Wah... si bobby formula ini, dari sekarang udah kelihatan bibit jadi professor! teruskan perjuanganmu, fren! --- BOBBY FORMULA <[EMAIL PROTECTED]> wrote:
> from: [EMAIL PROTECTED] > > menangkap energi luar angkasa dan mengirimkannya ke > bumi > > kalau saja hal ini bisa terjadi dengan mengirimkan > energi lewat > gelombang microwave. wah, tentunya sumber geothermal > indonesia yang > sudah terbukti terbesar didunia ini bisa dipakai > sebagai sumber energi dunia yg baru. dengan > membangun geothermal electric generator dan > mengirimkannya atau meng"export"nya. > > > > =solar power satellite= > http://www.answers.com/ > > A solar power satellite, or SPS, is a proposed > satellite built in high Earth orbit that uses > microwave power transmission to beam solar power to > a very large antenna on Earth where it can be used > in place of conventional power sources. The > advantage to placing the solar collectors in space > is the unobstructed view of the Sun, unaffected by > the day/night cycle, weather, or seasons. However, > the costs of construction are very high, so it is > unlikely the SPS will be able to compete with > conventional sources unless there is a big reduction > in the costs associated with launching massive > satellites into space, unless a space-based > manufacturing industry develops and they can be > built in orbit. > > History > > The SPS concept has been around since late 1968, but > was considered > impractical due to the lack of an efficient method > of sending the > power down to the Earth for use. Things changed in > 1974 when Peter > Glaser was granted patent number 3,781,647 for his > method of > transmitting the power to Earth using microwaves > from a small antenna on the satellite to a much > larger one on the ground, known as a rectenna. > > Glasser's work took place at Author D. Little, Inc., > who employed > Glaser as a vice-president. NASA then became > interested and granted > them a contract to lead four other companies in a > broader study in > 1972. They found that while the concept had several > major problems, > chiefly the expense of putting the required > materials in orbit and the lack of experience on > projects of this scale in space, it showed > enough promise to merit further investigation and > research. > > Most major aerospace companies then became briefly > involved in some > way, either under NASA grants or on their own money, > to preserve a > chance at the large contracts that would have been > let out had the > decision been made to go ahead with this concept. At > the time the > needs for electricity were booming, and there seemed > to be no end in > demand. When power use levelled off in the 1970s, > the concept was shelved. > > More recently the concept has again become > interesting, generally due to increased energy > demands and costs. At some price point the high > construction costs of the SPS become favourable due > to their low-cost delivery of power, but this price > point remains far higher than current rates. > Nevertheless continued advances in material science > and space transport continue to whittle away at the > startup cost of the SPS. > > Description > > The SPS essentially consists of three parts: > > 1. a huge solar collector, typically made up of > solar cells > 2. a microwave antenna on the satellite, aimed at > Earth > 3. an antenna occupying a large area on Earth to > collect the power > > The SPS concept arose because space has several > major advantages over earth for the collection of > solar power. There is no air in space, so the > satellites would receive somewhat more intense > sunlight, unaffected by weather. In a geosynchronous > orbit an SPS would be illuminated over 99% of the > time. The SPS would be in Earth's shadow on only a > few days at the spring and fall equinoxes; and even > then for a maximum of an hour and a half late at > night when power demands are at their lowest. This > allows expensive storage facilities necessary to > earth-based system to be avoided. > > In most senses the SPS concept is simpler than most > power systems here on Earth. This includes the > structure needed to hold it together, which in orbit > can be considerably lighter due to the lack of > gravity. > Some early studies looked at solar furnaces to drive > conventional > turbines, but as the efficiency of the solar cell > improved this > concept eventually became impractical. In either > case another > advantage of the design is that waste heat is > re-radiated back into > space, instead of warming the biosphere as with > conventional sources. > > The Earth-based "rectenna" is also key to the > concept. It consists of a series of short dipole > antennas, connected with a diode. Microwaves > broadcast from the SPS are received in the dipoles > with about 85% efficiency. With a conventional > microwave antenna the reception is even better, but > the cost and complexity is considerably greater. > Rectennas would be about 5 km across, and receive > enough microwaves to be a concern. Some have > suggested locating them offshore, but this presents > problems of its own. > > For best efficiency the satellite antenna must be > between 1 and 1.5 > kilometers in diameter and the ground rectenna > around 14 kilometers by 10 kilometers. For the > desired microwave intensity this allows > transfer of between 5 and 10 gigawatts of power. To > be cost effective it needs to operate at maximum > capacity. To collect and convert that much power the > satellite needs between 50 and 150 square kilometers > of collector area thus leading to huge satellites. > > "Huge" is by no means an understatement. Most > designs are based on a > rectangular grid some 10 km on a side, much larger > than most man-made structures here on Earth. While > certainly not beyond current > engineering capabilities, building structures of > this size in orbit > has never been attempted before. > > Problems > > Launch costs > > Without a doubt, the biggest problem for the SPS > concept is the > currently immense cost of all space launches. > Current rates on the > Space Shuttle run between $3,500 and $5,000 per > pound ($8,000/kg and > $11,000/kg), depending on whose numbers are used. In > either case the > concept of building a structure some kilometres on a > side is clearly > out of the question. Development of a vehicle that > can launch 100 ton loads at less than $400/kg is > likely to be necessary. > > Gerard O'Neill noted this problem in the early > 1970s, and came up with the idea of building the > SPS's in orbit with materials from the Moon. > The costs of launch from the Moon are about 100 > times lower than from Earth, due to the lower > gravity. However this concept only works if the > number of satellites to be built is on the order of > several hundred, otherwise the cost of setting up > the production lines in space and mining facilities > on the Moon are just as huge as launching from Earth > in the first place. However it appears that O'Neill > was more interested in coming up with a > justification for his space habitat designs than any > particular interest in the SPS concept on its own. > > More recently the SPS concept has been suggested as > a use for a space elevator. The elevator would make > construction of an SPS considerably less expensive, > possibly making them competitive with conventional > sources. However it appears unlikely that even > recent advances in materials science, namely carbon > nanotubes, can reduce the price of construction of > the elevator enough in the short term. > > Safety > === message truncated === __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/uBfwlB/TM --------------------------------------------------------------------~-> _____________________________________________________________ Keluarga Besar Mahasiswa Siantar-Bandung (KBMSB) [email protected] http://groups.yahoo.com/group/KBMSB http://www.mail-archive.com/[email protected] Disclaimer : Isi tanggung jawab pembaca ! 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