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Let’s talk about rockets, fish, and plants today. In the last post, we covered how solid rocket motors or SRM affected stratospheric and mesospheric layers of the environment but we’ll be more down to earth today 😉
Most of the environmental studies conducted on space programmes focus on the ground cloud produced from SRM propellants. As previously mentioned, the particles emitted are HCl, alumina, and soot but the main issue on the ground is what happens to these molecules. Specifically, turbulence atomises water and causes it to coagulate with both alumina and HCl, forming extremely acidic liquid droplets (pH < 0.5) (Anderson, 1983). As seen in Figure 1, these droplets affect the area within the vicinity of launch but can also be carried by wind to for up to 22 km! Pellet et al. (1983) discovered that acidic range of pH below 1.5 can result from acidic droplets from these SRM-based space launches.
![The environmental impact of emissions from space launches: A comprehensive review - ScienceDirect](https://ars.els-cdn.com/content/image/1-s2.0-S0959652620302560-fx1.jpg)
Evidently, this is a cause for concern to the surrounding biota. The changes to the environment, particularly soil acidification, can physically damage (through defoliation) and chemically damage terrestrial vegetation within a very large radius of launch (Dallas, 2020). It is found that severe damage can be observed within a 10 km stretch, causing species decline as some grasses and shrubs tend to be resistant to ground cloud and the associated impacts (Schmalzer et al, 1985).
Even aquatic habitats are prone to groud cloud-induced changes in pH. Similar to terrestrial conditions, the pH of lakes near launch sites can drop to as low as 1 immediately after launch, recovering to baseline conditions only three days after launch. The result? A massive dying of fish especially within shallow waters near the launch and stormwater ditches leading away from it (Hall et al., 2014). Hawkins et al. (1984) found that the lowered pH over the course of the three days caused physiological damage to the gills, resulting in fatal anoxia.
It is clear that SRMs are a cause for concern especially since they are powerful, easy to store and have relatively simple design requirements, meaning that they will be the preferred source of propellants for lift-off. At the same time, they have one of the largest environmental impact of all the types of motors. I hope to explore other issues with liquid and hybrid propellants in the next post, where we’ll see how there are also dangers to human health with these alternatives. Ciao!
References
Anderson, B. J., & Keller, V. W. (1983). Space shuttle exhaust cloud properties (No. NASA-TP-2258).
Dallas, J. A., Raval, S., Gaitan, J. A., Saydam, S., & Dempster, A. G. (2020). The environmental impact of emissions from space launches: A comprehensive review. Journal of Cleaner Production, 255, 120209.
Hall, C. R., Schmalzer, P. A., Breininger, D. R., Duncan, B. W., Drese, J. H., Scheidt, D. A., … & Stolen, E. D. (2014). Ecological impacts of the space Shuttle Program at John F. Kennedy Space Center, Florida (No. KSC-E-DAA-TN12459).
Hawkins, W. E., Overstreet, R. M., & Provancha, M. J. (1984). Effects of space shuttle exhaust plumes on gills of some estuarine fishes: a light and electron microscopic study.
Pellett, G. L., Sebacher, D. I., Bendura, R. J., & Wornom, D. E. (1983). HCI in rocket exhaust clouds: atmospheric dispersion, acid aerosol characteristics, and acid rain deposition. Journal of the Air Pollution Control Association, 33(4), 304-311.
Schmalzer, P. A., Hinkle, C. R., Breininger, D., Knott III, W. M., & Koller Jr, A. M. (1985). Effects of space shuttle launches STS-1 through STS-9 on terrestrial vegetation of John F. Kennedy Space Center, Florida (No. NAS 1.15: 83103).