Author Topic: Solar Power Satellites  (Read 30788 times)

Offline Greg Hullender

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Solar Power Satellites
« on: 06/21/2014 09:04 PM »
If Japan really decides to build one or more 10,000-ton solar power farms, that would provide business for lots of launches.

http://spectrum.ieee.org/green-tech/solar/how-japan-plans-to-build-an-orbital-solar-farm

The IEEE article includes lots of reasons why this may never get off the ground, of course, but it's interesting to think about what sort of economies of scale might be possible given projects like this. And what sort of projects might be possible given further reductions in price.

Offline Lar

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Re: Solar Power Satellites
« Reply #1 on: 06/22/2014 05:40 AM »
This article was mentioned already in the  SpaceX advances drive for Mars rocket via Raptor power thread

http://forum.nasaspaceflight.com/index.php?topic=34197.msg1192997#msg1192997 

Interested readers may want to review the post I referenced and some of the posts immediately after.
« Last Edit: 06/22/2014 05:43 AM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline TrevorMonty

Re: Solar Power Satellites
« Reply #2 on: 06/22/2014 08:21 AM »
They have a long way to go to compete with terrestrial solar power but there some technologies in pipeline to make it more viable.

SpaceX BFR if it us fully reusable.
Tethers Unlimited SpiderFab.
Increasing Watts/ kg of solar panels.

Japan has talked about beaming power from moon to earth but actually sending power to lunar base from SSP satellite or even earth may be ideal for supplying power 24/7.

Offline cordwainer

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Re: Solar Power Satellites
« Reply #3 on: 06/23/2014 01:56 AM »
Unlike, Musk I think the conversion rates can be made efficient enough for this to be physically practical.  What makes it difficult is the initial cost in infrastructure which makes it non-competitive over other forms of power though. I think fusion research has a better chance in the short term of creating results than all the things that would have to come together to make space based solar power economical.

On a positive note you might be able to increase the efficiency of your microwave rectenna by using photonic crystals to tune the incoming microwaves for better absorption. You could also put your rectenna on a ground tethered high altitude dirigible to lower losses and prevent communication interference posed by beaming through the lower atmosphere.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #4 on: 06/26/2014 11:05 AM »
On a positive note you might be able to increase the efficiency of your microwave rectenna by using photonic crystals to tune the incoming microwaves for better absorption. You could also put your rectenna on a ground tethered high altitude dirigible to lower losses and prevent communication interference posed by beaming through the lower atmosphere.
85% efficient rectennas (5.8GHz) have already been demonstrated in the lab. The way to improve further is to eliminate the schottky diode losses by using synchronous rectification and impedance matching for maximum power transfer.

Beam power losses through the atmosphere are less than 2% for 99% of all weather (including "very cloudy and severe rain" [Kantak, JPL, 2003]). Given that the rectenna needs to be at-least 4.5km across (for 5.8GHz) to meet the diffraction limit of a 1km satellite antenna located at GEO, I'm afraid the prospect of floating it is slim (and unnecessary).

5.8GHz is one of the ISM bands (industrial, scientific & medical), as-is 2.4GHz wi-fi. Interference is possible, but would be confined to the vicinity of the rectenna and the frequency band. Peak beam intensity for most proposals is kept below 300W/m2 (about 1/4 to 1/3 mid-day sun), a level safe for birds, bees and aircraft to fly through.

Offline Nomadd

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Re: Solar Power Satellites
« Reply #5 on: 06/26/2014 11:10 AM »
On a positive note you might be able to increase the efficiency of your microwave rectenna by using photonic crystals to tune the incoming microwaves for better absorption. You could also put your rectenna on a ground tethered high altitude dirigible to lower losses and prevent communication interference posed by beaming through the lower atmosphere.
85% efficient rectennas (5.8GHz) have already been demonstrated in the lab. The way to improve further is to eliminate the schottky diode losses by using synchronous rectification and impedance matching for maximum power transfer.

Beam power losses through the atmosphere are less than 2% for 99% of all weather (including "very cloudy and severe rain" [Kantak, JPL, 2003]). Given that the rectenna needs to be at-least 4.5km across (for 5.8GHz) to meet the diffraction limit of a 1km satellite antenna located at GEO, I'm afraid the prospect of floating it is slim (and unnecessary).

5.8GHz is one of the ISM bands (industrial, scientific & medical), as-is 2.4GHz wi-fi. Interference is possible, but would be confined to the vicinity of the rectenna and the frequency band. Peak beam intensity for most proposals is kept below 300W/m2 (about 1/4 to 1/3 mid-day sun), a level safe for birds, bees and aircraft to fly through.
85% efficient over what distance?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #6 on: 06/26/2014 11:37 AM »
85% efficient over what distance?
Good question!

That is the efficiency for converting the incident beam power falling within the confines of the rectenna.

84% of the beam power is confined within a circular region called the "Airy disk" (George Biddell Airy), which dictates the minimum size of the rectenna and transmit antenna for a given frequency and beam path length. A larger rectenna would capture more of the beam, and could operate away from the equatorial band, e.g. a 12km rectenna could capture 88.5% of the beam power arriving at 20 degrees elevation, or 94.7% from directly overhead.

Other losses are at the satellite-end of the beam and include:

PV efficiency - 40% expected from multi-junction concentrated cells (44.7% demonstrated)
                    -  20% --> >50% expected from future thin-film (e.g. perovskite research, 19% demonstrated)
                    -  bear in-mind that earth-orbit solar flux is 57% greater than equatorial mid-day terrestrial sun, for 24/365.
PMAD (Power Management and Distribution)
                    - early (and some recent) proposals transport electrical power over multi-kilometre distances (from PV cells to microwave generators) and across rotating joints. Peter Glaser's (RIP 2014) original proposal required liquid helium-cooled superconductors.
                     - modern PMADs use "sandwich panel" concepts with distribution distances measured in cm
                     - overall conversion efficiency (electrical --> microwave) could achieve >70%

Offline floss

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Re: Solar Power Satellites
« Reply #7 on: 06/29/2014 01:16 AM »
Beaming power to earth is a pretty non starter (efficency of energy transfer) but using large solar plants to power antimater factories seems plausable .

Plus this would usher in the antimater era and give humanity the stars .

Offline mheney

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Re: Solar Power Satellites
« Reply #8 on: 06/29/2014 01:54 AM »
Beaming power to earth is a pretty non starter (efficency of energy transfer) but using large solar plants to power antimater factories seems plausable .

Plus this would usher in the antimater era and give humanity the stars .


I'm not sure you can say that transmission losses (a well-understood problem) makes a concept a non-starter, but then turn around and call antimatter factories is a plausible alternative...

Offline TrevorMonty

Re: Solar Power Satellites
« Reply #9 on: 06/29/2014 06:32 AM »
Japan plan to test power beaming in next few years by fitting a transmitter to ISS. With 300kw on tap it makes a great test bed.

Offline floss

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Re: Solar Power Satellites
« Reply #10 on: 06/29/2014 11:03 AM »
Beaming power to earth is a pretty non starter (efficency of energy transfer) but using large solar plants to power antimater factories seems plausable .

Plus this would usher in the antimater era and give humanity the stars .


I'm not sure you can say that transmission losses (a well-understood problem) makes a concept a non-starter, but then turn around and call antimatter factories is a plausible alternative...



Just one alternative the fact is that every environmentalist will be up in arms and the building of anything that shoots death rays at earth will have a leagle minefield before it is built .
If the power is used to produce antimatter it would be of great benefit to humanity as a whole and the SSP need not be in Earth Orbit.
I know that initially Antimatter production would be brutally inefficent seeing as none has yet been built yet but we are talking about centuries of upgrades.

Producing power from off world is going to have massive startup costs and there is plenty of resorces on Earth humanity is only tapping the tip of the iceburg so far .

Plus the first Antimatter factory be a high risk effort and it would be handy to put it far away from Earth in case of accidents.







Offline Tass

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Re: Solar Power Satellites
« Reply #11 on: 06/29/2014 01:12 PM »
Beaming power to earth is a pretty non starter (efficency of energy transfer) but using large solar plants to power antimater factories seems plausable .

Plus this would usher in the antimater era and give humanity the stars .


I'm not sure you can say that transmission losses (a well-understood problem) makes a concept a non-starter, but then turn around and call antimatter factories is a plausible alternative...



Just one alternative the fact is that every environmentalist will be up in arms and the building of anything that shoots death rays at earth will have a leagle minefield before it is built .
If the power is used to produce antimatter it would be of great benefit to humanity as a whole and the SSP need not be in Earth Orbit.
I know that initially Antimatter production would be brutally inefficent seeing as none has yet been built yet but we are talking about centuries of upgrades.

Producing power from off world is going to have massive startup costs and there is plenty of resorces on Earth humanity is only tapping the tip of the iceburg so far .

Plus the first Antimatter factory be a high risk effort and it would be handy to put it far away from Earth in case of accidents.

Sending a ray down with the same intensity as sunlight, and which will defocus harmlessly if the pilot signal is interrupted, will have the environmentalists "up in arms", but shipping down packages of power which will explode like a nuke if containment fails, won't?

Offline floss

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Re: Solar Power Satellites
« Reply #12 on: 06/29/2014 01:52 PM »
Beaming power to earth is a pretty non starter (efficency of energy transfer) but using large solar plants to power antimater factories seems plausable .

Plus this would usher in the antimater era and give humanity the stars .


I'm not sure you can say that transmission losses (a well-understood problem) makes a concept a non-starter, but then turn around and call antimatter factories is a plausible alternative...



Just one alternative the fact is that every environmentalist will be up in arms and the building of anything that shoots death rays at earth will have a leagle minefield before it is built .
If the power is used to produce antimatter it would be of great benefit to humanity as a whole and the SSP need not be in Earth Orbit.
I know that initially Antimatter production would be brutally inefficent seeing as none has yet been built yet but we are talking about centuries of upgrades.

Producing power from off world is going to have massive startup costs and there is plenty of resorces on Earth humanity is only tapping the tip of the iceburg so far .

Plus the first Antimatter factory be a high risk effort and it would be handy to put it far away from Earth in case of accidents.

Sending a ray down with the same intensity as sunlight, and which will defocus harmlessly if the pilot signal is interrupted, will have the environmentalists "up in arms", but shipping down packages of power which will explode like a nuke if containment fails, won't?


Who said anything about shipping anything to Earth there is massive markets in space already .Next gen power systems for next gen jobs .(Terraforming Mars and Venus )
You will not get much power with just sunlights intensity and weather happens plus any rectenna will be out in the boonies so power will decrease rapidy .Unless superconducters are avalible which opens other cheaper alternatives.

Offline mheney

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Re: Solar Power Satellites
« Reply #13 on: 06/30/2014 01:03 AM »
According to the web site at http://www.daviddarling.info/encyclopedia/A/antimatterprop.html, current annual antimatter production at CERN and Fermilab (combined) is between 1- 10 nanograms/year.  Hardly an industrial process, and we don't have any facilities the size of CERN in orbit ....  Whereas microwave transmisson of power has been demonstrated many times already ...

And if you're talking about having massive markets in space, then there's your market for beamed power.  Point-to-point power transmission works very well in space.

Finally, if you want to talk environmentalist outrage (politely known as "regulatory issues"), then if you think microwaves is going to cause howling, just wait until you start talking antimatter in industrial quantities.   Because there's a bit of a difference in an accident with a microwave beam and an accident with antimatter.  I'll take the microwaves any day of the week, thank you very much.

Bottom line, dismissing a (technically) demonstrated technology because a speculative, non-existant technology would be superior is a non-starter.  See http://en.wikipedia.org/wiki/Unobtainium

Offline su27k

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Re: Solar Power Satellites
« Reply #14 on: 06/30/2014 03:11 AM »
Peak beam intensity for most proposals is kept below 300W/m2 (about 1/4 to 1/3 mid-day sun)

This may be a problem, think about it, if the power density is less than that of the sun, why not just use the sun light directly? Yes I know there're nights, weather issues with terrestrial solar power, but they seem to be much easier to solve than the problems facing SPS.

Offline bubbagret

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Re: Solar Power Satellites
« Reply #15 on: 06/30/2014 03:30 AM »
Peak beam intensity for most proposals is kept below 300W/m2 (about 1/4 to 1/3 mid-day sun)

This may be a problem, think about it, if the power density is less than that of the sun, why not just use the sun light directly? Yes I know there're nights, weather issues with terrestrial solar power, but they seem to be much easier to solve than the problems facing SPS.

Having the beam at 1 relatively narrow frequency band, even at a lower total areal power, would be considerably more efficient than trying to convert full spectrum sunlight in to usable power. Solar electric usually only converts very specific, narrow frequencies as does solar thermal. That would only be a small percentage of the total solar flux reaching the surface and then at conversion efficiencies that reduce that small percentage even further.

Offline Vultur

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Re: Solar Power Satellites
« Reply #16 on: 06/30/2014 04:07 AM »
Why does the beam intensity have to be so low? Couldn't you just not put the beams on airplane flight routes? Surely the occasional bird being cooked would be greatly outweighed by all the environmental damage from other forms of power that wouldn't be happening (I doubt it would even remotely be comparable to all the bird deaths from hitting skyscrapers and towers and things).

