The electric solar wind sail, or electric sail for short, is a propulsion invention made in 2006 at the Kumpula Space Centre by Pekka Janhunen. For E-sail related news, please see the electric sail blog (it is in Finnish, but carries a Translate button to your language). See also the continuously updated list of scientific papers and the list of Frequently Asked Questions.
The Finnish startup company Aurora Propulsion Technologies Oy is commercialising electric sail and the closely related plasma brake technology.
The electric sail is a new space propulsion concept which uses the solar wind momentum for producing thrust (Janhunen, P., Electric sail for spacecraft propulsion, AIAA Journal of Propulsion and Power, 20, 4, 763-764, 2004, Janhunen, P. and A. Sandroos, Simulation study of solar wind push on a charged wire: solar wind electric sail propulsion, Ann. Geophys., 25, 755-767, 2007). The electric sail is somewhat similar to the more well-known solar radiation pressure sail which is often called simply the solar sail.
A full-scale electric sail consists of a number (50-100) of long (e.g., 20 km), thin (e.g., 25 microns) conducting tethers (wires). The spacecraft contains a solar-powered electron gun (typical power a few hundred watts) which is used to keep the spacecraft and the wires in a high (typically 20 kV) positive potential. The electric field of the wires extends a few tens of metres into the surrounding solar wind plasma. Therefore the solar wind ions "see" the wires as rather thick, about 100 m wide obstacles. A technical concept exists for deploying (opening) the wires in a relatively simple way and guiding or "flying" the resulting spacecraft electrically.
The solar wind dynamic pressure varies but is on average about 2 nPa at Earth distance from the Sun. This is about 5000 times weaker than the solar radiation pressure. Due to the very large effective area and very low weight per unit length of a thin metal wire, the electric sail is still efficient, however. A 20-km long electric sail wire weighs only a few hundred grams and fits in a small reel, but when opened in space and connected to the spacecraft's electron gun, it can produce several square kilometre effective solar wind sail area which is capable of extracting about 10 millinewton force from the solar wind. For example, by equipping a 1000 kg spacecraft with 100 such wires, one may produce acceleration of about 1 mm/s^2. After acting for one year, this acceleration would produce a significant final speed of 30 km/s. Smaller payloads could be moved quite fast in space using the electric sail, a Pluto flyby could occur in less than five years, for example. Alternatively, one might choose to move medium size payloads at ordinary 5-10 km/s speed, but with lowered propulsion costs because the mass that has to launched from Earth is small in the electric sail.
The main limitation of the electric sail is that since it uses the solar wind, it cannot produce much thrust inside a magnetosphere where there is no solar wind. Although the direction of the thrust is basically away from the Sun, the direction can be varied within some limits by inclining the sail. Tacking towards the Sun is therefore also possible.
The electric sail won the 2010 Finnish Quality Innovation Prize among Potential innovations. The prize was handed out by the President of Finland Tarja Halonen on November 11, 2010.
Added Feb 6 2021: This site also hosts pages of my Ceres megasatellite settlement proposal.
Meli ya umeme ya jua (kwa Kiingereza: Solar Wind Sail) ni kifaa cha kuendesha ndege kilichotengenezwa mwaka 2006 na Pekka Janhunen. Kwa habari zinazohusiana na e-sail, tafadhali angalia blogi ya mashua ya umeme (ni kwa Kifini, lakini ina kitufe cha Tafsiri kwa lugha yako). Angalia pia orodha ya mara kwa mara updated ya karatasi za kisayansi na orodha ya maswali ya mara kwa mara. Kampuni ya kuanza ya Finland Aurora Propulsion Technologies Oy inauza mashua ya umeme na teknolojia ya breki ya plasma inayohusiana sana. "Kama mfano, ""mwisho wa upepo wa jua"" ni mfano wa ""mwisho wa upepo wa jua"" (Jan Huhnen, A.P. (Jarida la AIA la Uendeshaji na Nguvu, 20, 4, 763, 764, 2004), ""mwisho wa upepo wa jua"" ni mfano wa ""mwisho wa upepo wa jua"" (Jan Huhnen, P. na A. Sandroes, 2004)." Geofumadas, 25 (mwaka wa 2007) Sail ya umeme ni sawa na saili ya shinikizo la mnururisho wa jua inayojulikana zaidi ambayo mara nyingi huitwa tu saili ya jua. Meli ya umeme ya kawaida ina idadi ya 50-100 ya urefu (kwa mfano, 20 km), nyembamba (kwa mfano, 25 microns) conductive tethers (kuongoza waya). Chombo cha angani kina bunduki ya umeme ya umeme (nguvu ya kawaida ya mamia ya watts) ambayo hutumiwa kuweka chombo cha angani na waya katika uwezo wa juu (kwa kawaida 20 kV). Eneo la umeme la waya huenea kwa makumi machache ya mita ndani ya plasma ya upepo wa jua inayozunguka. Kwa hiyo, ion za upepo wa jua huona waya kama vizuizi vyenye unene wa mita 100 hivi. Dhana ya kiufundi ipo kwa ajili ya kupeleka (kufungua) waya kwa njia rahisi na kuongoza au "kuruka" chombo cha angani kinachotokana na umeme. Shinikizo la upepo wa jua ni la kawaida na ni karibu 2 nPa kwa umbali wa dunia kutoka jua. Hii ni mara 5000 dhaifu kuliko shinikizo la mnururisho wa jua. Kwa sababu ya eneo kubwa sana na uzito mdogo sana kwa urefu wa kitengo cha waya mwembamba wa chuma, meli ya umeme bado ni ufanisi, hata hivyo. Wire ya umeme ya 20km ya urefu wa wire ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme ya umeme Kwa mfano, kwa kuandaa 1000 kg chombo cha anga na 100 waya kama hizo, mtu anaweza kuzalisha kasi ya kuhusu 1 mm s2 Baada ya kufanya kazi kwa mwaka mmoja, kasi hii itazalisha kasi ya mwisho ya 30 km s. Kwa mfano, mizigo midogo inaweza kusafirishwa kwa kasi sana katika anga kwa kutumia mashua ya umeme, na kuruka karibu na Pluto kwa muda wa chini ya miaka mitano. Kwa upande mwingine, mtu anaweza kuchagua kusonga mizigo ya ukubwa wa kati kwa kasi ya kawaida ya 5-10 km s, lakini kwa gharama za chini za propulsion kwa sababu wingi ambao lazima uanzishwe kutoka duniani ni mdogo katika mashua ya umeme. Upungufu mkubwa wa mashua ya umeme ni kwamba kwa kuwa hutumia upepo wa jua, haiwezi kutokeza nguvu nyingi ndani ya anga la sumaku ambapo hakuna upepo wa jua. Ingawa mwelekeo wa kusukuma ni kimsingi mbali na Jua, mwelekeo unaweza kubadilishwa ndani ya mipaka fulani kwa kuinamisha tanga. Kwa hiyo, inawezekana pia kugeuka kuelekea Jua. Meli hiyo ya umeme ilishinda tuzo ya Finnish Quality Innovation Prize ya mwaka 2010 kati ya ubunifu wa uwezekano. Tuzo hiyo ilitolewa na Rais wa Finland Tarja Halonen mnamo Novemba 11, 2010. "Kama ilivyoelezwa hapo juu, tovuti hii pia inakaribisha kurasa za ""Ceres Megasatellite Settlement Proposal."""