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Space based solar is one of many interesting ideas that only works if you hand wave a lot of extremely hard or intractable problems. Just to construct some mas

Space based solar is one of many interesting ideas that only works if you hand wave a lot of extremely hard or intractable problems. Just to construct some massive structure in space is a monumental challenge. Every ton of solar panels or support structure needs some bus to get it to the right orbit and maneuver it in place. Even if you assume fully automated construction you need buses for all the construction robots and tankers to refuel them. Any collisions could scrap the whole project by making a debris cloud in the same orbital plane as the relatively fragile solar panels. That all ignores the sourcing of raw materials, finished components, fuel, and buses to flit everything around. The "easy" answer is "use in-situ materials". In-space mining, refining, and fabrication are all entirely unsolved problems. Even the cheapest vapor ware SpaceX heavy lift rocket isn't cheap enough to build a space based solar plant with components from Earth. The technical difficulty and cost would be ridiculous compared to just building ground based renewables. Ones of billions of dollars will get you gigawatts worth of off-shore wind power or ground based solar. Unless you have access to literal magic there's no situation where space based solar ends up more efficient or cheaper than ground based renewables. The capital expense is literally and figuratively astronomical.

qayxc 5y ago
Even if the "cost" of getting the required infrastructure into orbit (assuming Earth-based manufacturing) was close to zero, the energy requirements would still eat up the benefits. SSP only works if every piece of the orbital infrastructure is sourced and built outside of Earth's gravity well. But that's not even the main concern with such system. The primary reason we won't see anything like this anytime soon is the simple fact that such system can easily be weaponised. An SSP is basically a potential space-based weapon. Even if there's no intention to use it as such, some governments are pretty much guaranteed to see it that way and proceed to install actual space-based weaponry in orbit.
- BurningFrog 5y ago
  > An SSP is basically a potential space-based weapon Asteroid mining has a similar problem. Any tech that can send a metal asteroid to Earth orbit can also smash it into Buenos Aires.
  - nkrisc 5y ago
    It doesn’t even have to be intentional.
  - iso1210 5y ago
    Any tech that can send a 1 ton roadster to mars can crash a 1 ton roadster into Buenos Aires at 20,000mph
    - wongarsu 5y ago
      Obviously. It all started as a way to drop bombs on London, and we are only now reaching a time where the majority of rocket models are not derivatives of ICBMs. Spaceflight is a story of a military technology finding civilian use. That has a very different ring to it than civilian technology being used as a weapon, even if the effect is similar.
    - foota 5y ago
      Wouldn't the car disintegrate in the atmosphere?
      - ac29 5y ago
        The car would obviously be a poor choice as a weapon. A big tungsten rod on the other hand... https://en.wikipedia.org/wiki/Kinetic_bombardment https://en.wikipedia.org/wiki/Kinetic_bombardment
    - Retric 5y ago
      Air resistance limits small kinetic kill weapons. Square cube law however means it’s less effective for larger objects.
      - iso1210 5y ago
        1 ton tungston rod wouldn't burn up.
        5y ago
- skissane 5y ago
  Maybe China will build such a system, not because it makes economic sense, rather for national prestige, so they can claim to be ahead of the US in that technology. Even if they spend a few billion for a modest sized demonstration system, that’s only a fraction of their national budget. How would the US respond? Possibly Congress will respond by paying to build its own bigger one, again not for the economics, simply for the prestige. I am not sure anyone will care that much about the “space-based weapon” angle. If it is a weapon, you just build your own and then you have one too, and now both sides have that weapon. The ability to have a (possibly illegal) space-based weapon yet publicly insist it is just a (completely legal) power generation demonstrator may even be attractive to military planners on both sides. However, in practice, a modest sized technology demonstrator may be quite limited in the damage it can inflict, unless it was enhanced with extra hardware that made it more obviously a weapon, and harming its plausible deniability.
  - chii 5y ago
    There's no need for space based weapons when hypersonic missiles can deliver megatonne grade nuclear arsenals "easily" today. But framing it as a weapons system, to attract military funding (which ultimately ends up as useful civilian technology) isn't so bad.
- formerly_proven 5y ago
  Is it? Article claims 2 GW / 30 km², which is ~70 W/m², a fraction of solar irradiance in most places.
  - ben_w 5y ago
    Sort of yes, sort of no. If there is at most one space based solar energy system visible from any given point on the ground, you can make strong safety claims based on wavelength and antenna size. However, if you limit yourself to one in any given sky, you necessarily either (1) put them in high orbit so they do useful things in local night, limiting you to a small total count planet-wide, or (2) put them in a low orbit, which means you can’t use them in local nighttime. If you want nighttime coverage and enough of these systems to be relevant to global power — and the current nameplate capacity of ground-based PV is just under a terawatt — you have to worry about multiple orbit-to-ground beams being directed at the same spot. While you could have up to about half a dozen giant ground-station for half a dozen giant beams, that needs ground level transmission over a significant fraction of the surface to be relevant to global energy needs, at which point you might as well make a planetary scale power grid and get your nighttime supplies from a mixture of the rooftops on the other side of the planet and some convenient deserts your energy supplier is renting.
