Solar sailing as a service

[yoram]

A couple months back there was an interview with the founders of "Reflect". That's a startup that is trying to build a constellation of hundreds (or thousands?) of solar sails in LEO that can supply extra sun near dawn and dusk to existing solar arrays on the earth surface. The space craft are supposed to do all their station keeping using solar sailing using the same mirror sail as is used for the main application.

One of  the people there mentioned that if the technology works they could also offer solar sailing as a service.  Attach a small payload to the sail and instead of staying in LEO use the sun to reach other places.

I don't think he meant that there is really a big market there, but just that it would be an interesting spin-off of the technology.

This would be perhaps analogous to Starlink starting to sell their existing high volume satellite buses for other applications. Everything apart from the payload could piggy back on other mass produced technologies:  The launch can be a cheap rideshare instead of a costly dedicated deep space launch.  If the basic Reflect concept works out the solar sails itself are already mass produced.
.
Now there are probably many challenges with such a concept. The payload is presumably quite small (since the Reflect sails are only a few square meters), so it will need extreme miniaturization including the communication facilities. Solar sailing will take a long time to get anywhere. It will probably not fit well into existing space craft funding schemes that rely on a team of people being available for the whole flight (probably it would need to be mostly automated with very little human intervention). There are also limits with energy supply and available photon pressure in the outer solar system.

On the other hand it seems to offer the promise of really cheep deep space probes if it works.

[volker2020]

I did read there first proposal, and it did break physics (not even talking about there business case). Hope this times they spend more time in the question of can it actually work, than they did before.

Until someone serious tells me, he checked there numbers, I will not even have a look.

[daedalus1]

It would really mess up the natural world, so even if possible, just wouldn't happen.

[mecko23]

I did read there first proposal, and it did break physics (not even talking about there business case). Hope this times they spend more time in the question of can it actually work, than they did before.

Until someone serious tells me, he checked there numbers, I will not even have a look.

Are you referencing the idea of reflecting light to ground as the first proposal? If so, the business case is indeed flimsy but I fail to see how this would break physics?

[volker2020]

They proposed to use space mirrors to enlighten solar cells on earth to prolong production time, and wanted to be paid for it. Taking the size of the mirrors, the size of the ground target, and the radiation expansion there was no way that this would produce any meaningful energy.

[InterestedEngineer]

They proposed to use space mirrors to enlighten solar cells on earth to prolong production time, and wanted to be paid for it. Taking the size of the mirrors, the size of the ground target, and the radiation expansion there was no way that this would produce any meaningful energy.

care to show some math so some of us can learn what the problem is?

[daedalus1]

I think it's the requirement of the thread to show maths to how it would be possible.
An answer to my earlier comment would be a start.

[yoram]

I think it's the requirement of the thread to show maths to how it would be possible.
An answer to my earlier comment would be a start.

At least my intention with the thread wasn't to talk about this at all, but  to talk about deep space solar sailing with mass produced cheap solar sails. If you want to talk about terrestrial space power there is an already fine other thread for it.

[yoram]

Also I rewatched the Reflect interview in the other thread, and the Reflect person actually mentioned that they plan to do a demo later this year. Launch two solar sails on a LEO ride share, and use one for demonstrating the terrestrial power application and another for a deep space demo.

Will certainly be interesting to see if that works. Perhaps a moon mission for cheap?

[StraumliBlight]

Concept study of solar sail orbital mission to Mercury

Transfer to Mercury:

With this Ac, the transfer from Earth to Mercury (with no C3 from launch) takes 7 years, plus 180 days to move into orbit (Fig. 3). This does not include the use of any planet flybys.

[daedalus1]

My comments directly address your opening point. Beaming light to the earths surface will mess with the natural world.

[Twark_Main]

They proposed to use space mirrors to enlighten solar cells on earth to prolong production time, and wanted to be paid for it. Taking the size of the mirrors, the size of the ground target, and the radiation expansion there was no way that this would produce any meaningful energy.

care to show some math so some of us can learn what the problem is?

The 600 km altitude means they can make a bright spot no smaller than 5 km in diameter, with an area of about 20 km². Their market claims to be giving solar farms an extra 30 minutes of light at dawn and dusk. If they have (optimistically) a 1 km² mirror, that means 5% extra production for 4% of the time, or a 0.2% increase in a solar farm's production.

This is with a 1 km² mirror in a 600 km polar orbit, which is about the most catastrophic thing imaginable for Kessler syndrome. It's in exactly the worst inclination (Sun-synchronous polar is highly crowded), at exactly the wrong altitude (600 km is right at the peak density) and with exactly the wrong payload (a huge surface area that will be constantly eroded by MMOD, producing more MMOD).

Even if they got so successful that they literally broke space travel, they still wouldn't make enough money. 


They better hope the solar sailing market has better feasibility!

[yoram]

They proposed to use space mirrors to enlighten solar cells on earth to prolong production time, and wanted to be paid for it. Taking the size of the mirrors, the size of the ground target, and the radiation expansion there was no way that this would produce any meaningful energy.

care to show some math so some of us can learn what the problem is?

The 600 km altitude means they can make a bright spot no smaller than 5 km in diameter, with an area of about 20 km². Their market claims to be giving solar farms an extra 30 minutes of light at dawn and dusk. If they have (optimistically) a 1 km² mirror, that means 5% extra production for 4% of the time, or a 0.2% increase in a solar farm's production.

