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Space Solar Power - A possible way of Reducing Rectenna size?
One of the drawbacks of SSP is the size of the Earth based rectenna.
This isn't an engineering challenge, but near populated areas will be a planning permission issue. In the UK, it's hard enough to get planning permission to put up a wind turbine. Even the offshore 1GW wind farms have had to go through a 3 years approvals process. SSP doesn't scale well. The original reference designs have a 5GW beam transmitted from a 5km diameter transmitter to a 5km diameter rectenna. I can't think of anywhere in the UK where you'd get planning permission for a 5km rectenna, except perhaps offshore. Even then .... One way of reducing the size of the Earth based rectenna is to increase the size of the space based rectenna. This though increases the power density and the cost of the space structure. A question: How do you steer a multi-gigawatt microwave transmitter? Is it steered electronically? If so, is it possible to switch the beam across say, 10 rectennas, perhaps 10 times per second? Consider a 20GW powersat, with a 20km diameter transmitter. This needs an Earth based rectenna of only 1.25km diameter. However, beaming all 20GW to this one site would make the beam unsafe (about 15KW/m2). If instead the beam was switched across 10 rectennas, each getting 0.01 seconds every 0.1 second, the average beam power density would be a relatively safe 1.5KW / m2. Each rectenna produces only 2GW, so as a source its much more manageable, and a 1.25km diameter rectenna might get planning permission. Disadvantages: - The transmitter is 16 times more massive, carrying 4 times the power. - Some capacitance is needed at the rectenna - though with clever design it might be possible to get an AC current out of the rectenna directly. - The device could now be used as weapon (but then so can a nuclear power station) Is this possible? |
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Space Solar Power - A possible way of Reducing Rectenna size?
On Jan 24, 3:35 pm, "Alex Terrell" wrote: SSP doesn't scale well. The original reference designs have a 5GW beam transmitted from a 5km diameter transmitter to a 5km diameter rectenna. I can't think of anywhere in the UK where you'd get planning permission for a 5km rectenna, except perhaps offshore. Even then .... Simple solution: shut off all electric power to the region that refuses to allow rectennae on land purchased for that purpose. Same for nukes. |
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Space Solar Power - A possible way of Reducing Rectenna size?
On Jan 24, 4:35 pm, "Alex Terrell" wrote: One of the drawbacks of SSP is the size of the Earth based rectenna. I have a solution. Eliminate it entirely. No rectenna, no problem. |
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Space Solar Power - A possible way of Reducing Rectenna size?
On Jan 24, 4:35 pm, "Alex Terrell" wrote:
One of the drawbacks of SSP is the size of the Earth based rectenna. ... SSP doesn't scale well. The original reference designs have a 5GW beam transmitted from a 5km diameter transmitter to a 5km diameter rectenna. One way of reducing the size of the Earth based rectenna is to increase the size of the space based rectenna. This though increases the power density and the cost of the space structure. If memory serves, one of the main reasons for the big receiving antenna was to keep power density below a level that could start to affect the environment, like mid-beam birds and such. - Ed Kyle |
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Space Solar Power - A possible way of Reducing Rectenna size?
"Alex Terrell" wrote in message oups.com... One of the drawbacks of SSP is the size of the Earth based rectenna. This isn't an engineering challenge, but near populated areas will be a planning permission issue. In the UK, it's hard enough to get planning permission to put up a wind turbine. Even the offshore 1GW wind farms have had to go through a 3 years approvals process. SSP doesn't scale well. This JPL presentation claims that SSP can bypass photovoltaics and microwaving completely, by using a light trap that directly converts sunlight into a high power laser using fiber optics. And use the laser beam as a source of transmission to earth or other points in space. http://space-power.grc.nasa.gov/ppo/...eaming_TIM.pdf And in this presentation, from the Univ of Alabama, of possible laser power beaming technologies, they speculate such a power beam could be used for thrust. ".1 GW of average optical power converted to thrust lifts 1 Metric ton to orbit" And they conclude this is possible for receiver size for laser transmission. "Terrestrial system is moderate size (3m x 1m for 1 MW), which allows location on a vehicle, could be developed in the near term (2-5 years) with focused program, and can serve as a stepping stone to the space SHEL Laser." http://space-power.grc.nasa.gov/ppo/...IM_9-11-02.pdf This link summarizes much of the latest research in SSP. Nasa Glenn Research Center Space Solar Power Concept And Technology Maturation Program Technical Interchange Meeting (SCTM TIM http://space-power.grc.nasa.gov/ppo/publications/sctm/ Of course much of this is still very speculative, but what if we gave our best and brightest that HUNDRED BILLION over twenty years? What kind of advances might they come up with if already they envision having the ability to .....power cars... directly from space. Or power colonies and space craft. Literally..power space craft as in thrust. But we're going to put a shelter for a few astronauts on the moon and mars instead. To look for fossils and establish colonies for ....dozens and well, maybe a dozen people. You know, how many conspiracy nuts are out there that imagine Big Corporate America is hiding those tires that never wear out. Or that magic perpetual motion machine etc etc. Well ya know, the more I read about how the Vision for Space Exploration came to be. The more I read about the advances and potential of SSP.The more I read about how the White House canned the X-33. And how all these things seemed to happen in that period just before and after 9/11. The more I think this is IT~ A Texas oilman long known to be beholden to Lockheed ....trashing solar power and reusable spacecraft ....for the sake of quick and easy profits....naw...only ....in the movies. Never happen, we'd have to be nuts to even think it...right? I think they would, and have, done just that. s |
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Space Solar Power - A possible way of Reducing Rectenna size?
