. Because of secrecy, the project was never opened to public discussion, and had no chance of gaining popular support. There was a narrow window of opportunity between the launch of Sputnik in October 1957 and the establishment of NASA in July 1958. As ARPA’s role in space was brought to a conclusion, military missions went to the Air Force and peaceful missions to NASA.

Orion was orphaned as a result. The Air Force was reluctant to adopt a project aimed at peacefully exploring the solar system. NASA was reluctant to adopt a project driven by bombs. Taylor’s original vision — that Air Force officers would man the bridge while civilian scientists sampled the rings of Saturn — missed its chance.

“You will perhaps recognize the mixture of technical wisdom and political innocence with which we came to San Diego in 1958, as similar to the Los Alamos of 1943,” Taylor’s colleague Freeman Dyson, my father, wrote to J. Robert Oppenheimer on March 17, 1965, when the project finally came to an end. “You had to learn political wisdom by success, and we by failure.”

In an Orion obituary notice that appeared in Science, my father, who had planned to be on board for the voyage to Mars and Saturn, elaborated: “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? Would we have achieved by now a cheap and rapid transportation system extending all over the Solar System? Or are we lucky to have our dreams intact?”

Adapted from the book Project Orion, with new material. Part 2 of this article, “Project Orion: Deep Space Force” will appear in MAKE, Volume 13.

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Comments

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