Their current mirror is 10 by 10m (but should not matter that much), but they plan to have over 600 of them (as a "virtual parabola" like terrestrial solar thermal installations). So if 10 hit the solar farm at a time it is 2% increase and if 50 hit it at a time it is 10% increase. Now these numbers depend on a lot of other things (your numbers are optimistic) and also more importantly how the orbit versus locations work out to get enough mirrors in position at the right time.

I suspect it makes commercial sense if it can increase the solar farm effective duty cycle by a singe digit percentage which might be possible.

What I don't quite get is how their demo flight is supposed to work since they won't have a constellation yet and the effect from a mirror or two could well be too small to have a measurable difference on the ground. They were already accepting reservations on their web site, so it has better do something. But I guess we'll find out later this year if it works or not.

But back to solar sailing I hope. Perhaps some moderator could move these off topic posts into the other solar power thread.

[Twark_Main]

They proposed to use space mirrors to enlighten solar cells on earth to prolong production time, and wanted to be paid for it. Taking the size of the mirrors, the size of the ground target, and the radiation expansion there was no way that this would produce any meaningful energy.

care to show some math so some of us can learn what the problem is?

The 600 km altitude means they can make a bright spot no smaller than 5 km in diameter, with an area of about 20 km². Their market claims to be giving solar farms an extra 30 minutes of light at dawn and dusk. If they have (optimistically) a 1 km² mirror, that means 5% extra production for 4% of the time, or a 0.2% increase in a solar farm's production.

Their current mirror is 10 by 10m (but should not matter that much), but they plan to have over 600 of them (as a "virtual parabola" like terrestrial solar thermal installations). So if 10 hit the solar farm at a time it is 2% increase and if 50 hit it at a time it is 10% increase.

Nope.  Bad math. You said the collectors are 10m x 10m, but I was assuming 1,000m x 1,000m.

If 10 mirrors are aimed at the same collector, they will increase its output by 0.0002%. With 50 it increases by 0.01%. With all 600 mirrors, 0.12%.

So by your own admission it's not workable:

I suspect it makes commercial sense if it can increase the solar farm effective duty cycle by a singe digit percentage

When evaluating economic feasibility we should be assuming SSaaS is a full-blown whole-company pivot, not just a supplemental source of side-revenue. That's why it's relevant to the immediate topic at hand.

[yoram]

Nope.  Bad math. You said the collectors are 10m x 10m, but I was assuming 1,000m x 1,000m.

In my (admittedly primitive) understanding of optics is that if you use a flat mirror, making it larger just increases the diameter of the spot on the ground, but at any given point the delivered photons aren't increased. I think you're assuming a curved mirror, but that's not what Reflect is building. All they do is sheets of Mylar on a light weight frame, as in a classical solar sail.

If they used 1000x1000 they could serve gigantic solar farms on the ground, but most installations are not that big. Even with 10x10 it is several km. iirc in one of the interviews Nowack mentioned ~5km diameter as their target which likely already requires a very good mirror to minimize spreading.

When evaluating economic feasibility we should be assuming SSaaS is a full-blown whole-company pivot, not just a supplemental source of side-revenue. That's why it's relevant to the immediate topic at hand.

Yes maybe we can just talk about solar sailing ...

[InterestedEngineer]

Nope.  Bad math. You said the collectors are 10m x 10m, but I was assuming 1,000m x 1,000m.

In my (admittedly primitive) understanding of optics is that if you use a flat mirror, making it larger just increases the diameter of the spot on the ground, but at any given point the delivered photons aren't increased. I think you're assuming a curved mirror, but that's not what Reflect is building. All they do is sheets of Mylar on a light weight frame, as in a classical solar sail.

If they used 1000x1000 they could serve gigantic solar farms on the ground, but most installations are not that big. Even with 10x10 it is several km. iirc in one of the interviews Nowack mentioned ~5km diameter as their target which likely already requires a very good mirror to minimize spreading.

When evaluating economic feasibility we should be assuming SSaaS is a full-blown whole-company pivot, not just a supplemental source of side-revenue. That's why it's relevant to the immediate topic at hand.

Yes maybe we can just talk about solar sailing ...

with a thousand 10x10 mirrors one can make a curved mirror.

[Twark_Main]

Nope.  Bad math. You said the collectors are 10m x 10m, but I was assuming 1,000m x 1,000m.

In my (admittedly primitive) understanding of optics is that if you use a flat mirror, making it larger just increases the diameter of the spot on the ground, but at any given point the delivered photons aren't increased. I think you're assuming a curved mirror, but that's not what Reflect is building. All they do is sheets of Mylar on a light weight frame, as in a classical solar sail.

I am assuming a flat mirror. Due to the non-zero solid angle of the Sun, the spot on the ground has a minimum size of 5 km diameter.

If you increase the size from 10 m to 1000 m, the spot size will increase in size from 5 km to 6 km in diameter. But mostly the effect is that it will get 1,000,000 times brighter within that central 5 km patch (and fading out around the edges).

If they used 1000x1000 they could serve gigantic solar farms on the ground, but most installations are not that big. Even with 10x10 it is several km. iirc in one of the interviews Nowack mentioned ~5km diameter as their target which likely already requires a very good mirror to minimize spreading.

Yep, thuis is one of their major problems. They can't deliver photons to an area smaller than 5 km in diameter, so for most customers most of the photons would be wasted (or worse, unwanted light pollution effecting the neighbors).

When evaluating economic feasibility we should be assuming SSaaS is a full-blown whole-company pivot, not just a supplemental source of side-revenue. That's why it's relevant to the immediate topic at hand.

Yes maybe we can just talk about solar sailing ...

The economics should be similar to solar-electric tugs like Rocket Lab's Photon. What can we learn from looking at their example?