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Peter Glaser once had this vision of giant solar power satellites beaming microwaves down to Earth to power cities. I was thinking that maybe we could try this idea on a much smaler scale to power a manned Mars mission. Take Mars Direct or NASA's Mars semidirect design reference mission and replace the nuclear power place on the ground with a receiver for beamed energy coming from a mini solar power satellite in Martian synchronius orbit. A Mars SPS would need about twice the area to collect the same amount of power from the Sun as it would if it were orbiting the Earth. Despite the fact that we don't have to land the SPS on the Martian surface as we would the reactor, their may be a mass penalty in launching an Actual power beaming SPS into orbit around Mars, but there is an advantage too. With Each Mars mission, you need to bring down a new nuclear power planet to power fuel production for the Earth return vehicle or the ascent rocket, and the Martian rovers as well as the bases lifesupport, but if we've take the trouble to orbit an SPS, we'd need only one. The SPS that power the first mission can also power the second and the third. An SPS is less of a maintenence nightmare, if the portable nuke breaks down or even worse it melts down, then the crew is in trouble. An SPS satellite has fewer moving parts than a nuclear reactor, and thus less maintenence headaches, it doesn't have fuel that it exhausts, and as long as the sun keeps on shining it keeps on beaming power.
I think the best way to get an SPS into Mars orbit is to dedicate an Ares V rocket to sending it there. The SPS would then unfold like a communication's satellite except that it would have much bigger solar panels. Also I don't see why an SPS satellite couldn't also be a communication's satellite as both types have to be in the same orbit anyway. If one SPS satellite is not enough to replace a reactor, then maybe two will do. There is no reason why you can't have two SPS satellites beaming power down to the same receiver at the same time. Ok so that's two Ares V launchers, it does get rid of the problem of how to get rid of nuclear waste on Mars. I mean after all, if people are going to live on Mars, then they'll eventually have to do something about nuclear waste from those portable nuke reactors. It might be worth having SPSs instead of Nukes for those first manned missions.
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For SpaceNut ... this item could go several places, but I'll start it here ...
https://www.yahoo.com/news/u-scientists … 10556.html
— CNN (@CNN) February 24, 2021
The Pentagon sent a prototype PRAM into orbit in May 2020 aboard its secretive X-37B unmanned drone. The 12-inch-square photovoltaic panel showed it's capable of producing 10 watts of energy, or enough to power an iPad, to transmit back to Earth, Paul Jaffe at the U.S. Naval Research Lab in Washington, D.C., told CNN. The advantages of putting solar panels in space include constant sunlight, more powerful light including blue waves filtered out by the Earth's atmosphere, and the ability to direct power to where it's needed most at any given time.
From my perspective, this is exceedingly good news! The small scale of the project is particularly exciting (to me at least)
We (humans) have been stuck in a mental trap created by Peter Glaser and others who proposed Solar Power Satellites....
There was no GOOD reason to design an SPS as large as a football field!
It is just human nature to think on large scales.
The Pentagon experiment is perfect for homeowners in the US and around the world.
A homeowner like SpaceNut could have a small SPS set up just for his use. The receiving rectenna would (presumably) fit on a city block, although I'd definitely be interested in details of how large the Pentagon experimental receiving antenna was actually was to receive 10 watts.
Never-the-less, to-order personal-SPS are going to be ** very ** attractive to people all over the world as soon as word gets out.
It isn't the demonstration by the Pentagon that is so important. What ** is ** important is the destruction of the massive scale mindset that has inhibited SPS for decades.
Bravo!
Peter Glaser
Peter Glaser, the father of the solar power satellite concept. (Image credit: Arthur D. Little Inc. ) Peter Glaser, a space pioneer who introduced the idea of using satellites to beam solar energy from space down to Earth, has died at the age of 90.
Jun 9, 2014
Peter Glaser, Father of Solar-Power Satellite Idea, Dies at 90 | Space
www.space.com › 26175-peter-glaser-solar-power-satellite-obituary
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Peter Glaser, Father of Solar-Power Satellite Idea, Dies at 90
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Jun 9, 2014 · Peter Glaser, a space pioneer who introduced the idea of using satellites to beam solar energy from space down to Earth, has died at the age of ...Edit#1: I read another article on this announcement, and am disappointed to have to report the X37b test was NOT a full test of the system. It was apparently only a test of a solar panel that might be used in a full system. I suppose that is good news, but solar panels have been working in space for many decades now.
