WHAT: Propulsive Small Expendable Deployer System (ProSEDS)
WHERE: Marshall Space Flight Center, Huntsville, Alabama
WHO: NASA Advanced Space Transportation Program
WHY: To study the electrodynamic tether's potential as a low-cost means of propelling spacecraft within Earth's orbit. Scientists hope to demonstrate that the tether - which NASA began developing as a tow line in the '60s, long before the agency considered employing electrodynamics - can be adapted as a lightweight, clean, and reusable power system. Tether-propulsion could also be used to help the International Space Station maintain its position.
HOW: NASA plans to conduct the first full ProSEDS trial in August, when it launches the system aboard a Delta II rocket. The tether (shown coiled beneath its 6.2-mile nonconductive leader cord) consists of 3.1 miles of aluminum wire. When pointed toward Earth's center, it forms an electrical circuit. The positively charged end attracts electrons in the ionosphere, which flow earthward through the line. The tether, and any craft attached to it, is pulled toward Earth by the planet's magnetic field. On future missions, a solar power supply will redirect the electrons, reversing the force exerted by the magnetic field and pushing the craft into space.