Offline SICA Design

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Re: Solar Power Satellites
« Reply #17 on: 06/30/2014 08:04 AM »
Why does the beam intensity have to be so low? Couldn't you just not put the beams on airplane flight routes? Surely the occasional bird being cooked would be greatly outweighed by all the environmental damage from other forms of power that wouldn't be happening (I doubt it would even remotely be comparable to all the bird deaths from hitting skyscrapers and towers and things).

There are two reasons:

1) There is already a large misplaced public perception that this would be a microwave "death ray", more dangerous than antimatter  :o. At least we have science on our side, giving a fundamental reason why that won't be the case:-

2) That fundamental reason is the diffraction limit; to halve the beam spot at the rectenna (and quadruple its intensity at the centre) requires doubling the diameter of the solar power satellite (SPS). To get the spot size down to 1 metre (where it could REALLY cause some sci-fi damage!) would require the satellite diameter (at GEO) to increase to 3,000km across.

For a geostationary SPS, the overall costs optimise for a design approximately 1km across and for power levels of 1GW or more. The reason we don't have one yet is due to launch costs, which Skylon and/or SpaceX FHR could address.
« Last Edit: 06/30/2014 09:09 AM by SICA Design »

Offline Asteroza

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Re: Solar Power Satellites
« Reply #18 on: 06/30/2014 08:59 AM »
All the more reason why laser SPS has it's ups and downs. Small sizes are easier to demo overall. Tight spot size is great for reducing receiver area, but then it functionally approaches weapons grade beam densities rather quickly. Though I like to roll out that most space things are weapons already (most if not all satellites potentially can become kinetic impactor weapons from orbit).

The old SPS studies chose microwave because laser wasn't ready, and they chose the density to appeal to the average man who subjectively didn't relish the idea of being microwaved from orbit. As mentioned above, the physics says it needs to be 1Km or more for the transmitting antenna, at around 1GW based on those constraints. That fundamentally makes GEO demos hard. The japanese intend to do a LEO microwave demo as a proof-of-concept though, which is easier due to the distances involved at the expense of antenna tracking.

I have a personal belief (not necessarily backed with facts mind you) that laser (either laser thermal or hybrid laser PV/thermal) would be a better choice for the receiver architecture considering the process heat applications and not just electrical use. That, and it would enable a favorite pet idea, laser assisted Skylons.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #19 on: 06/30/2014 09:46 AM »
All the more reason why laser SPS has it's ups and downs. Small sizes are easier to demo overall. Tight spot size is great for reducing receiver area, but then it functionally approaches weapons grade beam densities rather quickly. Though I like to roll out that most space things are weapons already (most if not all satellites potentially can become kinetic impactor weapons from orbit).

Very true!

Quote
The old SPS studies chose microwave because laser wasn't ready, and they chose the density to appeal to the average man who subjectively didn't relish the idea of being microwaved from orbit. As mentioned above, the physics says it needs to be 1Km or more for the transmitting antenna, at around 1GW based on those constraints. That fundamentally makes GEO demos hard. The japanese intend to do a LEO microwave demo as a proof-of-concept though, which is easier due to the distances involved at the expense of antenna tracking.

Microwaves between 1-10GHz were also chosen for their ability to pass through thick cloud and rain; the 5.8GHz ISM band is near optimal.

I have a concept for a 1 gigawatt SPS called HESPeruS - Highly Elliptical Solar Power Satellite - which traverses a Molniya orbit, a highly-elliptical orbit first used by the Russians. Like GEO, this is also a synchronous orbit, in-that the SPS loiters over the same two northern hemisphere locations alternately every 12 hours. There are several benefits:

* HESPeruS is of rigid construction, built from multiple hexagonal modules into an essentially flat structure capable of collecting sunlight and beaming to any latitude  above 45 degrees, without the complex rotating optics as needed for the 2nd Japanese option (and ALL GEO satellites).
* HESPeruS is complementary to GEO space solar power proposals, which suffer additional losses when beaming to high latitudes; 30% of Earth's ice-free land and a $7 trillion economy is located above 45 degrees latitude.
* It's 5.8GHz antenna is distributed over the full 4.4km diameter, with individual elements vacuum-spaced by <25mm, drawing power (10s of milliwatts) from local PV cells which point directly at the sun throughout the orbit - so negligible distribution losses.
* The large antenna to PV ratio means it can operate within the diffraction limit at one-tenth scale (100MW), meaning a pilot system can be launched at lower cost, and then expanded later (Molniya is a servicable orbit!).
* It costs less than half as much (principally propellant mass) to place a satellite on a Molniya orbit than it does to GEO.
* Just 3 HESPeruS satellites can supply 1GW continuous (24/365) power to two rectenna sites, such as the UK and Japan.

Quote
I have a personal belief (not necessarily backed with facts mind you) that laser (either laser thermal or hybrid laser PV/thermal) would be a better choice for the receiver architecture considering the process heat applications and not just electrical use. That, and it would enable a favorite pet idea, laser assisted Skylons.

That's Keith Henson's idea (he comments here) - hopefully his paper will be published around the same time as mine!

(Edited for typos)
« Last Edit: 06/30/2014 07:42 PM by SICA Design »

Offline SICA Design

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Re: Solar Power Satellites
« Reply #20 on: 06/30/2014 07:36 PM »
Peak beam intensity for most proposals is kept below 300W/m2 (about 1/4 to 1/3 mid-day sun)

This may be a problem, think about it, if the power density is less than that of the sun, why not just use the sun light directly? Yes I know there're nights, weather issues with terrestrial solar power, but they seem to be much easier to solve than the problems facing SPS.

If you have access to a desert wasteland then why not use it? India announced "The World's Largest Solar Power Plant" at 4GW: http://www.scientificamerican.com/article/india-to-build-worlds-largest-solar-power-plant/

When you look deeper, that 4GW is actually "6.4 billion kilowatt-hours per year", in other words an average of 730MW. At a construction cost of $4.4 billion, that's $6B/GW (the build cost for a typical nuclear power station is $8B/GW) - and that doesn't include any provision for energy storage; a 17.5 million kilowatt-hour battery would probably cost many times the plant itself - and would supply an average of 730MW for...     one day.

I'm sure all these cost and storage issues can be resolved (and will be) over time.

The solar plant covers an area of 77 square kilometres - which arranged as a disc would be nearly 10km across, or nearly 5 times greater land area than a 4.5km diameter rectenna. The land under solar panels is shaded and unsuitable for farming. The land under the rectenna receives just 5% of the stray microwave beam (max 15W/m2 for 300W/m2 peak beam intensity), but more than 90% of the sunlight.

The mature launch price for a 1GW HESPeruS is $3.2B (for all costs recovered, according to REL data).

[EDIT: to be fair, you need 3 HESPeruS to supply 2GW total for 24/365 shared between UK & Japan, so that's $4.8B/GW]

« Last Edit: 06/30/2014 07:56 PM by SICA Design »

Offline gospacex

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Re: Solar Power Satellites
« Reply #21 on: 06/30/2014 09:02 PM »
The land under solar panels is shaded and unsuitable for farming.

There are forest plants which *require* shade to grow. Some of them have edible berries.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #22 on: 06/30/2014 09:50 PM »
The land under solar panels is shaded and unsuitable for farming.

There are forest plants which *require* shade to grow. Some of them have edible berries.

Thanks for the info

Offline bad_astra

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Re: Solar Power Satellites
« Reply #23 on: 06/30/2014 10:14 PM »
Why not just pump a fraction of the vast amount of money this project would cost into a commercial fusion reactor?

It was a nice idea in the 70's when shuttles were going to fly once a week, fusion was 50 years away, and O'neal needed  a reason to design his wondrous colonies. This idea makes little sense now.
"Contact Light" -Buzz Aldrin

Offline dror

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Re: Solar Power Satellites
« Reply #24 on: 06/30/2014 10:26 PM »
85% efficient over what distance?
Good question!

That is the efficiency for converting the incident beam power falling within the confines of the rectenna.
...
84% of the beam power is confined within a circular region called the "Airy disk" (George Biddell Airy), which dictates the minimum size of the rectenna and transmit antenna for a given frequency and beam path length.
...
Other losses are at the satellite-end of the beam and include:

PV efficiency - 40% expected from multi-junction concentrated cells (44.7% demonstrated)
                    -  20% --> >50% expected from future thin-film (e.g. perovskite research, 19% demonstrated)
                    -  bear in-mind that earth-orbit solar flux is 57% greater ...
...
                     - overall conversion efficiency (electrical --> microwave) could achieve >70%

So we add to that 2.5 longer time (24 hours instead of ~10) and we get:

Solar satelite energy = solar power plant energy × 0.85 × 0.84 × 0.7 × 1.57 × 2.5 = ~1.96×solar_power_plant_energy

So the satelite produces about twice as much energy per unit area, but requiers launch, structure and transmiter/antena/rectena infrastructure and 4.5 km radius on the ground.
The land solar plant uses about 5 times more erea of some desert..
I seriously dought the economics for that to succeed.

On top of that, any beamed energy from GEO is aditional heat for earth and will increase global warming as a fact.
 
"If we crave some cosmic purpose, then let us find ourselves a worthy goal. "
Carl Sagan, Pale Blue Dot

Offline SICA Design

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Re: Solar Power Satellites
« Reply #25 on: 06/30/2014 10:33 PM »
Why not just pump a fraction of the vast amount of money this project would cost into a commercial fusion reactor?

It was a nice idea in the 70's when shuttles were going to fly once a week, fusion was 50 years away, and O'neal needed  a reason to design his wondrous colonies. This idea makes little sense now.

I'm all for fusion, but the closest thing to a commercial reactor is ITER, predicted to produce 500MW of HEAT (zero electricity) at a development cost "expected to be in excess of €15 billion" (Wikipedia).

That's $20B, or $40B/GW, or $67B/GW if you assume 60% thermal-->electrical efficiency.

Meanwhile, we have access to a fully functioning fusion reactor just 150 million km away.

We KNOW how to beam microwaves from space; we do it all the time from comms sats and GPS, it's a matter of scaling up and lowering launch costs.

Offline QuantumG

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Re: Solar Power Satellites
« Reply #26 on: 06/30/2014 10:34 PM »
It was a nice idea in the 70's when shuttles were going to fly once a week, fusion was 50 years away, and O'neal needed  a reason to design his wondrous colonies. This idea makes little sense now.

Fusion is still 50 years away, reusable rockets are almost here (well, first stage reuse anyway, if SpaceX can actually launch again), the good professor's name was O'Neill, his colonies are still a good idea, and space solar power does indeed make more sense if you're looking at it from the perspective of people in space trying to produce something to trade with people on Earth.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #27 on: 06/30/2014 10:55 PM »
So we add to that 2.5 longer time (24 hours instead of ~10) and we get:

Solar satelite energy = solar power plant energy × 0.85 × 0.84 × 0.7 × 1.57 × 2.5 = ~1.96×solar_power_plant_energy

So the satelite produces about twice as much energy per unit area, but requiers launch, structure and transmiter/antena/rectena infrastructure and 4.5 km radius on the ground.
The land solar plant uses about 5 times more erea of some desert..
I seriously dought the economics for that to succeed.

As I said, if you have access to a handy desert, use it - just use it more effectively than India or Ivanpah (Ivanpah... ask me, please  :D).

http://www.contemporaryenergy.co.uk/picts/solarm1.gif

The UK averages about 2.5kWh/m2 insolation per day, or 104W/m2. In-space average is 1367W

I make that 13 times better, not "twice as much"

Quote
On top of that, any beamed energy from GEO is aditional heat for earth and will increase global warming as a fact.

An 85% efficient rectenna reflects about 5% beam power back into space, so 10% is direct waste heat.
For 1GW to the grid, that's <120MW into the environment.

The best gas power stations have about 60% thermal efficiency, i.e. 40% direct waste heat into the environment.

For 1GW to the grid, that's 667MW into the environment.

Replacing 1GW of gas-fired power with equivalent SBSP reduces Earth's heat load by 547MW (fact).

In practice, the waste heat is negligible compared with the Earth's total insolation and the effect of C02.

Offline Asteroza

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Re: Solar Power Satellites
« Reply #28 on: 06/30/2014 11:52 PM »
All the more reason why laser SPS has it's ups and downs. Small sizes are easier to demo overall. Tight spot size is great for reducing receiver area, but then it functionally approaches weapons grade beam densities rather quickly. Though I like to roll out that most space things are weapons already (most if not all satellites potentially can become kinetic impactor weapons from orbit).

Very true!

Quote
The old SPS studies chose microwave because laser wasn't ready, and they chose the density to appeal to the average man who subjectively didn't relish the idea of being microwaved from orbit. As mentioned above, the physics says it needs to be 1Km or more for the transmitting antenna, at around 1GW based on those constraints. That fundamentally makes GEO demos hard. The japanese intend to do a LEO microwave demo as a proof-of-concept though, which is easier due to the distances involved at the expense of antenna tracking.

Microwaves between 1-10GHz were also chosen for their ability to pass through thick cloud and rain; the 5.8GHz ISM band is near optimal.

