Paul A. Penzo’s scientific contributions

A collection of papers on the applications of tethers in space is presented. Tether flight experiments of the past, in planning stages, and in the future are examined. Tether dynamics and the applications and technical aspects of electrodynamic tethers are addressed. The use of tethers on the Space Station and applications in the Space Station era are considered. Individual tether technology issues, including tether materials and instrumentation for atmospheric measurements are discussed.

Contents: 1. What can tethers do in space? A tutorial. 2. Shuttle flights: opening the era of tethers. 3. Tether dynamics: understanding behavior and control. 4. Electrodynamics: new approaches to space power. 5. The Space Station era: tethers for science, technology and operations. 6. Technology development: the key to success. 7. Panel discussion: the future impact of tethers in space.

The principle and applications of tethering are examined. Tethering works by momentum transfer; the center of mass of a system consisting of (for example) a Space Shuttle and a tethered payload such as the Advanced X-ray Astrophysical Facility continues to follow the original orbit. Given a slight outward velocity, the payload begins to lag behind because it has the same linear velocity as the Shuttle but is at a greater distance from the earth. Any displacement from the local vertical causes a restoring force at each end tending to restore the system to a vertical orientation. When vertically above the Shuttle, the payload has the same angular velocity but a greater linear velocity; thus momentum is transferred from the Shuttle to the payload. It is computed that a tether 32 nautical miles long could deploy AXAF into a 320-nautical mile orbit from a lower, elliptical Shuttle orbit, thus saving 5000 pounds of Shuttle propellant. Various types of tether are considered: Kevlar and steel, uniform and tapered. Numerous cases appear to be feasible for boost and deboost as well as momentum transfer, using such reaction masses as the Space Station, a lunar orbiter, the Martian moons Phobos and Deimos, various asteroids, and moons of the major planets.