NASA Begins Testing of the Revolutionary E-Sail Technology
Animation of Heliopause Electrostatic Rapid Transport System (HERTS) concept. NASA engineers are conducting tests to develop models for the Heliopause Electrostatic Rapid Transport System. HERTS builds upon the electric sail invention of Dr. Pekka Janhunen of the Finnish Meteorological Institute. An electric sail could potentially send scientific payloads to the edge of our solar system, the heliopause, in less than 10 years. (NASA)
The sun releases protons and electrons into the solar wind at very high speeds of 400 to 750 kilometers per second – the E-Sail would use these protons to propel the spacecraft.
Testing has started at NASA’s Marshall Space Flight Center in Huntsville, Alabama, on a concept for a potentially revolutionary propulsion system that could send spacecraft to the edge of our solar system, the heliopause, faster than ever before.
The test results will provide modeling data for the Heliopause Electrostatic Rapid Transit System (HERTS). The proposed HERTS E-Sail concept, a propellant-less propulsion system, would harness solar wind to travel into interstellar space.
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. Each tether is extremely thin, only 1 millimeter – the width of a standard paperclip – and very long, nearly 12 and a half miles – almost 219 football fields. As the spacecraft slowly rotates at one revolution per hour, centrifugal forces will stretch the tethers into position.
The testing, which is taking place in the High Intensity Solar Environment Test system, is designed to examine the rate of proton and electron collisions with a positively charged wire. Within a controlled plasma chamber simulating plasma in a space, the team is using a stainless steel wire as an analog for the lightweight aluminum wire. Though denser than aluminum, stainless steel’s non-corrosive properties will mimic that of aluminum in space and allow more testing with no degradation.
Engineers are measuring deflections of protons from the energized charged wire within the chamber to improve modeling data that will be scaled up and applied to future development of E-Sail technology. The tests are also measuring the amount of electrons attracted to the wire. This information will be used to develop the specifications for the required electron gun, or an electron emitter, that will expel excess electrons from the spacecraft to maintain the wire’s positive voltage bias, which is critical to its operation as a propulsion system.
In 2012, NASA’s Voyager 1 became the first spacecraft to ever cross the heliopause and reach interstellar space. Launched in 1977, Voyager 1 took almost 35 years to make its 121 AU journey. The goal of HERTS is to develop an E-Sail that could make the same journey in less than one-third that time.
“Our investigation has shown that an interstellar probe mission propelled by an E-Sail could travel to the heliopause in just under 10 years,” he said. “This could revolutionize the scientific returns of these types of missions.”
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.