I have a concept for a 1 gigawatt SPS called HESPeruS - Highly Elliptical Solar Power Satellite - which traverses a Molniya orbit, a highly-elliptical orbit first used by the Russians. Like GEO, this is also a synchronous orbit, in-that the SPS loiters over the same two northern hemisphere locations alternately every 12 hours. There are several benefits:

* HESPeruS is of rigid construction, built from multiple hexagonal modules into an essentially flat structure capable of collecting sunlight and beaming to any latitude  above 45 degrees, without the complex rotating optics as needed for the 2nd Japanese option (and ALL GEO satellites).
* HESPeruS is complementary to GEO space solar power proposals, which suffer additional losses when beaming to high latitudes; 30% of Earth's ice-free land and a $7 trillion economy is located above 45 degrees latitude.
* It's 5.8GHz antenna is distributed over the full 4.4km diameter, with individual elements vacuum-spaced by <25mm, drawing power (10s of milliwatts) from local PV cells which point directly at the sun throughout the orbit - so negligible distribution losses.
* The large antenna to PV ratio means it can operate within the diffraction limit at one-tenth scale (100MW), meaning a pilot system can be launched at lower cost, and then expanded later (Molniya is a servicable orbit!).
* It costs less than half as much (principally propellant mass) to place a satellite on a Molniya orbit than it does to GEO.
* Just 3 HESPeruS satellites can supply 1GW continuous (24/365) power to two rectenna sites, such as the UK and Japan.

Quote
I have a personal belief (not necessarily backed with facts mind you) that laser (either laser thermal or hybrid laser PV/thermal) would be a better choice for the receiver architecture considering the process heat applications and not just electrical use. That, and it would enable a favorite pet idea, laser assisted Skylons.

That's Keith Henson's idea (he comments here) - hopefully his paper will be published around the same time as mine!

(Edited for typos)

How does HESPeruS handle local sunrise/sunset orientation with respect to downlink antenna tracking? You appear to describe a single flat panel, but at local sunrise it will be edge-on with respect to the ground so the phased array aspect of the distributed aperture won't do you any favors there.

Offline su27k

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Re: Solar Power Satellites
« Reply #29 on: 07/01/2014 04:14 AM »
The mature launch price for a 1GW HESPeruS is $3.2B (for all costs recovered, according to REL data).

[EDIT: to be fair, you need 3 HESPeruS to supply 2GW total for 24/365 shared between UK & Japan, so that's $4.8B/GW]

Thanks for the numbers, they're interesting to look at. For the launch price, I assume this is using Skylon? Also what about the cost of the satellite themselves and the receivers? Japanese's plan seems to have an artificial island as receiver, that can't be cheap.

Offline dror

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Re: Solar Power Satellites
« Reply #30 on: 07/01/2014 07:10 AM »
So we add to that 2.5 longer time (24 hours instead of ~10) and we get:

Solar satelite energy = solar power plant energy × 0.85 × 0.84 × 0.7 × 1.57 × 2.5 = ~1.96×solar_power_plant_energy

So the satelite produces about twice as much energy per unit area, but requiers launch, structure and transmiter/antena/rectena infrastructure and 4.5 km radius on the ground.
The land solar plant uses about 5 times more erea of some desert..
I seriously dought the economics for that to succeed.

As I said, if you have access to a handy desert, use it - just use it more effectively than India or Ivanpah (Ivanpah... ask me, please  :D).

http://www.contemporaryenergy.co.uk/picts/solarm1.gif

The UK averages about 2.5kWh/m2 insolation per day, or 104W/m2. In-space average is 1367W

I make that 13 times better, not "twice as much"
But satelites has about 50% convertion panelty (0.84×0.85×0.7) that ground based facility dont have so it is about 7.5 times better for England and "about twice as much" for low altitude ereas.
Quote
Quote
On top of that, any beamed energy from GEO is aditional heat for earth and will increase global warming as a fact.

An 85% efficient rectenna reflects about 5% beam power back into space, so 10% is direct waste heat.
For 1GW to the grid, that's <120MW into the environment.

The best gas power stations have about 60% thermal efficiency, i.e. 40% direct waste heat into the environment.

For 1GW to the grid, that's 667MW into the environment.

Replacing 1GW of gas-fired power with equivalent SBSP reduces Earth's heat load by 547MW (fact).

In practice, the waste heat is negligible compared with the Earth's total insolation and the effect of C02.
All of the energy ends up as heat either way. 1 GW heat of microwave beam equals 1 GW heat of burnt coal or degraded plutonium.
When comparing to another non sustainable alternative, of course both are as bad.
I compared it to solar energy which uses the heat flux that is already coming to earth so it does not add to global warming (disregarding albedo difrences caused by the ground based panels) to show that space based solar energy cant be counted as sustainable, in opose to the general opinion.
"If we crave some cosmic purpose, then let us find ourselves a worthy goal. "
Carl Sagan, Pale Blue Dot

Offline SICA Design

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Re: Solar Power Satellites
« Reply #31 on: 07/01/2014 07:58 AM »
How does HESPeruS handle local sunrise/sunset orientation with respect to downlink antenna tracking? You appear to describe a single flat panel, but at local sunrise it will be edge-on with respect to the ground so the phased array aspect of the distributed aperture won't do you any favors there.

HESPeruS modules comprise a 3:1 stepped planar array, with fully integrated elements (PV + PMAD + Tx) at the half-wavelength scale (~25mm). The PV is at 90 degrees to the nominal boresight ( = rotation axis, normal to ecliptic), with the whole SPS rotating once-per-year to maintain PV directly sun-facing. The diagram shows the polar plot and local radiation pattern modelled for 22 elements.

HESPeruS travels along a highly elliptical Molniya orbit, loitering at northern apogee (40,000km) with a high-speed pass of the southern hemisphere at 450km perigee ("Molniya" == "Lightning", IIRC for its speed). I've defined "sunrise" as an SPS elevation of 20 degrees seen at the rectenna (northern latitudes above 45 degrees), which is sized accordingly (12km diameter).

Typical beam times are 9 hours 29 minutes for each 11 hour 58 minute orbit, satisfying elevation (>20 deg), beam sweep (+/- 50 deg) and diffraction limits (using effective apertures).

Offline Alf Fass

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Re: Solar Power Satellites
« Reply #32 on: 07/01/2014 08:07 AM »


As I said, if you have access to a handy desert, use it - just use it more effectively than India or Ivanpah (Ivanpah... ask me, please  :D).

http://www.contemporaryenergy.co.uk/picts/solarm1.gif

The UK averages about 2.5kWh/m2 insolation per day, or 104W/m2. In-space average is 1367W

I make that 13 times better, not "twice as much"


that 104W/m2 is for an unsteered surface flat to the ground.
When my information changes, I alter my conclusions. What do you do, sir?
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Offline SICA Design

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Re: Solar Power Satellites
« Reply #33 on: 07/01/2014 08:13 AM »
The UK averages about 2.5kWh/m2 insolation per day, or 104W/m2. In-space average is 1367W

I make that 13 times better, not "twice as much"
But satelites has about 50% convertion panelty (0.84×0.85×0.7) that ground based facility dont have so it is about 7.5 times better for England and "about twice as much" for low altitude ereas.
Quote
Quote
On top of that, any beamed energy from GEO is aditional heat for earth and will increase global warming as a fact.

An 85% efficient rectenna reflects about 5% beam power back into space, so 10% is direct waste heat.
For 1GW to the grid, that's <120MW into the environment.

The best gas power stations have about 60% thermal efficiency, i.e. 40% direct waste heat into the environment.

For 1GW to the grid, that's 667MW into the environment.

Replacing 1GW of gas-fired power with equivalent SBSP reduces Earth's heat load by 547MW (fact).

In practice, the waste heat is negligible compared with the Earth's total insolation and the effect of C02.
All of the energy ends up as heat either way. 1 GW heat of microwave beam equals 1 GW heat of burnt coal or degraded plutonium.
When comparing to another non sustainable alternative, of course both are as bad.
I compared it to solar energy which uses the heat flux that is already coming to earth so it does not add to global warming (disregarding albedo difrences caused by the ground based panels) to show that space based solar energy cant be counted as sustainable, in opose to the general opinion.
Yes, SBSP is typically 7.5 times better than non-tracking terrestrial PV (including all losses) for northern latitudes. How much benefit do you associate with predictable baseload power? How much cost do you associate with storage to overcome intermittency?

The best terrestrial PV (concentrated) is still about 40% efficient, with low albedo, so 40%-60% waste heat rejected to the environment. I'm happy to disregard albedo; all rejected and useful power ends up as heat - it's still negligible compared with solar influx and heat trapping due to C02.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #34 on: 07/01/2014 08:27 AM »
The mature launch price for a 1GW HESPeruS is $3.2B (for all costs recovered, according to REL data).

[EDIT: to be fair, you need 3 HESPeruS to supply 2GW total for 24/365 shared between UK & Japan, so that's $4.8B/GW]

Thanks for the numbers, they're interesting to look at. For the launch price, I assume this is using Skylon? Also what about the cost of the satellite themselves and the receivers? Japanese's plan seems to have an artificial island as receiver, that can't be cheap.

Yes, launch price is based on mature Skylon operations, including servicing missions for Fluyt. Data was kindly supplied by REL specifically for launching 10 tonnes payload (HESPeruS + Fluyt propellant) to 300km orbit at 63.4deg inclination, with construction via Fluyt carrying 49 tonnes of HESPeruS to Molniya before returning to 300km.

From memory, JAXA was assuming much higher beam intensity - which would have to be away from population centres.

I've focussed on launch price, which has traditionally been the dominant factor. I don't yet have useful materials costs, which will depend on mass production.

Fortunately, wireless comms (incl 5.8GHz WiFi) and terrestrial solar are both driving research and mass production in the right direction.
« Last Edit: 07/01/2014 08:32 AM by SICA Design »

Offline Asteroza

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Re: Solar Power Satellites
« Reply #35 on: 07/01/2014 08:59 AM »
Japanese construction companies (the big general contractors) are addicted to large civil works projects like a crack fiend. That, and the general japanese government view that large civil works projects are the preferred form of economic stimulus (via construction worker salary trickle down economics effects).

That said, rather than a true artificial island, they may go for a megafloat modular concrete barge island. There's currently on the table a potential project for a large offshore megafloat based heliport structure to service offshore oil/gas rigs which are too far to service by conventional helicopter easily from japan. Though at the scales involved, a PSP type module for the megafloat rather than a conventional rectangular barge may be a better option.

Offline Asteroza

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Re: Solar Power Satellites
« Reply #36 on: 07/01/2014 09:16 AM »
How does HESPeruS handle local sunrise/sunset orientation with respect to downlink antenna tracking? You appear to describe a single flat panel, but at local sunrise it will be edge-on with respect to the ground so the phased array aspect of the distributed aperture won't do you any favors there.

HESPeruS modules comprise a 3:1 stepped planar array, with fully integrated elements (PV + PMAD + Tx) at the half-wavelength scale (~25mm). The PV is at 90 degrees to the nominal boresight ( = rotation axis, normal to ecliptic), with the whole SPS rotating once-per-year to maintain PV directly sun-facing. The diagram shows the polar plot and local radiation pattern modelled for 22 elements.

HESPeruS travels along a highly elliptical Molniya orbit, loitering at northern apogee (40,000km) with a high-speed pass of the southern hemisphere at 450km perigee ("Molniya" == "Lightning", IIRC for its speed). I've defined "sunrise" as an SPS elevation of 20 degrees seen at the rectenna (northern latitudes above 45 degrees), which is sized accordingly (12km diameter).

Typical beam times are 9 hours 29 minutes for each 11 hour 58 minute orbit, satisfying elevation (>20 deg), beam sweep (+/- 50 deg) and diffraction limits (using effective apertures).

Maybe I'm not understanding correctly, but what happens when the SPS lines up with the day/night terminator line while near the top of the Molniya loiter then, unless you phase orbits to avoid that scenario?

Offline gospacex

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Re: Solar Power Satellites
« Reply #37 on: 07/01/2014 10:16 AM »
The best terrestrial PV (concentrated) is still about 40% efficient, with low albedo, so 40%-60% waste heat rejected to the environment. I'm happy to disregard albedo; all rejected and useful power ends up as heat - it's still negligible compared with solar influx and heat trapping due to C02.

You didn't understand the argument. With terrestrial solar panels, you capture as useful energy some energy which *would otherwise end up absorbed by Earth anyway*. With SBSP, the energy you capture and send to Earth *would otherwise fly past the planet*.

Offline Alf Fass

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Re: Solar Power Satellites
« Reply #38 on: 07/01/2014 10:21 AM »
The best terrestrial PV (concentrated) is still about 40% efficient, with low albedo, so 40%-60% waste heat rejected to the environment. I'm happy to disregard albedo; all rejected and useful power ends up as heat - it's still negligible compared with solar influx and heat trapping due to C02.

You didn't understand the argument. With terrestrial solar panels, you capture as useful energy some energy which *would otherwise end up absorbed by Earth anyway*. With SBSP, the energy you capture and send to Earth *would otherwise fly past the planet*.

A pointless argument, whether space or surface based the difference it makes to the amount of energy the Earth receives is truly negligible.
When my information changes, I alter my conclusions. What do you do, sir?
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Offline SICA Design

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Re: Solar Power Satellites
« Reply #39 on: 07/01/2014 10:33 AM »
Maybe I'm not understanding correctly, but what happens when the SPS lines up with the day/night terminator line while near the top of the Molniya loiter then, unless you phase orbits to avoid that scenario?

HESPeruS is never in Earth's shadow when other beam constraints are met. A Molniya orbit is inclined at 63.4deg taking it WAY above the northern hemisphere. The diagram is not to scale (obviously), but the solar angle (shown from Earth's tilted perspective) and orbit proportions are correct. The "SPS" represents a small section of one module - the tiered arrangement is at ~25mm scale.

