Lyaponov Tubes (popularly called "Transfer Manifolds" after Poincare' or "The Ell") are particularly low energy courses used to navigate between massive bodies such as planets, moons or megastructures.
Lyaponov Tubes join libration (Lagrange) points L1 or L2 of a system of bodies to the L1 or L2 points of another system of bodies. A famous example is the mythical "Northwest Passage" a supposed Lyaponov tube between Mars and Cis-Luna or (in earlier stories, Mars and Earth) with a circuit time of less than a decade. The actual Mars/Cis-Luna Lyaponov circuit time is tens of thousands of years. The first highly successful Ell system was the Jupiter/Saturn Ell which has been refined to a circuit time of 32 years 78 days, Martian. The second busiest Ell is the Venus/Mars/Jupiter route, actually a fortunate intersection of two complete Ell systems. For technical reasons the outbound Ell is often called the "Unstable Ell" the inbound is known as the "Stable Ell." Thus the favorite Belter folk-lyric, "Tell her I'm on the Stable Ell and burning mass for glory."
Text by Bill Glover
Initially published on 01 September 2003.