Project Orion (nuclear propulsion)
Project Orion was a study conducted in the 1950s and 1960s by the United States Air Force, DARPA,[1] and NASA into the viability of a nuclear pulse spaceship that would be directly propelled by a series of atomic explosions behind the craft.
[2][3] Following preliminary ideas in the 1940s,[4] and a classified paper co-authored by physicist Stanisław Ulam in 1955,[5] DARPA agreed to sponsor and fund the program in July 1958.
The design effort took place at General Atomics in San Diego,[5] and supporters included Wernher von Braun,[8] who issued a white paper advocating the idea.
[2][9] NASA also created a Mars mission profile based on the design, proposing a 125 day round trip carrying eight astronauts with a predicted development cost of $1.5 billion.
"[6] In 1979, General Dynamics donated a 26 inch (56 cm) tall wooden model of the craft to the Smithsonian, which displays it at the Steven F. Udvar-Hazy Center in Fairfax County, Virginia.
[4][3][11] In August 1955, Ulam co-authored a classified paper proposing the use of nuclear fission bombs, "ejected and detonated at a considerable distance", for propelling a vehicle in outer space.
[6] In July 1958, DARPA agreed to sponsor Orion at an initial level of $1 million per year, at which point the project received its name and formally began.
[5] The concept investigated by the government used a blast shield and shock absorber to protect the crew and convert the detonations into a continuous propulsion force.
[6][14] The extreme power of the nuclear explosions, relative to the vehicle's mass, would be managed by using external detonations, although an earlier version of the pulse concept did propose containing the blasts in an internal pressure structure, with one such design prepared by The Martin Company.
Missions that were designed for an Orion vehicle in the original project included single stage (i.e., directly from Earth's surface) to Mars and back, and a trip to one of the moons of Saturn.
[25] Freeman Dyson performed the first analysis of what kinds of Orion missions were possible to reach Alpha Centauri, the nearest star system to the Sun.
Dyson estimated that if the exposed surface consisted of copper with a thickness of 1 mm, then the diameter and mass of the hemispherical pusher plate would have to be 20 kilometers and 5 million tonnes, respectively.
In order to improve on this performance while reducing size and cost, Dyson considered an alternative momentum limited pusher plate design where an ablation coating of the exposed surface is substituted to get rid of the excess heat.
[29] The dimensions and performance of Dyson's vehicles are given as: Later studies indicate that the top cruise velocity that can theoretically be achieved are a few percent of the speed of light (0.08–0.1c).
The concept of using a magnetic sail to decelerate the spacecraft as it approaches its destination has been discussed as an alternative to using propellant; this would allow the ship to travel near the maximum theoretical velocity.
[32] As part of the development of Project Orion, to garner funding from the military, a derived "space battleship" space-based nuclear-blast-hardened nuclear-missile weapons platform was mooted in the 1960s by the United States Air Force.
[39] For the perhaps simpler fission pulse units to be used by one Orion design, a 1964 source estimated a cost of $40,000 or less each in mass production, which would be up to approximately $0.3 million each in modern-day dollars adjusted for inflation.
The whole unit was built into a can with a diameter no larger than 6 inches (150 mm) and weighed just over 300 pounds (140 kg) so it could be handled by machinery scaled-up from a soft-drink vending machine; Coca-Cola was consulted on the design.
On November 14, 1959 the one-meter model, also known as "Hot Rod" and "putt-putt", first flew using RDX (chemical explosives) in a controlled flight for 23 seconds to a height of 184 feet (56 m).
Film of the tests has been transcribed to video[44] and were featured on the BBC TV program "To Mars by A-Bomb" in 2003 with comments by Freeman Dyson and Arthur C. Clarke.
Freeman Dyson, group leader on the project, estimated back in the 1960s that with conventional nuclear weapons, each launch would statistically cause on average between 0.1 and 1 fatal cancers from the fallout.
The danger to electronic systems on the ground from an electromagnetic pulse was not considered to be significant from the sub-kiloton blasts proposed since solid-state integrated circuits were not in general use at the time.
The comparison is not quite perfect as, due to its surface burst location, Ivy Mike created a large amount of early fallout contamination.
The launch of such an Orion nuclear bomb rocket from the ground or low Earth orbit would generate an electromagnetic pulse that could cause significant damage to computers and satellites as well as flooding the van Allen belts with high-energy radiation.
A few relatively small space-based electrodynamic tethers could be deployed to quickly eject the energetic particles from the capture angles of the Van Allen belts.
All chemical rocket designs are extremely inefficient and expensive when launching large mass into orbit but could be employed if the result were cost effective.
[50] The test's experimental designer Dr. Robert Brownlee performed a highly approximate calculation that suggested that the low-yield nuclear explosive would accelerate the massive (900 kg) steel capping plate to six times escape velocity.
As discussed by Arthur C. Clarke in his recollections of the making of 2001: A Space Odyssey in The Lost Worlds of 2001, a nuclear-pulse version of the U.S. interplanetary spacecraft Discovery One was considered.
However the Discovery in the movie did not use this idea, as Stanley Kubrick thought it might be considered parody after making Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb.
The crafts' designers, constrained by a 1960s level of industrial capacity, intend it to be used to explore parallel worlds and to act as a nuclear deterrent, leapfrogging their foes more contemporary capabilities.
