The Wellstone

Appendix B. Technical notes

This book owes a great deal to the technical support and advice of Hal Clement, Geoffrey A. Landis, Johnathan Sullivan, Ken Wharton, and the Right Reverend Gary E. Snyder. The idea of diamond-encapsulated neutronium originates with Robert L. Forward, although the term “neuble” is unique to this series.

Wellstone

The wellstone of this book’s title is an actual, patent-pending invention, although one that is unlikely to be built or tested in the near future, owing mainly to the nanometer-scale manufacturing tolerances required. Also, for purposes of the story, I’ve taken a rather generous view of the material’s ultimate capabilities.

However, “programmable” substances of much lesser sophistication, but still based on the manipulation of individual electrons in quantum-dot traps, have already been demonstrated in the laboratory. The real-world implications of this are so astounding that I’ve written a nonfiction book on the subject: Hacking Matter (Basic Books, Feb. 2003). Readers interested in a quicker and less comprehensive history of the field are encouraged to check out Wired magazine’s “Ultimate Alchemy” at http://www.wired.com/wired/archive/9.10/atoms.htm

Planettes

A spherical planette sized to hold an Earthlike atmosphere indefinitely, at room temperature, would require a surface escape velocity greater than the average (thermal) molecular velocity of the atmosphere. This requires a mass of well over 10¹⁹ kilograms (0.02% the mass of Earth’s moon), and a diameter of around 20 kilometers, for a surface gravity of 1.0 gee. Paradoxically, lower gravity requires both a larger radius and a larger mass if the high escape velocity is to be preserved.

The atmospheres of planettes like Varna and Camp Friendly are not stable over geologic time, nor even probably over thousands of years, without a replenishment mechanism or possibly a mechanism for keeping the upper atmosphere very cold. Make no mistake: these are technological artifacts, like buildings, and will not persist forever without stewardship.

Lune, the Goliath of planettes, does not have this problem, and will keep its atmosphere indefinitely. With a radius of 707 km, a surface gravity of 1.0 gee, and an unaltered mass of 7.3×10²² kg, Lune’s escape velocity is a whopping 3.72 kilometers per second (versus 11.9 km/s for Earth). The delta-velocity necessary to reach Varna— in an orbit 50,000 km high—from Lune’s surface is very close to the escape velocity:

V = (2μ/707E3 − μ/25350E3)^0.5 = 3,697 m/s

Fortunately, this is achievable through low-tech means, as we shall see in the next volume.

Note that Lune’s sphere of influence—the maximum radius of a stable circular orbit—is just over 65,000 km. Past this point, the gravity of Earth (even murdered Earth) will perturb the orbit of an orbiting object over time, until the object either crashes, is ejected from the Earth-moon system, or becomes a stable satellite of Earth. Of the eight planettes orbiting Lune, Varna is the most remote.

The dimensions of Lune give it a surface area of 6.28 million square kilometers—about 17% of its original area, or 1.7% of Earth’s. This is slightly smaller than the continent of Australia, and while it includes ocean as well as land surfaces, it does create a plausible home for hundreds of millions of human beings even at sub-Queendom technology levels.

Fetula (Star Sail) and Sila’a (Pocket Star)

Camp Friendly’s “star” is a pinpoint fusion generator consisting of a wellstone-sheathed core of industrial neubles surrounded by gaseous deuterium in a state of continuous hot fusion. Orbiting the planette at a distance of 47,500 kilometers and with a period of 24 hours, it requires a total power output of 3.1×10¹³ watts in order to provide Earthlike insolation to the planette.

When focused into a laser beam and shone on a perfect, 1 km ² light sail, this radiation produces the following maximum forces:

In fact, these forces are so high that for the first seconds of the journey it is necessary to throttle the sail’s reflectivity in order to avoid crushing the cabin and its passengers. Pushing the star sail ( fetula) using starlight alone is rather more difficult. The energy flux from starlight is approximately 1E−5 w/m². If the sail is 100% transparent in one direction and 100% reflective in the other, the resulting force is:

Not much, but it does add up over time. If the sail were able to reflect high-energy cosmic rays, with a flux of 2E−4 W/m², then its maneuvering ability would be about twenty times greater.

Tongan Culture

Some readers may note that I’ve taken liberties—or Bascal and Conrad have—with the Polynesian fairy tales. Two of three are not from Tonga at all, but from other parts of the South Pacific, and all have been modified to fit your screen.

Similarly, the prince’s boastful accounting of Tongan navigational prowess—while accurate—properly belongs to the entire Polynesian culture. Excellent references on this include Bryan Sykes’ The Seven Daughters of Eve, Jared Diamond’s Guns, Germs, and Steel, and the Lonely Planet travel guide for Tonga, which includes a surprising wealth of historical detail. An excellent English-Tongan dictionary is published by Friendly Isles Press (no known affiliation with the Friendly Products Corporation).

(On a related note, the Latin word viriditas, or “greenness,” generally connotes inexperience rather than vigor— an irony of which Bascal Edward is unaware at the time of the Children’s Revolt.)

The Cyades

Approximating each body of the near-contact comet pair as a clathrate sphere 100 km in diameter, with the approximate density of liquid water (typical for methane hydrates), yields a mass of 5.2e17 kg (or half a million neubles’ worth) apiece. Orbiting their mutual center of mass with an apoapsis of 500 km and periapsis of 50 km (just close enough to collide), the two bodies will complete a revolution in 3.7e9 seconds, or 118 years.

Decelerating with Magnets

The force of a magnet on a ferromagnetic material (such as iron or neutronium) drops off with the square of the distance between them, and is a function of the magnet’s residual flux density. The strongest fixed magnets in existence at the time of this writing are alloys of iron, boron, and the rare-earth (lanthanide) element neodymium, with residual flux densities of 13,300 gauss.

The acceleration profile described in this story requires a fixed magnet approximately 100 times more powerful than the NdFeB—speculative but not implausible given the nature of quantum-dot materials.

Observing the Neutronium Barge Telescopically

As any astronomer will tell you, light waves can’t be magnified forever. Over large distances, the resolving power of a telescope is constrained by the limit of diffraction, where the light breaks down into interference patterns rather than images. This is a function of wavelength, lens diameter, and range. At a distance of 0.2 AU, the smallest feature resolvable by a 200-meter lens in visible light is around 94 meters, or one-tenth of the barge’s diameter.