However, the ** real ** breakthrough remains ... the mind set of colossal SPS is set aside in favor of thinking of small systems able to reliably serve a much smaller customer requirement.
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TH, that is an interesting development. From what I remember, the beam coherence for magnetron based microwave generators is poor. A satellite power station designed to serve a national grid would be located in GEO at at altitude of 36,000km. At that altitude, it would be in sunlight for 95% of the time. An SPS in LEO would be out of sunlight 50% of the time and it would be in darkness at the same time as your local night time.
Over a 36,000km distance the beam would attenuate to the point where any rectenna would need to be around 10km in diameter. I believe that this is why solar power satellites were planned for power levels of around 10GWe. It wouldn't be practical to power an individual home in this way because of the size of the rectenna.
That said, it is encouraging that microwave power transmission has been demonstrated through the Earth atmosphere. Manufacturing of SPS is one of the few Martian industries that could be profitable for direct export to Earth. It is energetically much easier to lift SPS components from the Martian surface into low Mars orbit, than it would be from Earth. An assembled SPS in low Mars orbit could be delivered to LEO using ion engines, powered by the SPS itself. A single 10GWe SPS would have a sale price of several tens of billions of dollars to an Earth based customer.
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For Calliban re #379
Thanks for helpful (to me for sure) reminder of the reasons for the massive size of the original proposals for SPS in GEO!
My enthusiasm was released by the announcement of X37b research activity, but (of course) that work was done in LEO.
Your point about the time when the transmitter would be in position to deliver power is (of course) correct.
However, in an attempt to salvage something from the hint of an opportunity provided by the X37b announcement, I'd like to offer the suggestion that an SPS in Leo could deliver power to customers in its field of view for about 30 minutes at a time.
For a given 90 minute path that is near the equator, the satellite should be able to serve three customers.
If there were a constellation of these smaller systems in orbit, comparable to the Starlink system, then coverage over the entire Earth should be substantial.
Management of a fleet of these satellites would seem to be comparable to management of Starlink, with the additional challenge of pointing at specific locations on the ground with 1 meter accuracy.
***
Now I have to admit (with some embarrassmen) that the X37b study did NOT include transmission to the ground. I found a second article yesterday that contained more detail. All the experimenters were able to prove is that the solar panel worked. Why the Defense Department chose to publicize such a paltry accomplishment is a mystery to me.Transmission through the atmosphere has been demonstrated for many decades. I don't know if any are still in service, but at one time, long ago, microwave towers were constructed to pass high volumes of data over considerable distances.
***
Your point about the size of the rectenna is a good one! If a project is sized to deliver 30 minutes of power to a given location, so that batteries can be charged to cover an entire 24 hour cycle, then it will become clear how much power has to be delivered through the atmosphere to a practical rectenna.The numbers might be alarming.
There was concern about the relatively low levels of microwave energy that would be arriving from GEO stations.
Concern about what would be required for LEO delivery would be much greater.
On the ** other ** hand, folks at the poles of the Earth might not mind if microwave levels are greater, because reliable energy supplies are hard to come by up (and down) that way.
Polar satellites might be the right answer for customers in this locations, and fewer would be needed because they would be useful at both poles on the same orbit, although the value at a given pole would change throughout the year, as the Sun's apparent elevation changes.
That would certainly be a complicated Orbital Mechanics problem!
Thanks again for your reminder of the basics!
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As Calliban indicated not very good at efficiency.
1100 watt / m^2 on orbit with a ft^2 receives approximate 110 watts in to create about 30 watts electrical to end in a beam to get 10 watts out is 1% and it can only achive this if we made a continous ring with this device...
edit reposting
For SpaceNut ... I searched topics for sps and found nothing.
I then searched for solar and power and satellites and found nothing ... You may have better luck ...