    - T-A 5y ago
      > put them in high orbit so they do useful things in local night, limiting you to a small total count planet-wide Geostationary orbit is a circle over the equator with radius 42241 km, circumference 265408 km. Yes, it's "limited" in the sense that it's finite, but it's not exactly small. In its current primary use, communication satellites, there is a problem with interference; things like residential TV-sat dishes need to be small, so they have limited resolution, so those satellites need to be relatively far apart. That is not an issue for space based solar power. > put them in a low orbit [...] worry about multiple orbit-to-ground beams being directed at the same spot From different directions, at different times.
      - ben_w 5y ago
Clewza313 5y ago
The game changer here is SpaceX's Starship. If you can lift 100T to orbit in one shot, that suffices to deploy around 6 MW worth of the current solar panels we use for the ISS, which clock in at around 120KW/2T. Solar panel efficiency has improved greatly since they were designed and built, so even accounting for the overhead of assembly, refueling, the transmission component etc, 10MW+ per launch seems quite feasible, particularly if Musk gets costs down to the mooted $20/kg or so. Charlie Stross does the napkin math here: https://www.antipope.org/charlie/blog-static/2021/09/fossil-fuels-are-dead.html https://www.antipope.org/charlie/blog-static/2021/09/fossil-...
- marcosdumay 5y ago
  Interesting. That's 0.20$/W on launch costs, what is actually not a showstopper. I still doubt it will happen any time soon, because by the time we have enough launch capacity to use on things like this, the 0.2$/W will be a sizeable fraction of the costs of solar on the ground. The advantage is that you don't need batteries, but like photovoltaics, the floor on the costs of batteries is very low.
  - giantrobot 5y ago
    Their math is wrong. The ISS solar panels plus supporting truss elements mass about 60t or 2KW/t. At the fantastical (unbelievable) $20/kg to LEO that's $10/W. That doesn't include the mass of thermal control elements, maneuvering systems, power conversion, or power transmission system. Also that's only to LEO which is useless for an SPS since the system wouldn't dwell over any receiver on the ground long enough to transmit a useful amount of power. You'd need all that mass in a geosynchronous orbit which trebles or quadruples that cost.
- giantrobot 5y ago
  You're missing a few details. 1. The current (public) Starship design has no facilities for cargo delivery. While it can lift a lot of mass it doesn't have doors to unload large payloads in space. SpaceX certainly can build cargo versions but that will require non-trivial changes to the craft. Cargo doors aren't load bearing structures. 2. Starship's "100t to orbit" is only to LEO. To get a payload to a better orbit you're going to need to also launch some sort of bus and lots of fuel. Even if it's just a buddy fueling Starship that's still more launches and rendezvous. 3. Musk's claims of $20/kg are unbelievable. He has a long colorful history or over promising and under delivering. A fully fleshed out Starship production pipeline will bring launch costs down but not that much. It'd be nice to be wrong but I'd take all of Musk's claims with a giant grain of salt. 4. You're vastly underestimating the amount of mass you'd need to put in orbit and then assemble. Solar panels aren't load bearing so they all need to be attached to some sort of support truss (like the ISS truss). Then you've got the power conversion system, thermal control system, maneuvering system, and power transmission system. Each of those systems will easily mass the same as the actual solar panels. 5. The ISS solar panels with the support truss elements mass about 60t [0], so they generate about 2KW/t. Assuming power conversion was 50% efficient (I think that's reasonable) a gigawatt SPS would need at least 1000t of panel assemblies with at minimum another 500t of supporting equipment/infrastructure. I'd argue the support structure would be at least 1000t. 6. To make that SPS even remotely useful you'd need it in a geosynchronous orbit, any lower and it would pass too quickly over the ground to transmit any power. So an SPS, sending just a gigawatt of power to the ground, would require a minimum of 1500t (~4x ISS) launched into a geosynchronous orbit. That's in addition to the fuel and buses launched to facilitate construction. All of that is just for assembly. None of that counts the component construction on the ground of the space-qualified hardware. Meanwhile a gigawatt of renewable power on Earth is orders of magnitude cheaper and doesn't require several square kilometers of rectenna on the ground. A bit of debris that breaks a ground based panel also won't cause a chain reaction that can destroy the entire installation. [0] https://space.stackexchange.com/a/9758 https://space.stackexchange.com/a/9758
simonebrunozzi 5y ago
The naive engineer in me thinks that a baloon floating at 4k-5k meters above sea level, covered with solar panels, would still get most of the efficiency, but would also be cheaper and simpler to build. Where am I horribly wrong?
- giantrobot 5y ago
  Transmission loses would probably make a balloon a wash vs ground-based solar. Then there's the liability of some mass of solar panels floating over populated areas. At 5km an untethered balloon would have a fairly wide area it could land on. A 5km tether dragging around or falling on the ground could cause a lot of damage as well. There's also dangerous conditions when atmospheric conditions cause the balloon to lower its altitude, slacking the tether, and low altitude wind whipping it around. I don't see any utility of untethered balloons.

