Deploy a large L1 positioned space object in orbit between the earth/sun to artificially shade sunlight and reduce the earth’s temperature.
The possibility of positioning a large sunshade between the sun/earth at the L1 Lagrange point has previously been published by (Angle 2006), see reference #1. The article estimates that 1.8% of the solar flux would need to be reflected, refracted, or adsorbed in order to reverse our global warming problem.
Offsetting a 400 ppm C02 Radiative Force of 1.9 watts/M^2 will require a circular shade 591 Miles in diameter, while at 500 ppm CO2 the Radiative Force will be 3.1 watts/M^2 and need a 754 mile circular shade. The reality is that even if this shading is performed in earth orbit or using atmospheric particulates or any other viable solution the heat reduction equivalent would need to be on the global order of 3.95E+14 watts for just CO2 levels of 500 ppm.
The L1 sunlight shade may require building a single large physical satellite or canopy of smaller satellites. Another option might be to periodically disburse some type of particle cloud (e.g. moon dust) to divert sunlight. Other variations would be to create an iron/dust filings cloud controlled using artificial magnetic/electrical fields to disrupt the L1 sunlight, or would it be possible to control the solar wind to produce an opaque sun screen. Any means or combination of reflecting, refracting, or absorbing the L1 sunlight would serve this purpose and should be fully investigated.
Use of a L1 orbit particle cloud as a sun shade would be a new concept and would require more understanding how well the sun-earth L1 point can contain dispersed particulate materials, remembering that the earth part of this association is actually impacted by the moons orbit around the earth which might be leveraged for better L1 containment.
Regardless of what method(s) of geoengineering is implemented in the future it must be used in conjunction with reduction/sequestration of CO2 emission and other greenhouse gases, including implementation of other possible geoengineering alternatives because of the scale of the problem
Category of the action
What actions do you propose?
The list below details information to be gathered and concepts to be developed in order to design and deploy a L1 sunshade platform for global climate heat mitigation.
The current and future energy accumulation from post-industrial anthropogenic emissions, and their cascading effects, needs to be fully quantified to determine the full scale of the climate change problem (1).
Determine the effect of the earth/moon (center of mass) system on the position, volume, and stability of the L1 orbit containment for viable sunshade technologies described below.
Shade Wheel Platform
Determine the surface area of space platform(s) that would be required to block an equivalent amount of sun energy described in the platform dynamics (1) requirements?
Investigate concepts for a L1 orbital platform that would:
- Provide a rotational disk type satellite design that uses centrifugal force to build out the shade in ever increasing circular diameter.
- Identify a foam-based material (2) that can be transported into space as light weight liquid(s), and can be vacuum expanded into a strong, high-volume, and stable solid shade material.
- Rotate the disk as a large spinning disk platform to force the foam liquids to the circumference of shade wheel for area expansion.
- Develop a center point manufacturing process to manage the build-out of the shade wheel, provide L1 orbit stabilization, and possibly human habitation.
- Power the entire platform and its operations using solar collectors on the disk itself to whatever capacity is required.
Particle Dispersion Shade
Consider using a dispersion of solid reflective materials (2) in association with the Shade Wheel platform to enhance the effective shade area beyond the size of the expanded platform’s circumference.
- Determine the volume, density, and retention time for a dispersion of light impeding shade materials (gas or solids) into L1 orbit free space that might enhance the effective shade area of the L1 shade wheel platform.
- Use the solar wheel rotation to fan out the material dispersions for improved solar interference over a larger circular area.
- Use the particle dispersion to help protect the sunshade from solar effects degradation.
- Understand any means available for re-focusing the solar wind to improve material dispersions, platform L1 orbital stability, or any other secondary effects that might be valuable for overall shade effect.
Who will take these actions?
This investigation would initially require the help of the space, physics, climate change scientists and concerned citizens to provide answers for the Earth Heat, Sun Energy, and Lagrangian Orbit Dynamics described in the proposed action plan. Once these first action requirements have been determined, then this proposal would require additional human resources for design concepts and alternative methods for implementing this proposal. Public and government support would be necessary if/when any viable options are identified
Where will these actions be taken?
Initially at universities and interested scientific people from around the world to prove viability of a L1 platform solution. Also NASA and the world-wide aerospace industries would be required to coordinate a plan for cost sharing and implementation. So this would need to be a global effort.
What are other key benefits?
Except for complete elimination of all anthropogenic greenhouse gases and return to 300 ppm C02 in the earths atmosphere, this approach is by far the cleanest and most non-intrusive geoengineering approach for moderating the earths heat content. The amount of energy hitting our planet could be precisely controlled to give our planet a managed radiative heat balance worldwide. In fact with the sun increasingly getting hotter, about 10%/1B years, so this approach may eventually be necessary far into the future if we are still around to worry.
This approach would avoid having to modify our atmosphere using alternative chemistries. This strategy would have no direct impact on our environment except to mimic the energy output of our sun from long ago. However, I do not want to minimize the additional value of CO2 sequestration or reduction from current and future levels.
What are the proposal’s costs?
The costs would escalate over time and operational phase:
- Start low to determine scientific feasibility.
- Increase to moderate levels during technical feasibility.
- Higher for system design and testing.
- Very high for implementation and maintenance.
I would think that this would be implemented long-term as a last option for earth climate preservation, so I would guess that this approach would require a 25 - 75 year timeframe.
1) Angel, R.: Feasibility of cooling the earth with a cloud of small spacecraft near the inner Lagrange point (l1), P. Natl. Acad. Sci. USA, 103, 17184–17189, 2006.
2) Document Created by Neil J. Cornish for WMAP Education and Outreach/ 1998, “The Lagrange Point” https://map.gsfc.nasa.gov/ContentMedia/lagrange.pdf
3) National Aeronautics and Space Administration, “The Lagrange Point” https://map.gsfc.nasa.gov/mission/observatory_l2.html