The Golden Age of Atomic Power in Space

© Laurence B. Winn

Jan 1, 2001

Part II: General Atomic

In Part I, we looked at atomic power from the viewpoint of post World War II science and learned about Dunne's friendship with Theodore Taylor. In Part II, Dunne comes to General Atomic in San Diego, where Project Orion took shape.

Dunne: There were about a hundred employees occupying an old grade school down on Barnard Street. It was very amusing because the drinking fountains were down very low for children, and the blackboards were low, and the machine shop used to be the kindergarten and all the drawers were way down there next to the floor. It was the spring of '57.

Our first project was TRIGA, the Training Research Isotope production General Atomic, that was the acronym, T-R-I-G-A. It was a brand new and exciting project. They had Edward Teller come down. They had Marshall Rosenbluth from Los Alamos. He was a brilliant mathematical physicist.

The first thing they settled on as being a worthwhile thing to do was to build a safe nuclear reactor. Teller had many ideas. Freeman Dyson had good ideas and sorted out a lot of the bad ideas. Marshall Rosenbluth made some key calculations. Finally we came up with this brand new concept in a reactor. It was sort of outrageous at the time, but it was really a key idea, and that was to put hydrogen right in with the reactor fuel elements. As the reactor went on an excursion, primarily a prompt excursion, the most dangerous kind, the hydrogen would get heat from the solid and any neutron that collided with it would get sped up, and hence the fission cross section of the whole assembly would be reduced. "Inherently safe" was the way it was described. We had unlimited budgets. We worked long hours. It was exciting. It was fun.

LW: Did TRIGA ever find commercial application.

Dunne: It was a huge success. They sold about 55 of the reactors. They were used for making isotopes, for doing studies of neutron irradiation, neutron activation ... then, of course, there was the training thing. They were not only fool-proof. They were PhD-proof, which is harder to do.

LW: And then the Russians launched Sputnik?

Dunne: Then Sputnik came along. We were working on TRIGA when the Sputnik thing hit. I called Taylor up, this was in 1957, and just raved on and on about this thing. It was on a Sunday, I remember. It was so sudden, such a tour de force.

Just at that point we began thinking about coupling nuclear energy to space. Ted was already bored with TRIGA, and I was getting bored with it, too. It was about the spring of 1958 that we started talking to Freddie (Frederich de Hoffman, General Atomic's director) about building rockets with bombs. At that time, nothing was too far out for General Atomic. Anyway, I met with Marshall Rosenbluth and Ted Taylor and others. They made some calculations, and the whole thing was very loose-jointed.

LW: How did the Orion name come about?

Dunne: The basic idea was "man in the heavens". Marshall Rosenbluth proposed that we spell it "O'Ryan" so that no one would know what it was, and they could keep the security a little better.

Taylor's first idea was that the spaceship would be doughnut-shaped, and it would have this diaphragm covering the doughnut, looking a little bit like one of those frisbees. I remember the picture he drew on the board. You shot the bombs out of the doughnut part to the point of detonation and the membrane would catch the blast. He asked me to put together some notions about what could be done in the way of experiments. I did this, drawing on some work that had been done earlier at Los Alamos. They had devised a method for producing a toroidal implosion with a high-explosive charge, and it made a jet of tremendous energy and velocity. With a plastic liner, that would be a good way of producing a jet of CH2 as a propellant.

LW: Something with low molecular weight?

Dunne: That's right, and so this was embodied in the first proposal that was put in to ARPA. ARPA had been founded just before that, and they were really looking for something far out. It was the Advanced Research Projects Agency, that was its title and its charter. Taylor was a marvelous salesman. He went in and came out with a million dollars, just like that.

Meanwhile, I went over to Europe to do this previous stint, and I told him that as soon as I finished over there that I would come back and work on Orion, which I did. And he asked me to run the experimental effort.

So we started at this Point Loma facility which the Navy was kind enough to give us the use of. There were big bunkers down there, this Atlas test tower. So we began the implosion experiments.

