If your thought solid rocket motors are bad, wait til you hear about liquid rocket engines (LREs). They are the most common propellant and use hypergolic fuels which ignites through mixing chemicals and are super reliable since you’d just have to open up and close some valves. In fact, these are the fuels used for orbital manoeuvring, like the ones you’d see in cartoons and movies! However, as previously discussed, the environmental concerns are often not overlooked or not heavily emphasised in the selection of which propellants to use.
This is a concern as LREs contain dimethylhydrazine (UMDH) which are highly toxic and corrosive. In fact, Naurybaev et al. (2005) estimate that an average of 30 to 40 kg of UMDH falls on the earth’s surface from every LRE launch. Despite decades of launch, only very recently have studies attempted to study its impact – because of this, there is still a dearth of research on how it actually impacts health and the environment (Dallas et al., 2020). For instance, a study on over 6000 aerospace workers found that mortality due to lung cancer was 1.7 to 2.1 times that of exposed compared to non-exposed personnel – the rates are very similar for other types of cancer (Ritz et al., 1999).
Due to the toxicity and carcinogenic nature of this hydrazine, areas where UMDH falls on turn into ecological disaster zones, areas deemed unsafe for life (UNDP, 2004). As of 2004, studies estimate that since the these zones are as large as over 770, 000 km2, accumulating across all LRE-based launches and missiles (UNDP, 2004). Although UMDH decays rapidly, it can persist in dry soils for over 30 years (Kennesov et al., 2008), in rivers for nine months, and in lakes for over 8 years (Carlsen et al., 2007). Beyond the toxicity of UMDH itself, there are also concerns that derivatives or synergisms with other materials within these environments could cause more harm than we know (Carlsen et al., 2008). The uncertainties from UMDH from the most prolific and commonly used fuel in space missions is one which is worth looking out for. The main other alternative to this is kerosene-based fuel which is no-doubt cleaner apart from major pollutant – carbon dioxide. That’s a big topic that I hope to tackle in the next post!
References
Carlsen, L., Kenesova, O. A., & Batyrbekova, S. E. (2007). A preliminary assessment of the potential environmental and human health impact of unsymmetrical dimethylhydrazine as a result of space activities. Chemosphere, 67(6), 1108-1116.
Carlsen, L., Kenessov, B. N., & Batyrbekova, S. Y. (2008). A QSAR/QSTR study on the environmental health impact by the rocket fuel 1, 1-dimethyl hydrazine and its transformation products. Environmental health insights, 1, EHI-S889.
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.
Nauryzbaev, M. K., Batyrbekova, S. E., Tassibekov, K. S., Kenessov, B. N., Vorozheikin, A. P., & Proskuryakov, Y. V. (2005). Ecological problems of central Asia resulting from space rocket debris. History and Society in Central and Inner Asia, Toronto Studies in Central and Inner Asia, 7, 327-349.
Ritz, B., Morgenstern, H., Froines, J., & Moncau, J. (1999). Chemical exposures of rocket-engine test-stand personnel and cancer mortality in a cohort of aerospace workers. Journal of occupational and environmental medicine, 903-910.
United Nations Development Program (UNDP). (2004). Environment and Development Nexus in Kazakhstan.