Sometimes humans get ahead of ourselves. We embark on grand engineering experiments without really understanding what the long-term implications of such projects are. Climate change itself it a perfect example of that - no one in the early industrial revolution realized that, more than 100 years later, the emissions from their combustion engines would increase the overall global temperature and risk millions of people's lives and livelihoods, let alone the impact it would have on the species we share the world with. According to a new release from the Salata Institute at Harvard, we seem to be going down the same blind path with a different engineering challenge in this century - satellite megaconstellations.
As of early January, there are over 14,000 operational satellites in orbit. Major organizations, such as SpaceX, Blue Origin, and China’s up-and-coming megastallation providers are planning on launching tens of thousands more in the coming years. These satellites, since they are relatively cheap and mass-produced, are only designed to have a lifespan of 5-10 years, with the intention of burning up in the atmosphere at the end of their useful life. To maintain a fleet of that many satellites with such a short lifespan would mean that megaconstellations would be burning up as many as 23 satellites in the upper atmosphere every day.
There’s a good reason for this - they don’t want to leave them sitting in orbit, where they could fall apart and begin a chain reaction of satellite destruction, known as Kessler Syndrome, which could lock us into being unable to access orbit for decades. At the same time, the regulations about satellite deorbiting have primarily focused on human safety on the ground. The Federal Aviation Administration understandably doesn’t want a piece of space debris hitting and killing someone to become a common-place occurrence.
Bloomberg Podcast about the hazards to the atmosphere of falling satellites.Without the ability to leave their satellites in orbit, or bring them back down to the ground, that leaves satellite megaconstellation operators with no choice but to burn them up in the atmosphere. But, as we’ve reported before, that in itself has plenty of unintended consequences. Satellites contain plenty of environmentally harmful substances, and they don’t just go away when they burn up in the atmosphere. They turn into particles that can potentially last indefinitely in the stratosphere, where weather patterns such as rain aren’t able to remove them.
Their very existence in the stratosphere might actually influence those weather patterns. Organic materials, such as plastic and carbon fiber, used in the satellites become a type of carbon soot when burned up. The type of soot matters a lot, as some is reflective to certain kinds of light, whereas others are more prone to absorbing it. Temperature changes in the stratosphere, which drive wind patterns lower down in the atmosphere, can have a major impact on weather patterns. So any changes to the amount of sunlight it absorbs or reflects, such as that caused by carbon soot, can have major and little understood impact on weather patterns on the surface.
Another potentially harmful material from satellites is the aluminum that many of their housing are made of. Aluminum itself is light and strong, which makes it great for space applications. But when it burns up in the stratosphere, it provides a platform from which chlorine can react with the ozone layer, potentially damaging it further. The Montreal Protocol, adopted in 1989 to limit the emission of chlorofluorocarbons, which had created a hole in the ozone layer above the poles, has done a great job of allowing natural processes to rebuild that protective shield over the planet. Now, further engineering experimentation is poised to slow that recovery, or potentially even reverse it.
Fraser discusses the potential of satellites crashing into each other, which creates even more problems for the atmosphere.The Montreal protocol itself is also a great example of how effective regulation can solve these kinds of engineering challenges when the science is well understood and policy is well designed. Unfortunately, for the impact of satellite burnup in the atmosphere, neither of those is true at this point. We need a better understanding of the direct impact of the environmental impacts of these de-orbiting events. And we need to understand the trade-offs in terms of risking locking ourselves out of space altogether by leaving them in orbit, or potentially damaging people and infrastructure on the ground.
Science is how we will come to understand those trade-offs, and it is still early days in terms of the exponential growth of satellite megaconstellations. More research is needed, and the sooner the better, because the early indications for the climate don’t look great. Since we’re only at the very beginning of the age of satellite megaconstellations, the faster we get a handle on the environmental implications, the better.
Learn More:
Salata Institute at Harvard - Burning satellites in the stratosphere: Emerging questions for climate
UT - Rethinking How We End A Satellite's Mission
UT - Watch a Satellite Reaction Wheel Melt in a Simulated Orbital Re-Entry
UT - We're Putting Lots Of Transition Metals Into The Stratosphere. That's Not Good.