LW: By "implosion" you mean... ?

Dunne: Implosion means "inward explosion". There are different styles and geometries of implosion. Nuclear weapons use a spherical implosion, but we were interested in directing energy in one direction. The types we used were called toroidal implosions. What you get out of this is a very directed jet of plasma at very high speeds, typically one million centimeters per second.

LW: This is with high explosives?

Dunne: High explosives, yes. We were able to simulate certain regimes of the Orion plasma-pusher plate interaction. And that turned out to be a very important theoretical problem, what happens when a fast-moving plasma piles up on a metal plate. It radiates in both directions, outward and into the plate, burning away some material, and it's got a lot of compression, and then it streams back. The experimentalists' contribution was the notion of the tapered pusher plate. The plate has to be thicker in the center and taper toward the outside.

And we did experiments on very light-weight shock absorbers. We discovered that we really didn't want to use springs, but we wanted gas as a shock-absorbing material. We had to have a high spring constant, so we used polyurethane foam, which has little bubbles of gas. It was encased in a heavy canvas cover.

We found out a lot of things about structures by exposing them to high explosives. And we were able to show how the phenomena scaled with charge size and ship size.

LW: How do they scale?

Dunne: It scales as the charge weight to the one-third power. The pressures are the same if distances are scaled to the third power.

LW: That would translate into nuclear equivalents?

Dunne: Pretty close. There's no exact equivalence between nuclear and high explosive yields because of radiation effects, but there is no question in my mind that you can push payloads in the 100,000-ton range with vehicles of this kind.

LW: The Apollo missions, Saturn V boosters and all, weighed just about 3,000 tons. By comparison, a Saturn V seems almost child's play.

Dunne: Yes. Ray Johnson, chief of ARPA, told Taylor. "Everyone is making plans to pile fuel on fuel to put a pea into orbit, but you seem to mean business." But I was not down on the Apollo mission as many Orion people were, They couldn't conceive of that working because they did calculations and they couldn't conceive of the landing being possible. But the calculations that some of the Orioners made were based on a faulty premise. They didn't take into account the possibility of a lunar orbit and then going down with a very light-weight vehicle.

LW: But the technology doesn't compare to the Orion concept. Where do you think we could be if it had been implemented?

Dunne: Dyson and Taylor were primarily interested in exploring the planets, particularly Mars and the rings of Saturn. Dyson envisioned trips to the outer planets, very big expeditions with very, very big payloads. That was their immediate goal, and they would have liked to do it in their lifetimes.

LW: So what happened?

Dunne: Orion was cancelled because it was the fly in the ointment of the nuclear test ban. Of course, there were also arguments that national resources shouldn't be spent on such a ridiculously wild, fantastic idea.

Author's note: On August 5, 1963, the Unites States, Britain and the U.S.S.R. signed a treaty in Moscow banning nuclear tests in space, in the atmosphere and under water.

LW: What about toxic effects, nuclear fallout, that kind of thing?

Dunne: I long have felt that the proper place for Orion is on the moon. But the political and economic view of the project was directed to lifting payloads off the earth. This was, of course, before we went to the moon and before there were any big rockets for lifting, even by chemical means. The idea of setting up a lunar city was so far out, so much in the arena of fantasy, that people couldn't take that and then add to it an Orion base. It was just too much for people to think about.

LW: What are the advantages?

Dunne: You get away from the hazards of going through the atmosphere and the designs of the ships are much simpler.

LW: So you would build the ships on the moon?

Dunne: Yes. You can envision a lunar base with manufacturing facilities of major proportions. I've advocated this for years, and I never could get much response from either Taylor or Dyson. I think it was because they were so interested in near term development. Taylor was very strong on that. In his own time he wanted to see these things fly. I think that (a lunar base) is really the future development of Orion. It may take somewhere up in the 2020s, 2050s, 2070s to do it, but I think eventually it will be done that way. And then you're talking about really major trips. And then, in future generations, we'll start thinking about trips to the stars.