If you look at Galaxy’s December, 1962 issue, which I have in front of me from my collection of old SF magazines, you’ll find a name that appears only once in the annals of science fiction publishing: George Peterson Field. The article, “Pluto – Doorway to the Stars,” is actually by Robert Forward, who was at that time indulging in a time-honored practice, concealing an appearance in a science fiction venue so as not to raise any eyebrows with management at his day job at Hughes Aircraft Company.

Aeronautical engineer Carl Wiley had done the same thing with an article on solar sails in Astounding back in May of 1951, choosing the pseudonym Russell Saunders as cover for his work at Goodyear Aircraft Corporation (later Lockheed Martin). Both these articles were significant, as they introduced propulsion concepts for deep space to a popular audience outside the scientific journals. While solar sails had been discussed by the likes of J. D. Bernal and Konstantin Tsiolkovsky, the idea of sails in space now begins to filter into popular fiction available on any newsstand.

But despite being frequently referenced in the literature, Forward’s foray into Galaxy did not focus on sail technologies at all. Instead, it dwells on an entirely different concept, one that Forward called a ‘gravitational catapult.’ This is itself entertaining, so let’s talk about it for just a moment before pushing on to the actual first appearance of laser beaming to a sail, which Forward would produce in a different journal in the same year.

Forward is the master of gigantic engineering projects. Pluto had caught his attention because its eccentric orbit matched up with what Percival Lowell had predicted for a planet beyond Neptune, but its size was far too small to account for its supposed effects. Lowell had calculated that it would mass about six times Earth’s mass, a figure later corroborated by W. H. Pickering. But given Pluto’s actual size, Forward found that if it were the outer system perturber Lowell had predicted, it would have to have a density hundreds of times greater than water.

Remember, this was 1962, and in addition to being a physicist, Forward was a budding science fiction author playing with ideas in Galaxy, which had just passed from the editorship of H. L. Gold to that of Frederick Pohl, a man of lively imagination and serious SF chops himself. Why not play with the notion of Pluto as artifact? I think this was Forward’s first gigantic project. Thus:

…we can envision how such a gravitational catapult could be made. It would require a large, very dense body with a mass larger than the Earth, made of collapsed matter many times heavier than water. It would have to be whirling in space like a gigantic, fat smoke ring, constantly turning from inside out.

The forces it would exert on a nearby object, such as a spaceship, would tend to drag the ship around to one side, where it would be pulled right through the center of the ring under terrific acceleration and expelled from the other side. If the acceleration were of the order of 1000 g’s, then after a minute or so it would take to pass through, the velocity of the ship on the other side would be near that of light…

Forward imagined a network of such devices, each of them losing a bit of energy each time they accelerated a ship, but gaining it back when they decelerated an incoming ship. The Pluto reference is a playful speculation that what was then considered the ninth planet was actually one of these devices, which we would find waiting for us along with a note from the Galactic Federation welcoming us to use it. A sort of ‘coming out present’ to an emerging species. I can see the twinkle in his eye as he wrote this.

In any case, we have to change the history of beamed sails slightly to reflect the fact that the Galaxy appearance did not deal with sails, despite having a name similar to an article Forward published in the journal Missiles and Rockets in that same year. “Pluto – Gateway to the Stars” ran in the journal’s April, 1962 issue as part of a series by various authors on technologies for sending spacecraft to other planets. I had never seen the actual article until my friend Adam Crowl was kind enough to forward it the other day. Adam’s collection of interstellar memorabilia is formidable and has often fleshed out my set of early deep space papers.

Here what Forward latches onto is the most significant drawback to solar sailing, which relies on the momentum imparted by photons. This is the inverse square law, which tells us that the push we can get from solar photons decreases with the square of our distance from the Sun. Solar sails lose their punch somewhere around the orbit of Jupiter. What Carl Wiley first discussed in Astounding was the utility of sails for interplanetary exploration. Forward wanted to go a lot farther.

“Pluto – Gateway to the Stars” ran through the options for deep space available to the imagination in 1962, homing in on antimatter and concluding “it would be a solution if you were a science fiction writer,” which of course Forward would become. But he noted “there are a few engineering details.” The first of these would be the problem of antimatter production. The second is storage. With both of these remaining huge problems today, it’s intriguing that Forward actually spends more of this article on antimatter than on his innovative laser concept but runs aground on the problem of gamma radiation.

When the hydrogen-anti-hydrogen streams collide, the matter in the atoms will be transformed into pure energy, but the energy will be in the form of intense gamma radiation. We can stop the gamma rays in heavy lead shields and get our thrust this way, but the energy in the gamma rays will turn into heat energy in the shields and it will not be long before the whole rocket melts. What is needed is a gamma-ray reflector – and such a material does not exist. In fact, there are strong physical arguments against every finding any such material since the wavelengths of the gamma rays are smaller than the atomic structure of matter.

But sails beckon, and here the innovation is clear: Leave the propellant behind. Forward made the case that standard reaction methods could not obtain speeds anywhere near the speed of light because their mass ratios would be appallingly high, not to mention thermal problems with any design carrying its own propellant plant and energy sources. For interstellar purposes, he mused, the energy source and the reaction mass would have to be external to the vehicle, as indeed they are in a solar sail. But to go interstellar, we have to get around the inverse square law. Hence the laser:

There is a way to extend the idea of solar driven sails to the problem of interstellar travel at large distances from the sun. This is to use very large Lasers in orbits close to the sun. They would convert the random solar energy into intense, coherent, very narrow light beams that can apply radiation pressure at distances of light years.

However, since the Laser would have to be over 10 kilometers in diameter, this particular method does not look feasible for interstellar travel and other methods of supplying propulsive energy from fixed power plants must be found.

The editors of Missiles and Rockets seem to have raised their eyebrows at this early instance of Forward’s engineering, as witness the end of their caption to the image that accompanied the text.

Image: This is the original image from the Missiles and Rockets article. Caption: Theoretical method for providing power for interstellar travel is use of a very large Laser in orbit close to sun. Laser would convert random solar energy into intense, very narrow light beams that would apply radiation pressure to solar sail carrying space cabin at distances of light years. Rearward beam from Laser would equalize light pressure. Author Forward observes, however, that the Laser would have to be over 10 kilometers in diameter. Therefore other means must be developed.

At this point in his career, Forward’s thinking leaned toward fusion to solve the interstellar conundrum, but as events would prove, he would increasingly return to beamed sails of kilometer scale, and power station and lensing structures that are far beyond our capabilities today. But if we ever do create smart assemblers at the nanotech level, the idea of megastructures of our own devising may not seem quite so preposterous. And this 1962 introduction to beamed sails is to my knowledge their first appearance in the literature. Today the concept continues to inspire research on beaming technologies at various wavelengths and using cutting edge sail materials.