qayxc 5y ago

Even if the "cost" of getting the required infrastructure into orbit (assuming Earth-based manufacturing) was close to zero, the energy requirements would still eat up the benefits. SSP only works if every piece of the orbital infrastructure is sourced and built outside of Earth's gravity well. But that's not even the main concern with such system. The primary reason we won't see anything like this anytime soon is the simple fact that such system can easily be weaponised. An SSP is basically a potential space-based weapon. Even if there's no intention to use it as such, some governments are pretty much guaranteed to see it that way and proceed to install actual space-based weaponry in orbit.

BurningFrog 5y ago
> An SSP is basically a potential space-based weapon Asteroid mining has a similar problem. Any tech that can send a metal asteroid to Earth orbit can also smash it into Buenos Aires.
- nkrisc 5y ago
  It doesn’t even have to be intentional.
- iso1210 5y ago
  Any tech that can send a 1 ton roadster to mars can crash a 1 ton roadster into Buenos Aires at 20,000mph
  - wongarsu 5y ago
    Obviously. It all started as a way to drop bombs on London, and we are only now reaching a time where the majority of rocket models are not derivatives of ICBMs. Spaceflight is a story of a military technology finding civilian use. That has a very different ring to it than civilian technology being used as a weapon, even if the effect is similar.
  - foota 5y ago
    Wouldn't the car disintegrate in the atmosphere?
    - ac29 5y ago
      The car would obviously be a poor choice as a weapon. A big tungsten rod on the other hand... https://en.wikipedia.org/wiki/Kinetic_bombardment https://en.wikipedia.org/wiki/Kinetic_bombardment
  - Retric 5y ago
    Air resistance limits small kinetic kill weapons. Square cube law however means it’s less effective for larger objects.
    - iso1210 5y ago
      1 ton tungston rod wouldn't burn up.
      - 5y ago
skissane 5y ago
Maybe China will build such a system, not because it makes economic sense, rather for national prestige, so they can claim to be ahead of the US in that technology. Even if they spend a few billion for a modest sized demonstration system, that’s only a fraction of their national budget. How would the US respond? Possibly Congress will respond by paying to build its own bigger one, again not for the economics, simply for the prestige. I am not sure anyone will care that much about the “space-based weapon” angle. If it is a weapon, you just build your own and then you have one too, and now both sides have that weapon. The ability to have a (possibly illegal) space-based weapon yet publicly insist it is just a (completely legal) power generation demonstrator may even be attractive to military planners on both sides. However, in practice, a modest sized technology demonstrator may be quite limited in the damage it can inflict, unless it was enhanced with extra hardware that made it more obviously a weapon, and harming its plausible deniability.
- chii 5y ago
  There's no need for space based weapons when hypersonic missiles can deliver megatonne grade nuclear arsenals "easily" today. But framing it as a weapons system, to attract military funding (which ultimately ends up as useful civilian technology) isn't so bad.
formerly_proven 5y ago
Is it? Article claims 2 GW / 30 km², which is ~70 W/m², a fraction of solar irradiance in most places.
- ben_w 5y ago
  Sort of yes, sort of no. If there is at most one space based solar energy system visible from any given point on the ground, you can make strong safety claims based on wavelength and antenna size. However, if you limit yourself to one in any given sky, you necessarily either (1) put them in high orbit so they do useful things in local night, limiting you to a small total count planet-wide, or (2) put them in a low orbit, which means you can’t use them in local nighttime. If you want nighttime coverage and enough of these systems to be relevant to global power — and the current nameplate capacity of ground-based PV is just under a terawatt — you have to worry about multiple orbit-to-ground beams being directed at the same spot. While you could have up to about half a dozen giant ground-station for half a dozen giant beams, that needs ground level transmission over a significant fraction of the surface to be relevant to global energy needs, at which point you might as well make a planetary scale power grid and get your nighttime supplies from a mixture of the rooftops on the other side of the planet and some convenient deserts your energy supplier is renting.
  - T-A 5y ago
    > put them in high orbit so they do useful things in local night, limiting you to a small total count planet-wide Geostationary orbit is a circle over the equator with radius 42241 km, circumference 265408 km. Yes, it's "limited" in the sense that it's finite, but it's not exactly small. In its current primary use, communication satellites, there is a problem with interference; things like residential TV-sat dishes need to be small, so they have limited resolution, so those satellites need to be relatively far apart. That is not an issue for space based solar power. > put them in a low orbit [...] worry about multiple orbit-to-ground beams being directed at the same spot From different directions, at different times.
    - ben_w 5y ago