In the mean time, here is a link to an article about US Air Force plans to test tactical solar power soon ...
https://currently.att.yahoo.com/finance … 00029.html
(th)
Ah beamed orbital power is an issue if the beam is narrow for the earth target and it misses and gets others is bad...
Here are three topics that pertain on newmars
Microwave Sattelites - Sending solar energy to from orbits.
Louis' Solar Power Strategy
Solar Power Satellites to Power Human to Mars Mission
Mars does not have this problem as there is going to be limited people to get in the beams path.
tahanson43206, The solar on orbit is collected and beamed by the rf bands to earth stations in the first link. The earth's atmosphere attenuated most of the rf bands due to moisture in the air. The antennas collection devices are usually an array spread over a large surface area.
For SpaceNut re #338
Your post here is interesting, because it propagates an effect of heavy rain as though it were generally the case for atmospheric conditions at the the proposed RF frequency of 2.45 GHz.
Can you find your source? I have never heard of such a concern, and I've read everything I could find about SPS since it was first proposed many decades ago.
You are certainly right that at the frequency of concern, heavy rain can attenuate the signal, but if you are not trying to send power into the Amazon Rain Forest, the amount of time your rectenna sees reduced signal strength is pretty small.
I'd appreciate your finding your resource for the post ... I ** do ** note that your wording covers "most of the rf bands". But the frequencies for power satellites were chosen long ago to be least affected by moisture in the air.
Here is what I was able to find in a quick search this evening:
https://en.wikipedia.org/wiki/Space-based_solar_power
Microwave optic requires GW scale due to Airy disk beam spreading. Typically a 1 km transmitting disk at 2.45 GHz spreads out to 10 km at Earth distance.
and ...
Earth-based receiver
The Earth-based rectenna would likely consist of many short dipole antennas connected via diodes. Microwave broadcasts from the satellite would be received in the dipoles with about 85% efficiency.[61] With a conventional microwave antenna, the reception efficiency is better, but its cost and complexity are also considerably greater. Rectennas would likely be several kilometers across.In an article I found along the way, SPS at Mars would be impacted by dust storms, so the concern about RF attenuation applies there as well.
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For SpaceNut re restoring this topic ...
I agree that this topic is a decent fit for continuing discussion of SPS in the current context of LEO, but it is not a perfect fit.
The original intent (as I understand the opening post) was to focus upon GEO orbit installations ....
However, be that as it may, the originator is no longer here to complain, so I will support your restoration of the topic with the new direction ...
Bitcoin Uses More Electricity Than Any Method Known To Mankind, Says Bill Gates
Benzinga Staff
Thu, February 25, 2021 5:40 AM
There (it would appear) is our (human kind's) funder for LEO SPS!
Currently Bitcoin mining is consuming all the inexpensive power it can find, but (of course) that means the power consumed is not available for use by others who may be more deserving.
If there are any Bitcoin miners in the forum you are welcome to explain how your activity is more deserving than anyone else.
What we (who are not Bigcoin miners) can do is to invite your consideration of SPS in LEO to meet your power needs without depriving other Earth residents of the power you are consuming.
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GEO is a stationary location and while its distance from the reciever its not that much lose in terms of power that one my receive. Not all satellites would be exposed to the sun and would cause a night time outage as the satellites would be blocked by the earth.
The LEO is due to orbital speed to stay in orbit is its issue for the moving target. Its solution is a continous ring of these that could share a common internal power bus to all transmitters for all the time beaming to all locations. The solar which would be only hitting half of the ring at any time.
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For SpaceNut re #7
Thank you for continuing to encourage development of this topic!
Apparently there is a class of LEO orbits that are always in sunlight.
I have asked for help in the Orbital Mechanics topic, in hopes it might be possible to gain a better understanding of what might be possible.
If what ( ** seems ** ) to be what the Wikipedia article is saying is correct, then there is a class of polar orbits that are also in LEO that can deliver constant power to customers on Earth, albeit for only 30 minutes at a time, and (again based on only limited understanding) once per day.
If that is correct, then the ground stations would be built to collect a day's worth of free, clean non-polluting power in 30 minutes.
Candidates for this service would include Electric Vehicle charging stations, which would be able to do without solar panels, and thus would be much more robust in weather events, because the wire of the rectenna would not be damaged by wind or rain.
