INTRODUCTION

In the past, space exploration has not received much environmental attention for good reason. For one, the industry has been small, sprinkled with very few launches per year, making any environmental impacts negligible compared to other industries.[1] Second, the space industry has a long history of being considered government-focused, similar to that of national security and defense. As an industry previously dominated publicly by NASA, it may have been afforded some leeway as its success has been considered “vital to the Nation’s economic well-being and national security.”[2]

Today, however, the space industry looks very different. Significantly, the number of launches per year has skyrocketed. According to the space launch report, there were 104 successful launches in 2020 and 133 successful launches in 2021.[3] Furthermore, the ultimate goals of the private space industry far exceed these numbers. For example, SpaceX’s CEO stated that the ultimate design goal for Starship is to launch up to three times a day, equivalent to approximately 1000 flights a year[4], with the hopes of reaching the goal of at least one flight every two weeks in the next year.[5] Similarly, Virgin Galactic’s CEO stated goal is to offer 400 flights per year per launch site.[6] In addition to a rise in the number of launches, the industry itself is changing. Georgetown Law Professor Hope Babcock describes this change, stating: “Private investment in space, not foreseen when the international framework regulating activities in space was put into place, has grown, while government investment in space has ‘shrunk'”.[7] An industry once focused on exploration and security has now expanded into new realms of tourism and commercialization.

As the industry changes, the regulatory scheme must adapt. As the number of rocket launches per year increases, the environmental impact does as well, and it is better for regulatory agencies to be ahead of this impact. Dr. Eloise Marais, professor of Physical Geography at the University College London, predicted that in order to consider harmful environmental impacts, launches would need to exceed 100 launches per year.[8] Rocket launches would not need to increase much from current levels to potentially induce harmful effects.[9] It may be time for environmental regulators to take a harder look at the impacts of these launches and determine if further regulation is necessary.

ENVIRONMENTAL EFFECTS

Prior to delving into environmental impacts, it is important to note that many rocket engines use different propellants to function; therefore, their environmental effects vary. For example, Virgin Galactic’s VSS Unity uses a hybrid propellant comprised of a “solid carbon-based fuel, hydroxyl-terminated polybutadiene (HTPB), and nitrous oxide” while Blue Origin’s New Shepard uses liquid propellants comprised of liquid hydrogen and liquid oxygen, and SpaceX’s Falcon series of orbit-capable reusable rockets use liquid kerosene and liquid oxygen.[10] These different propellants have different chemical make-ups which cause different emissions. Some of the distinctions in emissions are exemplified in Table 1 reproduced from Limits on the Space Launch Market Related to Stratospheric Ozone Depletion and provided below. The table demonstrates common types of propellants utilized in rocket engines and the emissions estimated for each use. Most rocket engines will use either one type or a mix of these propellants to launch.

Table 1: Approximate Emissions Given as Mass Fraction of Each Component[11]

Propellant type	Emission
	Inert N2	Inert CO2+CO	OH source H2O + H2	Radicals CIOx, HOx, NOx	Radical Reservoirs HCI	Particles Alumina soot
Solid  (NH4CIO4/AI)	0.08	0.27	0.48	0.1	0.15	0.33
Cryogenic (LOX/H2O)	—	—	1.24	0.02	—	—
Kerosene (LOX/RP-1)	—	0.88	0.30	0.02	—	0.05
Hypergolic (UDMH/N2O4)	0.29	0.63	0.25	0.02	—	Trace

Emissions provided as a mass fraction for each propellant. “The total mass fraction exceeds unity because of the assumption that air missed into the plum oxides CO and H₂“.[12]

 A. Climate Impacts

One impact of increased rocket launches is from launch exhaust. Exhaust can contain greenhouse gasses such as CO₂ and H₂O, as well as particles of alumina and black carbon.[13] These types of emissions trap heat, absorbing sunlight, and contribute to climate change and warming.[14] Black carbon is particularly concerning. Black carbon is defined by the EPA as “a major component of soot” with a “complex light absorbing mixture that also contains organic carbon” and is “a solid form of mostly pure carbon that absorbs solar radiation (light) at all wavelengths”.[15] According to scientists, some rockets can emit approximately 10,000 times more black carbon particles than modern turbine engines found in airplanes and jets.[16] Put into perspective, scientists also predicted that in 2018, the amount of black carbon emitted by rockets into the stratosphere was comparable to that emitted by the entire aviation industry.[17] In addition to black carbon, alumina and water vapor particles are also of potential concern; however, this effect is more nuanced. The effect of alumina particles and water vapor (H₂O) has proven difficult for scientists to predict as both can cause simultaneous heating and cooling effects which still impact climate change but in a less clear manner.[18]^{, [19]}

