The Songs of Distant Earth (28 page)

Ten years later, H. D. Froning of McDonnell Douglas Astronautics introduced the idea at the British Interplanetary Society’s Interstellar Studies Conference, London (September 1979) and followed it up with two papers: “Propulsion Requirements for a Quantum Interstellar Ramjet”
(JBIS,
Vol. 33,1980) and “Investigation of a Quantum Ramjet for Interstellar Flight”
(AIAA Preprint
81-1534, 1981).

Ignoring the countless inventors of unspecified “space drives,” the first person to use the idea in fiction appears to have been Dr. Charles Sheffield, Chief Scientist of Earth Satellite Corporation; he discusses the theoretical basis of the “quantum drive” (or, as he has named it, “vacuum energy drive”) in his novel
The McAndrew Chronicles (Analog
magazine 1981; Tor, 1983).

An admittedly naive calculation by Richard Feynman suggests that every cubic centimetre of vacuum contains enough energy to boil all the oceans of Earth. Another estimate by John Wheeler gives a value a mere seventy-nine orders of magnitude
larger.
When two of the world’s greatest physicists disagree by a little matter of seventy-nine zeros, the rest of us may be excused a certain scepticism; but it’s at least an interesting thought that the vacuum inside an ordinary light bulb contains enough energy to destroy the galaxy … and perhaps, with a little extra effort, the cosmos.

In what may hopefully be an historic paper (“Extracting electrical energy from the vacuum by cohesion of charged foliated conductors,”
Physical Review,
Vol. 30B, pp. 1700-1702, 15 August 1984) Dr. Robert L. Forward of the Hughes Research Labs has shown that at least a minute fraction of this energy can be tapped. If it can be harnessed for propulsion by anyone besides science-fiction writers, the purely engineering problems of interstellar
–
or even intergalactic – flight would be solved.

But perhaps not. I am extremely grateful to Dr. Alan Bond for his detailed mathematical analysis of the shielding necessary for the mission described in this novel and for pointing out that a blunt cone is the most advantageous shape. It may well turn out that the factor limiting high-velocity interstellar flight will not be energy but ablation of the shield mass by dust grains, and evaporation by protons.

The history and theory of the “space elevator” will be found in my address to the Thirtieth Congress of the International Astronautical Federation, Munich, 1979: “The Space Elevator: “Thought Experiment” or key to the Universe?” (Reprinted in
Advances in Earth Orientated Applications of Space Technology,
Vol. I, No. 1, 1981, pp. 39-48 and
Ascent to Orbit:
John Wiley, 1984). I have also developed the idea in the novel
The Fountains of Paradise
(Del Rey, Gollancz, 1978).

My apologies to Jim Ballard and J. T. Frazer for stealing the title of their own two very different volumes for my final chapter.

My special gratitude to the Diyawadane Nilame and his staff at the Temple of the Tooth, Kandy, for kindly inviting me into the Relic Chamber during a time of troubles.