Parados this is indeed a brute force means of traveling in space however as nuclear bombs/devices had power to throw away it does not matter as long as the efficiently does not drop too low and it is George who had claimed here that once out of the atmosphere it efficiently does indeed drop to the point it is a worthless means of getting very large payloads around the solar system.
This is not Dyson position and the others scientists that did work on the project for many years or even others scientists who had look at their works over the following decades.
Here is some of the non-real physics references dealing with the subject.
^ a b Cosmos by Carl Sagan
^ Ross, F.W. - Propulsive System Specific Impulse. General Atomics GAMD-1293 8 Feb. 1960
^ Dyson, George. Project Orion - The Atomic Spaceship 1957-1965. Penguin. ISBN 0-140-27732-3
^ Dunne; Dyson and Treshow (1959). Dimensional Study of Orion Type Spaceships. General Atomics. GAMD-784.
^ a b Dyson, George (2002). Project Orion: The True Story of the Atomic Spaceship. New York, N.Y.: Henry Holt and Co.. ISBN 0-8050-7284-5.
^ "Nuclear Pulse Propulsion: A Historical Review" by Martin and Bond, Journal of the British Interplanetary Society, 1979 (p.301)
^ "The Starflight Handbook" by Mallove and Matloff, John Wiley & Sons, 1989, ISBN 0-471-61912-4 (page 66)
^ Bond & Martin, page 302
^ Cosmos series, Episode 8
^ "Antimatter Space Propulsion at Penn State University (LEPS)". Engr.psu.edu. 2001-02-27. http://www.engr.psu.edu/antimatter/documents.html.
^ Teichmann, T. - The angular effects due to asymmetric placement of axial symmetric explosives: GAMD-5823, 26 Oct 1963
^ David, C. V. Stability study of Nuclear Pulse Propulsion (Orion) Engine System. GAMD-6213, 30 Apr 1965
^ 6 augustus 2007. "Project Orion". YouTube. http://www.youtube.com/watch?v=E3Lxx2VAYi8.
^ a b Disturbing the Universe- Freeman Dyson
^ "Operation Plumbbob". July 2003. http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#PascalB.
^ Brownlee, Robert R. (June 2002). "Learning to Contain Underground Nuclear Explosions". http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html.
"Nuclear Pulse Propulsion (Project Orion) Technical Summary Report" RTD-TDR-63-3006 (1963"1964); GA-4805 Vol. 1, Reference Vehicle Design Study, Vol. 2, Interaction Effects, Vol. 3, Pulse Systems, Vol. 4, Experimental Structural Response. (From the National Technical Information Service, U.S.A.)
"Nuclear Pulse Propulsion (Project Orion) Technical Summary Report" 1 July 1963"30 June 1964, WL-TDR-64-93; GA-5386 Vol. 1, Summary Report, Vol. 2, Theoretical and Experimental Physics, Vol. 3, Engine Design, Analysis and Development Techniques, Vol. 4, Engineering Experimental Tests. (From the National Technical Information Service, U.S.A.)
"Dynamic America; a history of General Dynamics Corporation and its predecessor companies", John Niven, Courtlandt Canby, and Vernon Welsh Designer, Erik Nitsche, 1960 Page Image
General Atomics, Nuclear Pulse Space Vehicle Study, Volume I -- Summary, September 19, 1964
General Atomics, Nuclear Pulse Space Vehicle Study, Volume III -- Conceptual Vehicle Designs And Operational Systems, September 19, 1964
General Atomics, Nuclear Pulse Space Vehicle Study, Volume IV -- Mission Velocity Requirements And System Comparisons, February 28, 1966
General Atomics, Nuclear Pulse Space Vehicle Study, Volume IV -- Mission Velocity Requirements And System Comparisons (Supplement), February 28, 1966
NASA, Nuclear Pulse Vehicle Study Condensed Summary Report (General Dynamics Corp), January 1964
Problems with the Orion project a somewhat negative opinion on the project.
 External links
Wikimedia Commons has media related to: Project Orion (nuclear propulsion)
Freeman Dyson talking about Project Orion on Peoples Archive
Project Orion: Its Life, Death, and Possible Rebirth