Overall, scientists have estimated that rocket emissions contributing to the warming of the stratosphere were caused 70% by black carbon and 28% by alumina, attributing only 2% to H₂O, and ≈0% for CO₂.[20] This indicates that rockets emitting black carbon and alumina are responsible for harmful warming impacts and should draw more concern from regulators.[21] Types of rockets with these emissions include rockets with engines dependent on kerosene propellants and liquid-based engines (LREs)[22], as well as some hybrid-based propellant engines (HREs)[23] which are likely to produce black carbon exhaust.[24] In addition, solid propellants (SRMs)[25] are likely to emit alumina.[26] Propellants used in Virgin Galactic’s VSS Unity and SpaceX’s Falcon,[27] and in China’s Long March 9 rocket fuels produce these types of exhaust.[28] Blue Origin’s BE-3 propellant produces large quantities of water vapor but emits no carbon through burning.[29]^,[30]

Currently, the impact of GHG emissions by rockets is dwarfed by that of other industrial sectors.[31] However, predictions suggest that if the industry continues to develop, it may have real impacts.  For example, scientists estimate that just ten years of “launches at a rate of 1000 per year, the fleet of hydrocarbon-based HREs (typical for space tourism applications)” could cause a surface temperature rise as much as 1 °C.[32] While the industry is far from 1000 launches per year at this time, it continues to flourish and commercialize. Furthermore, additional perspective is provided by looking at the estimated carbon footprint of a single passenger. The footprint of a single passenger to a sub-orbital exploration is comparable “to that of a passenger travelling thousands of times in aircraft between Los Angeles and London.”[33] This comparison alone signifies the impact of these explorations. As regulators turn their focus on concerns over environmental justice and social equity, this industry should also draw concern. Even while the current amount of greenhouse gases emitted by rockets is relatively low, it may be important to take note of these potential impacts as the industry continues to grow.[34]

B. Ozone Depletion

Another environmental impact of rocket launches is ozone depletion. High temperatures during launch and re-entry events can convert nitrogen in the air into nitrogen oxides which can deplete ozone in the stratosphere.[35] In addition, emissions of compounds such as NOx, HOx, and ClOx are highly reactive and are directly involved in catalytic cycles, leading to an increase in the ozone removal rate.[36] This reaction can occur even if present only in trace amounts.[37] Water vapor emissions may also contribute to depletion of ozone.[38] The composition of the stratosphere containing the ozone layer is characterized by low water vapor, compared to that of the troposphere, so the impact of water vapor emissions more severely impacts the composition of the stratosphere.[39]

Again, this impact is not of immediate concern. However, it may become important to pay attention to as the industry continues to grow. For example, scientists estimated that a “fleet of 1000 launches per year of hydrocarbon based HREs typically used for space tourism would cause ozone loss up to 6% in polar regions”.[40] Other studies highlighted that considering proposed launch rates, even if using only liquid-based propellant engines (LREs), the global ozone loss due to rocket launches could still become significant.[41] While the industry is far from hitting this threshold, it is important to consider sooner rather than later as estimations of harmful impacts to ozone depletion are severe. Additionally, scientific studies indicate that even with a smaller number of launches such as weekly launches, rockets could be responsible for an ozone loss at “upper limit acceptable to the international community that established the Montreal protocol”.[42] Scientists warn that if left unregulated, rocket emissions could deplete ozone more than Ozone-Depleting Substances (ODSs)[43] ever did by 2050.[44] This would be a major setback in the progress made under the Montreal Protocol and EPA’s current efforts under the Clean Air Act. Furthermore, considering environmental justice and social equity concerns, scientists estimate that during launch, “rockets can emit between 4 and 10 times more nitrogen oxides than Drax, the largest thermal power plant in the UK, over the same time period”.[45] This is a significant amount of emissions if considered on a person-to-person scale. Given the potentially significant impact increased launches could have on ozone depletion, it is important to account for in considering environmental impacts. Again, as with climate impacts, even while the current amount of ozone depletion is relatively low, it may be important to consider as the industry continues to develop.

