World Space Week this year, which runs between Oct. 4 and Oct. 10,is celebrating how space technology is aiding us in our fight against climate change on Earth — but sometimes it pays to also look outward at what technology can offer us as we expand into space to harness the energy and the worlds that lie out there.
Here we highlight four technologies, look at the challenges that they pose and give some indication of when they might come to fruition — if ever. The time estimates are not necessarily a prediction of when they might happen, but are intended to give a rough idea of how much work still needs to be done on them.
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2040s-2050s: Space solar farms
Currently, solar power provides just over 5% of the world’s total electricity supply, but we can do much better than that.
The best place to feel the sun’s energy is in space, without clouds to block the view or an atmosphere to absorb our star’s rays. A huge array of solar panels would therefore have an unfettered view of the sun , but the tricky part of this idea concerns building such a space-based array in the first place. Plus, even if we manage that somehow, how would we get the harvested solar energy down to Earth ?
Compared to most technologies on this list, power beaming from space is actually ahead of the curve. In January of 2023, the Caltech-built Space Solar Power Demonstrator launched into Earth orbit. On board was an instrument called MAPLE, the Microwave Array for Power-transfer Low-orbit Experiment. MAPLE successfully converted solar energy into microwaves and then beamed the microwaves down to a receiving station at Caltech, where it was converted into electricity. It was a pretty low amount of power — just milliwatts — but it was an exciting proof of concept.
An artist’s impression of what JAXA’s Space Solar Power System might look like if it used laser transmission to beam solar power down to Earth. (Image credit: JAXA)
Now, the Japanese Aerospace Agency, JAXA, working with commercial interests, are exploring their own program that the agency hopes to culminate in a solar farm capable of producing one gigawatt of energy and beaming it down to Earth. However, building a solar farm isn’t easy.
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A solar panel in space, above the absorbing effects of the atmosphere, receives about a kilowatt of energy per square meter (10 square feet) of the sun. Solar panels are not 100% efficient, however; currently available commercial models have an efficiency of just 30%, meaning a solar panel in space can realistically produce just 300 watts per square meter. To scale this up to producing 1 gigawatt of energy, which would be the equivalent of a nuclear power station on Earth, would require an enormous array of solar panels, multiple kilometers in diameter, with a mass of 10,000 metric tons. Compare this to the International Space Station , which has a mass of 419 metric tons , and that shows just what a daunting engineering task this would be.
Supposing a solar farm could be built in space, it would be placed in geosynchronous orbit, 35,786 km (22,236 miles) above the Earth. The challenge would then be to keep the microwave beam narrow and on target — you wouldn’t want the microwave beam to stray and fry something accidentally. Although lasers instead of microwaves would be easier to direct, laser energy can be absorbed by water vapor in the atmosphere or blocked by clouds, whereas microwaves pass freely through them.
Lasers, though, might be more suitable for space-to-space power transfer. This could extend the life of satellites, for example, but they would have to be built with some kind of receiver to accept the incoming laser power beam. We could also imagine a network of solar farms and relay satellites around the moon , beaming power via lasers to a lunar base on the surface.
Second half of the 21st century: Space elevators
This is an old science fiction concept, first conceived by Russian scientist Konstantin Tsiolkovsky — rather than blasting off in a rocket atop a dangerous column of flame, why not ride into space on an elevator car?
The basic design of a space elevator sounds simple. A thick cable extends from a location within 10 degrees of the Earth’s equator up into space. The forces acting on the cable would be fierce, with Earth’s gravity trying to pull it down, and the centrifugal force on a mass at the end of the cable in Earth orbit pulling it the other way, keeping it taut. The stresses and tension of this cable would be so great that it would need to be made from a material 50 times stronger than steel, however. The only material strong enough are carbon nanotubes, which are
4 futuristic space technologies – and when they might happen
