An Increase in Rocket Launches Could Have a Significant Environmental Impact
Once a formative event in a person’s life, rocket launches are now becoming a weekly occurrence anyone can access and follow online. However, we rarely stop to think about the environmental costs of commercial space flight. With space exploration becoming increasingly significant in the coming years, what are the trade-offs between propellant types and which threats should we get ready to address?
During the past few days, we’ve seen a Russian Soyuz rocket depart from Plesetsk Cosmodrome, a Chinese Long March 4B rocket lift off from the Taiyuan launch in Shanxi, and a SpaceX Falcon 9 leave Kennedy Space Center in Florida. Captivated by the sights, we rarely stop to think about the environmental costs of space flight.
The depletion of stratospheric ozone is a widely studied and immediately concerning phenomenon, however, there are limited studies about how emissions from rocket engines that use liquid propellants can result in more significant losses.
As space exploration becomes a tangible every-day reality, it’s becoming essential to consider the cumulative impacts of frequent rocket launches on all areas of the environment, including global climate and ecosystem and human toxicity.
A 2020 Review
In May 2020, the Journal of Cleaner Production published a study that evaluated the impact of emissions from space launches. The study, called “The environmental impact of emissions from space launches: A comprehensive review,” was carried out by J. A. Dallas from the Australian Centre for Space Engineering Research and team.
The research determined that the growing interest in human settlements in space and the possibility of extracting resources from extraterrestrial bodies have set to increase the frequency of space launches in the coming years. The impact of such an increase in emissions would be considerable, and it’s essential to analyze its repercussions to make more informed decisions about the future of space exploration.
Emissions by Type of Fuel
Solid rocket motors consist of solid aluminum fuel with ammonium perchlorate oxidizer and sometimes hydrocarbon and hydroxyl-terminated polybutadiene. Once this type of fuel ignites, it cannot be turned off or throttled as it sends numerous dangerous compounds such as hydrochloric acid and alumina particles into the air. On the other hand, Liquid rocket engines use one of three common fuel combinations: liquid oxygen and kerosene, liquid oxygen and liquid hydrogen, or dinitrogen tetroxide and unsymmetrical dimethylhydrazine, or hypergolic propellant.
While solid fuels are generally used in the first stage of launches, liquid fuels are more frequently utilized for the upper rocket stages, resulting in emissions at higher altitudes.
Kerosene is a commonly used propellant but being a hydrocarbon means its combustion creates considerable environmental concerns, particularly concerning global climate change. Liquid oxygen and liquid hydrogen propellants, in contrast, produce exhausts that are composed primarily of water vapor — although as happens with all types of fuel at high temperatures, some nitrous oxide is also created.
To prepare ourselves for a future of frequent launches, we need to consider the different types of propellants in different environmental areas and their cumulative effect.
Threat 1: Ozone Depletion
The ozone layer has an abundance of ozone (O3) but also other atmospheric gases and catalysts such as nitrogen oxides, chlorine, bromine, and hydroxyl radicals. These all cause a degree of ozone destruction, which is significantly increased when adding those exhaust plumes created by rocket launches, regardless of propellant type.
The ozone layer is crucial to protect us from ultraviolet (UV) radiation. Its depletion has been a concern for years and is an issue of pressing importance as rocket launches increase in quantity.
Threat 2: Ecosystem Toxicity
The majority of known ecological impacts that result from space launches have been studied on the space shuttle missions. These covered the impacts close to the launch site, such as ground clouds that can trap water and coagulate it with alumina particles, which causes the droplets to become acidic. In 1975, for example, the ground cloud produced by the launch of the Titan III crossed paths with a rainstorm 20 minutes after launch, resulting in very acidic rain.
This means that rocket launches can impact soil quality and local ecology. NASA stated that the soils around their launch sites are alkaline and therefore have a higher buffering capacity that prevents the fumes from affecting them. However, a United Nations Development Programme report noted that the areas impacted by rocket stages for the UDMH-propelled Proton launch system used in the Baikonur Cosmodrome in Kazakhstan had become ecological crisis zones. Transformation products took 34 years to degrade in dry soils.
Threat 3: Human Toxicity
Finally, although there are few studies covering human toxicity in rocket launches, a degree of risk to human health is expected — for example, exposure to UDMH can be carcinogenic, mutagenic, and toxic to embryos.
The use of remote locations for launch sites emphasizes the importance of choosing such places while evaluating prevailing winds and launch trajectories. It should also be noted that the focus of future studies should be placed on longer periods of intermittent exposure, rather than the more studied short exposures at high concentrations.
We live in a time when space exploration feels closer than ever. The space launches calendar is already showing an immense variety of events growing at a regular pace.
Advances in technology can help us study our planet and the celestial bodies around us, allowing for discoveries that can have an impact on everyday life — we are, for example, at the brim of global broadband internet coverage thanks to SpaceX’s Starlink.
With new spacecraft designs being developed each day, we need only to remain aware that different propellants and launch locations will have different effects — and act accordingly. After all, we all share one planet — at least for the moment.