 and use the solar wind as its thrust source.)
ELECTRIC SOLAR WIND SAIL: A Finnish Meteorological Institute researcher is developing an electric space sail that will consist of up to 100 aluminum or copper alloy wires (each about 12.4 miles, or 20 kilometers, long and 20 microns in diameter) and use the solar wind as its thrust source.
Image: Courtesy of Pekka Janhunen, the Finnish Meteorological Institute
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
How do you power a spacecraft in deep space? NASA's Voyager 1, which was launched three decades ago and is now about 10 billion miles (16 billion kilometers) from Earth, is using inertia from its blast off as well as the gravitational fields of the planets it has passed to speed toward the edge of the solar system at 10.6 miles (17.1 kilometers) per second. Unfortunately, it has taken Voyager 1 so long to get to its current location that by 2025 the space probe will have consumed all of the power provided by its radioisotope thermoelectric generators, or RTGs (which convert heat from decaying radioactive materials such as plutonium into electricity), and will no longer have enough energy to run its scientific instruments or send messages back to NASA as it crosses into interstellar space. Any missions hoping to go farther will need a means of acceleration that can get the spacecraft to the edge of explored space faster—before it has depleted its radioactive power source.
Many believe the answer lies in using a space sail that harnesses the sun's energy to keep a spacecraft accelerating long after it escapes Earth's atmosphere and reaches deep space. Heading beyond the sun's influence, the spacecraft would have attained a faster cruising speed than Voyager 1 and could maintain it via inertia with plenty of life left in its RTG and/or other generators to power its instruments and radio to communicate with Earth, allowing it to continue its mission for many decades to come. NASA is preparing to test a new space sail this summer that uses sunlight to provide this acceleration, whereas a scientist at the Finnish Meteorological Institute is refining a design for a different type of space sail that would have spacecraft surfing the solar wind, a continuous stream of charged particles that emanates from the sun, at speeds nearly twice that of Voyager 1 (18.6 miles, or 30 kilometers, per second).
The concept of space sails dates back the 16th century, when German astronomer Johannes Kepler first came up with the idea of using the sun's energy to propel objects through space. Today, there are three main types of space sail: solar (the one NASA plans to test), electric (being developed in Finland) and magnetic (a concept popular in the 1980s that never quite took off).
Scientists at NASA's Marshall Space Flight Center in Huntsville, Ala., and Ames Research Center at Moffett Field, Calif., within a week plan to test their solar sail, which will travel to space onboard a Falcon 1 rocket developed by Space Exploration Technologies (SpaceX) of Hawthorne, Calif. NASA says that during its two-week mission the 10-pound (4.5-kilogram) NanoSail-D solar sail will be the first ever be fully deployed in space and the first to use sunlight as a primary means of flight or orbital maneuvering. The kite-shaped sail is constructed of aluminum and plastic and unfurls to about 100 square-feet (9.3 square-meters) of light-catching surface. NASA has already spent more than $2.3* million developing its NanoSail-D technology.
The NanoSail-D may be followed over the next three years by another solar sail, this one built by The Planetary Society, a nonprofit space advocacy organization in Pasadena, Calif. The group is designing the electronics, solar array and solar sail motors for the Cosmos 2, which it hopes to launch with a Russian Soyuz–Fregat booster rocket, similar to the technology used to take astronauts, cosmonauts and tourists to the International Space Station. The Cosmos 1 solar sail was shot into space in 2005 (after five years of development and a failed launch in 2001) onboard a Russian Volna rocket. The submarine-launched Volna, however, malfunctioned and never made it into orbit, so the sail did not have the chance to deploy and demonstrate solar sail propulsion.
Louis Friedman, executive director of the Planetary Society, says that the sails must be launched to test them, because there is no solar wind in Earth's atmosphere. Russia and Japan have tested technologies that are similar to space sails, but because these tests were conducted near the Russian Mir space station (no longer in orbit) or in suborbital flight, "they aren't solar sails truly," he says.
Pekka Janhunen, an academy research fellow at the Finnish Meteorological Institute in Helsinki, meantime, is developing an electric space sail that uses the solar wind as its thrust source and does not need fuel or propellant. He says the sail will consist of up to 100 aluminum or copper alloy wires—each about 12.4 miles, or 20 kilometers, long and 20 microns in diameter (one micron equals about one four hundred-thousandths of an inch)—attached to reels that can adjust wire length. Each wire would be charged at up to 20 kilovolts via a solar-powered electron gun attached to the sail. The electrical charge emitted by the wires would react with the solar wind's plasma to generate momentum. Janhunen says it would take a 440-pound (200-kilogram) spacecraft using an electric sail less than five years to travel between Earth and dwarf planet Pluto.
It's too early to estimate the cost of building an electric sail, he says, but notes that it would be as much as four times cheaper to construct and fly a spacecraft attached to an electric space sail, because it would be lighter than conventional spacecraft and require only enough fuel to launch it out of Earth's atmosphere. Increasing thrust once in space could be a matter of adding more wires to the sail or making the wires longer.
Janhunen's work is moving from the drawing board to the lab and he hopes to build a prototype within three years that he could fly outside Earth's atmosphere to test the thrust produced by the electric sail. If his theory proves correct (and he can use long, electrified wires to take advantage of the solar wind), it would be a few more years before he and his colleagues could build the equipment required to mount the wires in the shape of a sail and test the structure's ability to propel some type of spacecraft.
