  I investigate the relativistic mechanics of an extended "cable" in an
arbitrary static, spherically symmetric spacetime. Such hypothetical bodies
have been proposed as tests of energy and thermodynamics: by lowering objects
toward a black hole, scooping up Hawking radiation, or mining energy from the
expansion of the universe. I review existing work on stationary cables, which
demonstrates an interesting "redshift" of tension, and extend to a case of
rigid motion. By using a partly restrained cable to turn a turbine, the energy
harvested is up to the equivalent of the cable's rest mass, concurring with the
quasistatic case. Still, the total Killing energy of the system is conserved.
