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For space-based solar to be efficient, ie for it to be better than just installing normal solar panels, the beamed energy would have to be at least as powerful
by stcredzero 6y ago
For space-based solar to be efficient, ie for it to be better than just installing normal solar panels, the beamed energy would have to be at least as powerful as sunlight
1) False. You just have to find contexts where installing solar panels is undesirable or impractical. A forward military camp in the hills of Afghanistan?
2) It's quite easy to exceed the energy density of solar panels with a microwave rectenna to receive power. In fact, a lot of the old designs were dedicated to reducing the power density for safety reasons.
One might say that space-based solar would operate 24/7 and so is better than normal solar panels. That's isn't reality. Low-orbit satellites spend half their day in darkness too.
Zero cloud cover. Zero dust buildup. In terms of access to solar flux, there are a lot of advantages to being in orbit. Also, there's a "simple" way to get around the tyranny of the rocket equation and get stuff to geosynchronous orbit cheaply: mine the moon, manufacture the silicon solar panels there, and use lunar electromagnetic mass drivers to deliver bulk cargo to geosynchronous orbit. So I would agree with a lot of what you're saying about impracticality with that caveat: "short of having lunar industrial infrastructure."
But, given a major power that has the above, how is this so different from having fusion power?
EDIT: But if you carry forward this thinking a few steps, you get to...Oh NO!
So let's say that we don't get fusion power, but we do get to the point where lunar industrial infrastructure looks within reach. In that case, control over lunar resources will mean control over the most plentiful, clean, and convenient form of energy. Basically, more than half of the motivation behind major power wars in the last century and a half, has been control over resources, particularly energy. Having energy resources gives one military power which gives control over energy resources.
This dynamic would seem to set up the next major power conflict past the Taiwan issue. Space could well wind up being the Caucasus Mountains/Persian Gulf of the early to mid 21st century. A major power conflict over energy resources which fundamentally involves the power densities implied by space travel just seems like BAD NEWS.
Even worse. We first get the start of the above conflict. Then only afterwards does rapid wartime R&D finally yields military grade fusion power. Yup, we're living in our really nifty, really interesting Sci-fi future. "May you live in interesting times."
- loeg 6y agoDoes the moon actually have any resources worth mining?
- DennisP 6y agoFor transport back to Earth, possibly not. For solar power satellites, it has lots of metal and silicon. For rocket fuel, it has some water and lots of oxygen. For large space colonies, it's a convenient source of bulk shielding material.
- loeg 6y agoSorry, I should have been more specific. Yes, I meant useful for building things up the gravity well. Sounds like the answer is "yes."
- stcredzero 6y agoFor transport back to Earth, possibly not He3, Perhaps. That stuff would be worth it by weight to send back, especially if done by electromagnetic mass driver and not rocket.
- DennisP 6y agoThat's often mentioned but there's a bit of a problem there. If you can get net power from fusing He3, then you can also get net power from the easier D-D reaction, and the waste product of D-D is....He3! Half directly, half as tritium which decays to He3 with a 12-year half-life. Even though D-D emits neutrons, they're at an energy similar to fission neutrons, rather than the extremely energetic (and easiest) D-T reaction. It's almost certainly going to be cheaper to get your He3 from D-D fusion, and get energy in the bargain, rather than sifting through millions of tons of lunar dirt. Fusion startup Helion, funded in part by YCombinator, is working on a hybrid D-D/D-He3 reactor, saying the combination will produce only 6% of its energy as neutron radiation, compared to 80% for D-T.
- stcredzero 6y ago
- deleted 6y ago[deleted]
- henearkr 6y agoNo nation could build this lunar mass driver alone. Maybe same thing for a Dyson swarm. So, all those are international projects, if not completely planetary projects. This reduces a lot risks of armed conflicts.
- DennisP 6y agoAccording to the National Space Society: > It is now believed that a lunar mass driver several kilometers long, designed conservatively with present technology, should be able to deliver 600,000 tons a year to L-5, or more easily to L-2, at a cost of about $1 per pound, assuming only ten years of operation. https://space.nss.org/l5-news-mass-driver-update/ https://space.nss.org/l5-news-mass-driver-update/ If SpaceX succeeds in dropping launch costs below $50/kg with Starship, this doesn't seem like it'd be all that expensive.
- henearkr 6y agoIn this case, doing it internationally is just an option that I hope will be taken... By the way most huge companies are already international in some sense, geographically or by employing many nationalities and origins. This also helps avoiding conflicts.