Before getting started on today’s post, a reminder that Tau Zero founder Marc Millis and I will be among those interviewed on the History Channel show Star Trek: Secrets of the Universe tonight at 10 PM Eastern US time (0200 UTC on Thursday). Many of the ideas discussed on that show parallel those found in Harry Stine’s program for interstellar exploration. Stine drew on the work of Stephen Dole, whose 1964 book Habitable Planets for Man identified 14 stars within a distance of 22 light years in the spectral classes between M2 and F2. Dole thought there was a 43 percent probability of at least one habitable planet around one of these 14 stars, and Stine’s interstellar program began with a series of probes that would investigate them, looking first for gas giants.

The idea is that a gas giant flags the presence of other, smaller planets, key information in Stine’s day. Forty years later, we know how to find gas giants through radial velocity and transit studies. It’s true that ‘hot Jupiters’ are relatively straightforward to find because of their pronounced radial velocity signature, but in coming decades we’ll have the technology in place to characterize entire solar systems using space- and ground-based instruments. Unmanned probes won’t be sent just to send back a ‘ping’ when they find a gas giant, as Stine would have it. They’ll be highly intelligent scientific stations that will give us a continuing presence in the destination system.


Stine, who died in 1997, was a familiar figure in science fiction and rocketry circles in the latter half of the 20th Century. A physics major at the University of Colorado in Boulder, he moved on to work at White Sands Proving Grounds and later became head of the Range Operations Division at the U.S. Naval Ordnance Missile Test Facility. His later career included employment at several aerospace companies in addition to numerous books. At left is the cover of his 1954 novel Starship Through Space, which went into depth on the operations of a star-faring vehicle in every respect save its propulsion system, which remained unexplored.

But propulsion is starflight’s greatest challenge, and two decades later it would be Project Orion that caught Stine’s eye. I have no idea when the first mention of Orion appeared in a science fiction magazine and I’ll ask this site’s resident SF gurus to help me out with this one. But Stine’s 1973 article in Analog is the first non-fiction treatment of Orion I’m aware of in the SF magazines.

Stine was taken with the idea of detonating nuclear or thermonuclear devices behind the craft, cushioning the blow with shock absorbers and using the explosion itself to drive the vehicle forward. He knew, too, that Dandridge Cole had played around with still more efficient nuclear-pulse designs that contained the explosion inside a huge spherical chamber, the benefit here being that venting the explosion through a rocket-like nozzle allows you much higher thrust and specific impulse. Says Stine:

Containing the explosion of a thermonuclear device may be a staggering idea to most people, but to an engineer it is just numbers. Give the idea to an engineer, and he’ll design it with an adequate safety factor and also determine how to make it. Engineers don’t get excited by big numbers or big gadgets.

Well, some engineers don’t, though I know many an engineer who would quail at the thought of building some of the Stine-era concepts routinely discussed by the likes of Cole, Gerard O’Neill and Robert Forward. But Stine seems to have drawn the line at Cole’s ideas, seeing an Orion-like propulsion system built in Earth orbit as the best solution. As to radiation, a 20-year development program of a newly awakened Orion project would give us the expertise to routinely work with nuclear materials in orbit, and a space environment in which, Stine notes, “the average small solar flare burps out more radiation than our largest conceivable thermonuclear device,” would forestall the objection of dangerous side effects to the planet.

Those gas giants I mentioned earlier weren’t to be identified solely because they flagged the presence of smaller worlds. Stine also saw them as what he called ‘interstellar filling stations’ for refueling starships. The point here is that a true program for interstellar exploration has to go beyond one-shot missions. What Stine envisioned was making starflight into a continuing effort of exploration and colonization, and that meant return capability as well as refueling for continuing on to other systems if desired. Although it doesn’t appear in his notes, I’m assuming that Freeman Dyson’s 1968 paper “Interstellar Transport,” which uses the early Orion work as the basis for a thermonuclear, interstellar Orion, played a role in Stine’s thinking.

Putting the Orion technology to work involved interstellar expeditions made up of fleets of between three and ten starships traveling together, on journeys lasting up to 100 years. With multiple target stars, we’re talking about a series of such fleets, each constructed using space-based resources that would feed off the new industries of resource extraction Stine assumed were a logical next step as we moved past the Moon and Mars. In fact, sustaining and growing that kind of infrastructure is in his view one of the reasons for starflight in the first place. See his book The Third Industrial Revolution (Putnam, 1975) for more.

Project Orion, terminated by the Nuclear Test Ban Treaty of 1963, left the concept of nuclear-pulse propulsion hanging, but Robert D. Enzmann, then working at Raytheon Corporation, went on to develop conceptual engineering designs for the starship Orion could become. I’ll close this three part series on Stine’s “A Program for Star Flight” tomorrow with a look at the Enzmann starship, a design that is seeing renewed interest in the interstellar community.