Were you considering something similar to 70 minute GEO outtages during Spring/Vernal equinoxes?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #40 on: 07/01/2014 10:42 AM »
You didn't understand the argument. With terrestrial solar panels, you capture as useful energy some energy which *would otherwise end up absorbed by Earth anyway*. With SBSP, the energy you capture and send to Earth *would otherwise fly past the planet*.

It does not matter whether you include terrestrial PV albedo (making light reflective sandy deserts much darker) or not:

It is still insignificant compared with total solar influx and GHG heat trapping.
« Last Edit: 07/01/2014 10:44 AM by SICA Design »

Offline gospacex

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Re: Solar Power Satellites
« Reply #41 on: 07/01/2014 10:45 AM »
You didn't understand the argument. With terrestrial solar panels, you capture as useful energy some energy which *would otherwise end up absorbed by Earth anyway*. With SBSP, the energy you capture and send to Earth *would otherwise fly past the planet*.

It does not matter whether you include terrestrial PV albedo (making light reflective sandy deserts much darker) or not:

It is still insignificant compared with total solar influx and GHG heat trapping.

I didn't say it matters. I said that your argument "but terrestrial solar PV also dissipates waste heat" is wrong, because that solar energy would arrive and be dissipated in this location *anyway*.
« Last Edit: 07/01/2014 10:47 AM by gospacex »

Offline SICA Design

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Re: Solar Power Satellites
« Reply #42 on: 07/01/2014 10:51 AM »
I didn't say it matters. I said that your argument "but terrestrial solar PV also dissipates waste heat" is wrong, because that solar energy would arrive and be dissipated in this location *anyway*.

I'm glad we agree it doesn't matter.

Offline dror

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Re: Solar Power Satellites
« Reply #43 on: 07/01/2014 12:56 PM »
I didn't say it matters. I said that your argument "but terrestrial solar PV also dissipates waste heat" is wrong, because that solar energy would arrive and be dissipated in this location *anyway*.

I'm glad we agree it doesn't matter.
It may not matter for one satelite.
How many satelites can you build befor it starts to matter?
50 GW?
500 GW?
5 TW?

Btw, tracking modules which combine concentrated thermal electric and pv can get 60 - 80% efficient.
"If we crave some cosmic purpose, then let us find ourselves a worthy goal. "
Carl Sagan, Pale Blue Dot

Offline JasonAW3

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Re: Solar Power Satellites
« Reply #44 on: 07/01/2014 01:20 PM »
Ok guys,

     This may seem like a dumb idea, but, instead of spending hundreds of billions of dollars to build a solar array in space, why not send up an inflatable array using thin film solar panels to convert sunlight to electricity, an inflatable directional microwave antenna on the back to transmit the energy back down to Earth and strategically placed solar electric thrusters to maintain attitude as needed.

     Using a thin mylar film as the inflatable structure, you should be able to get at least 1 kilometer of solar array per ton of mass.  Assuming the microwave antenna and gear plus the solar electric thrusters mss about 10 tons, bosting a 30 ton mass into Geosynch orbit should give us a 20 kilometer array that should be able generate at least 215 Gigawatts.

     There are a number of launchers that should be able to boost it into orbit and more than enough upper stages that can boost 30tons to Geosynch orbit.
My God!  It's full of universes!

Offline SICA Design

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Re: Solar Power Satellites
« Reply #45 on: 07/01/2014 01:21 PM »
I didn't say it matters. I said that your argument "but terrestrial solar PV also dissipates waste heat" is wrong, because that solar energy would arrive and be dissipated in this location *anyway*.

I'm glad we agree it doesn't matter.
It may not matter for one satelite.
How many satelites can you build befor it starts to matter?
50 GW?
500 GW?
5 TW?

World consumption in 2008 was about 16.4TW, it would need to grow by 8-10,000 times to reach parity with total insolation:
http://en.wikipedia.org/wiki/Solar_energy
http://en.wikipedia.org/wiki/World_energy_consumption

Quote
Btw, tracking modules which combine concentrated thermal electric and pv can get 60 - 80% efficient.

Ivanpah manages 2.7% peak efficiency at $19.6B/GW build cost.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #46 on: 07/01/2014 01:24 PM »

Offline Asteroza

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Re: Solar Power Satellites
« Reply #47 on: 07/02/2014 12:33 AM »
Maybe I'm not understanding correctly, but what happens when the SPS lines up with the day/night terminator line while near the top of the Molniya loiter then, unless you phase orbits to avoid that scenario?

HESPeruS is never in Earth's shadow when other beam constraints are met. A Molniya orbit is inclined at 63.4deg taking it WAY above the northern hemisphere. The diagram is not to scale (obviously), but the solar angle (shown from Earth's tilted perspective) and orbit proportions are correct. The "SPS" represents a small section of one module - the tiered arrangement is at ~25mm scale.

Were you considering something similar to 70 minute GEO outtages during Spring/Vernal equinoxes?

No no, it wasn't equinox outages. I had pictured HESPeruS to be a single contiguous flat panel, along the lines of currently proposed sandwich panels for SPS, thus only showing one large contiguous planar area (where the emitters would be mounted across the entire area of the panel) and one nadir edge to earth. Thus, if edge on to earth or close, you go beyond the reasonable beam steering limits of a phased array. The stepped venetian blind structure you show where the emitters line the long linear strip panel edges neatly sidesteps that problem. Are the steps a fully fixed structure then? Though that makes for interesting orientation issues, likely compensated by smart precession and beam steering.


Bad thought of the day, the high speed pass portion is pretty low (as you say, 450 Km perigee).  Is there the possibility of using the beamed power of the SPS to power an LV upper stage or orbital tug during the high speed pass, as nominally the odds of a terrestrial power user being in the footprint of the high speed pass would be low? At such close range, the beam spot is much tighter and have utility in various ways. An inflated ring rectenna for an orbital tug could power electric propulsion systems, and Parkin's microwave thermal rocket work would be applicable (AKA microwave Skylon variant of Henson's laser Skylon, and the associated SPS bootstrapping)

Offline SICA Design

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Re: Solar Power Satellites
« Reply #48 on: 07/02/2014 08:18 AM »
Asteroza,

HESPeruS has some commonality with sandwich panels including:
* modular construction
* short distance power distribution
* no single point power bottleneck, such as a rotating joint

As shown, the "venetian blind" sections combine into a hexagonal module <4.8m across vertices. Each module is actually a subtle 3D tetrahedron for rigidity, which is continued across multiple fractal scales (eliminating the requirement for additional truss sections or other support backbone). I have done some further work which solves high density stacking issues within the Skylon hold (must be limited by payload mass not volume!).

The diagram also shows the option for thin-film or concentrated PV at each element. Quad junction CPV has been demonstrated at 44.7% efficiency (40% assumed). Thin film PV (eg perovskite) offers lower mass, but cannot yet match efficiency (though huge gains have been made in a short period, from 3% to currently 19%).

I have discussed the possibility of boot-strapping construction (using one SPS to boost the components for another into Molniya via microwave thermal propulsion) with Keith Henson. However, he suggests the orbital phasing and beam times will not work in its favour.

[Edit]
Quote
Though that makes for interesting orientation issues, likely compensated by smart precession and beam steering.
The boresight beam axis is also the rotation axis, aligned normal to the ecliptic. The whole SPS rotates once per year to maintain PV (or concentrating fresnel reflectors) face-on to the sun. At perigee, the SPS will be travelling mostly edge-on to the residual atmosphere. Not quite GOCE streamlining, but better than the alternative if drag is to be minimised. OTOH, there is no junkyard orbit required for end-of-life modules; only a small nudge will ensure re-entry happens in a predictable timeframe.

Beam steering is retrodirective, based on synchronised sampling and time-reversal of the incoming 40.68MHz pilot beam wavefront (with minimally accurate targeting performed by the rectenna ground facility). The SPS requires no "knowledge" of where the rectenna actually is, but may need to perform small phase corrections (e.g. linear prediction) to allow for RF time-of-flight delays.

« Last Edit: 07/02/2014 12:17 PM by SICA Design »

Offline Hanelyp

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Re: Solar Power Satellites
« Reply #49 on: 07/02/2014 07:51 PM »
How does HESPeruS keep modules on opposite sides of the array in phase for beam forming?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #50 on: 07/02/2014 09:53 PM »
How does HESPeruS keep modules on opposite sides of the array in phase for beam forming?
The key is synchronisation, both inter-module and intra-module (between all 25 billion elements). Its covered over several pages, but I'll try and summarise:

* Distribute a synchronised timing reference across the whole system, linked to the Pilot Beam frequency (40.68MHz)
* Perform synchronised sampling of the Pilot Beam wave-front at several points across each module to determine phase values (three points on a plane).
* Use time-of-flight knowledge and recent phase history to predict small phase corrections for RF round-trip delay.
* Distribute two time-reversed phase values (and the timing reference) to each element in a linear string.
* At each element, synchronise a 1:143 PLL to the position-weighted average of the two phases to generate a local 5.8GHz power beam.

Inter-module uses 100GHz duplex fibre (as for standard Ethernet) at the six module sides - there are no electrical connections between modules. One module is designated as "Master" (could be any; not position dependent).

A unique duplex path is determined between all functioning modules (routes around any failures). The Master sends out a regular timing burst passed module-module until it reaches the End Node, where it is reflected back along the same duplex path to the Master - averages about 62ms for the million modules.

At any module, the timing reference is defined as the average of the outbound and return bursts. The outbound and return paths are regularly swapped to eliminate path length errors.

The same thing happens intra-module, but at 40.68MHz and broadcast (not element-to-element).




Offline Asteroza

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Re: Solar Power Satellites
« Reply #51 on: 07/02/2014 11:36 PM »

I have discussed the possibility of boot-strapping construction (using one SPS to boost the components for another into Molniya via microwave thermal propulsion) with Keith Henson. However, he suggests the orbital phasing and beam times will not work in its favour.


That's a little unexpected, but possible. Skylon dumping direct to a Molniya inclination but a sub-450 km circular parking orbit seemed to be a good choice at first. After that trade against full construction then apogee raising of a completed SPS or apogee raise all parts module by module before joining. Single module apogee raising using something like a microwave powered Flyut while the bootstrap SPS sweeps towards perigee seems doable even if microwave Skylon itself is unattractive due to launch site distance from perigee ground track specific to the Molniya orbit you wish to service.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #52 on: 07/03/2014 05:46 AM »

I have discussed the possibility of boot-strapping construction (using one SPS to boost the components for another into Molniya via microwave thermal propulsion) with Keith Henson. However, he suggests the orbital phasing and beam times will not work in its favour.

That's a little unexpected, but possible. Skylon dumping direct to a Molniya inclination but a sub-450 km circular parking orbit seemed to be a good choice at first. After that trade against full construction then apogee raising of a completed SPS or apogee raise all parts module by module before joining. Single module apogee raising using something like a microwave powered Flyut while the bootstrap SPS sweeps towards perigee seems doable even if microwave Skylon itself is unattractive due to launch site distance from perigee ground track specific to the Molniya orbit you wish to service.

I haven't tried to model this; Keith has for laser-thermal GTO, but I'd presume not for Molniya. Would anyone here like to have a go?

The diffraction limit at 5.8GHz, from a 4.4km diameter antenna down to a 1 metre spot, gives <35km beam distance, which is one reason for pessimism.

[Edit]
Could make a good anti-missile defence for the SPS though; provided the missiles abide by the rules and don't try to attack the non-beaming side!  :)

[Edit2]
...and the missiles agree to play fair and send out a 40.68MHz homing signal  :) :)

« Last Edit: 07/03/2014 05:53 AM by SICA Design »

Offline Hanelyp

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Re: Solar Power Satellites
« Reply #53 on: 07/03/2014 05:15 PM »
[Edit2]
...and the missiles agree to play fair and send out a 40.68MHz homing signal  :) :)
If you were serious about anti-missile capability on the solar array, a less directional system could illuminate a target missile with the homing signal.  Though with a 40MHz homing signal the warhead bus might be made too small to reflect the signal well.

Offline Asteroza

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Re: Solar Power Satellites
« Reply #54 on: 07/04/2014 12:11 AM »

I have discussed the possibility of boot-strapping construction (using one SPS to boost the components for another into Molniya via microwave thermal propulsion) with Keith Henson. However, he suggests the orbital phasing and beam times will not work in its favour.

That's a little unexpected, but possible. Skylon dumping direct to a Molniya inclination but a sub-450 km circular parking orbit seemed to be a good choice at first. After that trade against full construction then apogee raising of a completed SPS or apogee raise all parts module by module before joining. Single module apogee raising using something like a microwave powered Flyut while the bootstrap SPS sweeps towards perigee seems doable even if microwave Skylon itself is unattractive due to launch site distance from perigee ground track specific to the Molniya orbit you wish to service.

I haven't tried to model this; Keith has for laser-thermal GTO, but I'd presume not for Molniya. Would anyone here like to have a go?

The diffraction limit at 5.8GHz, from a 4.4km diameter antenna down to a 1 metre spot, gives <35km beam distance, which is one reason for pessimism.