There's a lot to like as we continue to think about this possibility.
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Following up on #8 ...
There is no reason why a particular location on Earth could not be supplied with abundant SPS power from LEO.
In post #7, the existence of a class of polar orbits that are always in sunlight was considered for delivery of power to a location on Earth for 30 minutes every 24 hours.
There is no reason that I can see for why there could not be multiple satellites in this particular polar orbit.
Each satellite would be busy sending power to fixed locations along its track, so the satellite would never be without a destination for collected energy.
The cost of delivery of power to the ground stations would thus be divided among the ground stations.
If a given satellite has an orbital period of 90 minutes ( and I do ** not ** know what the orbital period of a sun synchronous satellite might be) then there would be three stations along the track to receive power. With 48 satellites in operation, there would be 3 x 48 or 150 - 6 or 144 ground stations in the network. As a reminder (for myself, in particular) the Sun Synchronous orbit plane passes through the center of the Earth. Satellites in that orbit can serve locations on Earth that are experiencing sunset (on one side of the Earth) and sunrise (on the other).
Many of these receiving stations would be on islands, where power could be collected and used to make useful products like hydrogen and oxygen, or whatever the market might find valuable.
A few locations might be on floating platforms where that would make economic sense.
The same principle could apply to Mars, with the distinct difference there are no oceans to worry about.
Edit #1 - SPS in LEO could be spaced every degree of latitude, or perhaps even more closely. Each could serve three clients for 30 minutes on a given orbit.
Service could be modified by demand through control from ground stations managing the network.
If there are 360 satellites (which seems reasonable (at least to me)) then they would serve 360 * 3 or 900 + 180 or 1080 ground stations in each orbit.
But the Earth is rotating underneath, so the total number of ground stations to be served would be greater.
I'm not sure how many ground stations could be served, but I'm assuming that at a minimum, 24*60 minutes divided by 90 minutes (16) tracks are possible.
That would yield 1080 * 16 service opportunities in 24 hours for 360 satellites. pr 17,280 in all.
Edit#2: Google came up with this citation from Wikipedia for Sun Synchronous Polar Orbits ...
Typical Sun-synchronous orbits around Earth are about 600–800 km in altitude, with periods in the 96–100-minute range, and inclinations of around 98°. This is slightly retrograde compared to the direction of Earth's rotation: 0° represents an equatorial orbit, and 90° represents a polar orbit.
Sun-synchronous orbit - Wikipedia
en.wikipedia.org › wiki › Sun-synchronous_orbit
Edit#3: Google came up with this estimate of the diameter of the Earth pole-to-pole
Image result for diameter of earth pole to pole
Equatorial vs Polar Diameter:
Because of this, the diameter of the Earth at the equator is about 43 kilometers (27 mi) larger than the pole-to-pole diameter. As a result, the latest measurements indicate that the Earth has an equatorial diameter of 12,756 km (7926 mi), and a polar diameter of 12713.6 km (7899.86 mi).Jun 14, 2008What is the Diameter of Earth? - Universe Todaywww.universetoday.com › diameter-of-earth
Circumference would be 24906 miles, so locating satellites every 100 miles would allow only 249.
Separating the satellites every 10 miles would allow for more interesting total of 2490.
That number times 16 yields 39840 power delivery opportunities.
Thus, the cost of 2490 satellites would be distributed over 39840 ground stations, each of which would receive 30 minutes of delivered solar power each day.
The cost of the ground stations would include storage capability, to allow the 30 minutes of input to be metered out over 24 hours.
Flow batteries might be a good fit for this application.
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For SpaceNut re topic ...
This is just FYI ... I don't expect anything to come of it ...
I would like to suggest use of Solar Power Satellites in Low Earth Orbit to help with Climate Change. How can I offer this suggestion to the correct person/department at the United Nations? The work of the United States Defense Department recently show that a Solar Power Satellite in Low Earth Orbit is feasible. A total of 360 satellites in a Sun Synchronous orbit could serve up to 17,280 ground stations for 30 minutes each 24 hours.
