Solar Power from Space? It’s complicated.
All that free power from the sun up in space, available all day, every day — as long as you are not in the earth’s shadow. Why can’t we capture it and send it to earth? Some day, it might be possible, but there are many obstacles….
<< Recap and continuation of a discussion which has been deleted from the Electrical Grid thread. Feel free to add your two cents and correct anything I’ve said wrong! >>The first thought that might come to mind is a using satellite with a huge array of solar panels, which orbits the earth and beams down power to a receiving station. The first problem is: due to the earth’s strong gravity, the super slow orbit that would take ~24 hours to complete (and thus keep a satellite constantly over the same spot on the earth), is only available at 35,000 km (22,000 miles) away from the earth. This is why geostationary internet satellites have such terrible latency — because to stay in one spot as earth rotates, so that fixed rooftop dishes will always point to it — the signals must travel far out into space, then all the way back.
Wikipedia:
A geostationary orbit can be achieved only at an altitude very close to 35,786 kilometres (22,236 miles) and directly above the equator. This equates to an orbital speed of 3.07 kilometres per second (1.91 miles per second) and an orbital period of 1,436 minutes, one sidereal day. This ensures that the satellite will match the Earth's rotational period and has a stationary footprint on the ground. All geostationary satellites have to be located on this ring.
https://en.wikipedia.org/wiki/Geostationary_orbitDue to the earth’s gravity, satellites in orbit closer than this must move faster, to prevent them from falling back to earth.
For example, the International Space Station in Low Earth Orbit circles the earth at a distance of about 250 miles [400 km]. It must maintain a speed of about 17,000 miles per hour [5 miles per second; 8 kps] to stay at that altitude. And that speed results in an the station circling around the earth every 90 minutes.
If the ISS slowed, gravity would pull it down until it succumbed to reentry. The station’s precise orbital speed at that altitude is what’s required to prevent the station from flying away from earth, or being pulled down to it.
Stable orbits require you going fast enough, in a direction pointed away from earth, so that you continually “fall toward earth but miss it.”
20 second video:
https://twitter.com/tyler0309/status/1397629811951128587—-
Yeah, but it would be better if the satellite were closerTo orbit closer to the surface, at approximately the edge of space (100 km) and not be pulled down to earth would require a speed of 7.84km/sec. This is much faster than the earth rotates — it theoretically would circle the earth every 87 minutes — but it would be stable only for a few minutes before collapsing.
https://en.wikipedia.org/wiki/Newton%27s_cannonballhttps://www.freemars.org/jeff/speed/index.htm —-
This is why we hear “Vehicle is pitching downrange” a few seconds after a rocket clears the launch tower. Because orbits require “sideways” speed. A bullet fired straight up might reach orbital velocity… but then gravity would pull it right back down.
Orbital mechanics: it’s the law!
If we launched a spacecraft straight up to the edge of space and wanted it to “hover” in place, it would require, essentially, a rocket engine firing forever, with just enough thrust at altitude to match the weight of the spacecraft, the rocket — and its crap-ton of forever fuel. Consider what is required to keep an airplane or helicopter over one spot. Much energy and fuel burned, and not able to be maintained for long.
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Near-earth power transfer from space might require a constellation of Low Earth Orbit satellites, each one beaming down power as it passed over an earth receiving station….
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There are
proposals for “Geostationary Balloon/Airship Satellites”, floating in the mid-stratosphere (~70hPa). But I see winds of up to 30 to 90kph at 70hPa altitude today, a relatively calm day, which would mean a lot of energy would be needed to remain in place, and quite a challenge to maintain a large array of solar panels, especially if an array is held up by multiple ships. A solar array on the earth’s surface could be
much larger, less vulnerable to the elements, and not require any energy to just remain in place.
Geostationary balloon satellites (GBS) are proposed high-altitude balloons that would float in the mid-stratosphere (60,000 to 70,000 feet (18 to 21 km) above sea level) at a fixed point over the Earth's surface and thereby act as atmosphere analogues to satellites.
https://en.wikipedia.org/wiki/High-altitude_balloon—-
What else? Some new kind of solar satellite? Laser links to send power to satellites on the dark side? Space batteries? How would power be transmitted from space down to earth? What about clouds? And how much Prohibited Airspace (it’s a thing) would be needed to keep airplanes away from where they might get burned up by it, let alone other satellites?
