5 ms·

Has anyone updated the economic feasibility studies based on using SpaceX's Starship as the heavy-lift reusable launcher? At first glance, it seems like this,

Has anyone updated the economic feasibility studies based on using SpaceX's Starship as the heavy-lift reusable launcher? At first glance, it seems like this, combined with today's greatly improved robotics and ion thrusters to move components from LEO to GEO, may be the key enablers.

simonh 3y ago
Musk is on record saying it's a complete non-starter. There are all sorts of problems with it. Beam spreading is a huge problem, the ground receiver would generally have to be about 10x the diameter of the transmitter and these would need to be really big arrays. A 1km transmitter is ballpark. Targeting the receiver is tricky as even minuscule angular offsets mean you would miss completely. Losses from transmission and reception are huge, and the enormous emissions leakage means you have to clear the big chunk of orbital 'real estate' of other satellites or they'd suffer serious problems.
- dexterdog 3y ago
  If he says it can't be done either it really is seriously unrealistic, or somebody else already has a lead on him.
  - xbmcuser 3y ago
    He has the cheapest way to get to space locked in for a few years so if he says it is not feasible than it probably is not feasible. Looking at how ground solar and battery prices are still falling 10-15% a year I think it will be hard for space solar to be economically viable let alone viable when you take it into account pollution.
- ben_w 3y ago
  Only 1km? Given the usual claims I hear about power density and total power, it's normally 100km^2, or square 10km on the side.
  - simonh 3y ago
    For the receiver yes that's ballpark. I'm talking about the size of the microwave transmitter array in orbit beaming power down to the surface.
    - ben_w 3y ago
      Ah! I misread. Thanks :)
  - mikepurvis 3y ago
    That's pretty sobering, since you can produce/capture quite a lot of energy with 100km^2 of clear, flat ground that has a view of the sky. Not least by just putting normal solar panels on it and jettisoning the whole space part.
    - DennisP 3y ago
      Yes but with SPS, that 100km^2 is mostly just antenna wire, and you don't need any sort of energy storage.
      - ben_w 3y ago
        At 6cm spacing, a 10km by 10km ground array with 1mm^2 cross section wires has total 1667 m^3 volume; this is as much conductor as you would get in the equivalent of a 1111 km long 1 GW HVDC cable: https://www.wolframalpha.com/input?i=10km*10km%2F6cm*1mm%5E2%2F1500mm%5E2 https://www.wolframalpha.com/input?i=10km*10km%2F6cm*1mm%5E2... It's not exactly the same thing, of course, but it means 40 such ground stations would use as much metal as a 1 GW line looping all the way around the planet and back to itself, and a global grid is another way to obviate storage. That's 1 GW with standard existing cables; I assume if you actually want to go that far one can improve the design as the optimisation goals are different. Parallel cables lower resistance. I'm also not sure how much maximum current would scale in such cases.
        mikepurvis 3y ago
- DennisP 3y ago
