Exploration History: Cocoon holds a special place in human history, as the first artifact to be discovered by human explorers, just as Cusp (see Entry 300) was the first to be discovered by the Cecropian clade. Cocoon was found in E. 1086 by a Crawlspace colony ship seeking habitable planets in the Lacoste system.

Physical Description: The form of Cocoon is a three-dimensional development of the familiar ring cities in place around many inhabited worlds. However, it goes far beyond the standard equatorial-plane assemblies, in both extent and presumed function. This artifact employs forty-eight Basal Stalks connecting Cocoon to the equatorial planetary surface and reaching up to the continuous ring structure at stationary altitude. Four hundred and thirty-two thousand exterior filaments stretch five hundred thousand kilometers from the planet. No two filaments are identical, but typical dimensions of the hollow cylindrical tubes are from two to four kilometers, exterior radius. Viewed from many locations, the surface of Savalle is completely obscured by Cocoon.

The corridors of Cocoon's interior are extensively patrolled by Phages (see Entry 1067). Explorers must monitor continuously for their presence.

Physical Nature: Construction of Cocoon employs the standard superstrength polymers used in most Builder artifacts. The absence of a second natural satellite for Savalle, even though the fossil record clearly shows that double-satellite tides occurred until twelve million years ago, suggests a now-vanished moon as the main source of Cocoon's construction materials.

Cocoon's filaments are held in stable position by a balance of gravity, rotating reference frames, and stellar radiation pressure. No unfamiliar science is needed to explain that stability, although the system design calls for the solution of large, discrete optimization problems beyond the best computers available within the Clades. Elephant (see Entry 859) was applied to the problem and reached a constrained solution (the so-called Cocoon Restricted Problem) in four standard years of computation time.

Intended Purpose: There are few secrets to Cocoon, if we except the need for such a massive system. The Basal Stalks permit materials to pass to and from the planetary surface of Savalle at negligible cost; the Exterior Filaments allow economical payload transfer to any point of the Lacoste stellar system, using the momentum-bank principle. The capacity of Cocoon is enormous: one fifty-thousandth of the mass of Savalle could in principle be transferred to space each year, enough to slow the planetary rotation rate appreciably and change Savalle's day by two seconds.

--From the Lang Universal Artifact Catalog, Fourth Edition.

Excerpt from Summertide by Charles Sheffield, ©1990 Charles Sheffield.

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