In article .com,
Alex Terrell wrote: A question: How do you steer a multi-gigawatt microwave transmitter? Is it steered electronically? Correct. Oh, there are alternatives, but for such a big transmitting antenna, electronic steering is overwhelmingly the preferred solution. If so, is it possible to switch the beam across say, 10 rectennas, perhaps 10 times per second? Better: it is possible to generate multiple beams *simultaneously* -- with electronic steering of a zillion-element transmitter, you can shape the output distribution to have peaks in several directions rather than just one. (Each beam is still subject to the same fundamental limits on how tight it can be; this trick doesn't get around that.) -- spsystems.net is temporarily off the air; | Henry Spencer mail to henry at zoo.utoronto.ca instead. | |
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Space Solar Power - A possible way of Reducing Rectenna size?
On Jan 24, 5:23 pm, "Ed Kyle" wrote:
On Jan 24, 4:35 pm, "Alex Terrell" wrote: One of the drawbacks of SSP is the size of the Earth based rectenna. ... SSP doesn't scale well. The original reference designs have a 5GW beam transmitted from a 5km diameter transmitter to a 5km diameter rectenna. One way of reducing the size of the Earth based rectenna is to increase the size of the space based rectenna. This though increases the power density and the cost of the space structure.If memory serves, one of the main reasons for the big receiving antenna was to keep power density below a level that could start to affect the environment, like mid-beam birds and such. I thought it was almost entirely to keep the size of the transmitting antenna (which, after all, has to be launched into space) under control. I could be wrong. - jake |
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Space Solar Power - A possible way of Reducing Rectenna size?
"Alex Terrell" wrote:
:- The device could now be used as weapon (but then so can a nuclear ower station) How can a nuclear power station be used as a weapon? -- "Some people get lost in thought because it's such unfamiliar territory." --G. Behn |
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Space Solar Power - A possible way of Reducing Rectenna size?
On 25 Jan, 03:01, "Jake McGuire" wrote: On Jan 24, 5:23 pm, "Ed Kyle" wrote: On Jan 24, 4:35 pm, "Alex Terrell" wrote: One of the drawbacks of SSP is the size of the Earth based rectenna. ... SSP doesn't scale well. The original reference designs have a 5GW beam transmitted from a 5km diameter transmitter to a 5km diameter rectenna. One way of reducing the size of the Earth based rectenna is to increase the size of the space based rectenna. This though increases the power density and the cost of the space structure.If memory serves, one of the main reasons for the big receiving antenna was to keep power density below a level that could start to affect the environment, like mid-beam birds and such. I thought it was almost entirely to keep the size of the transmitting antenna (which, after all, has to be launched into space) under control. I could be wrong. Both to reduce the size of the transmitting antenna, and to limit the radiation flux. It is unlikely the transmitting antenna would be launched from Earth, unless a space elevator arrives before a moon base. |
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Space Solar Power - A possible way of Reducing Rectenna size?
On 25 Jan, 02:53, (Henry Spencer) wrote: In article .com, Alex Terrell wrote: A question: How do you steer a multi-gigawatt microwave transmitter? Is it steered electronically?Correct. Oh, there are alternatives, but for such a big transmitting antenna, electronic steering is overwhelmingly the preferred solution. If so, is it possible to switch the beam across say, 10 rectennas, perhaps 10 times per second?Better: it is possible to generate multiple beams *simultaneously* -- with electronic steering of a zillion-element transmitter, you can shape the output distribution to have peaks in several directions rather than just one. (Each beam is still subject to the same fundamental limits on how tight it can be; this trick doesn't get around that.) -- Thanks. This implies to an advantage for power sats over the 5GW reference design. The right strategy might be to start with one powersat, and just keep building it up as big as possible. Though of course, this goes against the issue of redundancy. Though if one 20GW power sat is exporting to 20 rectennas across a continent, the temporary loss of 20GW might be bearable. At what size do tidal forces become an issue (rather than a design factor) in Geostationary Orbit? Perhaps in 2100 we could have 50TW from 1,000 50GW power sats. (Still masses about half an O'Neill cylinder). |
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