NASA is designing a massive solar sail to reach interstellar space
by Ryan Whitwam
The edge of our solar system is much farther away than many of us would expect. After all, New Horizons made it to Pluto in about a decade, and isn’t that pretty far out there? In reality, the edge of our solar system is known as the heliopause, and it’s roughly 2.5 times as far away from the sun as Pluto is. In hopes of reaching deep space faster, NASA’s Marshall Space Flight Center is investigating a plan to use massive solar sails to reach the heliopause in just 10 years.
None of the propulsion technologies we have now are both fast and efficient enough to reach the edge of the solar system in such a short time. A chemical fueled rocket would never have the endurance for such a trip. Meanwhile, ion engines are highly efficient, but they’re much slower. The Voyager spacecraft relied upon gravity assists for most of its velocity, and it took more than 30 years to exit the solar system. Solar sails are an appealing alternative because such a craft wouldn’t have to bring much fuel with it, and it could continue accelerating much longer. Once it had deployed the sails, it would only need maneuvering propellant.
NASA is calling this ambitious project the Heliopause Electrostatic Rapid Transit System (HERTS) E-Sail. The craft’s main drive would consist of 10 to 20 aluminum wires extending from a central hub. These electrically charged wires might be up to 20 kilometers (more than 12 miles) in length, but only 1mm across. That would give it an effective surface area of 600 square kilometers (about 372 square miles) when near Earth, but as much as 1200 square kilometers (744 square miles) when it is fully deployed (by centrifugal force) around the Great Asteroid Belt.
So how does that get you thrust? Like all solar sails, the HERTS system would take advantage of the solar wind. The sun is constantly blasting out a stream of photons and electrons into the solar system. If you want to travel away from the sun, you can ride that solar wind with a sail. The wire structure of HERTS would be positively charged, causing a repulsion force when electrons from the solar wind strike it. This force should be able to accelerate the craft all the way to the edge of the solar system. There would be no way to turn such a craft around, though. It’d be a one-way trip.
Researchers at Marshall Space Flight Center are looking at how to engineer the sail, but also how to maintain the correct charge. The electrons that provide propulsion could interfere with the positive bias on the wires. An “electron gun” of some sort would be required to discharge the negative charge as the craft moves through space. This is one of many questions that still need to be answered, but we may see interstellar probes sooner than anyone would have thought.
Note: This article was originally published on ExtremeTech.com.