ENVIRONMENTAL REGULATION

Today, very little environmental regulation exists for rockets. As noted previously, at current levels, significant regulation may be considered premature and unnecessary. However, as space tourism continues to boom in popularity and feasibility, the environmental impacts of these explorations become more significant.

A. National Environmental Policy Act

Currently, environmental regulation of launches is mainly under the National Environmental Policy Act (NEPA). NEPA requirements include environmental impact statements for launch sites, including impacts such as those accounted for in an Environmental Impact Statement compiled for the Mars 2020 Mission: land use, air quality, soil, water quality, offshore impacts, biological resources, hazardous waste, and environmental justice.[46] The Environmental Impact Statements from past launches have included comments that emissions caused by launching activities would be unlikely to cause short-term or long-term effects and focus almost exclusively on effects taking place on the ground.[47] In addition some effects are not considered through categorical exclusions. [48]

In the future it may be vital to consider cumulative effects as the number of rocket launches continues to rise. Scientific research would suggest that the ‘number’ in which cumulative effects become ‘significant’ may be 100 or may be 1000.[49] While the current position of the ‘cumulative impacts’ consideration under NEPA is in flux between the Trump Era Rules and Biden’s Delay Rule, if the consideration of cumulative effects is ultimately reinstated within the Act, then effects such as increased GHGs and stratospheric ozone depletion should be considered in the future. Additionally, as emissions leading to instances of warming are thought to be impacted majorly by black carbon particles and alumina rather than CO₂, studies considering only CO₂ emissions to assess the contribution of rockets to climate change may gravely underestimate its impact by several orders of magnitude.[50] If this is the case, then regulators should focus on including these metrics in Environmental Impact Statements when considering cumulative effects. When it becomes clear that the industry threshold is consistently within reach, if the technology behind these different types of rockets remains relatively consistent to the types of engines available today, it will be important to consider these cumulative impacts.

B. Clean Air Act

EPA should also consider regulating rocket launches as mobile sources under the Clean Air Act. In a letter dated January 12, 2000, EPA Director John S. Seitz suggests EPA considers rockets to be mobile sources under the Clean Air Act.[51] The letter states that “rocket launching is a mobile source and thus the emissions from rocket launching do not need to be counted for a Title V applicability purpose” further stating that Hazardous Air Pollutants Standards (CAA 112) are irrelevant to rocket launches as mobile sources.[52]

Under the current interpretation of Massachusetts v. EPA, EPA has the ability to regulate GHG’s of mobile sources under the Clean Air Act.[53] Recently, in 2020, EPA utilized this to finalize GHG standards for airplanes used in commercial aviation and in 2021, EPA promulgated a rule to set GHG emission standards for airplanes.[54] Considering the potential impact of the space industry by 2050, perhaps similar action should be considered for rocket launches sooner rather than later in regard to not just GHGs, but also other pollutants such as particulate matter and NO_x in exhaust. Furthermore, EPA should consider implementing tech-based regulations to push the industry in a more emissions-friendly direction. In addition, under Title VI of the Clean Air Act, EPA may consider establishing standards and requirements regarding rocket launches in order to prevent ozone depletion, especially as impacts may affect the United States’ progress in keeping its international promises in the Montreal Protocol.[55]

CONCLUSION

The state of the space industry at present yields climate impacts which are not overwhelmingly concerning. However, when considering the potential growth of the industry and the imbalance of emissions from a position of equity, it may be worth paying attention to the climate impacts of this industry in the near future. While currently the impact of rocket launches is seemingly negligible compared to that of other industries, with the rise of space tourism and the continued privatization of space, it may be time for environmental regulators to turn their attention to the new space race.

 

 

[1] See Loïs Miraux, Review Environmental Limits to the Space Sector’s Growth, 806-4 Sci. of the Total

Env’t 1, 2 (2022).

[2] Commercial Space Transportation Competitiveness Act of 2000, 114 Stat. 1751 (2000).

