Comments URL: https://news.ycombinator.com/item?id=41573796

Points: 1

# Comments: 0

Problems with orbital power designs include poor efficiency converting sunshine, in place, to electrical power to drive the microwave antenna array to beam power to rectennas on the ground; huge expense to loft big arrays of heavy solar panels to orbit; and scaremongering about microwaves from space affecting wildlife. To be useful at all, such orbital arrays would need to be very large to drive a microwave antenna array broad enough to focus its beam tightly to drive a practical rectenna array on the ground. And they would need huge, dedicated, otherwise useless rectenna arrays.

But I haven't seen a proposal like this one.

You need some background information to follow this, some of it obvious, some less so. First, stacking microscopically thin layers of transparent material of differing refractive indices six or seven deep makes a super-lightweight mirror that reflects only one or a few wavelengths of light, letting the rest pass through. Second, a laser tube can be pumped by monochromatic light coming in from all sides. Third, terrestrial solar farms illuminated with monochromatic laser light can convert it to electrical power at radically higher efficiency than they can blackbody sunshine. Fourth, a laser beam operating at an optical wavelength with intensity at ground level no greater than sunshine creates no risks to the public or wildlife. Fifth, existing solar farms sit idle at night; but even in the daytime, they could produce more power given more input illumination.

If the orbital arrays to collect solar radiation are mostly just extremely light mirrors, and no conversion to electrical power occurs in orbit because the light they collect directly pumps a laser tube, mass and efficiency problems are eliminated. Even a relatively small satellite would be useful, as the laser does not need to be large to achieve good focus. Each unit, of whatever size, may collect and beam its power independently. And, no dedicated receiver is needed; any existing solar farm the laser points at converts the delivered illumination. And, no one worries about the safety of ordinary visible light.

Such satellites would be cheap to produce in quantity and to loft, and their illumination could be sold to any existing solar farm, reducing need for energy storage.

(I acknowledge Alexis Gilliland for inspiration.)

Comments URL: https://news.ycombinator.com/item?id=41494018

Points: 4

# Comments: 0

Michael Levin has been discovering lately that biology is more complicated than we thought. His YT videos are mind-boggling. Flatworm genetics are a dog's breakfast that the cells work around by means nobody understands.

Strontium-90 decays by beta emission, ending up as stable zirconium, meaning you don't have to vent helium.

Seems there would only be a problem on some proprietary compiler for an embedded, bespoke target.

It seems as if were both engines to fail, either one prop would be feathered and the lift spoiler on that side extended, or neither prop would be feathered. Presumably the pilot could feather the props himself. It is not apparent whether this would extend both lift spoilers too, or if those were controlled separately.

They might have reached North America, too. Anyway we know people got there because they butchered the Hartley mammoth 37kya.

We have reliable evidence of people in North America 37kya, at the Hartley mammoth butchery site, perhaps from the same rootstock as the Australians. Curiously, they lacked the fancy stone tool industry the Siberians brought in much, much later, which might trace all the way back to Europeans 20kya. Apparently there are plenty of other mammoth sites not excavated because they are dated "too old" to involve people. It took Tim Rowe, a decorated paleontologist whose land it was was found on, to get that one dug up properly. Still it seems like no one will talk about it.

The millennium of 12,000 years ago was also when Gobekli Tepe and related sites were constructed, right at the sudden end of the Younger Dryas cold spell. Maybe innovation was newly acceptable in response to the fast-changing climate.

If you have a Tesla, get the suspension checked at least twice a year, and after hitting any pothole. A broken suspension can kill you.