Quote from: fatjohn1408 on 06/09/2016 08:44 amI worked on a concept at Uni back in the day and my own idea which I still find very attractive is to just put the sats in LEO and have two GEO satellites with individual mirrors per LEO sat. Instead of microwave beaming you use laser to transfer the energy from the LEO sat to the GEO sat to the groundstation on Earth. From LEO to GEO the airy disk (which contains 86% of the energy of the laser beam) only widens to something like 5 meter. If the laser would have a pointing accuracy of an order of magnitude worse than the hubble telescope it would still be very spot on.Lasers are much less efficient than microwave generators. Photovoltaics, even designed for a single wavelength, can't beat a rectina for efficiency. Lasers don't deal well with overcast, while microwaves of a well chosen wavelength have little loss through the atmosphere even with heavy clouds. On the other hand, you can get a much tighter, even dangerous, power beam.
I worked on a concept at Uni back in the day and my own idea which I still find very attractive is to just put the sats in LEO and have two GEO satellites with individual mirrors per LEO sat. Instead of microwave beaming you use laser to transfer the energy from the LEO sat to the GEO sat to the groundstation on Earth. From LEO to GEO the airy disk (which contains 86% of the energy of the laser beam) only widens to something like 5 meter. If the laser would have a pointing accuracy of an order of magnitude worse than the hubble telescope it would still be very spot on.
Quote from: Hanelyp on 06/09/2016 05:14 pmQuote from: fatjohn1408 on 06/09/2016 08:44 amI worked on a concept at Uni back in the day and my own idea which I still find very attractive is to just put the sats in LEO and have two GEO satellites with individual mirrors per LEO sat. Instead of microwave beaming you use laser to transfer the energy from the LEO sat to the GEO sat to the groundstation on Earth. From LEO to GEO the airy disk (which contains 86% of the energy of the laser beam) only widens to something like 5 meter. If the laser would have a pointing accuracy of an order of magnitude worse than the hubble telescope it would still be very spot on.Lasers are much less efficient than microwave generators. Photovoltaics, even designed for a single wavelength, can't beat a rectina for efficiency. Lasers don't deal well with overcast, while microwaves of a well chosen wavelength have little loss through the atmosphere even with heavy clouds. On the other hand, you can get a much tighter, even dangerous, power beam.ACTUAL very high frequency (i.e. ~1mm) microwave generators and rectennas are actually pretty close to the round-trip efficiency of direct-diode lasers and concentrating, single-wavelength photovoltaics.
Quote from: Robotbeat on 06/09/2016 05:34 pmQuote from: Hanelyp on 06/09/2016 05:14 pmQuote from: fatjohn1408 on 06/09/2016 08:44 amI worked on a concept at Uni back in the day and my own idea which I still find very attractive is to just put the sats in LEO and have two GEO satellites with individual mirrors per LEO sat. Instead of microwave beaming you use laser to transfer the energy from the LEO sat to the GEO sat to the groundstation on Earth. From LEO to GEO the airy disk (which contains 86% of the energy of the laser beam) only widens to something like 5 meter. If the laser would have a pointing accuracy of an order of magnitude worse than the hubble telescope it would still be very spot on.Lasers are much less efficient than microwave generators. Photovoltaics, even designed for a single wavelength, can't beat a rectina for efficiency. Lasers don't deal well with overcast, while microwaves of a well chosen wavelength have little loss through the atmosphere even with heavy clouds. On the other hand, you can get a much tighter, even dangerous, power beam.ACTUAL very high frequency (i.e. ~1mm) microwave generators and rectennas are actually pretty close to the round-trip efficiency of direct-diode lasers and concentrating, single-wavelength photovoltaics.Is that not another way of saying 1mm (300 GHz) microwave conversion and atmospheric propagation is far less efficient than "well chosen" 52mm (5.8 GHz) or 122mm (2.45 GHz) wavelengths?
Calculate the size of satellite antenna and ground station for 2.45GHz. You're talking a dish 1km wide for transmitting and 4km wide for receiving.Additionally, please show me microwave conversion efficiencies for specific components in that range, as well as rough operating temperatures.
Youtube video on AFRL progress in space solar power. Google "AFRL SSPIDER" to find more.
Quote from: TrevorMonty on 04/22/2021 03:15 amYoutube video on AFRL progress in space solar power. Google "AFRL SSPIDER" to find more.Presumably you mean "AFRL SSPIDR"??.. odd that they've been working on this for years now, and yet only just released this video.https://afresearchlab.com/technology/successstories/space-power-beaming/
A major objective of SSPIDR is to break the one-meter-squared aperture threshold for solar power capture and conversion, and beam that energy to the ground which AFRL will do with Arachne – SSPIDR’s flagship flight experiment.
when is it supposed to launch?
