Heinlein's Torchships may have been more useful and powerfull than an Orion, but the Orion is still niftier.

Torchships for the engineers, Orions for the nerds. I want the Orion wings. lol

Are you possibly referring to the article about the MiniMag Orion?
The paper I'm thinking of was done in 2000, and is entitled: "Mini-MagOrioin: A Pulsed Nuclear Rocket for Solar System Exploration" by Ralph Ewig, and Dana Andrews. This paper is available in PDF format at:

http://www.andrews-space.com/en/news/Pub-MiniMagOrion(200307).pdf

I must admit, this is an exciting concept in that it uses high current EM implosion to create supercriticality in very small masses of fissionable isotopes. Pulse energies of a few tons of TNT equivalent to about 100 tons equivalent are possible. Several pulses per second should give a nice smooth ride, and it should achieve 'reactor' powers in the 300 GW range so the vehicle is fairly high thrust and high Isp at the same time. Also, the machine would permit the use of 'nonconventional' isotopes, not normally associated with nuclear weapons: isotopes of cerium, curium, and americium (I think) can be used instead of plutonium (although ol' Pluto might provide increased cost effectiveness if it were 'recycled' from say old weapons' stockpiles!)

Anways, this machine operates on the external pulse, plasma mode. So I think this may have been what you were referring to. It's a nice way around some of the political 'log jams' associated with a conventional nuclear pulse Orion.

Well, the ground launch would be entirely dependent upon the thrust to weight ratio, which must be greater than one for the rocket to lift off. Orion is theoretically able to achieve this with ease. I would imagine that the Mini-MagOrion may be able to do so, however, its operating mode uses a lot of electricity which must be generated dynamically from a combination of induction coils surrounding the magnetic nozzle, and probably some kind of thermal conversion system that scavenges energy from the waste heat. Also, the machine must have a large array of radiators. All of this cries out to me: vacuum operation, which presumes operation in a space environment.

The paper mentioned above shows a nice diagram of something that looks a lot like JIMO's very big brother: reactor and nozzle propulsion structures at one end of a long boom, with crew modules and cargo modules at the other end, with a large array of thermal radiators somewhere in between.

The vehicle theoretically could achieve 30,000 seconds of specific impulse, or better, and do it with a moderately high level of thrust in the neigborhood of millions of newtons (hundreds of kilopounds-force.) Still, I suspect that such a vehicle when fully loaded with fuel mass and cargo, could probably achieve at best about 0.2 g's acceleration. Which is phenomenal performance for a vehicle with ion-engine like efficiency--such a vehicle could pretty easily fly to Mars and back without breaking a sweat!

As for your second question, the answer is: it depends. I would much rather have the grudging cooperation of the government, than to have clandestine opposition. In otherwords, a fully funded private project making progress on its own is much preferred to a secretive private project that gets the governments attention--enough so that the black-clad HALO paratroopers with submachine guns drop in for a visit!

I would rather have IAEA inspections, than to try to have a maverick operation that operates outside of international law and ultimately gets shut down by Navy SEALs with satchel charges!

The point is that without the financial resources available to someone like Bill Gates, or some other billionare, such a project could not hope to aquire the precision milling machines, exotic alloys, the high current switches, the super computers, miles of superconducting cables, cryogenic storage and refigeration systems, and space suits, let alone fissionables for such a project to move forward. A well funded private project benefits from positive PR, as do govenrment projects. They key to achieving govenment cooperation and support is to show them that the project can go forward in another country, but the financeers would prefer to do it in the US for technical and financial reasons. And then dangle a big dollar sign about tax revenues that the government could get from payrolls, etc.

Ashley,

I agree with some of that. Although, with a well funded private research direction composed and overseen by accredited personel under the auspicies of a Corporation constructed specifically for the purpose, I would imagine that great things could be done. Who knows, the government may become interested enough to want to become a more active participant. It's one thing to make a proposal to an agency like NASA for a research direction or a project proposal--it is another thing completely to announce that the design is completed and construction is underway. It would be a better thing still to simply unveil the prototype with a banner reading "Here It Is!"

But then, I guess that was your point!

Have a safe journey.

Sincerely,

"One of the Watched"

To use a contemporary example, back in 1974 or so, the CIA initiated a little known project to recover the Soviet ballistic missile submarine K-129 from 16000 ft of water. The CIA paid for several hundred million dollars for the construction of a special vessel for this purpose called the Glomar Explorer. The Glomar Explorer, as a cover story, was publically funded by Howard Hughes (of Hughes Aircraft fame,) as a wild project to recover manganese nodules from the bottom of the ocean. The ship was built in plane sight, and had all kinds of heavy derricks, deck cranes and support for ROV's and extensive teams of divers. The press was invited to come onto the deck of the 'research ship' and scientists and engineers talked about mining minerals off the bottom of the ocean. For years afterward, there were periodic articles about deep sea mining in Popular Science.

And it was all a sham!

Anyways, a really good history of Glomar Explorer can be found at:

http://w3.the-kgb.com/dante/military/explorer.html

The point is that the CIA managed to hide a super secret project, in plain view of everyone. Whether the Soviets were fooled, I don't know. They certainly would have been embarrased to admit that one of their submarines was recovered by Americans, but nothing really sensitive would have come of it. K-129 was an obsolete diesel-electric sub, with outmoded liquid fueled ballistic missiles, which would have been state of the art in 1962, but not in 1974. The project failed, however, when only a small portion of the bow was recovered, and not the whole boat.

Back on topic: it is possible to 'hide' such a project as Orion, but it would be extremely difficult to do so, and the added expense of secrecy would probably not make it cost effective.

The only way I could see an Orion being developed under secrecy was if there was a National Defense Imperitive to do so. As in the fine book: Footfall secrecy was paramount to a successful counter attack against the alien invaders. Under those circumstances, as with the Manhattan Project of WWII, cost is not an issue, secrecy is an absolute priority (more so than the lives of the participants!) and failure is not an option (to use the Apollo 13 movie-cliche')

Sans an alien invasion, or China building Star Destroyers in orbit, I don't forsee a National Security Imperitive to build an Orion. However, that's not to say we couldn't.
But the ground testing of portions of Orion, the initial intermediate scale flight test demonstators with live nuclear pulse units, fallowed by the full up consctruction of the actual flight model would likely require the resources of an industrial country. The space needed for the project would likely be thousands of square miles; the initial testing of hardware with nuclear pulse units; and the manufacture of additional pulse units requires substantial infrastructure and organization. Not to say that it couldn't be built privately; but the endeavour would realistically require the efforts of either a government, a consortium of large companies, or both.