An aerial explorer of some kind is just the ticket, Lorenz said. Airplanes pose difficulties for surface access and either require high flight power or must have wings that are too flimsy to remain airborne. The most promising concepts appear to be airships and helicopters. Solar sail technology holds the promise of greatly opening up an era of low-cost space exploration missions, said Manfred Leipold, an engineer at the German Aerospace Center in Cologne. He gave a progress report on joint solar sail efforts between Germany, the European Space Agency, and NASA's Jet Propulsion Laboratory.
Solar sails are spacecraft that use the push of photons emitted by the sun for propulsion.
Work is proceeding on a demonstration project of solar sail technology, Leipold said. Next up for the sailcraft idea, Leipold said, is a possible launch aboard a modified Russian SS-18 ballistic missile. In orbit, the mechanisms to roll out the sail could be studied. For an operational sailcraft, a French Ariane 5 booster would carry the hardware as a piggyback payload. Once unleashed, the sail would spiral out to conduct a lunar fly-by or even enter lunar orbit, he said.