[LINK] On Project Orion

[rfmcdonald]

A recent Centauri Dreams post highlighted Freeman Dyson's Project Orion spacecraft design and his intent. Wikipedia's precis of the project is worth reproducing.

Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft (Nuclear pulse propulsion). Early versions of this vehicle were proposed to have taken off from the ground with significant associated nuclear fallout; later versions were presented for use only in space.

A 1955 Los Alamos Laboratory document states (without offering references) that general proposals were first made by Stanislaw Ulam in 1946, and that preliminary calculations were made by F. Reines and Ulam in a Los Alamos memorandum dated 1947.[1] The actual project, initiated in 1958, was led by Ted Taylor at General Atomics and physicist Freeman Dyson, who at Taylor's request took a year away from the Institute for Advanced Study in Princeton, US to work on the project.

The Orion concept offered high thrust and high specific impulse, or propellant efficiency, at the same time. The unprecedented extreme power requirements for doing so would be met by nuclear explosions, of such power relative to the vehicle's mass as to be survived only by using external detonations without attempting to contain them in internal structure. As a qualitative comparison, traditional chemical rockets—such as the Saturn V that took the Apollo program to the Moon—produce high thrust with low specific impulse, whereas electric ion engines produce a small amount of thrust very efficiently. Orion would have offered performance greater than the most advanced conventional or nuclear rocket engines then under consideration. Supporters of Project Orion felt that it had potential for cheap interplanetary travel, but it lost political approval over concerns with fallout from its propulsion. The Partial Test Ban Treaty of 1963 is generally acknowledged to have ended the project.

Centauri Dreams also shared Dyson's October 1968 Physics Today paper, "Interstellar Travel", exploring the mechanics of Project Orion and likely economic surround (a cost of 100 billion 1968 US dollars in the late 22nd century, after sustained economic growth of 4% per annum, was cited) and justifications.