Caltech tile concept for SBSP. https://www.researchgate.net/publication/361417363_A_Lightweight_Space-based_Solar_Power_Generation_and_Transmission_SatelliteBasic figures based on their 651kg GEO concept vehicle, will deliver 491kw to grid or 0.75kw/kg to grid based on 10% overall efficiency they say between 7-14%. The collection area is 60x60m. They use x20 concentrators to maximise solar cells power generation. Paper also went into launch costs but given how fluid they are becoming not that important at present. Likely to be lot cheaper when this launches.While getting from LEO to GEO is currently very expensive using chemical proplusion and even SEP there are other alternatives. Solar sails driven by high powered lasers on earth, something Caltech is also working on.Edit. Beam Microwave propulsion is another way to transport these from LEO to GEO. Microwave beam heats hydrogen resulting in very simple 900ISP thruster. With microwave power coming from GEO power farm.
Quote from: TrevorMonty on 10/12/2023 09:44 amCaltech tile concept for SBSP. https://www.researchgate.net/publication/361417363_A_Lightweight_Space-based_Solar_Power_Generation_and_Transmission_SatelliteBasic figures based on their 651kg GEO concept vehicle, will deliver 491kw to grid or 0.75kw/kg to grid based on 10% overall efficiency they say between 7-14%. The collection area is 60x60m. They use x20 concentrators to maximise solar cells power generation. Paper also went into launch costs but given how fluid they are becoming not that important at present. Likely to be lot cheaper when this launches.While getting from LEO to GEO is currently very expensive using chemical proplusion and even SEP there are other alternatives. Solar sails driven by high powered lasers on earth, something Caltech is also working on.Edit. Beam Microwave propulsion is another way to transport these from LEO to GEO. Microwave beam heats hydrogen resulting in very simple 900ISP thruster. With microwave power coming from GEO power farm.There are concepts for getting far more Isp from beamed power to hydrogen. One of them involves "smog" in the hydrogen that absorbs the beamed energy rather than the physical engine. Supposed t do wonders for engine cooling with a far hotter reaction mass. .Beaming from astern obviously.
The Dream is Over?https://spacenews.com/nasa-report-offers-pessimistic-take-on-space-based-solar-power/
Quote from: Tywin on 01/19/2024 09:14 pmThe Dream is Over?https://spacenews.com/nasa-report-offers-pessimistic-take-on-space-based-solar-power/Pretty terrible report. Unprofessional and technically incorrect.
The NASA study did address the baseline model's sensitivity to factors such as lower launch costs, use of electric propulsion and assuming a longer lifetime for components in GEO than the 10 years included in the baseline. Incorporating all of those factors reduces the electricity costs of the SBSP systems to levels similar to terrestrial renewable alternatives.
The following combination of revised assumptions yields SBSP solutions that are cost competitive with terrestrial alternatives, with lower GHG emissions: • lower launch cost: $50M per launch, or $500/kg; $425/kg with 15% block discount • electric propulsion orbital transfer from LEO to GEO • extended hardware lifetimes: 15 years • cheaper servicer and debris removal vehicles: $100M and $50M, respectively • efficient manufacturing at scale: learning curves of 85% and belowOur sensitivity analyses highlight the need for advances across a wide range of SBSP enabling capabilities
Quote from: Robotbeat on 01/20/2024 12:26 amQuote from: Tywin on 01/19/2024 09:14 pmThe Dream is Over?https://spacenews.com/nasa-report-offers-pessimistic-take-on-space-based-solar-power/Pretty terrible report. Unprofessional and technically incorrect.The report is fine. The headline writing is (as always and by design) unnecessarily divisive and clickbait-y.From the article:Quote from: SpaceNewsThe NASA study did address the baseline model's sensitivity to factors such as lower launch costs, use of electric propulsion and assuming a longer lifetime for components in GEO than the 10 years included in the baseline. Incorporating all of those factors reduces the electricity costs of the SBSP systems to levels similar to terrestrial renewable alternatives.From the report:Quote from: NASAThe following combination of revised assumptions yields SBSP solutions that are cost competitive with terrestrial alternatives, with lower GHG emissions: • lower launch cost: $50M per launch, or $500/kg; $425/kg with 15% block discount • electric propulsion orbital transfer from LEO to GEO • extended hardware lifetimes: 15 years • cheaper servicer and debris removal vehicles: $100M and $50M, respectively • efficient manufacturing at scale: learning curves of 85% and belowOur sensitivity analyses highlight the need for advances across a wide range of SBSP enabling capabilitiesThat's no obituary. It's a shopping list.