  People sure put a lot of weight on an off-the-cuff comment Musk made in 2012, before Starship was even a gleam in his eye. That was the same year NASA published their SPS-ALPHA study[1] on modern SPS design, so Musk may not have been aware of it. Modern designs use a phased-array transmitter, and a reference signal from the ground for targeting. Overall energy loss is 40 to 60% according to the book The Case for Space Solar Power. [1] https://www.nasa.gov/pdf/716070main_Mankins_2011_PhI_SPS_Alpha.pdf https://www.nasa.gov/pdf/716070main_Mankins_2011_PhI_SPS_Alp...
  - ben_w 3y ago
    60% loss is also what you would get with a single 1GW existing HVDC cable, connecting anywhere on Earth to its antipode. IIRC, for n identical parallel resistors of rΩ, Σ = nrΩ, so this only gets better for bigger systems.
  - giantrobot 3y ago
    Elon Musk's most fantastic/unrealistic prediction for Starship cost to orbit is $10/kg. To get to GEO roughly doubles that cost because the cargo Starship needs to rendezvous with a tanker for the fuel to GEO then back home. Intermodal surface freight reaching most of the planet is about $1/kg on the high end. To even begin to make sense, space freight to would need to be 1/10th of Musk's overly optimistic $10/kg. You could ship the panels air freight and still beat those numbers by a huge margin. That says nothing of the construction costs. Which for SBS will cost orders of magnitude more than day laborers in t-shirts assembling arrays on the ground. Every aspect of SBS is ridiculously expensive and requires as-yet entirely undeveloped space-based construction technologies. There's no near-term horizon where it's anywhere close to competitive with ground-based solar. This holds even if you assume over-building surface solar to 3x to match the duty cycle of SBS.
    - DennisP 3y ago
      You don't have to get to surface freight numbers to make SPS viable, because SPS has advantages that compensate for the higher transport cost. Those include a 99.5% capacity factor, a 5X higher solar flux per panel over 24 hours, and much lighter construction due to the lack of weather and gravity. As for construction cost, NASA's design would self-assemble in orbit. I linked the full study report.
jackmott 3y ago
[dead]
ZeroGravitas 3y ago
It's probably the lower cost of earthbound solar and batteries that are the bigger factor in updating the feasability, trending in the opposite direction.
deleted 3y ago
[deleted]
T-A 3y ago
There has been a surge of interest over the past year: https://spacenews.com/nasa-to-reexamine-space-based-solar-power/ https://spacenews.com/nasa-to-reexamine-space-based-solar-po... https://www.esa.int/Enabling_Support/Space_Engineering_Technology/SOLARIS/SBSP_overview https://www.esa.int/Enabling_Support/Space_Engineering_Techn... https://spaceenergyinitiative.org.uk/ https://spaceenergyinitiative.org.uk/ https://www.spacesolar.co.uk/ https://www.spacesolar.co.uk/ https://www.solarspacetechnologies.com.au/ https://www.solarspacetechnologies.com.au/ Here's a nice recent summary (despite the publication date): https://aerospaceamerica.aiaa.org/features/harvesting-sunlight-in-space/ https://aerospaceamerica.aiaa.org/features/harvesting-sunlig...

