Rocket launches are a breathtaking culmination of human ingenuity as they propel us into the future, but there is a growing concern that not enough research has been done on their effect on the environment.
While some may be worried about potential greenhouse gas emissions that’s not the main issue. Instead, it’s ozone depletion and the potential effects in our upper atmosphere, specifically the stratosphere, along with concerns about toxic fuels.
The problem has flown under the radar, according to Martin Ross, an atmospheric scientist at The Aerospace Corporation, because people still think of rocket launches as rare.
But it’s time to face the fact that we may be entering a boom era, he said.
“One of the arguments that people have used in the past was to say that we don’t really need to pay attention to rockets or to the space industry, or the space industry is small, and it’s always going to be small,” Ross said.
“But I think the developments that we’re seeing the past few years show that … space is entering this very rapid growth phase like aviation saw in the ’20s and ’30s.”
Black soot in the atmosphere
The stratosphere is an important weather driver for Earth’s systems, and that’s where some particles from rocket launches are ending up.
The ozone layer, which helps protect us from the sun’s harmful ultraviolet rays, is also located in the stratosphere. In 1990, the Montreal Protocol was signed into law, banning harmful ozone-depleting substances, such as chlorofluorocarbons (CFCs), used in things like refrigerators and air conditioners, after it was revealed that the ozone layer was being stripped away by these chemicals. While the protocol touched on airlines, there was no mention of the aerospace industry.
But now some industry experts are concerned that with no oversight, we could be in for a problem.
There are different types of rocket propellants. Some, like liquid oxygen and liquid hydrogen, produce mainly water vapour and have little environmental impact. These were used in past shuttle launches and even in the Apollo-era Saturn V vehicles.
Then there are those that produce alumina particles in the stratosphere, such as those in solid rocket boosters, which were also used in past shuttle launches, and are still being used today by some launch companies.
Finally, there are those that deposit black soot in the stratosphere, such as kerosene used in SpaceX’s Falcon 9 and Russia’s Soyuz rockets.
It’s the alumina and black soot that is most concerning to experts.
“The atmosphere is complex,” said Jessica Dallas, a PhD candidate at the Australian Centre for Space Engineering Research, in New South Wales. “We don’t have a complete understanding of atmospheric circulation and how all of the mechanisms in the atmosphere actually work. And so that means that we also don’t have a good idea of what happens when we’re injecting these particles into the stratosphere.”
Dallas, who wrote a comprehensive analysis of research on rocket propellants, said that she’s concerned that there haven’t been studies on how these particles interact in our atmosphere.
“Things tend to stay in the stratosphere for a long time, because there’s actually a very low rate of mixing [lower in the atmosphere],” she said.
“So what you’re having is black particles being deposited into the stratosphere and then they’re staying in the stratosphere for something like three or four years … whereas with the alumina particles, they sort of stay a little more locally, because they’re larger and heavier.”
Dawn of the new space age
While experts say these rocket emissions aren’t a pressing problem now, there’s concern they will become one as the industry grows.
Launches into space are far from rare: In 2016, there were roughly 80; in 2018, there were about 111, marking the first time since 1990 that there were more than 100 launches. Since then, there have been close to 100 launches annually, and as of April 20, there have already been 30 launches this year, with half of them from the United States alone.
And there doesn’t seem to be any indication of it slowing down. On the contrary: with more and more countries getting involved in the “new space race,” smaller and cheaper satellites and NASA and commercial entities like SpaceX and Blue Origin eyeing the moon and possibly Mars, there is likely to be an increase in launches.
In a 2018 report by The Aerospace Corporation’s Center for Space Policy and Strategy, the authors compared the potential of atmospheric rocket emissions to that of orbital space debris — another problem that wasn’t tackled when it was small half a century ago. Today, spent rocket engines, defunct satellites or debris from collisions are a threat to satellites and even the International Space Station. Several space agencies, including NASA and the European Space Agency, as well as private companies, are trying to develop ways to either collect it or mitigate it.
“If the potential magnitude of the space debris problem had been recognized early in the space age, and coordinated international actions had been taken at the time to address it, space debris may not have become the significant risk we face today,” the authors wrote.
“Today, launch vehicle emissions present a distinctive echo of the space debris problem.”
Developing cleaner fuels
Aside from the atmospheric impacts, there’s also the danger to the environment here on Earth.
Producing some fuels, such as hydrazine used mainly in satellites, is highly toxic and carcinogenic. There’s also a risk of spills. But there are some companies trying to develop fuel that may not only be less toxic here on Earth, but also in the atmosphere.
Tomislav Friscic, a professor in the chemistry department at McGill, is developing a new type of propellant that can be used for satellites in orbit that doesn’t use hydrazine. Instead, it’s a metal-organic framework (MOF), where molecules form a literal framework.
“Because this framework is full of holes, and you can put things in them, that means you have a material which you can modify on a number of levels,” Frscic said. “You can put high energy components in them to increase energy density … and make a material that is more responsive or maybe less responsive, if needed.”
And there’s a lot of Canadian research going on in terms of “greener” fuel, including by Quebec-based companies like Advanced Chemical Synthesis and Manufacturing (ACSYNAM) and Reaction Dynamics.
“My vision of how things are going to be is that we’re not limited anymore by the chemical limitations that we have,” said Cristina Mottillo, co-founder of ACSYNAM. “My vision is that … we can actually learn more about how to unlock the chemical energy in in the new propellant candidates … versus just happening to find chemicals from the periodic table that have the necessary chemical energy.”
But even those agencies or companies launching today are looking for better options.
SpaceX’s Starship, which CEO Elon Musk hopes will one day ferry people to the moon or Mars, is in its testing phase, but unlike its Falcon 9 rocket, it uses methane and liquid oxygen, which burns cleaner compared to some of the other available propellants. And in 2019, NASA conducted its own test of a greener fuel.
While the good news is that there’s research going on, there’s more that’s needed from players around the globe, Dallas said.
“What’s missing is that kind of international collaboration. We need to start considering all of the launches that are going on globally, because it’s not just the U.S.. It’s India and China, and there are so many more launches everywhere.”