Saving the Future Earth? Giant Space Umbrella Climate Change Solution Gains Attention

1. History and Mechanism of the Sunshade Concept

The prototype of the space sunshade dates back to the 2006 NIAC study and Roger Angel's cloud of countless microlenses proposalen.wikipedia.org. Theoretically, reducing the solar constant by about 2% could "freeze" global warming,

• by placing it at L1, where the gravitational forces of the Sun and Earth balance with solar radiation pressure, allowing for stability with minimal propellant.

• Using solar sails (thin films) allows for autonomous attitude and orbit control
  , which is an advantage.

2. Overview of the Precursor Mission

The current proposal is led by a team including Associate Professor Marina Coco from the Polytechnic University of Turin, Italy, with a total budget of $10 million, assuming a rideshare launch. A 12U CubeSat (weighing 15-20 kg) equipped with a deployable solar sail will verify the following:

1. Durability of the sunshade film (against UV rays, temperature fluctuations, and micrometeoroids)

2. Long-term station-keeping ability using solar sail propulsion

3. AI autonomous navigation (with communication delays over 10 seconds)

4. Swarm control algorithms (eventually forming a formation of thousands of units)universetoday.com

After successful testing, the plan is to gradually scale up to hundreds or thousands of units, ultimately aiming to reduce the Earth's average temperature by up to 1.5°C.

3. Technical Challenges and Breakthroughs

• Ultra-lightweight materials: Mass production of PI/Kapton films a few micrometers thick and SiO₂ nanotube composites

• Solar sail deployment mechanism: Proven by IKAROS and LightSail 2, but requires a two-digit increase in area

• Degradation by cosmic rays and plasma: Development of coating technology and self-healing polymers

• Space debris: While L1 is low-density, control precision is needed to prevent collisions within formations and orbital drift due to solar radiation pressure

Researchers are also considering "in-space manufacturing of raw materials infrastructure" using lunar resources.

4. Cost & Schedule Estimation

• Precursor: Launch in 2028, 1-year operation

• Demonstration (100 units): 2032

• Full Operation (over 1,000 units): Early 2040s
  The estimated total cost isin the tens of billions of dollars, but if based on the assumption of a Starship-class reusable large rocket, the transportation cost per kg is estimated to be significantly reducedspace.com.

5. Scientific Benefits and Risks

Compared to the traditionally discussedstratospheric aerosol injection, concerns about chemical dispersion and acid rain are smaller, while recovery from mechanical failure or orbital deviation remains a challenge.

6. International Opinion on Geoengineering

The New Yorker described it as a "desperate but increasingly realistic option," advocating for simultaneous research and regulationnewyorker.com. In COP negotiations, there is strong criticism that it serves as an "excuse to delay emission reductions," focusing on who guarantees the freedom 'not to act', and conversely, who bears the responsibility to 'act.'

7. Domestic Debate and Impact in Japan

In Japan, institutions like JAXA, Tohoku University, and the University of Tokyo, which have global achievements in climate modeling and thin-film materials, have shown interest, and the Ministry of Economy, Trade and Industry'sGX Strategyalso mentions "negative emissions through space technology."

• As the introduction rate of renewable energy increases, there is a proposal to divert surplus power for grid stabilization to lunar resource development

  .

• In the Kishida Cabinet's Space Security Concept, there is a need for consistency with debris and orbital traffic management

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• In the food and agriculture sector, adaptation technologies (smart agriculture, LED supplemental lighting) for the risk of insufficient sunlight are urgently needed

  .

8. The spread of pros and cons on social media

On X (formerly Twitter), surprising comments such as "A dream can be opened with just a $10 million budget!" and "Are they really going to launch 1,000 units?" have spread. A post by science influencer **@Kyukimasa received thousands of impressions in an hour, and in the replies, the technology faction and environmental justice faction** clashed head-on with comments like "Solar sail control has been proven with ICAROS" and "Emission reduction should come first"x.comx.com. Meanwhile, many joking posts likened it to a game mod, saying "A parasol mod for Earth has arrived," and younger generations tend to perceive it as "SF reality."

9. Points of ethics and governance

1. Global public goods: Changes in sunlight exposure could lead to differences in agricultural yields and water cycles across regions

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2. Decision-making: The applicability of the Outer Space Treaty and the Liability Convention, separate from the UN Framework Convention on Climate Change (UNFCCC), is unclear

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3. Military diversion: There is a risk that light pressure control technology could be diverted to blind weapons or communication interference

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4. Reversibility: The "Termination Shock" issue where a "temperature rebound" occurs when a large system is stopped

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In light of these, the research community proposes a high-transparency demonstration phase roadmap and a citizen-participatory multi-stage consensus-building process.

10. Future prospects

• 2025-27: Ground experiments, material exposure tests

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• 2028: Precursor launch, data release

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• Early 2030s: International joint demonstration unit (100 units) → Partial shading test at L1

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• 2040s: As commercial rocket costs decrease, the feasibility of full-scale system construction will be determined
  . While running parallel to emission reductions, establishing its position as an insurance measure to avoid critical points will be key.

Summary

As a "trump card" for combating global warming, the deployment of a massive space sunshade at L1, the Planetary Sunshade System, is once again garnering attention. The team from Politecnico di Torino in Italy has announced plans to launch a 12U CubeSat equipped with a 144 m² solar sail in 2028 to simultaneously verify core technologies such as the durability of shading materials, solar sail control, and AI autonomous navigation. The total budget is a relatively low $10 million. If successful, it could be expanded to a scale of thousands of units in the 2040s, potentially suppressing the average temperature rise by up to 1.5°C. However, the risks are significant, including disruption of weather balance, termination shock, and the lack of a legal framework, making international consensus and transparent governance essential. In Japan, while opinions are divided on X, with some calling it a "game changer" and others a "loophole for global warming," scientists need to accelerate both demonstration and discussion.

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