20 thoughts on “The Latest SPS Study From NASA”

      1. Whichever one that has the Starship using Hydrolox fuel and puts Elon Musk in the agony booth each time it explodes.

  1. “However, the report assumed a Starship launch cost of $1,000 per kilogram, with a 15% block buy discount. That is not much less than current Falcon 9 and Falcon Heavy prices, while SpaceX has been promoting much steeper cost reductions for Starship. At a panel discussion last week during the Space Mobility conference, also in Orlando, officials from both SpaceX and the Air Force Research Lab projected a future where Starship costs would approach as little as $20 to 30 per kilogram. There is plenty of time to try to reach that cost: the NASA study projected that the SBSP systems would be launched in the 2040s.”

    Maybe by 2040s, if NASA would stop delaying Lunar and Mars crewed exploration.
    Whether the Moon has mineable water or not seems rather important in regards SPS happening anytime soon {within a few decades].
    NASA can’t determine nor make lunar water mineable.
    Just as, in simplest reality, that NASA was never able to lower launch cost. But NASA could explore the lunar polar and then explore Mars.
    I think the faster NASA does it’s Mars crewed missions is biggest effect that NASA could have on “making lunar water mineable” though of course the reality could be, that lunar water is “simply” not mineable.
    NASA should do an adequate level of exploring both lunar polar, and then quickly move forward with Mars crew exploration.
    But before Mars crew exploration, it needs some testing of artificial gravity. And more seriously consider using a Venus return pathway from and to Mars

  2. If the question is what new clean power sources could be brought online in the 2040s, I’d prefer to focus on fusion. Wind, solar, and even space-based solar require a lot more raw materials, real estate, and waste disposal. Even pessimistically, several fusion startups should be building commercial power plants by the 2040s. (Personally, I think it will be sooner.) But climate activists think that will be too late to save the planet – and it’s nuclear! – so they aren’t interested.

  3. A typical nuclear power plant is about 1GW. a 3J solar cell is 29.5% efficient beginning of life. That drops several % after being in space for a few years. Just for ball park calculation, assume average lifetime efficiency of 25% including all other loss factors.

    Total LASER or RF transmission losses are way worse than 25% but for the sake of argument assume 25% transmission and Earth conversion losses.

    So if you want 1GW: Area=1GW/(0.25*0.25*1360)=12e6 m^2
    (actual arrays have a packing factor around 80% which means that if your structure is 12e6m^2 you only have about 80% of that available for your solar cells but lets forget about that)

    Solar pressure is about 10e-6 N/m^2. —-> 120N of force pushing on your array. Don’t forget to convert that force to lb or you might run into Mars! 🙂

    So you need a 29lb thruster running continuously for the lifetime of every 1GW generator in space.

    Bring along some extra propellant!

    And don’t even get me started on gravity gradient torques and huge flexible body dynamic control!

    1. The simplest argument I’ve heard against SSPS is the maintenance argument. Why put all that solar energy in space when you could set up those panels on the ground and easily service and/or replace them when something goes wrong.

      Of course the counter argument goes along the lines that SSPS satellites work 24/7 except for the hour or so that they pass through the Earth’s shadow, but that is usually local midnight for the ground station when demand should be low. Plus if you space multiple SPSS along the GEO orbital plane that outage won’t happen for all satellites at the same time.

      The counter counter argument to that is you shouldn’t be using up valuable GEO orbital slots for SPSS that operate in near frequencies to more valuable communication satellites. Where compared to COMSATS, the orbital footprint of an SPSS is enormous by comparison. Less so if it uses LASERS instead of microwaves for a down link. But then the potential as a weapon increases.

      By far the maintenance aspect is a hard argument to win. Also when cost per kwh is compared against terrestrial solutions.

      Now for providing electrical power for space-based activities. That is another matter.

    2. Photovoltaics are not the way to go. Theyre heavy, brittle, and inefficient. Use a big reflector and heat engine instead. In the experiment I did at San Jose State in 2008, we were getting 40% efficiency using Fresnel lenses focused on boilers. At the same time Sandia was pretty happy to get 32% efficiency with their giant mirror / boiler combination.

      A reflector can be arbitrarily large. It’s a lot cheaper to launch 12 square kilometers of Aluminized Mylar than it is to launch solar panels, much easier to repair.

      1. But now you have moving coolant and plumbing and unless you are using TPVs. Then you need some way to convert that moving coolant into electricity, via a generator spinning via piston or turbine? Too many moving parts? But from an energy perspective I will grant you your design is more efficient. The TPV link claims 40% conversion efficiency with no moving parts. Was that what you were describing?


        Long term I just don’t see anything competing with terrestrial nuclear.

        1. No, we had the lenses (10 of them, 4’x3′ each) focused on small boilers, all linked together. These fed a turbine attached to a generator; total of two coaxial moving parts.

  4. A few years ago, a coworker made the best point I’ve heard about the heavy reliance on “fossil” fuels to include even uranium as it relates to global warming. Generally, you are taking stored potential energy from the Earth’s crust and converting it to kinetic energy on the surface at a greater rate than might otherwise naturally occur.

    Other’s opinion on that point may vary, but the idea of collecting solar energy that might otherwise not make it to the Earth’s surface and transmitting it directly to the Earth’s surface is a very bad idea to reduce global warming.

    If the goal is to reduce emissions, because emissions are bad (although plants seem to like CO2, and they do some great things for animals when we give plants CO2), then I guess space based solar is an idea that still is limited on other merits.

    1. In terms global warming “science” heat generated on Earth is not factor. If was factor geothermal energy would be part of climate energy budget. Or most geothermal energy occurs within the Ocean, one aspect is ocean floor is 70% of Earth surface, another factor is there simply more volcanic activity and ocean floor is young and thinner than continental land masses.
      Or Geothermal heat dwarfs all heat generated by humans and nature- as in forest fires.
      I think ocean Geothermal heat is part Earth climate energy budget- but it’s widely regarded as wrong.

      1. I remember reading about ultra deep ocean floor trenches that are essentially volcanic rift zones. The amount of heat they put into the ocean is a staggering number.

  5. Rand, congratulations on having that albatross removed from your neck.
    On the subject of the article, why are we talking about collecting energy from space and beaming it to the ground? I believe this is backwards, and will limit our development of robust, long-term space vehicles.
    Most advancements our standard of living came about from better access to, and lower cost of energy. A meteorite-proof space station immune to most space radiation which can be used for any number of near-Earth missions will need a lot of power. A heck of a lot. Why not produce power on the surface and beam it up, not down.
    Our current limit is about 1KW/M square. A base load power plant dedicated to power space vehicles could beam about 1GW to orbit, and on a bad day could be used to vaporize small rocks before they could do damage. Argon or Krypton hall thrusters could be scaled up to a practical size for cis-lunar orbit ops. Most space junk could be either destroyed or re-directed to minimize their threat to people and satellites, while providing power to hundreds of space stations.

    1. Art along similar lines I’ve read of the possibility of building monopropellant rockets and using high powered ground based lasers to flash it into high pressure gas all the way to orbit.

  6. Railroads are a relatively short-lived historical anomaly. Self-propelled goes anywhere, anytime vehicles are the norm. Airports and seaports are regulatory abuse, as are “highways.” It’s relatively easy to imagine a modern world without any of those. Try it! You’ll like it!

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