by Joshua Schertz, SGAC Treasurer

The Planetary Sunshade Foundation supports the ambitious project of developing an architecture for building megastructures in space, including a planetary sunshade capable of climate stabilization. The Foundation’s work directly contributes to the United Nations’ Sustainable Development Goal (SDG) 13 on climate action, while also supporting the establishment of a sustainable lunar economy. Read on for insights from the director of the Foundation.

Figure 1: Artist’s impression of a sunshade shielding Earth from solar heating. Image Credit: Planetary Sunshade Foundation

Josh Schertz: Ross Centers, could you tell us a little bit more about the Planetary Sunshade Foundation?

Ross Centers: I’d be happy to, and thanks for having me. The Planetary Sunshade Foundation is a new non-profit organization, dedicated to developing a space-based climate cooling solution to mitigate the disastrous consequences of climate change that we’ve inherited. We’re working at the intersection of space technology and climate policy, trying to come up with a space-based approach to repairing climate damage on a planetary scale. If you look at the degree to which we’ve failed to meet our climate goals so far, it’s looking like we’re going to need a plan B for climate, and we think space should play a role in that conversation.

JS: Honestly, this sounds like a miracle solution. What does a structure capable of cooling Earth actually look like?

RC: Well, it looks like a very, very large parasol for the Earth itself, on the order of 1,000 kilometers across, parked way out at Sun-Earth Lagrange-1. That’s about four times farther than the Moon and is a stable position where it can provide constant shade to the whole planet. It will block about 1% of sunlight and cool Earth by about a degree, and you won’t be able to see it with the naked eye but with eclipse glasses, it will look like a large sunspot.

To be clear, this would be a miraculous outcome, but it isn’t a silver bullet. It’s only a very large band-aid over a climate catastrophe, and it in no way means that we can just go on emitting like business as usual. We have to change. But the sunshade is like a medical intervention between our society and the planet to help us all go on living through this process.

JS: This is directly addressing climate mitigation. What sort of numbers are you looking at with regard to this?

RC: What causes global warming is the physical process of radiative forcing, which is the difference between the net energy inflow from the sun and the net energy outflow radiated to space by the Earth. Before industrial civilization came along and we started burning fossil fuels, the radiative forcing was in balance and Earth’s temperature was stable. But lately, every year we’ve been adding about 50 billion tonnes of CO2 equivalent into the atmosphere a year. That permanently goes into the atmosphere and creates a blanket around the earth. This is the magnitude of the greenhouse effect; it’s gigatonnes of CO2 annually and about a trillion tonnes of cumulative emissions. Already our climate has warmed by over 1 degree Celsius, and even if we cease emissions now, the Earth is going to continue to warm until we hit thermal equilibrium. We’ve basically already blown the Paris Accord goal of 1.5 degrees warming, and we’re still emitting carbon. This is the defining problem of our century.

JS: According to your assessment, a planetary sunshade structure would relieve the Earth of about 1 percent of its usual energy from the sun. Could you give us a few examples of the effects that would have? What could we expect to see on Earth as a benefit of this structure?

RC: The planetary sunshade orbits at Sun-Earth Lagrange 1, so it’s always between us and the sun. It’s a thin film structure that, in blocking about a percent of sunlight, pushes the energy balance of the Earth about 1 degree cooler. It won’t be visible to the naked eye, but through a solar telescope you’d see it as a large sunspot. By mitigating the radiative forcing, it provides us some breathing room and keeps the planet cool enough to reduce the chances of runaway tipping points like ice caps melting, methane releases from permafrost, ocean currents stopping and the like. Just a little bit of cooling can mean the difference between life and death for millions in the tropics in the latter half of the century. And it can mitigate the catastrophe of climate related extinction, famine, and conflict.

JS: So, I’m beginning to wonder with such a huge megastructure, what kind of materials would be used? How does one begin to reconcile the increasing questions and the space industry about sustainable infrastructures that do not, you know, degrade under radiation, which will then cause debris, and so on?

RC: Yeah, I’m really glad you asked. And there’s a lot of questions of sustainability with this much mass, I think the first issue of sustainability is it becomes pretty clear from a back of the envelope analysis, that building this with materials from Earth is questionable at best. The amount of mass required and the amount of launches you’d need – something on the order of 1,000,000 Starship flights, you can’t really build this with materials from Earth.

So we need to be looking at materials in space. In our neighborhood, that means the Moon and near-Earth asteroids. There are things you need from each. We think you can get at least 100 to 1 and maybe 1,000 to 1 mass leverage from a really well-designed space resource utilization plan, and that brings you down the order of 1,000 to 10,000 Starship flights, which is doable. So, we launch construction equipment from Earth, and then we use raw materials in space to fabricate the planetary sunshade. For a thin film structure, your best, most common materials are aluminum and silicon, maybe iron. In vacuum and microgravity, you can make these materials very thin through cold rolling or vacuum deposition. You can even make photovoltaics with these materials by adding layers of silicon and electrical contacts. There’s going to be wear from micrometeorites and degradation from radiation, so you have to also have an active repair process in mind.

Sustainability is a huge goal. The use of space resources, I think, unlocks that because one of the most fundamental things about space resources is while our resources on Earth are really limited, especially those that we can actually get to without environmental devastation, there is a whole lot more resources available in space. For instance, there’s enough resources in space to be able to support a trillion human beings between here and the main asteroid belt. I hope that we can unlock a future where we could actually have a human population that large sustainably, and have it in space. The key to that will be cherishing Earth as our home, keeping Earth as pristine as possible, a cradle of humanity. One real key to that is to make use of space resources to improve Earth to deal with the real effects of our industrial civilization.

JS: This will be a multi-year, trillion-dollar project. What kind of ecosystem would you see fostering such an ambitious project that requires a lot of buy in? For instance, how do you consider fitting this within a multinational forum?

RC: Climate change and global warming is a problem that affects literally everybody. While it’s been something that was predominantly led to by the industrialization of advanced economies, it’s something that we now all share, and the impact is generally inversely proportional to our responsibility with the rich countries better able to withstand the consequences than developing nations. So, the sunshade should be developed through international agreements, with climate justice in mind. I think the United Nations is really the body that should be advocating the planetary sunshade concept the most as a form of living up to our ideals of having space be for all humanity, as dedicated in the Outer Space Treaty, and also in terms of climate justice, in terms of making right the wrongs that are otherwise going to fall upon countries that were later to develop, and may experience much more difficult changes from climate change. So, I think the planetary sunshade provides an opportunity to work together in living up to our highest principles. It wouldn’t be the first time in history that catastrophe has stimulated us to do that.

JS: What responsibility do you think we have as young professionals and students in the space sector to educate ourselves and propel ourselves for the climate crisis ahead?

RC: For all of us who are going to grow into positions of responsibility in space, technology, and policy, we need to understand the real challenges that we’re going to face in the world and not shy away from addressing them head on. I think that SGAC members have both the opportunity and the moral authority to demand and develop systems for addressing the number one crisis on Earth using space technology, which is revolutionary and transformative. It doesn’t just have to be the planetary sunshade, as there are so many things to be done. I think that thinking bigger than has ever been thought before and holding higher hopes for what humans are capable of than we’ve ever known ourselves to be capable of before is a really good moral foundation and a vision for a better future that we, as young space professionals, can use to change not just the world, but humanity’s future in the solar system.

JS: I love that vision. I think it’s a great takeaway for all of our members. If someone is interested in learning more, where can they go?

RC: We’re at https://planetarysunshade.org, and I’m on clubhouse @rcenters. We’d love to hear from you.