A magnetic space sail would also rely on the solar wind for momentum. Robert Zubrin, founder and president of the Mars Society and president of Pioneer Astronautics, an aerospace R&D company located in Lakewood, Colo., and Dana Andrews, chief technology officer of Andrews Space, Inc., in Seattle, Wash., conceived the magnetic sail in the 1980s as a way to improve on the solar sail design. Instead of relying on sunlight, it would use the solar wind's plasma (which travels at 310 miles, or 500 kilometers, per second) as its means of propulsion.
Taking advantage of the fact that plasma is deflected by magnetic fields, Zubrin and Andrews proposed putting a magnetic field around a spacecraft like a bubble and having the solar wind push the spacecraft. There was, however, one small hitch: the superconducting wires required create a magnetic field have never been developed. (The project briefly received some funding from the NASA Institute for Advanced Concepts, but that organization was shuttered last year.) "The magsail is a concept waiting for a technology," Zubrin says.
The European Space Agency studied the magnetic sail concept to use during a manned trip to Mars but ultimately came to the same conclusion as Zubrin.
Of course, none of these sails are effective once they are out of the sun's range. By the time any spacecraft reaches about 37 billion miles (60 billion kilometers) from the sun "the solar wind becomes very tenuous and then stops," Janhunen says. At that point, he envisions his electric space sail being jettisoned from its spacecraft so that its momentum would fly it beyond the solar system, tapping an onboard source of nuclear energy (similar to Voyager 1) to power its systems.
The reward for building a successful space sail would be to increase the velocity of a spacecraft indefinitely without the need for propellant. "This would let you go enormous distances at enormous speeds," the Planetary Society's Friedman says. "It's the only technology that we know of that can one day take us to the stars."
See what we're tweeting about
12 Comments
Add CommentPlease, are we that desperate to just throw mony down the drain to say in the New York Times we put a satellite in space that can go fast but we have no control of where it goes. Crack pot concept.
Reply | Report Abuse | Link to thisIf you are really interested in a practical solution look for near light speed propulsion engine now in development that will go 66,000,000 miles/hr and can be steered to what ever direction is desired. Realistic concept.
I really want to know why there isn't any sort of engine. If there are all these particles out there from the sun that can be repelled against then why don't we treat them like air and use the like we do in a jet engine. Clearly I am oversimplifying here but it seems to me that the suns of the universe have filled the cosmos with these particles for billions of years so they should be every where like the air in earths atmosphere.
Reply | Report Abuse | Link to thisearth has a magnetic field to deflect these particles, though.....
Reply | Report Abuse | Link to thisAd astra!
Reply | Report Abuse | Link to thisI think you are referring to a Bussard Ramjet
Reply | Report Abuse | Link to thishttp://en.wikipedia.org/wiki/Bussard_ramjet
Why isn't the concept of a continuous laser propulsion system from earth directed at the sail a viable concept? That way you would have a continuous source of outbound power beyond the range of solar winds and could even significantly increase the speed of the craft.
Reply | Report Abuse | Link to thisthe machine you are talking about is a Buzzard ram, it gathers ions and free atoms from space and accelerates them via a particle accelerator, the trouble is that this atoms are so disperse (acording to Sagan's Cosmos about one atom in 10 cubic centimeters, that is the avarage size of a grape handful), that you would need a collector dish in the order of hundreds of kilometers wide to get enough mater for a decent trust.-
Reply | Report Abuse | Link to thisI believe this kind of sails would handle about the same way as the old wind sails of yesteryear, where you position it in an angle that generates trust to the point you want to go to.
Reply | Report Abuse | Link to thisWhich kind of engine are you talking about? near light speed seems to be to hot to handle (radiation due to impacts, trouble looking beyond your nose
quote: "I really want to know why there isn't any sort of engine. If there are all these particles out there from the sun that can be repelled against then why don't we treat them like air and use the like we do in a jet engine." You are right, but the density is a million times lower, so any kind of airplane jet engine would not work.
Reply | Report Abuse | Link to thisFor goal #5: A sail with 1 gram per square meter?
Reply | Report Abuse | Link to thisCould that be done?
Why do you think we could not control the direction of such spacecraft?!! ... Very strange!
Reply | Report Abuse | Link to thisAlso, why do you need to precisely steer a spacecraft on a journey out of our solar system once you set the course once (which is basically away from the Sun)??!! Beats me... or probably you are clueless to the vastness of this cosmos and our insignificantly (in size and distance to near by stars/objects) solar system!
Even doubling or tripling the speed of Voyager 1, 2 - as these technologies promise as of now - would not make the possibility of reaching another star very likely! Get a clue man!
And ... a near speed of light propulsion engine?! Have I been knocked out and unconscious for the last decade?! ... So Strange!
I have invented a novel propulsion engine but it is in no way similar to the ion propulsion. It's an electro-mechanical engine, which means it converts electricity directly into mechanical force instead of using fuel. It's a novel concept and it's hard to explain how it works and creates thrust because some people (as I expected) told me it violates conservation of momentum. In theory yes but in practice I don't think so. I hope I will have a prototype of it fabricated and put to test soon. You may check it out on my website:
Reply | Report Abuse | Link to thiswww.hosseinnabipour.ca
-Hossein Nabipour, inventor of the first practical interstellar propulsion engine