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For Louis re #25
First, thanks for taking a look at the links provided by a relative whose expertise is in the music business. I have not yet had a chance to review the links, so appreciate your doing so, and providing a comment.
One suggestion I would like to offer is to try to bring the vision a bit closer to home. The US Defense Department exercise is intended (as I understand it) to operate over a distance of 1000 miles (1600 kilometers) at the most, and for 30 minutes per session compared to 24 hours for the GEO version.
In my view, the LEO version is far more likely to come to pass before the GEO version, for the simple reason that military leadership is looking for an alternative to shipping vulnerable fuel supplies through enemy territory.
I have launched an inquiry of a group of ** real ** electrical/electronics engineers, so hope to interest at least one of them in taking a look at the situation as recast by the change from GEO to LEO.
As GW Johnson has confirmed in Orbital Mechanics, there is a class of LEO orbits that has the useful property of rotating about the Earth with calculated precession, so that the satellite is always in the sunlight.
I have a clarification to offer the reader of this topic who may have noticed my earlier prediction that a given ground station would be served only once a day by a particular satellite. I'm now considering the possibility that that ground station might be served by a particular satellite more than once a day, depending upon when the two passes occur. The passes will necessarily be more than 90 minutes apart, but dawn and dusk last for at least that long.
In addition, any ground station experiences dawn and dusk (taken together) twice a day, so total charging time could be as much as 60 minutes using just that factor. If more than one charging session is possible for a given ground station served by a particular satellite, then potentially the charge time might be increased to as much as two hours.
Furthermore (having had a day or two to think about this situation) there is no reason why a particular satellite has to be limited to serving one ground station. A given satellite could serve multiple ground stations on the path, and to the side of the path.
The number of ground stations that could be served at least twice a day seems much greater than I was imagining in the first posts on this subject.
The band of energy that is to be tapped by this method would have gone past the Earth in any case, and thus been lost forever, so the efficiency of the energy collection is 100% if ** any ** is collected at all. Talk of efficiency seems curious to me, since the entire Earth consumes only a tiny fraction of the energy generated by the Sun.
Thanks again for taking a look at the links. I'm planning to so so later today.
(th)
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The beam breakdown distance in Earth's atmosphere is related to the frequency over which the radiated power is transmitted. The beam is not attenuated by traveling through a hard vacuum, so placing the solar power satellite in geosynchronous orbit versus a low orbit means very little to power attenuation, except as it relates to the beam's continual increase in area as the transmitting antenna moves away from the receiving antenna.
Suitable 1MW to 10MW gyrotrons for power transmission that operate over frequencies of 170GHz to 320GHz have been developed for nuclear fusion reactors. Earth's atmosphere is nearly electromagnetically transparent to the beam over the aforementioned frequency range, so very little power is lost through attenuation when the beam strikes the molecules in Earth's atmosphere. Beam focusing / shaping and maintaining acceptable power densities per unit area, to prevent the radiated power from frying something between the emitter on the power satellite and the rectifying antenna on the ground, or having the beam spill over the area covered by the ground antenna array and lose transmitted power that way, are far more challenging to overcome than atmospheric power attenuation.
It should be noted that while we're talking about very large antennas covering multiple square kilometers, these are not particularly challenging or expensive to construct. The cost associated with covering an equivalent land area with solar panels would be far greater, for example.
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For kbd512 re #27
Thank you for contributing to the development of this topic ...
It seems to me that a person with experience in this field would be helpful, at this point.
I would like to see an analysis of the various factors that would go into design of a network of SPS in LEO that would serve a large population of Earth residents.
Elon Musk is demonstrating the technology that would be needed, with with the Starlink system. The individual satellites are inter-communicating and serving ground stations while moving at orbital velocity.
The SPS in LEO would (presumably) be moving a bit more slowly (if I understand Wikipedia's article on Sun Synchronous orbits correctly), but they still will need to interact with ground controllers and with customer receiving sites on the ground in a real time basis.
The entire enterprise needs to be organized so that the costs can be distributed over enough customers for a long enough period to return the initial investment with a reasonable profit.
I can see a role for the Space Force in maintaining the security of the system, although because this would be a global undertaking, the equivalent services of other Nations would and should participate in protecting the assets.
(th)
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Here's an update with a bit more information about the nature of the test on the X37b...
https://currently.att.yahoo.com/finance … 00288.html
Science
The Pentagon Successfully Tests Solar Panel In Space
Editor OilPrice.com
Oilprice.comThu, March 4, 2021, 5:00 PM
The Pentagon has successfully tested a solar panel in low-earth orbit as a prototype of potential future power-generating systems capturing light from the Sun and beaming it back as energy to earth.In May 2020, engineers at the U.S. Naval Research Laboratory launched the Photovoltaic Radio-frequency Antenna Module (PRAM) aboard an Air Force X-37B Orbital Test Vehicle, as part of a study into prospective terrestrial use of solar energy captured in space.
The tile module the size of a pizza box was designed to test the ability to harvest power from its solar panel and transform the energy to a radio frequency microwave, the U.S. Naval Research Laboratory said at the time.
The system is attached to a Pentagon unmanned drone looping the Earth every 90 minutes.
The panel’s position in orbit makes it more powerful in capturing the light of the Sun than solar systems capturing sunlight that reaches the surface of the earth, the developers of the project tell CNN.
“We're getting a ton of extra sunlight in space just because of that,” Paul Jaffe, a co-developer of the solar panel in space project, told CNN.
According to the latest tests the scientists have analyzed, the solar panel in orbit can produce some 10 watts of energy, enough to power a tablet computer, Jaffe told CNN’s Nick Paton Walsh.
Related Video: Four of the Coolest Fictional Power Sources
The solar panel has not sent power generated from the Sun to the Earth yet, but the advantage of such a system in space would be that the energy can be transmitted from space to any corner of the earth, where grids need it.
One of the biggest disadvantages of such systems is, unsurprisingly, cost.
Additional challenges that need to be resolved include regulatory concerns, including spectrum and safety, and potential international coordination, the team of scientists said when they published part of their findings in the January edition of IEEE Journal of Microwaves.
The first results of the tests with the solar panel in space have shown that “the experiment is working,” Jaffe told CNN.
By Tsvetana Paraskova for Oilprice.com
Apparently the test was more than just a test to see if a solar panel would work in space.
The few words in the article that hint at a dual function are encouraging, so I hope even more data will be provided at some point.
(th)
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here is another of those duplicate topics.
Scientists and engineers at Caltech recently launched a special spacecraft into orbit called the Space Solar Power Demonstrator (SSPD). This spacecraft was designed as part of the Caltech Space Solar Power Project (SSPP) and will act as a direct test for what scientists call space-based solar power, or SBSP tech, which will try to beam solar power down directly from space.
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