[Edit]
Could make a good anti-missile defence for the SPS though; provided the missiles abide by the rules and don't try to attack the non-beaming side!  :)

[Edit2]
...and the missiles agree to play fair and send out a 40.68MHz homing signal  :) :)

Fore reference, what are the distances for 2,3,4,5, and 10m spots? I suspect even then the distances would be unattractive for a Skylon but potentially usable for a orbital tug which can open up a large rectenna via an inflatable ring with 10m not being unreasonable.

It's probably unrealistic to do the external heating for a Skylon via microwave if you have to do the heating as two smaller spots on the wing upper surface of the current Sklyon configuration. Which is why I always imagined externally heated Skylon to be a flipped configuration, with the wing on the top of the fuselage and the payload bay opening towards the bottom. This allows a much larger single receiver surface which can double as thermal protection for reentry, provided you did reentry upside-down. That 180 roll before and after reentry is the obnoxious part (since a passenger module will need seats that rotate 180), but it keeps the hot side uninterrupted with landing gear doors. 180 degree roll is potentially a deal-breaker, but then again, many nose first reentry VTVL SSTO designs had "swoop-of-death" maneuver that people felt was acceptable.

Perhaps a different bootstrap concept might be in order. If one could accept the bootstrap/demo sat can't be reasonably used for continuous utility power service, a low SSO SPS riding the day/night terminator to supply dedicated propulsion power might be possible. How that propulsion power is beamed (Henson uses laser, but microwave might work here) determines the utility of it. Oddly enough, that would force you to do predawn and post-dusk Skylon flights or tug boosts.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #55 on: 07/04/2014 07:47 AM »
The diffraction limit is approximated by the inequality:

(A x D) / (λ x R) > 2.44

where A is antenna aperture (diameter), D is rectenna diameter, λ is the wavelength (51.7mm for 5.8GHz) and R is the beam distance. So the maximum beam length will change in proportion to the spot size if everything else stays constant.

I like the idea of a Skylon without breaks in the TPS for wheel wells, but as recently commented on 'Skylon Thread 4', it's not designed for combat manouvres - which I guess includes barrel rolls!

Offline SICA Design

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Re: Solar Power Satellites
« Reply #56 on: 10/15/2014 08:25 PM »
Article on HESPeruS published in the IET's magazine recently:

http://eandt.theiet.org/magazine/2014/10/space-based-solar-power.cfm


Offline Robotbeat

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Re: Solar Power Satellites
« Reply #57 on: 10/15/2014 11:43 PM »
Should use lasers and find a customer that needs a lot of power and is willing to pay a LOT more than $0.10/kWh and lives above the clouds and could use a system at the hundreds of kW range to start.
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Offline QuantumG

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Re: Solar Power Satellites
« Reply #58 on: 10/16/2014 12:51 AM »
Should use lasers and find a customer that needs a lot of power and is willing to pay a LOT more than $0.10/kWh and lives above the clouds and could use a system at the hundreds of kW range to start.

Cloud servers in the clouds.

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Offline Vultur

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Re: Solar Power Satellites
« Reply #59 on: 10/17/2014 06:26 AM »
How much would a HESPeruS satellite cost? (not including launch costs as obviously that's highly dependent on how cheap Skylon and/or SpaceX reusability turn out to be in actual practice...)

Offline MP99

Re: Solar Power Satellites
« Reply #60 on: 10/17/2014 07:59 AM »


Should use lasers and find a customer that needs a lot of power and is willing to pay a LOT more than $0.10/kWh and lives above the clouds and could use a system at the hundreds of kW range to start.

Cloud servers in the clouds.

Dunno, that perigee sounds a bit low. ;-)

Cheers, Martin

Offline Asteroza

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Re: Solar Power Satellites
« Reply #61 on: 10/17/2014 08:15 AM »
Should use lasers and find a customer that needs a lot of power and is willing to pay a LOT more than $0.10/kWh and lives above the clouds and could use a system at the hundreds of kW range to start.

Cloud servers in the clouds.

Well, Facebook/Ascenta or Google/Titan Aerospace have solar electric HALE drone projects. Tuned solar cells for receiving laser light from above is not entirely crazy (see Lasermotive UAV demos). Good pointing accuracy isn't necessary if the spot is wide and at light sunburn levels of power...

Offline SICA Design

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Re: Solar Power Satellites
« Reply #62 on: 10/17/2014 08:48 AM »
How much would a HESPeruS satellite cost? (not including launch costs as obviously that's highly dependent on how cheap Skylon and/or SpaceX reusability turn out to be in actual practice...)
To estimate the future cost (1-2 decades hence) of materials and manufacture is incredibly difficult and prone to inaccuracy.

What I can state is that the HESPeruS design uses very few types of component:

Almost the entire functionality is modular down to a 25mm scale - including photovoltaics (either concentrated multi-junction, or future thin fim, e.g. perovskite), dc to microwave conversion at <100mW levels (single CMOS ASIC) and micro-wave beam formation (dual crossed dipole / crossed elliptical antenna).

Combining 25,000 of these elements into a modular panel (~5m across), including several pilot beam receivers, allows coherent microwave beam formation and retro-directive steering. Up to 1 million panels would be necessary for a complete system delivering 1GW to the grid.

Getting costs down to economical levels will require extreme mass-production and automation, the same drive which has put powerful processing and microwave technology into peoples pockets, to be discarded as throw-away items after one or two years.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #63 on: 10/17/2014 08:55 AM »
Should use lasers and find a customer that needs a lot of power and is willing to pay a LOT more than $0.10/kWh and lives above the clouds and could use a system at the hundreds of kW range to start.

Cloud servers in the clouds.

Well, Facebook/Ascenta or Google/Titan Aerospace have solar electric HALE drone projects. Tuned solar cells for receiving laser light from above is not entirely crazy (see Lasermotive UAV demos). Good pointing accuracy isn't necessary if the spot is wide and at light sunburn levels of power...

John Mankins is promoting space-based servers as a good means to kick-start Space Based Solar Power

http://www.nss.org/adastra/volume25/spsalpha.html

Offline SICA Design

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Re: Solar Power Satellites
« Reply #64 on: 06/07/2017 09:10 AM »
Including one notable and impending reversal, there are currently 191 signatories to the Paris Climate Agreement, all recognising the need to reduce man-made greenhouse gas emissions, due primarily to the combustion of fossil fuels. With widespread distrust and lack of nuclear power investment, there are few options which can replace the guaranteed baseload power provided by coal, oil and gas.

There is rapid and increasing uptake of both wind and solar power, but almost zero grid-scale storage necessary to overcome their unpredictable nature. In 2015, the three largest terrestrial solar photovoltaic farms provided (on-average) just 5 watts per square metre. This is similar for solar-thermal plants and less for wind-power.

To generate the 28 terrawatts predicted total world power requirement by 2050 (for a global population expected to peak below 10 billion), a massive increase in wind and solar will likely compete with food production for available land. However, there is a band located around the Earth from which we could extract all this power many-times over, beamed as biologically and ecologically benign microwaves, converted with over 90% efficiency to electricity (50% end-to-end efficiency), from which we can then meet all our energy needs.

We’ve known about this since the early 1970’s, and we have had daily demonstrations of the fundamental technology ever since the first geostationary communications satellite was placed in orbit. The only significant difference between a communications and a power satellite is the scale required to capture the majority of the beam.

From geosynchronous orbits, fundamental physics dictates a kilometre-scale transmit antenna to beam microwave power across 36,000 km of space, through the atmosphere during all weathers, to a multi-kilometre terrestrial receiving station (rectifying antenna or “rectenna”) – and do this without prohibitive losses. This is irrespective of how much power, so it better be in the region of gigawatts (GW) delivered, to justify the massive transmitter, which still leads to a peak beam intensity weaker than sunlight at the ground (so forget those “space-weapon” fears).

Nearly all proposals take a high-level systems approach, splitting the satellite into the antenna facing the Earth and the collector facing the Sun. This inevitably leads to a complex kilometre-scale 3D structure with continuously moving parts as the satellite traverses its orbit. In 1971, one proposed 5 GW solar power satellite (SPS) massed 34,000 tonnes, with typical concepts today still around 5,000-10,000 T/GW.

HESPeruS (JBIS, Vol. 69, pp 127-138, 2016 http://jbis.org.uk/paper.php?p=2016.69.127 ) is a proposal which eliminates the moving parts in-favour of a solid state design. Its essentially-flat and highly modular structure reduces mass to around one tenth that of competing designs, and simplifies robotic orbital construction - but that orbit needs to be a highly elliptical (Molniya) orbit in order to both face the Sun and stay within its beam steering limits.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #65 on: 06/07/2017 09:22 AM »
IN THE INTERESTS OF PUBLIC DISCLOSURE:

CASSIOPeiA – Constant Aperture, Solid State, Integrated, Orbital Phased Array


The recent invention of CASSIOPeiA (patent applied for), has realised a scalable design which can work in any orbit, capable of both directly facing the Sun and beaming continuously through 360 degrees, solving the beam steering issues of a planar array without any mass penalty.

CASSIOPeiA deploys from a highly compact stowed form, into a gossamer large-scale helical array, having sufficient self-rigidity to support itself in microgravity. Unlike a parabolic dish (for example), there is no need to maintain a perfect rigid geometry in the presence of varying thermal expansion, nor precision pointing accuracy. Instead, the power beam is formed and locked on target by measuring the spherical wavefront of a pilot signal emitted by the terrestrial station, synchronously sampled by numerous receivers across the orbital array, with phase measurements reversed in time to generate the coherent power beam.

Key to the design are the half-wavelength spaced elements, which combine highly efficient concentrated photovoltaics with a triple antenna configuration - able to electronically steer a shaped radiation pattern (cardioid) through 360 degrees. This combination of steerable element pattern and the constant aperture (cross-sectional area as seen from the Earth) of a helical surface results in a high quality beam, matching that of an equivalent planar array’s ideal boresight direction, but invariant throughout 360 degrees azimuth, combined with +/-55 degrees elevation (elevation limits where peak intensity drops by 3dB, “azimuth” and “elevation” with respect to the rotational axis of the array).

This integration allows the flexible substrate to provide mechanical support, electrical interconnect and simplified thermal management – functions typically assigned to distinct large-scale structures in other SPS proposals.

By matching CASSIOPeiA’s RF aperture to the area of intercepted sunlight, the design is completely scalable from 200 kW to 600 MW predictable delivered power. Examples:

1)   A pseudo-satellite measuring 34m across, massing 200-400kg and situated at 20 km altitude inside the transparent envelope of a station-keeping stratospheric blimp (see Thales Stratobus for a near-term example), providing 200 kW continuous power throughout daylight hours.
2)   A constellation of 300m diameter, 20-40 tonne satellites following offset Sun-synchronous 2-hour orbits, skipping over Earth’s shadow to provide near-continuous power at 20 MW. Each satellite conceivably launched and deployed as a single payload.
3)   Similar 400m diameter, 33-66 T satellites delivering 33 MW from 2-hour 24-minute Sun-synchronous orbits.
4)   A constellation of 5 satellites, each 650 m diameter, massing 90-180 T, delivering 90 MW to multiple northern latitude sites from 3-hour, Sun-synchronous elliptical orbits. Rectenna utilisation is > 95% at 45 degrees latitude, >98.5% at 60 degrees (see figure).
5)   A single 1.4 km diameter geosynchronous satellite, massing 430 - 860 T 600 – 1200 T, delivering 430 600 MW with >99% utilisation.

All these examples provide surface beam intensities no-greater than one-quarter sunlight, intrinsically safe to wildlife, with average delivered surface power densities ten times greater than the current best wind and terrestrial solar sites. The option to safely and aesthetically combine rectenna sites with agriculture (by raising the mesh-like rectenna several metres above the ground) removes the potential future conflict between food and power production.

[Edit: correction to GSO example 5, for delivered power, not total RF power]
« Last Edit: 06/10/2017 04:26 PM by SICA Design »

Offline TrevorMonty

Re: Solar Power Satellites
« Reply #66 on: 06/07/2017 06:05 PM »
Unfortunately all current solar installations can't provided base load.
For SPS to every be viable they need to be built in space from space materials eg moon or asteriods. The technology to do this is evolving but we have long way to go.
The other critical item is pilot satellite to prove beaming high quatities of power back is possible.

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Offline Robotbeat

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Re: Solar Power Satellites
« Reply #67 on: 06/07/2017 06:21 PM »
Unfortunately all current solar installations can't provided base load.
For SPS to every be viable they need to be built in space from space materials eg moon or asteriods. The technology to do this is evolving but we have long way to go.
The other critical item is pilot satellite to prove beaming high quatities of power back is possible.

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Oft-repeated myth. Terrestrial photovoltaics can provide baseload if oversized (to provide power during cloudy days) or geographically diversified and coupled with batteries.

Additionally, I don't think building SBSP with space resources is required (or even competitive) if you get launch costs low enough.
« Last Edit: 06/07/2017 06:25 PM by Robotbeat »
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Offline Asteroza

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Re: Solar Power Satellites
« Reply #68 on: 06/07/2017 11:27 PM »
IN THE INTERESTS OF PUBLIC DISCLOSURE:

CASSIOPeiA – Constant Aperture, Solid State, Integrated, Orbital Phased Array



I think I get the design, but is the helix central axis actively pointed at the sun, or are you willing to take the off-angle power efficiency loss to utilize passive pointing? Like Mankin's SPS-ALPHA, unless you have a lot of good orientation/beaming pictures, people will have trouble visualizing the arrangement and usage. If passive, would you also be using an upward tether mass to gravity gradient stabilize the nadir pointing of the phased array, or will you also be using active means to roll the helix to improve pointing at specific ground targets?

