[FPSPACE] FW: Centauri Dreams - Electric Sails: Leave the Propellant at Home

[LARRY KLAES]

>From: Centauri Dreams <gilster at mindspring.com>
>Reply-To: Centauri Dreams <gilster at mindspring.com>
>Subject: Centauri Dreams
>Date: Thu, 24 Apr 2008 14:04:27 -0500 (CDT)
>
>Centauri Dreams
>
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>Electric Sails: Leave the Propellant at Home
>
>Posted: 24 Apr 2008 09:25 AM CDT

>http://www.centauri-dreams.org/?p=1842
>
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>A Finnish design making the news recently is hardly the only concept for 
>near-term space sailing, but the possibility of testing it in space for a 
>relatively small sum of money is attractive. This is especially true at a 
>time when strapped budgets like NASAs are focused on ratcheting up 
>conventional propulsion techniques to get us back to the Moon and on to 
>Mars. Yes, lets keep pushing outward into nearby space with what weve got, 
>but we need next-generation thinking, too, and the Finnish sail, the work 
>of Pekka Janhunen and Arto Sandroos, points in that direction.
>
>Unlike magnetic sails that create an artificial magnetosphere around the 
>spacecraft, the Finnish concept is to use long, thin conductive wires that 
>are kept at a positive potential through the use of an onboard electron 
>gun. The two researchers considered how the charged particles of the solar 
>wind would interact with a single charged wire in a 2007 paper that we 
>looked at in this Centauri Dreams article just over a year ago. A 
>full-scale mission would use fifty to one hundred 20-kilometer long charged 
>tethers. Supercomputer simulations come up with potential speeds of 100 
>kilometers per second, which is about five times what New Horizons is doing 
>on its way to Pluto/Charon.
>
>Thats also a speed that gets you into the nearby interstellar medium in 
>about fifteen years, a time frame that should quicken the heart of many a 
>deep space scientist. When he looked at some of the potential mission 
>concepts in Next Big Future, Brian Wang mentioned the possibility of 
>transporting raw materials from the asteroids for use in making fuel at 
>high Earth orbit. I see that Janhunen noted the asteroid idea in a recent 
>interview, tying it to a broader human future: Starting the long-awaited 
>asteroid resource utilization could be significant for the longer-term 
>well-being and survival of our civilization on this planet.
>
>That article, published in Space.com (and thanks to John Hunt for the 
>link), notes the nature of the sails first prototype, seen as a smaller 
>sail using 8-kilometer long tethers in an elliptical Earth orbit, a 
>scenario that would allow tests on the force of the solar wind on the 
>spacecraft. The team would also investigate using radio waves to excite 
>solar wind particles in an attempt to boost the possible thrust.
>
>So many good concepts, so many budgetary constraints. Long an admirer of 
>Robert Winglees Mini-Magnetospheric Plasma Propulsion concept, I watched 
>with growing enthusiasm as it sailed through Phase I and Phase II rounds at 
>NASAs Institute for Advanced Concepts and went on to further scrutiny, but 
>getting some kind of solar, magsail or electric sail concept into actual 
>space testing now seems a remote possibility. The Finnish teams sail awaits 
>the resolution of its own funding issues, a quick fix being the infusion of 
>somewhere around 5 million Euros.
>
>One thing is for sure: Propulsion concepts that let us leave the fuel on 
>Earth have a huge future in opening up the outer planets and the 
>interesting places beyond. Solar sails can do this by using the momentum 
>provided by photons from the Sun, but these effects drop dramatically as we 
>move beyond  Jupiter. The solar wind, streaming outward from the Sun at 
>speeds approaching 1.5 million kilometers per hour, may offer a way to 
>boost sail performance through magsail and electric concepts, but we have 
>much to learn about how sails might interact with it. In both cases, we 
>need sail deployment in space to take the necessary next steps.
>
>A good way to keep up with the Finnish sail studies is to track the latest 
>papers and press releases here. Youll also find the latest paper I know 
>about, which is Mengali et al., Electric sail performance analysis, Journal 
>of Spacecraft and Rockets Volume 45, Issue 1 (Jan-Feb, 2008), pp. 122-129, 
>available as an abstract with included figures on the site. Its interesting 
>as well to see that a workshop on electric sailing will be held at the 
>European Space Research and Technology Centre in the Netherlands on Monday, 
>May 19.
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