NASA engineer Bruce Wiegmann demonstrates the long, thin wires that will construct the E-Sail. (NASA/MSFC/Emmett Given)
Testing has started at NASA on a concept called the Heliopause Electrostatic Rapid Transit System (HERTS), a propellant-less propulsion system that would harness solar wind to travel into interstellar space. “The sun releases protons and electrons into the solar wind at very high speeds -- 400 to 750 kilometers per second,” said Bruce Wiegmann an engineer in Marshall’s Advanced Concepts Office and the principal investigator for the HERTS E-Sail. “The E-Sail would use these protons to propel the spacecraft.”

Extending outward from the center of the spacecraft, 10 to 20 electrically charged, bare aluminum wires would produce a large, circular E-Sail that would electrostatically repel the fast moving protons of the solar wind. The momentum exchange produced as the protons are repelled by the positively charged wires would create the spacecraft’s thrust.

Steering can be accomplished by modulating the wire’s voltage individually as the spacecraft rotates. Affecting a difference in force applied on different portions of the E-Sail, would give engineers the ability to steer the spacecraft, similar to the sails of a boat.