Thanks!Another contact method is www.newmars.com/forums, where I serve as a moderator as tahanson43206
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Sadly this technology doesn't yet appear practical for reasons of energy loss in conversion and cost. Some progress has been made but it's very slow.
Following up on #8 ...
There is no reason why a particular location on Earth could not be supplied with abundant SPS power from LEO.
In post #7, the existence of a class of polar orbits that are always in sunlight was considered for delivery of power to a location on Earth for 30 minutes every 24 hours.
There is no reason that I can see for why there could not be multiple satellites in this particular polar orbit.
Each satellite would be busy sending power to fixed locations along its track, so the satellite would never be without a destination for collected energy.
The cost of delivery of power to the ground stations would thus be divided among the ground stations.
If a given satellite has an orbital period of 90 minutes ( and I do ** not ** know what the orbital period of a sun synchronous satellite might be) then there would be three stations along the track to receive power. With 48 satellites in operation, there would be 3 x 48 or 150 - 6 or 144 ground stations in the network. As a reminder (for myself, in particular) the Sun Synchronous orbit plane passes through the center of the Earth. Satellites in that orbit can serve locations on Earth that are experiencing sunset (on one side of the Earth) and sunrise (on the other).
Many of these receiving stations would be on islands, where power could be collected and used to make useful products like hydrogen and oxygen, or whatever the market might find valuable.
A few locations might be on floating platforms where that would make economic sense.
The same principle could apply to Mars, with the distinct difference there are no oceans to worry about.
Edit #1 - SPS in LEO could be spaced every degree of latitude, or perhaps even more closely. Each could serve three clients for 30 minutes on a given orbit.
Service could be modified by demand through control from ground stations managing the network.
If there are 360 satellites (which seems reasonable (at least to me)) then they would serve 360 * 3 or 900 + 180 or 1080 ground stations in each orbit.
But the Earth is rotating underneath, so the total number of ground stations to be served would be greater.
I'm not sure how many ground stations could be served, but I'm assuming that at a minimum, 24*60 minutes divided by 90 minutes (16) tracks are possible.
That would yield 1080 * 16 service opportunities in 24 hours for 360 satellites. pr 17,280 in all.
Edit#2: Google came up with this citation from Wikipedia for Sun Synchronous Polar Orbits ...
Typical Sun-synchronous orbits around Earth are about 600–800 km in altitude, with periods in the 96–100-minute range, and inclinations of around 98°. This is slightly retrograde compared to the direction of Earth's rotation: 0° represents an equatorial orbit, and 90° represents a polar orbit.
Sun-synchronous orbit - Wikipedia
en.wikipedia.org › wiki › Sun-synchronous_orbitEdit#3: Google came up with this estimate of the diameter of the Earth pole-to-pole
Image result for diameter of earth pole to pole
Equatorial vs Polar Diameter:
Because of this, the diameter of the Earth at the equator is about 43 kilometers (27 mi) larger than the pole-to-pole diameter. As a result, the latest measurements indicate that the Earth has an equatorial diameter of 12,756 km (7926 mi), and a polar diameter of 12713.6 km (7899.86 mi).Jun 14, 2008What is the Diameter of Earth? - Universe Todaywww.universetoday.com › diameter-of-earth
Circumference would be 24906 miles, so locating satellites every 100 miles would allow only 249.
Separating the satellites every 10 miles would allow for more interesting total of 2490.
That number times 16 yields 39840 power delivery opportunities.
Thus, the cost of 2490 satellites would be distributed over 39840 ground stations, each of which would receive 30 minutes of delivered solar power each day.
The cost of the ground stations would include storage capability, to allow the 30 minutes of input to be metered out over 24 hours.
Flow batteries might be a good fit for this application.
(th)
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For Louis ... re Post #11
By any chance, are you (possibly?) a few decades behind in your references?
We are talking about distances on the order of 1000 miles (1600 km) or less, as compared to the GEO distance of 22,236 miles (35,786 km).
I'll be very interested in any trustworthy reporting on actual experiments with RF transmission over 1000 miles or less.
Humans have a ** lot ** of experience transmitting (and receiving) RF over that distance.