Clewza313 5y ago

The game changer here is SpaceX's Starship. If you can lift 100T to orbit in one shot, that suffices to deploy around 6 MW worth of the current solar panels we use for the ISS, which clock in at around 120KW/2T. Solar panel efficiency has improved greatly since they were designed and built, so even accounting for the overhead of assembly, refueling, the transmission component etc, 10MW+ per launch seems quite feasible, particularly if Musk gets costs down to the mooted $20/kg or so. Charlie Stross does the napkin math here: https://www.antipope.org/charlie/blog-static/2021/09/fossil-fuels-are-dead.html https://www.antipope.org/charlie/blog-static/2021/09/fossil-...

marcosdumay 5y ago
Interesting. That's 0.20$/W on launch costs, what is actually not a showstopper. I still doubt it will happen any time soon, because by the time we have enough launch capacity to use on things like this, the 0.2$/W will be a sizeable fraction of the costs of solar on the ground. The advantage is that you don't need batteries, but like photovoltaics, the floor on the costs of batteries is very low.
- giantrobot 5y ago
  Their math is wrong. The ISS solar panels plus supporting truss elements mass about 60t or 2KW/t. At the fantastical (unbelievable) $20/kg to LEO that's $10/W. That doesn't include the mass of thermal control elements, maneuvering systems, power conversion, or power transmission system. Also that's only to LEO which is useless for an SPS since the system wouldn't dwell over any receiver on the ground long enough to transmit a useful amount of power. You'd need all that mass in a geosynchronous orbit which trebles or quadruples that cost.
giantrobot 5y ago
You're missing a few details. 1. The current (public) Starship design has no facilities for cargo delivery. While it can lift a lot of mass it doesn't have doors to unload large payloads in space. SpaceX certainly can build cargo versions but that will require non-trivial changes to the craft. Cargo doors aren't load bearing structures. 2. Starship's "100t to orbit" is only to LEO. To get a payload to a better orbit you're going to need to also launch some sort of bus and lots of fuel. Even if it's just a buddy fueling Starship that's still more launches and rendezvous. 3. Musk's claims of $20/kg are unbelievable. He has a long colorful history or over promising and under delivering. A fully fleshed out Starship production pipeline will bring launch costs down but not that much. It'd be nice to be wrong but I'd take all of Musk's claims with a giant grain of salt. 4. You're vastly underestimating the amount of mass you'd need to put in orbit and then assemble. Solar panels aren't load bearing so they all need to be attached to some sort of support truss (like the ISS truss). Then you've got the power conversion system, thermal control system, maneuvering system, and power transmission system. Each of those systems will easily mass the same as the actual solar panels. 5. The ISS solar panels with the support truss elements mass about 60t [0], so they generate about 2KW/t. Assuming power conversion was 50% efficient (I think that's reasonable) a gigawatt SPS would need at least 1000t of panel assemblies with at minimum another 500t of supporting equipment/infrastructure. I'd argue the support structure would be at least 1000t. 6. To make that SPS even remotely useful you'd need it in a geosynchronous orbit, any lower and it would pass too quickly over the ground to transmit any power. So an SPS, sending just a gigawatt of power to the ground, would require a minimum of 1500t (~4x ISS) launched into a geosynchronous orbit. That's in addition to the fuel and buses launched to facilitate construction. All of that is just for assembly. None of that counts the component construction on the ground of the space-qualified hardware. Meanwhile a gigawatt of renewable power on Earth is orders of magnitude cheaper and doesn't require several square kilometers of rectenna on the ground. A bit of debris that breaks a ground based panel also won't cause a chain reaction that can destroy the entire installation. [0] https://space.stackexchange.com/a/9758 https://space.stackexchange.com/a/9758

simonebrunozzi 5y ago

The naive engineer in me thinks that a baloon floating at 4k-5k meters above sea level, covered with solar panels, would still get most of the efficiency, but would also be cheaper and simpler to build. Where am I horribly wrong?

giantrobot 5y ago
Transmission loses would probably make a balloon a wash vs ground-based solar. Then there's the liability of some mass of solar panels floating over populated areas. At 5km an untethered balloon would have a fairly wide area it could land on. A 5km tether dragging around or falling on the ground could cause a lot of damage as well. There's also dangerous conditions when atmospheric conditions cause the balloon to lower its altitude, slacking the tether, and low altitude wind whipping it around. I don't see any utility of untethered balloons.