NASA has selected 15 industry, government and academic organisations to pursue 22 propulsion technology research proposals that could revolutionise exploration and scientific study of the solar system.

The $20 million, three-year programme will focus on five space propulsion technology areas - aerocapture, advanced chemical propulsion, solar electric propulsion, space-based tether propulsion, and solar sail technologies.

Each technology identified for development is part of the In-Space Propulsion Programme, managed by NASA's Office of Space Sciences. Colleen Hartman, director of NASA's Solar System Exploration Division, says: "We want to increase the frequency, speed and return on our missions and enable whole new missions that are impossible or impractical with today's propulsion technologies."

Tethers Unlimited (TUI) of Lynwood, Washington, has received two contracts valued at more than $2 million to develop key technologies for its Momentum-Exchange/Electrodynamic-Reboost (MXER) tether system.

TUI aims to deploy a 100km (62 mile) cable in orbit which will rotate like a giant sling, swinging down and picking up spacecraft launched into low orbits and then tossing them to higher orbits.

TUI president and chief scientist Robert Hoyt says: "The MXER tether will serve as a fully reusable transport hub in orbit, like a space railroad." He hopes that by eliminating the need to launch an upper-stage rocket with each satellite, the propulsion costs for space missions could be reduced by a factor of 10 or more. TUI will use some of the funds to develop its Hoytether failsafe, multi-line tether structure.

NASA's Langley Research Center is to study the development of solar sail technology with Team Encounter, which plans to send a 76 x 76m (249 x 249ft) sailcraft into orbit in 2006.

The sail, constructed of aluminised Mylar 1/76th the thickness of a human hair, will weigh only 19kg (42lb) and will be steered using tabs on the edge of the sail. Encounter plans to use the sail, powered by photons from the sun, to propel its craft beyond the solar system at about 108,000km/h (67,000mph). Encounter is hoping to place its first test sail, called Earthview, into a "polesitter" orbit piggybacking on an Ariane 5 launch in 2005.

Source: Flight International