Researchers have proposed placing a ‘bubble screen’ in space to combat global warming

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Droughts, extreme heat waves and large wildfires are now affecting the entire world. Many cities have broken their summer temperature records this summer. Despite international efforts to combat global warming, perhaps we have already reached the point of no return? What if we fail to keep the temperature below +2 degrees Celsius? In these situations, scientists are working on “last chance” solutions, geo-engineering solutions that will limit the damage or even reverse climate change.

Geo-engineering combines all the techniques that make it possible to control the Earth’s climate and environment. Inspired by an idea proposed by astronomer Robert Engel, an MIT team is currently working on a concept for a solar shield, whose role would be to reduce solar radiation reaching our planet. Indeed, if efforts aimed at reducing CO2 emissions prove insufficient to combat climate change, then direct action on our main source of heat will already be essential.

The project, known as the “Space Bubble,” involves a giant raft of frozen bubbles (roughly the size of Brazil, according to the team) that will be positioned at the Lagrange point L1, between the Sun and Earth. The structure will be designed to reflect some sunlight. The advantage of this method over other geoengineering projects – such as dissolving chemicals in the stratosphere to increase its albedo – is that it will not directly affect Earth’s biosphere.

Thin-film bubbles are directly inflated in space

When it comes to geoengineering, solar geoengineering has been little explored. In 1989, James Early presented in the journal British Interplanetary Society A “thin glass shield” concept compensates for the greenhouse effect of CO2 accumulation. This shield was made from lunar materials and placed at the first Lagrange point of the Earth-Sun system to absorb some of the radiation. Such a slope would reduce incident light by 1.8%—enough to reverse current warming. The problem at the time was the amount of material needed to build that giant sun visor and the power needed to launch it to its destination.

James Early and Roger Angel proposed placing a thin absorbing or reflecting film at the Lagrange L1 point to reduce the amount of solar radiation reaching Earth. The implementation of the concept, however, was complex and irreversible. © MIT

From this work, Roger Angell in 2006 envisioned not one, but several small solar shields. This swarm of shields would aim to deflect light rather than absorb it, to minimize the equilibrium shift of L1 caused by radiation pressure, the scientist then explained. Despite having less mass than James Early’s project and employing electromagnetic acceleration to escape Earth’s gravity, ion propulsion (to limit transport costs), the production and deployment of this array of sun visors was extremely complex.

A few other ideas have since been floated, but none have gotten past the stage of a rough feasibility study. As we slowly move toward a climate emergency, a team from MIT has taken another look at Angel’s proposal: It proposes deploying a set of bubble rafts composed of a network of tiny interconnected inflatable bubbles near the Lagrange point L1. ” We believe that swelling thin-film spheres directly in space from a homogeneous molten material – such as silicon – can provide thickness variations that refract a broad wave spectrum and allow us to avoid the need to cast large structural film components. “, explain the researchers.

A shield that may be before the end of the century

Here it is a question of making the reflecting spheres directly in space, which will limit the transport costs. The solution would also be completely reversible: bubbles could be destroyed simply by breaking their surface balance, which would also reduce space debris compared to other methods. It can therefore be one of the most effective thin-film structures for reflecting solar radiation.

(a) Location of Lagrange point L1; (b) Bubble raft on a water surface (courtesy of University of Wisconsin); (c) Bubble freezing in a thin film about 20 mm in diameter at 0.0028 atm (experiment performed at MIT). © MIT

Appropriate materials and technologies for building and maintaining such spheres in space remain to be determined. The team has already tested bubble formation in the laboratory, under the conditions of outer space; They are particularly interested in silicon-based molten and graphene-enhanced ionic liquids, which have ultra-low vapor pressures and relatively low densities. Thermal and optical properties of the materials will also be taken into consideration for the feasibility study.

According to the researchers, the minimum thickness of the liquid film forming the bubble could theoretically be as little as 20 nanometers; But to deflect sunlight, it must be comparable to the solar wavelength, ie around 400 to 600 nanometers. Finally, the mass density of the bubble raft will be less than 1.5 g/m2. Its best position to reduce radiation pressure would be a little closer to the Sun, about 2.5 million kilometers from Earth.

Several questions remain to be studied before considering the implementation of such a project. In particular, you need to think about the maintenance of the shield once in place, because the bubbles will be particularly fragile. It is also essential to reflect the impact that the reduction in solar radiation will have on our planet and the transition phase that is necessary both when the shield is in place and when it is no longer effective. According to preliminary studies, 50 to 200 years of activity will be needed to reverse the effects of global warming.

An estimate by Roger Angell puts the cost of such a project at about 0.5% of global GDP over 50 years. If initial laboratory tests prove conclusive, additional research will aim to improve its design and tests will be conducted in low orbit. ” We believe that once a technological solution is identified, its implementation could be before the end of the century “, the researchers say.

Source: MIT

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