Author: Steven Dufresne / Source: Hackaday
Rockets with nuclear bombs for propulsion sounds like a Wile E. Coyote cartoon, but it has been seriously considered as an option for the space program. Chemical rockets combust a fuel with an oxidizer within themselves and exhaust the result out the back, causing the rocket to move in the opposite direction.
What if instead, you used the higher energy density of nuclear fission by detonating nuclear bombs?Detonating the bombs within a combustion chamber would destroy the vehicle so instead you’d do so from outside and behind. Each bomb would include a little propellant which would be thrown as plasma against the back of the vehicle, giving it a brief, but powerful push.
That’s just what a group of top physicists and engineers at General Atomic worked on between 1958 and 1965 under the name, Project Orion. They came close to doing nuclear testing a few times and did have success with smaller tests, exploding a series of chemical bombs which pushed a 270-pound craft up 185 feet as you’ll see below.
How Orion Works
The rear of the spacecraft design consists of a pusher plate, so called because it’s what the propellant pushes against. Since each explosion is discrete, the propellant arrives in pulses. Two stages of shock absorbers cushion the acceleration of those pulses and dampen them so that the overall structure and the passengers in the payload section receive tolerable accelerations of only 2 to 4 g. Depending on the vehicle size, as many as 1000 bombs could be required to get to orbit and those would be stored in magazines and moved through the center of the craft where they are thrown out an opening in the middle of the pusher plate.
The bombs themselves are made in the form of shaped charges. The nuclear device is surrounded by a radiation case shaped to channel the initial blast toward the propellant. The propellant is in the shape of a flat disk so that the resulting plasma is cylindrical, optimizing its effect on the pusher plate.
Making Orion
Polish-American scientist Stanislaw Ulam is credited with having come up with the idea for using nuclear bombs for propulsion in 1946. Shortly after Sputnik in 1957, theoretical physicist Ted Taylor decided to turn the idea into reality and initiated Project Orion at General Atomic, a division of General Dynamics. Taylor’s passion was making things which explode and specifically making smaller and smaller nuclear bombs, just what Orion needed.
Getting funding for Project Orion was always difficult because none of the branches of the military could find a military use for it and NASA, a civilian organisation, had its own program for large spacecraft. They did manage to get some funding and support from ARPA, the US Air Force, the AEC (Atomic Energy Commission), and to a lesser extent, NASA.
Many in the Air Force and later, NASA, doubted that a craft could be lifted using bombs and so a flying model of some sort needed to be built to at least prove the concept.
The Flying Model
General Atomic never got permission to do testing with nuclear bombs, though a few times they came close. Instead, they did a series of tests using chemical explosives on a mesa near San Diego. These tests are detailed in the book Project Orion: The True Story of the Atomic Spaceship by George Dyson.
The…
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