The physical arrangement is unique and very interesting as a solution to the power slip ring bearing issue that plagues classic SPS designs. Recent designs like the NASA butterfly tend to end up with a GEO fixed sandwich panel design of sorts, though SPS-ALPHA does the psuedo-cone arrangement, and the recent FISO presentation on Z step sandwich panel module research had a rather interesting central stepped cone arrangement replacing the traditional fixed flat disk of the NASA butterfly design (which is conceptually similar to this helix arrangement even if visually not so). Nice to see more people thinking beyond rectilinear 3D.

I guess you could also call it a heliogyro style of sorts...

But how does the GEO case work without relay mirrors like the NASA butterfly design, for a single satellite design? Wouldn't a 24 hour sun tracking spin to keep the PV panels lit also point the phased array primary axis so far off orthogonally that you would get terrible transmission efficiency?
« Last Edit: 06/07/2017 11:36 PM by Asteroza »

Offline QuantumG

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Re: Solar Power Satellites
« Reply #69 on: 06/08/2017 01:08 AM »
I really don't care if terrestrial solar is better than solar power satellites.

Can we talk about the topic please?

34,000 tons sounds like fun. 100 ITS flights or 200 mini-ITS?



Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline TrevorMonty

Re: Solar Power Satellites
« Reply #70 on: 06/08/2017 03:23 AM »
IN THE INTERESTS OF PUBLIC DISCLOSURE:

CASSIOPeiA – Constant Aperture, Solid State, Integrated, Orbital Phased Array



I think I get the design, but is the helix central axis actively pointed at the sun, or are you willing to take the off-angle power efficiency loss to utilize passive pointing? Like Mankin's SPS-ALPHA, unless you have a lot of good orientation/beaming pictures, people will have trouble visualizing the arrangement and usage. If passive, would you also be using an upward tether mass to gravity gradient stabilize the nadir pointing of the phased array, or will you also be using active means to roll the helix to improve pointing at specific ground targets?

The physical arrangement is unique and very interesting as a solution to the power slip ring bearing issue that plagues classic SPS designs. Recent designs like the NASA butterfly tend to end up with a GEO fixed sandwich panel design of sorts, though SPS-ALPHA does the psuedo-cone arrangement, and the recent FISO presentation on Z step sandwich panel module research had a rather interesting central stepped cone arrangement replacing the traditional fixed flat disk of the NASA butterfly design (which is conceptually similar to this helix arrangement even if visually not so). Nice to see more people thinking beyond rectilinear 3D.

I guess you could also call it a heliogyro style of sorts...

But how does the GEO case work without relay mirrors like the NASA butterfly design, for a single satellite design? Wouldn't a 24 hour sun tracking spin to keep the PV panels lit also point the phased array primary axis so far off orthogonally that you would get terrible transmission efficiency?
Mirrors can be aluminum or another metal, if produced in space then there won't be any oxidisation. Plus it can be very thin and lite.



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Offline Robotbeat

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Re: Solar Power Satellites
« Reply #71 on: 06/08/2017 04:02 AM »
I really don't care if terrestrial solar is better than solar power satellites.

Can we talk about the topic please?

34,000 tons sounds like fun. 100 ITS flights or 200 mini-ITS?
That's the thing about ITS:

Musk may think SBSP is dumb, but ITS actually gives it a shot at working.

And same with Bezos' New Armstrong, if it's competitive with ITS. And Bezos might actually BUILD it, since:
1) Bezos is way richer than Musk and will still be super rich after developing New Armstrong and
2) Bezos doesn't explicitly think SBSP is dumb; he talks a lot about moving industry off-planet, and energy production is one of (if not THE) largest.

Bezos could actually afford to finance a few full-sized SBSP stations himself, especially if he finds clever ways of leveraging his own cash (as all self-made billionaires tend to do).
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Stan-1967

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Re: Solar Power Satellites
« Reply #72 on: 06/08/2017 04:17 AM »

1) Bezos is way richer than Musk and will still be super rich after developing New Armstrong and
2) Bezos doesn't explicitly think SBSP is dumb; he talks a lot about moving industry off-planet, and energy production is one of (if not THE) largest.

Bezos could actually afford to finance a few full-sized SBSP stations himself, especially if he finds clever ways of leveraging his own cash (as all self-made billionaires tend to do).

That lucky Bezos guy is going to retire as a millionaire if he jumps into SBSP.

Offline Robotbeat

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Re: Solar Power Satellites
« Reply #73 on: 06/08/2017 04:31 AM »

1) Bezos is way richer than Musk and will still be super rich after developing New Armstrong and
2) Bezos doesn't explicitly think SBSP is dumb; he talks a lot about moving industry off-planet, and energy production is one of (if not THE) largest.

Bezos could actually afford to finance a few full-sized SBSP stations himself, especially if he finds clever ways of leveraging his own cash (as all self-made billionaires tend to do).

That lucky Bezos guy is going to retire as a millionaire if he jumps into SBSP.
Ya can't take it with you...

But I think you underestimate how rich Bezos is.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline RocketmanUS

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Re: Solar Power Satellites
« Reply #74 on: 06/08/2017 05:10 AM »
I really don't care if terrestrial solar is better than solar power satellites.

Can we talk about the topic please?

34,000 tons sounds like fun. 100 ITS flights or 200 mini-ITS?
That's the thing about ITS:

Musk may think SBSP is dumb, but ITS actually gives it a shot at working.

And same with Bezos' New Armstrong, if it's competitive with ITS. And Bezos might actually BUILD it, since:
1) Bezos is way richer than Musk and will still be super rich after developing New Armstrong and
2) Bezos doesn't explicitly think SBSP is dumb; he talks a lot about moving industry off-planet, and energy production is one of (if not THE) largest.

Bezos could actually afford to finance a few full-sized SBSP stations himself, especially if he finds clever ways of leveraging his own cash (as all self-made billionaires tend to do).
Solar power for use in space for industry use. Perhaps in the future solar from space for use on Earth might work , but for now I would say in space use. Products made in space for space use and for Earth.

Offline Robotbeat

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Re: Solar Power Satellites
« Reply #75 on: 06/08/2017 05:51 AM »
I really don't care if terrestrial solar is better than solar power satellites.

Can we talk about the topic please?

34,000 tons sounds like fun. 100 ITS flights or 200 mini-ITS?
That's the thing about ITS:

Musk may think SBSP is dumb, but ITS actually gives it a shot at working.

And same with Bezos' New Armstrong, if it's competitive with ITS. And Bezos might actually BUILD it, since:
1) Bezos is way richer than Musk and will still be super rich after developing New Armstrong and
2) Bezos doesn't explicitly think SBSP is dumb; he talks a lot about moving industry off-planet, and energy production is one of (if not THE) largest.

Bezos could actually afford to finance a few full-sized SBSP stations himself, especially if he finds clever ways of leveraging his own cash (as all self-made billionaires tend to do).
Solar power for use in space for industry use. Perhaps in the future solar from space for use on Earth might work , but for now I would say in space use. Products made in space for space use and for Earth.
Not buying it unless you can be SPECIFIC. What would move a significant amount of industrial activity off planet? How many Gigawatts?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline RocketmanUS

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Re: Solar Power Satellites
« Reply #76 on: 06/08/2017 06:18 AM »
I really don't care if terrestrial solar is better than solar power satellites.

Can we talk about the topic please?

34,000 tons sounds like fun. 100 ITS flights or 200 mini-ITS?
That's the thing about ITS:

Musk may think SBSP is dumb, but ITS actually gives it a shot at working.

And same with Bezos' New Armstrong, if it's competitive with ITS. And Bezos might actually BUILD it, since:
1) Bezos is way richer than Musk and will still be super rich after developing New Armstrong and
2) Bezos doesn't explicitly think SBSP is dumb; he talks a lot about moving industry off-planet, and energy production is one of (if not THE) largest.

Bezos could actually afford to finance a few full-sized SBSP stations himself, especially if he finds clever ways of leveraging his own cash (as all self-made billionaires tend to do).
Solar power for use in space for industry use. Perhaps in the future solar from space for use on Earth might work , but for now I would say in space use. Products made in space for space use and for Earth.
Not buying it unless you can be SPECIFIC. What would move a significant amount of industrial activity off planet? How many Gigawatts?
NEA and Lunar mining, product for space exploration and living off Earth. Why make it on Earth when it would be used off Earth. For Earth based use, environmental issues making a product on Earth that could be made in space or mined in space without the environmental impact here on earth.

So that is how I would see large solar power used in space.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #77 on: 06/08/2017 10:05 AM »
IN THE INTERESTS OF PUBLIC DISCLOSURE:

CASSIOPeiA – Constant Aperture, Solid State, Integrated, Orbital Phased Array



I think I get the design, but is the helix central axis actively pointed at the sun, or are you willing to take the off-angle power efficiency loss to utilize passive pointing? Like Mankin's SPS-ALPHA, unless you have a lot of good orientation/beaming pictures, people will have trouble visualizing the arrangement and usage. If passive, would you also be using an upward tether mass to gravity gradient stabilize the nadir pointing of the phased array, or will you also be using active means to roll the helix to improve pointing at specific ground targets?

Ideally (at GSO), the helix axis is normal to the ecliptic. A dielectric mirror inclined at 45 degrees allows a CPV chip to be mounted on the same substrate as the electronics (with radiation shielding provided by the secondary  Kohler concentrator), and may be integrated with the triple-antenna arrangement which generates the steerable cardioid pattern. Thermal management is by simple heat spreading by the conductive layers within the substrate.

The comparison here is with a standard square planar array (having side D, no rear reflector/absorber) having the same number of RF elements, power and spacing. The side-view RF aperture of the array equals its solar collecting area, and is given by 2*D^2/pi

The RF surface intensity animation is modelled for a slightly larger array, as it rotates through 360 degrees of orbit (as seen from Earth), continuously and directly facing the sun (one physical rotation/year).

As can be seen, from a mass distribution POV, the design is rotationally symmetric (so no GG stabilisation). Attitude and maneuvering control is still required, though a means of using passive sunlight pressure to aid sun-pointing is being investigated.
« Last Edit: 06/08/2017 10:45 AM by SICA Design »

Offline Robotbeat

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Re: Solar Power Satellites
« Reply #78 on: 06/08/2017 01:21 PM »
I really don't care if terrestrial solar is better than solar power satellites.

Can we talk about the topic please?

34,000 tons sounds like fun. 100 ITS flights or 200 mini-ITS?
That's the thing about ITS:

Musk may think SBSP is dumb, but ITS actually gives it a shot at working.

And same with Bezos' New Armstrong, if it's competitive with ITS. And Bezos might actually BUILD it, since:
1) Bezos is way richer than Musk and will still be super rich after developing New Armstrong and
2) Bezos doesn't explicitly think SBSP is dumb; he talks a lot about moving industry off-planet, and energy production is one of (if not THE) largest.

Bezos could actually afford to finance a few full-sized SBSP stations himself, especially if he finds clever ways of leveraging his own cash (as all self-made billionaires tend to do).
Solar power for use in space for industry use. Perhaps in the future solar from space for use on Earth might work , but for now I would say in space use. Products made in space for space use and for Earth.
Not buying it unless you can be SPECIFIC. What would move a significant amount of industrial activity off planet? How many Gigawatts?
NEA and Lunar mining, product for space exploration and living off Earth. Why make it on Earth when it would be used off Earth. For Earth based use, environmental issues making a product on Earth that could be made in space or mined in space without the environmental impact here on earth.

So that is how I would see large solar power used in space.
No, still not specific enough. Again, what product or mineral or whatever are you proposing to make industrially off-Earth that significantly would reduce impact on Earth, and how many Gigawatts does this replace?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline gongora

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Re: Solar Power Satellites
« Reply #79 on: 06/08/2017 10:34 PM »
Split recent earth vs. space solar posts into separate thread:
Earth Solar vs. Solar Power Satellites

Offline Asteroza

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Re: Solar Power Satellites
« Reply #80 on: 06/09/2017 01:22 AM »
IN THE INTERESTS OF PUBLIC DISCLOSURE:

CASSIOPeiA – Constant Aperture, Solid State, Integrated, Orbital Phased Array



I think I get the design, but is the helix central axis actively pointed at the sun, or are you willing to take the off-angle power efficiency loss to utilize passive pointing? Like Mankin's SPS-ALPHA, unless you have a lot of good orientation/beaming pictures, people will have trouble visualizing the arrangement and usage. If passive, would you also be using an upward tether mass to gravity gradient stabilize the nadir pointing of the phased array, or will you also be using active means to roll the helix to improve pointing at specific ground targets?

Ideally (at GSO), the helix axis is normal to the ecliptic. A dielectric mirror inclined at 45 degrees allows a CPV chip to be mounted on the same substrate as the electronics (with radiation shielding provided by the secondary  Kohler concentrator), and may be integrated with the triple-antenna arrangement which generates the steerable cardioid pattern. Thermal management is by simple heat spreading by the conductive layers within the substrate.

The comparison here is with a standard square planar array (having side D, no rear reflector/absorber) having the same number of RF elements, power and spacing. The side-view RF aperture of the array equals its solar collecting area, and is given by 2*D^2/pi

The RF surface intensity animation is modelled for a slightly larger array, as it rotates through 360 degrees of orbit (as seen from Earth), continuously and directly facing the sun (one physical rotation/year).