simonh 3y ago

Musk is on record saying it's a complete non-starter. There are all sorts of problems with it. Beam spreading is a huge problem, the ground receiver would generally have to be about 10x the diameter of the transmitter and these would need to be really big arrays. A 1km transmitter is ballpark. Targeting the receiver is tricky as even minuscule angular offsets mean you would miss completely. Losses from transmission and reception are huge, and the enormous emissions leakage means you have to clear the big chunk of orbital 'real estate' of other satellites or they'd suffer serious problems.

dexterdog 3y ago
If he says it can't be done either it really is seriously unrealistic, or somebody else already has a lead on him.
- xbmcuser 3y ago
  He has the cheapest way to get to space locked in for a few years so if he says it is not feasible than it probably is not feasible. Looking at how ground solar and battery prices are still falling 10-15% a year I think it will be hard for space solar to be economically viable let alone viable when you take it into account pollution.
ben_w 3y ago
Only 1km? Given the usual claims I hear about power density and total power, it's normally 100km^2, or square 10km on the side.
- simonh 3y ago
  For the receiver yes that's ballpark. I'm talking about the size of the microwave transmitter array in orbit beaming power down to the surface.
  - ben_w 3y ago
    Ah! I misread. Thanks :)
- mikepurvis 3y ago
  That's pretty sobering, since you can produce/capture quite a lot of energy with 100km^2 of clear, flat ground that has a view of the sky. Not least by just putting normal solar panels on it and jettisoning the whole space part.
  - DennisP 3y ago
    Yes but with SPS, that 100km^2 is mostly just antenna wire, and you don't need any sort of energy storage.
    - ben_w 3y ago
      At 6cm spacing, a 10km by 10km ground array with 1mm^2 cross section wires has total 1667 m^3 volume; this is as much conductor as you would get in the equivalent of a 1111 km long 1 GW HVDC cable: https://www.wolframalpha.com/input?i=10km*10km%2F6cm*1mm%5E2%2F1500mm%5E2 https://www.wolframalpha.com/input?i=10km*10km%2F6cm*1mm%5E2... It's not exactly the same thing, of course, but it means 40 such ground stations would use as much metal as a 1 GW line looping all the way around the planet and back to itself, and a global grid is another way to obviate storage. That's 1 GW with standard existing cables; I assume if you actually want to go that far one can improve the design as the optimisation goals are different. Parallel cables lower resistance. I'm also not sure how much maximum current would scale in such cases.
      - mikepurvis 3y ago
DennisP 3y ago
People sure put a lot of weight on an off-the-cuff comment Musk made in 2012, before Starship was even a gleam in his eye. That was the same year NASA published their SPS-ALPHA study[1] on modern SPS design, so Musk may not have been aware of it. Modern designs use a phased-array transmitter, and a reference signal from the ground for targeting. Overall energy loss is 40 to 60% according to the book The Case for Space Solar Power. [1] https://www.nasa.gov/pdf/716070main_Mankins_2011_PhI_SPS_Alpha.pdf https://www.nasa.gov/pdf/716070main_Mankins_2011_PhI_SPS_Alp...
- ben_w 3y ago
  60% loss is also what you would get with a single 1GW existing HVDC cable, connecting anywhere on Earth to its antipode. IIRC, for n identical parallel resistors of rΩ, Σ = nrΩ, so this only gets better for bigger systems.
- giantrobot 3y ago
  Elon Musk's most fantastic/unrealistic prediction for Starship cost to orbit is $10/kg. To get to GEO roughly doubles that cost because the cargo Starship needs to rendezvous with a tanker for the fuel to GEO then back home. Intermodal surface freight reaching most of the planet is about $1/kg on the high end. To even begin to make sense, space freight to would need to be 1/10th of Musk's overly optimistic $10/kg. You could ship the panels air freight and still beat those numbers by a huge margin. That says nothing of the construction costs. Which for SBS will cost orders of magnitude more than day laborers in t-shirts assembling arrays on the ground. Every aspect of SBS is ridiculously expensive and requires as-yet entirely undeveloped space-based construction technologies. There's no near-term horizon where it's anywhere close to competitive with ground-based solar. This holds even if you assume over-building surface solar to 3x to match the duty cycle of SBS.
  - DennisP 3y ago
    You don't have to get to surface freight numbers to make SPS viable, because SPS has advantages that compensate for the higher transport cost. Those include a 99.5% capacity factor, a 5X higher solar flux per panel over 24 hours, and much lighter construction due to the lack of weather and gravity. As for construction cost, NASA's design would self-assemble in orbit. I linked the full study report.

jackmott 3y ago

[dead]

ZeroGravitas 3y ago

It's probably the lower cost of earthbound solar and batteries that are the bigger factor in updating the feasability, trending in the opposite direction.

deleted 3y ago

[deleted]

T-A 3y ago

There has been a surge of interest over the past year: https://spacenews.com/nasa-to-reexamine-space-based-solar-power/ https://spacenews.com/nasa-to-reexamine-space-based-solar-po... https://www.esa.int/Enabling_Support/Space_Engineering_Technology/SOLARIS/SBSP_overview https://www.esa.int/Enabling_Support/Space_Engineering_Techn... https://spaceenergyinitiative.org.uk/ https://spaceenergyinitiative.org.uk/ https://www.spacesolar.co.uk/ https://www.spacesolar.co.uk/ https://www.solarspacetechnologies.com.au/ https://www.solarspacetechnologies.com.au/ Here's a nice recent summary (despite the publication date): https://aerospaceamerica.aiaa.org/features/harvesting-sunlight-in-space/ https://aerospaceamerica.aiaa.org/features/harvesting-sunlig...