A questo punto mi sembra giusto segnalare il seguente articolo di Micheal Flora “Project Orion:
Its Life, Death, and Possible Rebirth” :
Robert McNamara, Defense Secretary under the Kennedy Administration, realized that Orion was not a military asset. His department consistently rejected any increase in funding for the project, effectively limiting it to a feasibility study (37). Taylor and Dyson knew that another money source had to be found if a flyable vehicle was to be built. NASA was the only remaining option. Accordingly, Taylor and James Nance, a General Atomics employee and later director of the project, made at least two trips to Marshall Space Flight Center (MSFC) in Huntsville, Alabama (38). MSFC was von Braun’s domain and it was where most of NASA’s space propulsion research and development took place. Von Braun was hard at work on the Saturn project, which NASA had inherited from the old Army Ballistic Missile Agency. The Saturn V would eventually transport men to the moon. The Orion workers had produced a new, “first generation” design that abandoned ground launch and instead would have been boosted into orbit as a Saturn V upper stage. The core of the vehicle was a 200,000-pound “propulsion module” with a pusher-plate diameter of 33 feet, limited by the diameter of the Saturn. This design limitation also restricted Isp to from 1800 to 2500 seconds (39). While disappointingly low by nuclear- pulse standards, this figure still far exceeded those of other nuclear rocket designs. The shock absorber system had two sections: a primary unit made up of toroidal pneumatic bags located directly behind the pusher plate, and a secondary unit of four telescoping shocks (like those on a car) connecting the pusher plate assembly to the rest of the spacecraft (40).
How many Saturn V’s would have been required to put this vehicle into orbit? Dyson says one or two (41); a simple inspection of published drawings indicates at least two, possibly three if the crew module (with crew aboard) was intended to be flown separately (42). In this case, some assembly would have been done on-orbit. Several mission profiles were contemplated; the one developed in greatest detail appears to have been a Mars flight. Eight astronauts, with around 100 tons of equipment and supplies, could have made a round trip to Mars in 125 days (43); most modern plans call for one-way times of at least nine months. Another impressive figure is that as much as 45% of the gross vehicle weight in Earth orbit could have been payload (44). Presumably the flight would have been made when Mars was nearest to the Earth; still, so much energy was available that almost the fastest-possible path between the planets could have been chosen. Inspection of the drawings indicates that a lander may also have been carried.
What about the cost? Pedersen’s 1964 estimate of $1.5 billion for the project (45) suggests the superior economics of nuclear pulse spaceships. Dyson felt that Orion’s appeal was greatly diluted by the chemical booster restriction: the Saturns would have represented over 50% of the total cost (46).
Von Braun became an enthusiastic Orion supporter, but he was able to make little headway among higher-level administration officials. In addition to the general injunction against nuclear power, very practical objections were raised: what if a Saturn bearing a propulsion module with hundreds of bombs aboard should explode? Was it possible to guarantee that not a single bomb would explode or even rupture? NASA’s understandable fear of a public-relations disaster contributed to its reluctance to provide money (47); however, its Office of Manned Spaceflight was sufficiently interested to fund another study (48).
A hammer blow was delivered in August 1963 with the signing of the nuclear test-ban treaty by the U.S., U.K., and U.S.S.R. Orion was now illegal under international law. Yet the project did not die immediately. It was still possible that an exemption could be granted for programs that were demonstrably peaceful. Surely the treaty reduced Orion’s political capital even further, though. Yet another problem was that, because Orion was a classified project, very few people in the engineering and scientific communities were aware of its existence. In an attempt to rectify this, Nance (now managing the project) lobbied the Air Force to declassify at least the broad outline of the work that had been done. Eventually it agreed, and Nance published a brief description of the “first generation” vehicle in October 1964 (49).
Giusto per intenderci, ognuno ha diritto alla propria opinione (ed “a posteriori” è sempre facile sparare sentenze) ma molta gente (anche di spessore) ha ritenuto il progetto Orion se non conveniente almeno fattibile.