As can be seen, from a mass distribution POV, the design is rotationally symmetric (so no GG stabilisation). Attitude and maneuvering control is still required, though a means of using passive sunlight pressure to aid sun-pointing is being investigated.


My RF literacy is not great, so I need to check something here. The three dipole antennas of a single transmission module all control of the beam such that you can transmit in any desired radial direction around an axis normal to the module "plate", correct? What does the radiation pattern look like in the other 2 axis (aka normal to the plate)?

Your original helix image shows what appear to be transmit plate squares hanging off the PV vanes like sub-fins, with all the plates aligned to make a single virtual flat plate that shares the same normal axis as the individual plates.

So, is the actual primary beam direction coming from the virtual flat plate normal axis ideally, or does it come from the side of the virtual plate? I guess I am asking if the correct ground orientation is a visually blocking plate like the upper left view of the helix model picture, or the mostly see through view of the lower left.

I get the feeling the helix design is more different between an SSO type and a GEO/GSO type, due to the pointing needs of the structure if the 45 degree mirror is fixed.

Offline SICA Design

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Re: Solar Power Satellites
« Reply #81 on: 06/12/2017 09:01 AM »
...The three dipole antennas of a single transmission module all control of the beam such that you can transmit in any desired radial direction around an axis normal to the module "plate", correct? What does the radiation pattern look like in the other 2 axis (aka normal to the plate)?

If you take the polar radiation pattern of an ideal vertical half-wave dipole, it is omnidirectional in azimuth (360 degrees), and like a figure 8 on its side (or infinity symbol) in elevation. CASSIOPeiA has an equivalent high-gain beaming capability: 360 degrees azimuth and +/-55 degrees in elevation. This capability arises through the combination of each element able to steer a cardioid pattern (in azimuth), and the distribution of these elements across a helical surface having constant aperture from any side view.

I've superimposed the ideal dipole pattern (in grey) and results from a small model CASSIOPeiA on the same polar plots. The peak intensity drops by half at +/- 55 degrees elevation. The azimuth plot includes beam sweeps at both 0 and 55 degrees elevation*.

Quote
Your original helix image shows what appear to be transmit plate squares hanging off the PV vanes like sub-fins, with all the plates aligned to make a single virtual flat plate that shares the same normal axis as the individual plates.

So, is the actual primary beam direction coming from the virtual flat plate normal axis ideally, or does it come from the side of the virtual plate? I guess I am asking if the correct ground orientation is a visually blocking plate like the upper left view of the helix model picture, or the mostly see through view of the lower left.

The "transmit plate squares" are actually the polymer Fresnel lenses (transparent to microwaves). The diagram shows how the actual triple dipoles (one RF element) can be integrated with the concentrating photovoltaic  (CPV) optics without shadowing.

The relationship between CPV and RF elements is not always 1:1, but follows the sine of the angle each layer makes with the sun. At middle layers, this angle is 90 degrees, hence full coverage by CPV optics, at outer layers the angle (and hence CPV coverage) approaches zero. RF element coverage, however, is essentially uniform across the array, with (at-most) half-wavelength separation to neighbouring elements to avoid grating lobes.

Quote
I get the feeling the helix design is more different between an SSO type and a GEO/GSO type, due to the pointing needs of the structure if the 45 degree mirror is fixed.

The helix design remains the same, however the concentrating optics may differ (such as using compound parabolic concentration - CPC) to allow a wider solar acceptance angle (*at the expense of optical concentration) - this will likely be the case for the stratospheric version where roll/yaw angles may be harder to maintain.

[*Edits for clarification]
« Last Edit: 06/12/2017 12:48 PM by SICA Design »

Offline Asteroza

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Re: Solar Power Satellites
« Reply #82 on: 06/13/2017 02:02 AM »
...The three dipole antennas of a single transmission module all control of the beam such that you can transmit in any desired radial direction around an axis normal to the module "plate", correct? What does the radiation pattern look like in the other 2 axis (aka normal to the plate)?

If you take the polar radiation pattern of an ideal vertical half-wave dipole, it is omnidirectional in azimuth (360 degrees), and like a figure 8 on its side (or infinity symbol) in elevation. CASSIOPeiA has an equivalent high-gain beaming capability: 360 degrees azimuth and +/-55 degrees in elevation. This capability arises through the combination of each element able to steer a cardioid pattern (in azimuth), and the distribution of these elements across a helical surface having constant aperture from any side view.

I've superimposed the ideal dipole pattern (in grey) and results from a small model CASSIOPeiA on the same polar plots. The peak intensity drops by half at +/- 55 degrees elevation. The azimuth plot includes beam sweeps at both 0 and 55 degrees elevation*.

Quote
Your original helix image shows what appear to be transmit plate squares hanging off the PV vanes like sub-fins, with all the plates aligned to make a single virtual flat plate that shares the same normal axis as the individual plates.

So, is the actual primary beam direction coming from the virtual flat plate normal axis ideally, or does it come from the side of the virtual plate? I guess I am asking if the correct ground orientation is a visually blocking plate like the upper left view of the helix model picture, or the mostly see through view of the lower left.

The "transmit plate squares" are actually the polymer Fresnel lenses (transparent to microwaves). The diagram shows how the actual triple dipoles (one RF element) can be integrated with the concentrating photovoltaic  (CPV) optics without shadowing.

The relationship between CPV and RF elements is not always 1:1, but follows the sine of the angle each layer makes with the sun. At middle layers, this angle is 90 degrees, hence full coverage by CPV optics, at outer layers the angle (and hence CPV coverage) approaches zero. RF element coverage, however, is essentially uniform across the array, with (at-most) half-wavelength separation to neighbouring elements to avoid grating lobes.

Quote
I get the feeling the helix design is more different between an SSO type and a GEO/GSO type, due to the pointing needs of the structure if the 45 degree mirror is fixed.

The helix design remains the same, however the concentrating optics may differ (such as using compound parabolic concentration - CPC) to allow a wider solar acceptance angle (*at the expense of optical concentration) - this will likely be the case for the stratospheric version where roll/yaw angles may be harder to maintain.

[*Edits for clarification]

Now it's starting to make sense! So if I understand correctly now, the dipoles are on the vanes (and normal to the vane), thus the beam covers 360 about the helix axis, and the virtual antenna provides some steering about the "face" of the antenna to track a ground target. So for GSO, the helix axis is normal to the ecliptic, and depending on the fresnel lens panels and and 45 degree mirrors, there might be some shadowing but usually not.

Couldn't you cheat a bit with the 45 degree mirror by changing to a half fresnel lens focusing to a spot just above the CPV cell, and place a much smaller 45 degree mirror there for the final turn?

However for the SSO case, if the helix axis is aligned to the ecliptic to allow easy ground tracking, would you essentially have fresnel lens sheets above the CPV that are coplanar to the vane?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #83 on: 06/15/2017 12:38 PM »
Now it's starting to make sense! So if I understand correctly now, the dipoles are on the vanes (and normal to the vane), thus the beam covers 360 about the helix axis, and the virtual antenna provides some steering about the "face" of the antenna to track a ground target. So for GSO, the helix axis is normal to the ecliptic, and depending on the fresnel lens panels and and 45 degree mirrors, there might be some shadowing but usually not.

The centre-feed points of the triple dipoles are located on the substrate (shown horizontal - this could be what you mean by "vanes"), spaced one-quarter wavelength apart from each other (12.9mm for 5.8GHz). These can fit around the concentrating optics where necessary, as shown in the diagram.

Yes, the beam can steer 360 degrees about the helix axis, which is typically at 90 degrees (normal) to the ecliptic plane. It can also steer +/-55 degrees with respect to this plane, only a fraction of which would be required from ~5 Earth radii distance (36,000 km, GSO).

There should be no self shadowing by the lenses; each directly faces the Sun, with no overlap from the Sun's viewpoint. There will be some area-fill efficiency losses due to the thin substrate and lens edges.

"virtual antenna"??

Quote
Couldn't you cheat a bit with the 45 degree mirror by changing to a half fresnel lens focusing to a spot just above the CPV cell, and place a much smaller 45 degree mirror there for the final turn?

The concentrating optics are non imaging, but the "focal point" has to be fixed with respect to the Kohler concentrator and CPV for even illumination across its surface.

Quote
However for the SSO case, if the helix axis is aligned to the ecliptic to allow easy ground tracking, would you essentially have fresnel lens sheets above the CPV that are coplanar to the vane?

You don't need CASSIOPeiA in a typical Sun-synchronous dusk/dawn orbit; a conventional design (but without rotating joints) can point continuously at the sun, while rotating every 100mins-or-so about a sun-pointing axis to keep a conventional antenna within beam-steer limits of the Earth target. The axis then needs to shift roughly 1 degree/day to maintain sun-pointing. Unfortunately this orbit is incapable of delivering high rectenna utilisation without a very large constellation.

I'm proposing a different 5-SPS, Sun-synchronous 3-hour elliptical orbit (in one-case), offering >23 hours baseload power to northern latitudes, and possibly to more than one rectenna simultaneously (I have not run the simulation yet for multiple rectenna sites), certainly with intermittent beaming to other rectenna sites at any latitude; the globe and map projections show a period where the "red" satellite's beam footprint covers anywhere within the African continent whilst the "orange" satellite covers North America, for example.

You are correct that the 45 degrees planar mirror angle could differ for each of the offset orbits, should the helix axis not remain normal to the Sun-line (the latter being my preference). Alternatively the optics could change to a compound parabolic concentrator configuration (lower concentration, but wider solar acceptance angle). The CPC would also comprise a dielectric reflector to avoid interference with the microwaves.
« Last Edit: 06/15/2017 12:43 PM by SICA Design »

Offline Asteroza

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Re: Solar Power Satellites
« Reply #84 on: 06/19/2017 12:00 AM »

You don't need CASSIOPeiA in a typical Sun-synchronous dusk/dawn orbit; a conventional design (but without rotating joints) can point continuously at the sun, while rotating every 100mins-or-so about a sun-pointing axis to keep a conventional antenna within beam-steer limits of the Earth target. The axis then needs to shift roughly 1 degree/day to maintain sun-pointing. Unfortunately this orbit is incapable of delivering high rectenna utilisation without a very large constellation.

I'm proposing a different 5-SPS, Sun-synchronous 3-hour elliptical orbit (in one-case), offering >23 hours baseload power to northern latitudes, and possibly to more than one rectenna simultaneously (I have not run the simulation yet for multiple rectenna sites), certainly with intermittent beaming to other rectenna sites at any latitude; the globe and map projections show a period where the "red" satellite's beam footprint covers anywhere within the African continent whilst the "orange" satellite covers North America, for example.

Constellation layout similar to a molniya or tundra orbit then? But why 5?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #85 on: 06/19/2017 11:55 AM »

You don't need CASSIOPeiA in a typical Sun-synchronous dusk/dawn orbit; a conventional design (but without rotating joints) can point continuously at the sun, while rotating every 100mins-or-so about a sun-pointing axis to keep a conventional antenna within beam-steer limits of the Earth target. The axis then needs to shift roughly 1 degree/day to maintain sun-pointing. Unfortunately this orbit is incapable of delivering high rectenna utilisation without a very large constellation.

I'm proposing a different 5-SPS, Sun-synchronous 3-hour elliptical orbit (in one-case), offering >23 hours baseload power to northern latitudes, and possibly to more than one rectenna simultaneously (I have not run the simulation yet for multiple rectenna sites), certainly with intermittent beaming to other rectenna sites at any latitude; the globe and map projections show a period where the "red" satellite's beam footprint covers anywhere within the African continent whilst the "orange" satellite covers North America, for example.

Constellation layout similar to a molniya or tundra orbit then? But why 5?

Starting small, a station-keeping pseudo-satellite in the stratosphere gives many of the same advantages as geostationary - i.e. its always visible over a fixed point on Earth throughout 24 hours. The disadvantage is that the stratosphere is still subject to the day/night cycle, whereas Earth's shadow is mostly avoided by a satellite at GSO/GEO (exception is daily outages of a few ten's of minutes around the spring and autumn equinox).

This particular set of 3-hour sun-synchronous orbits is a compromise; it allows satellites approximately 1/5 the mass to feasibly be deployed as a single payload (given future ITS-scale heavy-lift), without complex on-orbit construction. Modelling has shown that a rectenna situated at latitudes north of 45 degrees can switch between satellites to maintain >23 hours power output (i.e. predictable, near-baseload power which repeats daily throughout the year, including mid-winter where the "red" satellite still skips over Earth's shadow, as shown).

What hasn't been proven yet is that this should also be possible simultaneously for a second rectenna (at similar latitude) half-way around the globe.

Without 5 satellites, the rectenna utlisation is much less.

I've previously looked at Molniya for the HESPeruS SPS - it was the most feasible orbit for a solid-state satellite (no moving/rotating parts) given the beam steer limitations of a phased array. It had much reduced mass (and requires less delta-vee), but still had to be very large to focus a beam from 40,000km to northern latitudes only.