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repost
For GW Johnson re Sun Synchronous orbits for Personal SPS
Here is a link to a Wikipedia article on sun synchronous orbits, for those in the readership who may wish to refresh ...
https://en.wikipedia.org/wiki/Sun-synchronous_orbit
For GW Johnson ... The US Defense Department just announced a test of a solar panel in the X37b. The announcement implied that the researchers had accomplished something, but I now understand that anything they achieved was of low impact.
What the announcement ** did ** accomplish was to awaken (in my mind at least) awareness that SPS need not necessarily ride out at GEO. Calliban then reminded me (in the Technology Updates topic) that SPS located in GEO would require a large rectenna on the ground, due to dispersion of the microwave beam over the distance involved.
An SPS operating in LEO could deliver substantial power to a smaller receiving antenna, but (as Calliban reminded me) the satellite would be in view for only part of the day, and the Sun would be available for less than half of a day.
In scanning the Wikipedia article cited above, I noted that spy and observation satellites have been placed into sun synchronous orbits for years. There is one category of these orbits (apparently) that allows the satellite to enjoy continuous illumination by the Sun.
Such a satellite, in such an orbit could (presumably) provide 30 minutes or so of high density power to a customer on the ground once a day, but always at the same time each day, although I'm less certain about that detail.
Do you have a suggestion for how to think about this potential business opportunity?
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Sure the orbital mechanics are important for placement but its not the only thing to consider
repost
TH:
Re sun-synchronous orbits: I'm no orbital mechanics expert, as I have said before. I can do the basic two-body textbook model, and I know the necessary "trick" to combine 2-body results to estimate delta-vee almost as accurately as a real 3-body computer code. I can support things on these forums with that capability, which is related to vehicle sizing, not to actual navigation. But I know next-to-nothing about the nonuniform mass distribution stuff that is behind the precession of these sun-synchronous orbits.
Re SPS applications: assuming SPS means "solar power satellite", what I know about that matches up with what you heard from Calliban - that geosynch distances suffer from excessive beam spreading, requiring a very large receiving antenna array.
I do know that this beam-spreading problem is compensated by a steady aiming of the antenna array at the satellite, and by a steady aiming of the beam at the receiving array. The danger, if that aim fails, is the beam irradiating unintended people or hardware: consequences are potentially deadly.
If you put one of these SPS things in a low orbit, and make it sun-synchronous, you solve the problem of always steadily receiving sunlight, but you greatly aggravate both of the aiming problems. The array has to rapidly track the satellite while it is in view, and the satellite has to "hit" (only) the array with its beam, which looks like a fast-moving target to the satellite. That greatly raises the risks of having the beam hit unintended targets.
It's one thing to aim a camera lens at a moving target (especially when rigged to an already-folded optics system in a spy satellite). It is quite another to steer a microwave beam at a fast-moving target very, very accurately, and with utter reliability.
Those are some very serious things to think about. Geosynchronous might well be the easier set of problems to solve.
GW
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The military will take the risk to defeat an enemy that civilians will not...
The already complain about rf energy from a variety of sources as to the cause for cancer and more so its not viable until research and more testing is done....
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Nope. No chance. I've followed this before in the last 5 years or so - because I would love this to be a practical technology - and I checked out the latest on Google and Wikipedia. Nothing much has changed. Meaningful wireless transmission of energy has only been demonstrated over something like a kilometre IIRC.
For Louis ... re Post #11
By any chance, are you (possibly?) a few decades behind in your references?
We are talking about distances on the order of 1000 miles (1600 km) or less, as compared to the GEO distance of 22,236 miles (35,786 km).
I'll be very interested in any trustworthy reporting on actual experiments with RF transmission over 1000 miles or less.
Humans have a ** lot ** of experience transmitting (and receiving) RF over that distance.
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This technology that would be fit for the moon as it does not have any atmosphere to attenuate and the risk to people would be less, as there are far greater risks for crew that would be there. Large satelite panels would block some of the thermal drift for the sun lit side as well as shield spots from radiation.
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For Louis re #16 --- thanks for confirming you've been following the field ...
I noted your use of the word "meaningful" .... that is a reasonable choice, as I think about it, because (of course) humans have been sending "meaningful" RF for over 100 years.
