- Electric sail
Electric sail (also called electric solar wind sail) is a proposed form of
spacecraft propulsion using thedynamic pressure of thesolar wind as a source of thrust. It is similar to themagnetic sail except that it uses anelectric field instead of amagnetic field for deflecting solar wind protons and extracting momentum from them.Principles of operation and design
The electric sail consists of a number of thin, long and conducting
tethers which are kept in a high positive potential by an onboardelectron gun . The positively charged tethers repel solar wind protons, thus deflecting their paths and extracting momentum from them. Simultaneously they also attract electron from the solar wind plasma. The arriving electron current is compensated by the electron gun. A way to deploy the tethers is to rotate the spacecraft and have thecentrifugal force keep them stretched.Potentiometers between each tether and the spacecraft can be used to fine-tune the tether potentials and thus the solar wind force individually and thus control the attitude of the spacecraft.Intrinsic limitations
The electric sail probably cannot be used inside planetary
magnetospheres because there is no solar wind there, only slower plasma flows and magnetic fields. While modest variation of the thrust direction can be achieved by inclining the sail, the thrust vector always points more or less radially outward from theSun .Applications
* Fast mission (>50 km/s or 10 AU/year) out of the
Solar system andheliosphere for small or modest payload
* As a brake for smallinterstellar probe which has been accelerated to high speed by some other means such as laser lightsail
* Inward-spiralling mission to study the Sun at closer distance
* Two-way mission to inner Solar System objects such asasteroids
* Off-Lagrange point solar wind monitoring spacecraft for predictingspace weather with longer warning time than 1 houree also
*
Magnetic sail
*Solar sail
*Spacecraft propulsion References
* Janhunen, P., "Electric sail for spacecraft propulsion", Journal of Propulsion and Power, 20, 4, 763-764, 2004.
* Janhunen, P. and A. Sandroos, " [http://www.space.fmi.fi/~pjanhune/papers/Esail/paper2/draft.pdf Simulation study of solar wind push on a charged wire: basis of solar wind electric sail propulsion] ", " [http://www.ann-geophys.net/25/755/2007/angeo-25-755-2007.html Annales Geophysicae, 25, 755-767, 2007] "External links
* [http://www.electric-sailing.com/ Electric Sailing] at [http://www.kumpulaspace.fi/ Kumpula Space Centre] / [http://www.space.fmi.fi/ Finnish Meteorological Institute/Space Research]
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