CASSIOPeiA doesn't have these beam-steer limitations! It is a new arrangement of phased array able to steer a beam through 360 degrees azimuth and +/-55 degrees elevation, suitable for any orbit (hence the patent application for a Constant Aperture, Solid State, Integrated, Orbital Phased Array).
« Last Edit: 06/19/2017 11:58 AM by SICA Design »

Offline Asteroza

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Re: Solar Power Satellites
« Reply #86 on: 06/19/2017 11:05 PM »

You don't need CASSIOPeiA in a typical Sun-synchronous dusk/dawn orbit; a conventional design (but without rotating joints) can point continuously at the sun, while rotating every 100mins-or-so about a sun-pointing axis to keep a conventional antenna within beam-steer limits of the Earth target. The axis then needs to shift roughly 1 degree/day to maintain sun-pointing. Unfortunately this orbit is incapable of delivering high rectenna utilisation without a very large constellation.

I'm proposing a different 5-SPS, Sun-synchronous 3-hour elliptical orbit (in one-case), offering >23 hours baseload power to northern latitudes, and possibly to more than one rectenna simultaneously (I have not run the simulation yet for multiple rectenna sites), certainly with intermittent beaming to other rectenna sites at any latitude; the globe and map projections show a period where the "red" satellite's beam footprint covers anywhere within the African continent whilst the "orange" satellite covers North America, for example.

Constellation layout similar to a molniya or tundra orbit then? But why 5?

Starting small, a station-keeping pseudo-satellite in the stratosphere gives many of the same advantages as geostationary - i.e. its always visible over a fixed point on Earth throughout 24 hours. The disadvantage is that the stratosphere is still subject to the day/night cycle, whereas Earth's shadow is mostly avoided by a satellite at GSO/GEO (exception is daily outages of a few ten's of minutes around the spring and autumn equinox).

This particular set of 3-hour sun-synchronous orbits is a compromise; it allows satellites approximately 1/5 the mass to feasibly be deployed as a single payload (given future ITS-scale heavy-lift), without complex on-orbit construction. Modelling has shown that a rectenna situated at latitudes north of 45 degrees can switch between satellites to maintain >23 hours power output (i.e. predictable, near-baseload power which repeats daily throughout the year, including mid-winter where the "red" satellite still skips over Earth's shadow, as shown).

What hasn't been proven yet is that this should also be possible simultaneously for a second rectenna (at similar latitude) half-way around the globe.

Without 5 satellites, the rectenna utlisation is much less.

I've previously looked at Molniya for the HESPeruS SPS - it was the most feasible orbit for a solid-state satellite (no moving/rotating parts) given the beam steer limitations of a phased array. It had much reduced mass (and requires less delta-vee), but still had to be very large to focus a beam from 40,000km to northern latitudes only.

CASSIOPeiA doesn't have these beam-steer limitations! It is a new arrangement of phased array able to steer a beam through 360 degrees azimuth and +/-55 degrees elevation, suitable for any orbit (hence the patent application for a Constant Aperture, Solid State, Integrated, Orbital Phased Array).

For a multisite requirement, would you favor 3 tundra orbits with 2-3 sats each to provide high latitude global coverage (something like the QZSS layout, but with three figure 8 footprints)?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #87 on: 06/20/2017 10:24 AM »

You don't need CASSIOPeiA in a typical Sun-synchronous dusk/dawn orbit; a conventional design (but without rotating joints) can point continuously at the sun, while rotating every 100mins-or-so about a sun-pointing axis to keep a conventional antenna within beam-steer limits of the Earth target. The axis then needs to shift roughly 1 degree/day to maintain sun-pointing. Unfortunately this orbit is incapable of delivering high rectenna utilisation without a very large constellation.

I'm proposing a different 5-SPS, Sun-synchronous 3-hour elliptical orbit (in one-case), offering >23 hours baseload power to northern latitudes, and possibly to more than one rectenna simultaneously (I have not run the simulation yet for multiple rectenna sites), certainly with intermittent beaming to other rectenna sites at any latitude; the globe and map projections show a period where the "red" satellite's beam footprint covers anywhere within the African continent whilst the "orange" satellite covers North America, for example.

Constellation layout similar to a molniya or tundra orbit then? But why 5?

Starting small, a station-keeping pseudo-satellite in the stratosphere gives many of the same advantages as geostationary - i.e. its always visible over a fixed point on Earth throughout 24 hours. The disadvantage is that the stratosphere is still subject to the day/night cycle, whereas Earth's shadow is mostly avoided by a satellite at GSO/GEO (exception is daily outages of a few ten's of minutes around the spring and autumn equinox).

This particular set of 3-hour sun-synchronous orbits is a compromise; it allows satellites approximately 1/5 the mass to feasibly be deployed as a single payload (given future ITS-scale heavy-lift), without complex on-orbit construction. Modelling has shown that a rectenna situated at latitudes north of 45 degrees can switch between satellites to maintain >23 hours power output (i.e. predictable, near-baseload power which repeats daily throughout the year, including mid-winter where the "red" satellite still skips over Earth's shadow, as shown).

What hasn't been proven yet is that this should also be possible simultaneously for a second rectenna (at similar latitude) half-way around the globe.

Without 5 satellites, the rectenna utlisation is much less.

I've previously looked at Molniya for the HESPeruS SPS - it was the most feasible orbit for a solid-state satellite (no moving/rotating parts) given the beam steer limitations of a phased array. It had much reduced mass (and requires less delta-vee), but still had to be very large to focus a beam from 40,000km to northern latitudes only.

CASSIOPeiA doesn't have these beam-steer limitations! It is a new arrangement of phased array able to steer a beam through 360 degrees azimuth and +/-55 degrees elevation, suitable for any orbit (hence the patent application for a Constant Aperture, Solid State, Integrated, Orbital Phased Array).

For a multisite requirement, would you favor 3 tundra orbits with 2-3 sats each to provide high latitude global coverage (something like the QZSS layout, but with three figure 8 footprints)?

Yes, it would also work in Tundra and other similar 24 hour orbits, but both the transmitter (CASSIOPeiA) and rectenna sizes would need to grow to accommodate the greater apogee (wrt GEO), yet still deliver 50W/m^2 mean, 230W/m^2 safe peak beam intensity at the intended site.

Offline Robotbeat

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Re: Solar Power Satellites
« Reply #88 on: 06/20/2017 12:51 PM »
That's really low.

I've often thought that if SBSP will ever be worthwhile, they have to up the beam intensity to greater than sunlight to reduce the footprint.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline SICA Design

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Re: Solar Power Satellites
« Reply #89 on: 06/20/2017 12:54 PM »
Split recent earth vs. space solar posts into separate thread:
Earth Solar vs. Solar Power Satellites
Gongora / Other-Mods - do you know what's happened to this thread (Earth Solar vs. Solar Power Satellites)?

Offline SICA Design

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Re: Solar Power Satellites
« Reply #90 on: 06/20/2017 01:04 PM »
That's really low.

I've often thought that if SBSP will ever be worthwhile, they have to up the beam intensity to greater than sunlight to reduce the footprint.

It's an environmentally acceptable level (NASA/other research - no impact to wildlife passing through the beam, safe for passenger carrying aircraft), far greater (x10 typical) mean power/area than any terrestrial solar farm.

It also offers reassurance that an SPS can't be turned into a space weapon - physical law dictates the peak beam intensity given transmitter aperture (e.g. 1.43km diameter, *projected area being equal to the solar collector), frequency (5.8 GHz is optimum available, >>10GHz is severely attenuated by atmosphere) and distance (e.g. 36,000 km GEO).

[Edit: Clarified RF aperture = Solar Collector area, for the CASSIOPeiA concept, hence peak intensity also limited by the available power, 1365 W/m^2, and the CPV efficiency, 30% - 45%] 
« Last Edit: 06/27/2017 04:03 PM by SICA Design »

Offline QuantumG

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Re: Solar Power Satellites
« Reply #91 on: 06/20/2017 11:16 PM »
That's really low.

I've often thought that if SBSP will ever be worthwhile, they have to up the beam intensity to greater than sunlight to reduce the footprint.

There are SBSP schemes that basically just try to solve the Sun-at-night problem of terrestrial solar. The dumbest being the space-mirrors idea.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline Lar

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Re: Solar Power Satellites
« Reply #92 on: 06/21/2017 12:46 AM »
Split recent earth vs. space solar posts into separate thread:
Earth Solar vs. Solar Power Satellites
Gongora / Other-Mods - do you know what's happened to this thread (Earth Solar vs. Solar Power Satellites)?

Investigating this ... it may not be back, it got kind of snarky.  But usually a PM is the way to go when wondering these sorts of things.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
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Offline QuantumG

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Re: Solar Power Satellites
« Reply #93 on: 06/21/2017 01:02 AM »
Investigating this ... it may not be back, it got kind of snarky.  But usually a PM is the way to go when wondering these sorts of things.

Seeing as we're talking about it... I don't really care if the thread comes back, but I will report-to-mod all attempts to bring that snarkiness back here.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline Nilof

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Re: Solar Power Satellites
« Reply #94 on: 07/08/2017 06:32 PM »
Personally I don't think I agree with low power beam designs. A beam with a spot size of ~10 meters and an average intensity of 100 solar constants is much more useful, since you can have them power vehicles such as boats or aircraft which pay more per kW of energy since they can not feasibly be connected to the grid. High power density SSP's are still less of an issue than concentrated solar thermal farms as far as birds or aircraft go. You could even put receivers on tethered high-altitude balloons if you're really that worried.

I don't see much point in space solar power if it's just "sunlight at night" unless you manage to make launches that much cheaper than batteries.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Asteroza

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Re: Solar Power Satellites
« Reply #95 on: 07/09/2017 11:40 PM »
Personally I don't think I agree with low power beam designs. A beam with a spot size of ~10 meters and an average intensity of 100 solar constants is much more useful, since you can have them power vehicles such as boats or aircraft which pay more per kW of energy since they can not feasibly be connected to the grid. High power density SSP's are still less of an issue than concentrated solar thermal farms as far as birds or aircraft go. You could even put receivers on tethered high-altitude balloons if you're really that worried.

I don't see much point in space solar power if it's just "sunlight at night" unless you manage to make launches that much cheaper than batteries.

Certainly an economic case can be made for large vehicles and fixed remote sites that require small receivers as early customers for bootstrapping. Notably, military forward bases and small islands, both of which pay through the nose for power, and both have little land reservable for large rectennas. Though that then pushes into laser territory due to the physics of it all, which is fine by me as a laser system allows launcher upgrades that accelerate bootstrapping. I have a dislike about having to weaken system designs for political purposes, but infrastructure projects by their nature are political in nature, so you're damned if do, damned if you don't.

Offline QuantumG

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Re: Solar Power Satellites
« Reply #96 on: 07/09/2017 11:55 PM »
I don't see much point in space solar power if it's just "sunlight at night" unless you manage to make launches that much cheaper than batteries.

Well, it's obviously not just batteries... even if you had 12 hour days you'd need over double the generation capacity (as the batteries have losses) and typically more than that... and as I keep saying, the real win of space solar power is for the people living in space. Neither energy farms, nor space projects are good investments. If your goal is to make money, go make a Facebook game or whatever.

If you want people living and working in space, selling sunlight is a pretty good business for them.

Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline TrevorMonty

Re: Solar Power Satellites
« Reply #97 on: 07/10/2017 11:54 AM »
I don't see much point in space solar power if it's just "sunlight at night" unless you manage to make launches that much cheaper than batteries.

Well, it's obviously not just batteries... even if you had 12 hour days you'd need over double the generation capacity (as the batteries have losses) and typically more than that... and as I keep saying, the real win of space solar power is for the people living in space. Neither energy farms, nor space projects are good investments. If your goal is to make money, go make a Facebook game or whatever.

If you want people living and working in space, selling sunlight is a pretty good business for them.
Beaming power by laser to lunar rovers and outposts could well be first use. For rovers even a few 100watts is all that is needed every few hours to operate through lunar night. Radio telescopes would also need power for lunar night.


Offline TrevorMonty

Re: Solar Power Satellites
« Reply #98 on: 01/03/2018 03:26 AM »


http://www.minesnewsroom.com/news/lange-studying-feasibility-space-based-solar-power

“The two markets that everyone is interested in as far as space-based solar power is advanced deployment of military units and remote mining operations,” Lange said. 

You can also add space mining operations to that list, especially lunar mines.


Offline bolun

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Re: Solar Power Satellites
« Reply #99 on: 06/02/2018 09:08 AM »
30% efficiency solar cell

Solar cells have a hard life in space – their efficiency at converting sunlight into energy at the end of their time there is more prized than their initial efficiency. This next generation solar cell having an area of around 30 sq. cm boosts the beginning of life efficiency of up to 30.9% and end of life efficiency to 27.5% - and in the future designers expect to push this figure above 30%.

Developed for ESA by a consortium led by German solar cell manufacturer Azur Space, CESI in Italy, Germany’s Fraunhofer Institute for Solar Energy Systems, Qioptiq in the UK, Umicore in Belgium, tf2 devices in the Netherlands, and Finland’s Tampere University of Technology, this design is a ‘four-junction’ 0.1 mm-thick device containing four layers of different materials (AlGaInP, AlGaInAs, GaInAs,Ge) to absorb separate wavelengths of sunlight.

This design was originated through ESA’s Technology Research Programme with further development and qualification testing supported through the Agency’s ARTES, Advanced Research in Telecommunications Systems, programme. It is currently intended to fly with ESA’s next generation Neosat telecom satellites.

https://www.esa.int/spaceinimages/Images/2018/05/30_efficiency_solar_cell

Image credit: Azur Space