Latest Carnival: Electric Sails and More

by Paul Gilster on September 27, 2008

The latest Carnival of Space is stuffed with good things, among them Dave Mosher’s manipulations of an asteroid impact calculator run by Cardiff University’s Ed Gomez. Dave works through a worst-case scenario — a 1300-foot wide asteroid striking the East River, turning most of New York City into a crater. Fascinatingly, the impact calculator lets users adjust the parameters on such strikes, so that turning the impactor into a 400-meter piece of ice produces a crater 3.5 miles wide, two miles less than the first scenario. The calculator looks to be a great educational tool.

NextBigFuture continues to study the electric sail concept, developed at the Finnish Meteorological Institute and under active examination. Electric sails ride the solar wind, but unlike magsails, they use a mesh of tethers kept at high positive voltage, held in place by centrifugal acceleration from the spinning spacecraft. Solar wind protons, repelled by the positive voltage of the mesh, create the needed thrust, with accumulating electrons discharged periodically to keep the mesh voltage positive.

Because the voltage on each tether might be controlled independently, the electric field around the craft could be adjusted to deal with variable solar wind activity, at least in theory. NextBigFuture has details from the ESA electric sail workshop at the European Space Research and Technology Centre in May. A perfectly optimized electric sail, Brian believes, could reach speeds comparable to the solar wind maximum of 800 kilometers per second. This seems like quite a stretch, but we need space-based deployment of a prototype to test the basic principles.

Haumea is the latest dwarf planet to be added to the IAU list, studied this week by Astronomy at the CCSSC. Accompanied by twin moons, the oblong Kuiper Belt world formerly known as 2003 EL61 is fifty times the Earth-Sun distance and seems to have an icy crust over a rocky body, possibly the result of an impact that blew away earlier ices. Regrettably, another discovery controversy has dogged the story, with questions about whether this object was found by Mike Brown’s team at Caltech or a Spanish team that made an earlier announcement.

Says Astronomy at the CCSSC:

[T]here’s a bit of an ugly story that goes along with this one. Briefly, Dr. Brown’s team had been watching and observing this object, gathering data before they decided to announce or publish a discovery. Another team (from an observatory in Spain) made the announcement before Dr. Brown’s team did. However, it turns out that the Spanish team may have looked at web logs showing where Dr. Brown’s team was observing, and “discovered” the planet in Dr. Brown’s data rather than in their own observations. The IAU lists Dr. Brown’s team as the discoverers of Haumea’s moons, and adopted their suggested planetary name; however, they have not committed themselves by listing either team as the “discoverers” of Haumea itself.

The competition for first announcement can get downright unhealthy at times, as Haumea’s sordid story shows. This case verged unusually close to actual cheating, but even when it’s just a case of a race to the finish line, it can have repercussions. For example, a scientist may announce results in the media which never pan out in the long run, leading the public to distrust new scientific findings.

All too true. Read the post for more, but also check Mike Brown’s site for a full rundown. The larger and more gratifying issue is the presence of so many large Kuiper Belt objects, and the growing belief that we have many more such discoveries ahead of us. Could Earth-sized worlds be lurking in these dark outer regions? The Solar System proves to be so much more complex than it seemed just a few decades ago, a situation that is presumably true around other stars as well. What an exciting time as we develop the needed tools to identify and study these objects.


James M. Essig September 27, 2008 at 18:22

Hi Folks;

Achieving 800 km/s with an electric sail is not bad. This works out to be about 0.0026 C.

The really cool aspect of this technology is that it seems relatively simple, and can obviously be scalled up to propell world ships perhaps with a diameter as great as 100 kilometers and a mass of 10 trillion metric tons.

These ships could be launched throughout the Milky Way and reach the far edge of the galaxy within about 15 million years.

The cool think about the electric sail method is that 800 km/s is better than the escape velocity of our galaxy cluster, correct me if I am wrong. As long as there is star wind, this technology could be useful for sending out huge populated space arks in droves all over the cosmos. The relatively low velocity of these ships would negate the need for more rigorous cosmic ray sheilding requirements. Medical human life expectancy enhancement would be useful also.



Meaux September 27, 2008 at 19:36

Electric Sails..

Please, not to be a jerk but..

“they use a mesh of tethers kept at high positive voltage”

I ask, ‘positive’ in relation to what?


Administrator September 27, 2008 at 20:32

Meaux, in relation to the solar wind. Solar wind protons are positively charged and are repelled by the positive voltage of the mesh. The design uses an onboard electron gun to prevent the accumulation of electrons that would otherwise neutralize the mesh voltage. In their recent solar sail book, Matloff, Johnson and Vulpetti point out that the opposite configuration — repelling electrons and re-emitting protons — would produce a thrust about 2000 times lower in value.

Michael Spencer September 28, 2008 at 8:02

I notice that the link in the second graph to ‘electric sail’ is actually pointing to the astroid simulator. Easy enough to find the site but if you are like me you like your code to be all tidy…

Administrator September 28, 2008 at 9:35

The result of keeping too many tabs open at once in Firefox! Thanks for catching that, Michael. I’ve fixed the link.

ljk April 20, 2009 at 9:26

April 17, 2009

How to Keep Asteroids Away: Tie Them Up

Written by Anne Minard

It may not look like much, but that drawing could save a life someday — or 7 billion.

David French, a doctoral candidate in aerospace engineering at North Carolina State University is proposing a new tool for the anti-asteroid arsenal.

French said his PhD advisor Andre Mazzoleni, an associate professor of mechanical and aerospace engineering at the university, were not beholden to grant funds and “we just decided to go off on a direction that’s interesting and exciting.”

Mazzoleni has worked with tethers in other applications, and the two have now come up with a way to effectively divert asteroids and other threatening objects from impacting Earth by attaching a long tether and ballast to the incoming object.

By attaching the ballast, French explains, “you change the object’s center of mass, effectively changing the object’s orbit and allowing it to pass by the Earth, rather than impacting it.”

NASA’s Near Earth Object Program has identified more than 1,000 “potentially hazardous asteroids” and they are finding more all the time. “While none of these objects is currently projected to hit Earth in the near future, slight changes in the orbits of these bodies, which could be caused by the gravitational pull of other objects, push from the solar wind, or some other effect could cause an intersection,” French explains.

Full article here:

Comments on this entry are closed.