There has been a range of proposals to reflect or deflect solar radiation from space, before it even reaches the atmosphere, commonly described as a
space sunshade. The most straightforward is to have mirrors
orbiting around the Earth—an idea first suggested even before the
wider awareness of climate change, with
rocketry pioneer
Hermann Oberth considering it a way to facilitate
terraforming projects in 1923. and this was followed by other books in 1929, 1957 and 1978. By 1992, the U.S.
National Academy of Sciences described a plan to suspend 55,000 mirrors with an individual area of 100 square meters in a
Low Earth orbit. Another contemporary plan was to use
space dust to replicate
Rings of Saturn around the
equator, although a large number of
satellites would have been necessary to prevent it from dissipating. A 2006 variation on this idea suggested relying entirely on a ring of satellites electromagnetically tethered in the same location. In all cases, sunlight exerts pressure which can displace these reflectors from orbit over time, unless stabilized by enough mass. Yet, higher mass immediately drives up launch costs. In 1997, a single, very large mesh of
aluminium wires "about one millionth of a millimetre thick" was also proposed. Two other proposals from the early 2000s advocated the use of thin metallic disks 50–60 cm in diameter, which would either be launched from the Earth at a rate of once per minute over several decades, or be
manufactured from
asteroids directly in orbit. for the most widely used launch vehicles. In June 2025, the
Air Force Research Laboratory and AFWERX awarded
Reflect Orbital a US$1.25 million Phase II
Small Business Innovation Research (SBIR) contract to develop space mirror technology. The company is developing an 18 meter by 18 meter (59 ft) deployable mirror weighing 16 kg (35 lbs) made from
mylar plastic and has announced plans to demonstrate active pointing control from
sun synchronous orbit for the first time in 2026.
Research and development proposals In 2002, the aerospace consulting company STAR Technology and Research proposed a concept which, like Hermann Oberth's concept, uses the near-Earth orbit. Star's experts calculated that a network of steerable space mirrors orbiting Earth's equator, like one of the rings of Saturn, could lower the average air temperature by up to 3 degrees Celsius (5.4 degrees Fahrenheit) while simultaneously generating power from onboard solar panels and beaming it to Earth. But such an approach could generate problems. Report author and Star Technology president Jerome Pearson calculated it would take 5 million spacecraft to achieve the desired result, and even if each individual craft could last 100 years, that means 137 ships would have to be replaced or repaired per day. And the craft would produce "stars" that would be visible from the ground. (Pearson's other hypothetical proposal, a ring of reflective rocks in the same position, would light the night sky with the equivalent of 12 full moons.). In the 1980s there were more theoretical proposals for space mirrors as scientists attempted to discover a feasible way to partially reflect sunlight and slow down the warming of the Earth's atmosphere using space mirrors. The glass shield would need to be constructed on the Moon using moon rock due to its sheer mass. While orbiting at the
Lagrange point 1, the space mirror would be able to remain in orbit without any additional energy supplies and continue to block sunlight. In 2006, Roger Angel, a researcher at the University of Arizona, proposed sending millions of smaller space mirrors as opposed to one large mirror to reduce costs and increase feasibility as a single mirror would need to be approximately 600,000 square miles to block just one percent of sunlight. == Russian space mirror experiments ==