December 12, 1901
On December 12, 1901, Marconi attempted to send the first radio signals across the Atlantic Ocean, in spite of predictions that the radio waves would be lost as the earth curved over that long distance.A Science Odyssey: People and Discoveries: Marconi ... - PBS
www.pbs.org › wgbh › aso › databank › entries
I understand you meant something other than "meaningful" so I'll give you the benefit of the doubt.
The energy required to send a signal to Voyager had to have been on the order of what is required for a power delivery application.
Military radar systems that can observe objects in LEO and beyond are also operating at power levels comparable to those required for this application.
These systems have been operating for many decades ...
June 17, 1935
It is historically correct that, on June 17, 1935, radio-based detection and ranging was first demonstrated in Britain. Watson Watt, Wilkins, and Bowen are generally credited with initiating what would later be called radar in this nation.History of radar - Wikipedia
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For SpaceNut re #17
The idea you've suggested is interesting (to me for sure) .... a polar orbiting SPS around the Moon could deliver power to ground stations under its track while remaining in sunlight. As you pointed out, there is no atmosphere to attenuate the signal.
The ground station would consist of rectenna, which are far more robust than solar panels.
The ground station would need energy storage, but they would need energy storage for a traditional solar panel installation.
That's a suggestion worth pursuing.
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I may be wrong but I think the examples you are quoting relate to radar and radio and are not really relevant because the initial power source becomes diffuse. The most powerful radio transmitter in the world is in any case only 2MW - similar to the capacity of a single, not largish wind turbine.
Meaningful in this case stands for "suggesting that this could be a practical source of energy in the short to middle term". No one disputes you can transfer energy by laser or microwave - it's just a question of how much, how effeciently and at what cost. If we can overcome the technical challenges it will be brilliant.
For Louis re #16 --- thanks for confirming you've been following the field ...
I noted your use of the word "meaningful" .... that is a reasonable choice, as I think about it, because (of course) humans have been sending "meaningful" RF for over 100 years.
December 12, 1901
On December 12, 1901, Marconi attempted to send the first radio signals across the Atlantic Ocean, in spite of predictions that the radio waves would be lost as the earth curved over that long distance.A Science Odyssey: People and Discoveries: Marconi ... - PBS
www.pbs.org › wgbh › aso › databank › entriesI understand you meant something other than "meaningful" so I'll give you the benefit of the doubt.
The energy required to send a signal to Voyager had to have been on the order of what is required for a power delivery application.
Military radar systems that can observe objects in LEO and beyond are also operating at power levels comparable to those required for this application.
These systems have been operating for many decades ...
June 17, 1935
It is historically correct that, on June 17, 1935, radio-based detection and ranging was first demonstrated in Britain. Watson Watt, Wilkins, and Bowen are generally credited with initiating what would later be called radar in this nation.History of radar - Wikipedia
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There is a need for qualified engineers to assist with evaluating the SPS in LEO idea.
I will post a request for assistance in an online list which includes a high proportion of electrical/electronics engineers who specialize in RF applications.
There is no guarantee anyone there will be interested (a) or (b) has the time, and there is no guarantee they will have anything other than a skeptical attitude when approaching the question, but at this point, authoritative guidance would be helpful.
If anyone in the forum active community has an acquaintance who could provide assistance, please invite them to contact NewMarsMember * gmail.com.
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In thinking about the matter over night, and in particular about the observation by GW Johnson (in the Orbital Mechanics topic) that an SPS in LEO would need to be able to establish and maintain pinpoint accuracy while moving in both latitude and longitude with respect to the customer rectenna site, I realized that existing human developed technology is available to handle the problem.
In the military arena, tracking systems capable of delivering payloads to targets moving in three dimensions with respect to the weapons platform are well proven and widely applied in practice around the world. In the civilian arena, the space docking systems that handle automated docking of unmanned vehicles with the ISS are an example of the technology required.
However, this application allows for the transmission of location information from the customer site, with positive (and negative) feedback from the receiver to assist the transmitter in adjusting the focus of the transmission in millisecond increments.
