If global warming cannot be resolved by controlling/minimising gas emissions, then extraordinary measures may be the only viable options, one of such ideas is placing a solar shield between the sun and earth at the L1 lagrangian point to obtain a reduction in solar insolation . It may sound crazy, more like science fiction to know that a disk of 2000km in diameter would be necessary to reduce solar radiation reaching earth by 1.7%. I wonder about the sort of stresses that would be experienced by such an enormous body. Also, what sort of materials' properties would be required to withstand the conditions at L1, for example solar radiation, other rays. While it is possible to calculate the disk's orbital velocity around the sun, its angular velocity (around its axis) is difficult to calculate. I would be grateful if those with relevant experience could share their thoughts about how such calculations could be achieved.
Dear Ameer,
The L1 point is perhaps the most immediately significant of the Lagrangian points, which were discovered by mathematician Joseph Louis Lagrange. It lies 1.5 million kilometres inside the Earth's orbit, partway between the Sun and the Earth. In the Earth-Sun system, for example, the first point, L1, lies between Earth and the Sun at about 1 million miles from Earth. L2 also lies a million miles from Earth, but in the opposite direction of the sun. At this point, with the Earth, Moon and Sun behind it, a spacecraft can get a clear view of deep space. A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of a star's radiation, preventing them from hitting a spacecraft or planet and thereby reducing its insolation, which results in reduced heating.
Natural orbits exist near the L1 equilibrium point, their period does not match that required for geoengineering purposes, thus forced orbits that require small changes to the disk attitude in order to control its motion. The most practical space-based concept, yet clearly still challenging, is that of deploying a large sunshade or occulting disk, or a swarm of smaller structures covering the equivalent shading area to reduce solar insolation. Typically, this require deploying the occulting structure close to the L1 Lagrange equilibrium point on the Sun-Earth line some 1.5x106(10 per the power 6) km sunward of the Earth. The estimated mass of the deployed structure is in the order of 107(10 per to the power 7–108(10 per to the power 8) tonnes. The preferred location for an occulting disk is at the position where the gravitational forces from the Sun and Earth, together with the solar radiation pressure (SRP), balance in a reference frame rotating along with the Earth. This location is generally known as the Sun-Earth Lagrange L1 point, and allows the occulting disk to remain in a position where it can cast continuous shade on the Earth. Different configurations of two orbiting occulting disks can achieve clear gains with respect to a static disk near the Sun-Earth L1 point. The ability of the sunshades may be clear indication to yield different shading patterns, with accordingly different climate responses.
Hope it is helpful for you.
Ashish
The following article is relevant:
Article Gravitationally bound geoengineering dust shade at the inner...
This paper presents a novel method of space-based geoengineering which uses the mass of a captured near Earth asteroid to gravitationally anchor a cloud of unprocessed dust in the vicinity of the L1 position to reduce the level of solar insolation at Earth. It has subsequently been shown that a cloud contained within the zero-velocity curve of the largest near Earth asteroid, Ganymed, can lead to an insolation reduction of 6.58% on Earth, which is significantly larger than the 1.7% required to offset a 2 °C increase in mean global temperature. The masses of the next largest near Earth asteroids are found to be too small to achieve the required level of insolation reduction, however, they are significant enough to be used as part of a portfolio of geoengineering schemes.
Cheers
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials