It took Voyager 1 over 30 years to reach interstellar space, but NASA’s Marshall Space Flight Center in Huntsville, Alabama is testing a new technology that could cut that time by two thirds. The Heliopause Electrostatic Rapid Transit System (HERTS) or E-sail concept is a novel form of propellant-less propulsion that catches the solar winds on electric sails and holds the promise of cutting the travel time from Earth to the heliopause – about 123 AU (18 billion km, 11 billion mi) from the Sun – to under 10 years.
Deep space travel is very slow, with the outer regions of the Solar System taking decades to reach using chemical rockets and complicated slingshot orbits. One solution is to do away with rockets altogether and replace them with solar sails – giant mylar sails spread on gossamer threads to catch the solar winds, which are the constant stream of protons and other charged particles that stream from the Sun at 400 to 750 km/s (900,000 to 1.7 million mph).
The idea is already being tested in Earth orbit, but it’s not a perfect solution. The huge sheets of plastic aren’t easy to deploy even in zero gravity, and operating them requires a complex assembly of miniature reels and winches. In addition, the force of the solar winds is proportional to the distance from the Sun, and once a solar sail is more than 5 AU (464 million mi, 747 million km) from the Sun, the acceleration falls off markedly.
Based on the work of Dr. Pekka Janhunen of the Finnish Meteorological Institute, The E-Sail concept consists of a small unmanned payload containing instruments and a power source. From this radiate 10 to 20 electrically-charged, bare aluminum wires that are about one millimeter thick, 12.5 mi (20 km) long and weighing only a few grams.