The customer site is going to be authorized to receive power by ground controllers. The ground controllers will provide the coordinates of the site, and the site itself will transmit a beacon. The SPS will lock onto the beacon when it becomes visible by line-of-sight connection, and the transmitter and receiver will exchange power transmission information as the connection continues. The objective of the two partners in this relationship is to maximize delivery of power, so any error in pointing will be corrected rapidly. The transmission will stop completely when the SPS has moved out of range of the receiver, and (presumably) at that point the beam will be directed toward the next authorized customer site in the orbital path.
Concerns about the amount of RF to be delivered by this system are valid and must be addressed.
Since humans have decades of experience with powerful radar transmitters located on Earth, there is (or should be) detailed knowledge of how powerful RF beams affect the air and objects in the path.
Somewhere along the line I read a report (which may be apocryphal) about a radar technician deciding to sit in front of the beam of one of the early warning radars in Alaska to warm up, and receiving too much of a good thing. That story may have been circulated to encourage radar technicians to stay away from the beam itself while it was in operation, but it stayed with me so it may have helped others to avoid a similar fate.
Research on GEO SPS systems (as I remember the reports) has concluded that objects flying through a beam to an Earth based rectenna would not experience excessive heating, and aircraft would not be affected at all if the fuselage is metal.
Still, I'd like to see reports of serious research in this area, as well as estimates of the amount of RF that would be needed in the LEO SPS scenario to justify the investment.
(th)
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This message was posted in the listserver of a group of Electrical and Electronics engineers ...
The NewMars.com/forum is discussing the recent announcement by the US Defense Department, of an experiment collecting solar energy by the X37b test vehicle. The announcement was written to imply that the intent is to determine the feasibility of operating a Solar Power Satellite from Low Earth Orbit, to supply a remote base on Earth.
The technology under development (or at least under consideration) might be applicable to civilian needs. The questions already raised have to do with the strength of RF needed to supply a ground station with enough power to last 24 hours given a 30 minute window once a day to deliver it.
It is normal for some of us humans to be worried about RF in our environment, and those who were advocating SPS from GEO have had to deal with it.
The signal would (presumably) be even stronger in the case of SPS from LEO, because the delivery window is only 30 minutes instead of 24 hours.
If someone in the <group> list is interested in helping the discussion along, please contact me at NewMarsMember * gmail.com
There are other concerns about imposition of microwaves from LEO, as well.
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The radar is simular to a microwave in that the frequency is in the gigs hertz range and that power is less focussed with distance.
The rf of a radio station is in the mega hertz range and it gets an even greater dispersal with distance and will reflect off from the ionosphere to spread it over miles from the transmitter to be received in microvolts of energy.
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Here is a set of links provided by a relative, when I asked what he thought about Solar Power Satellites.
The response I received was surprisingly positive. It included concern about possible risks, but leaned toward concern about saving the environment from fossil fuel use.
I haven't followed these links yet, but trust that they are on point.
https://www.allaboutcircuits.com/news/w … rom-space/
https://www.electronicdesign.com/power- … less-power
https://ijeir.org/administrator/compone … _Final.pdf
https://newatlas.com/energy/wireless-po … interview/
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Hmmm...re the New Atlas story, Emrod seem to making a lot of inflated claims when theircurrent prototype transmits "Just a few watts. Our current prototype is relatively small. It transmits about 40 meters (130 ft). "
The Japanese invested a lot more in this technology and I think got to the position of transmitting over maybe 1 or 2 Kms but development seems to have stalled.
To go from having a 40 metre prototype to claiming there are no major obstacles to transmitting from a geosyncrhonous solar power satellite stationed 36,000 kms away seems a bit bizarre to me.
I hope the development programme goes well but I don't think we are anywhere near beamed solar power from satellites yet.
Here is a set of links provided by a relative, when I asked what he thought about Solar Power Satellites.
The response I received was surprisingly positive. It included concern about possible risks, but leaned toward concern about saving the environment from fossil fuel use.
I haven't followed these links yet, but trust that they are on point.
https://www.allaboutcircuits.com/news/w … rom-space/
https://www.electronicdesign.com/power- … less-power
https://ijeir.org/administrator/compone … _Final.pdf
https://newatlas.com/energy/wireless-po … interview/
(th)
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