[3] See Ed Kyle, Space Launch Report: Orbital Launch Summary by Year (last updated Dec. 31, 2021), https://www.spacelaunchreport.com/logyear.html; Eloise Marais, The Jaw-dropping High, Out-of-this-world Carbon Footprint of Space Tourism, Ideas.TED.com (June 20, 2021), https://ideas.ted.com/environmental-impact-carbon-emissions-of-space-tourism.

[4] See Elon Musk (@elonmusk), Twitter (Jan. 16, 2020, 9:01PM), https://twitter.com/elonmusk/status/1217990326867988480?lang=en.

[5] See Tom Huddleston Jr., Elon Musk has worried about SpaceX bankruptcy before – early on he thought it would be ‘worth $0’, CNBC (Nov. 30, 2021), https://www.cnbc.com/2021/11/30/elon-musk-warning-not-first-time-spacex-has-risked-bankruptcy.html.

[6] See Michael Sheetz, Virgin Galactic says each spaceport it launches from is a $1 billion annual revenue opportunity, CNBC (Nov.6 2020), https://www.cnbc.com/2020/11/06/virgin-galactic-each-spaceport-is-1-billion-annual-revenue-opportunity.html.

[7] Hope M. Babcock, The Public Trust Doctrine, Outer Space, and the Global Commons: Time to Call Home ET, 69 Syracuse L. Rev, 191, 198 (2019).

[8] See Marais, supra note 4.

[9] See Kyle, supra note 4; Marais, supra note 4.

[10] Marais, supra note 4; See Paul Rincon, Virgin Galactic: Richard Branson’s Long, Winding Path to Space, BBC (July 11, 2021), https://www.bbc.com/news/science-environment-57798167.

[11] Martin Ross, Darin Toohey, Manfred Peinemann & Patrick Ross, Limits on the Space Launch Market Related to Stratospheric Ozone Depletion, 7 Astropolitics, 50, 60 (2009).

[12] Sylvie Durrieu, Ross F. Nelson, Earth Observation from Space – The Issue of Environmental Sustainability, 29 Space Policy, 238, 241 (2013).

[13] See Marais, supra note 4; Miraux, supra note 2 at 6.  

[14] See Miraux, supra note 2 at 6; Marais, supra note 4.

[15] Report to Congress on Black Carbon: Executive Summary, EPA (Mar. 2012) https://www3.epa.gov/airquality/blackcarbon/2012report/ReportHighlightsExecSummary.pdf.

[16] Miraux, supra note 2 at 6 (referencing study described in Ross & Sheaffer, Radiative Forcing Caused by Rocket Engine Emissions, 2(4) Earth’s Future, 177 (2014)).

[17] Miraux, supra note 2 at 6 (referencing study described in Ross & Toohey, The Coming Surge of Rocket Emissions, Eos (Sept. 24, 2019) https://eos.org/features/the-coming-surge-of-rocket-emissions).

[18] See Marais, supra note 4; Miraux, supra note 2 at 6.

[19] These emissions can cause warming in the stratosphere while simultaneously causing a reduction in ‘solar flux’ leading to cooling in the troposphere (lower atmosphere) and ground by reflecting some incoming solar radiation into space and absorbing some upwelling radiation from Earth. See Marais, supra note 4; Miraux, supra note 2 at 6.

[20] Miraux, supra note 2 at 6 (referencing study described in Ross et al. supra note 18).

[21] See Id.

[22] Liquid Rocket Engines (LREs) use “propellants in the liquid form, such as liquid oxygen combined with liquid hydrogen as a fuel (e.g. [European Space Agency’s] Ariane 5) or kerosene (e.g. SpaceX’s Falcon 9)”. Id.

[23] Hybrid Rocket Engines (HREs) use “a liquid oxidizer and a solid fuel, often a hydrocarbon … (e.g. Virgin Galactic’s SpaceShipTwo)”. Id.

[24] See Id.

[25] Solid Rocket Motors (SRMs) “use a combination of solid aluminum fuel with ammonium perchlorate as an oxidizer” and are often coupled with LREs (e.g. Ariane 5). Id.

[26] See Id.

[27] SpaceX’s Mars Colonization project, based on its Starship, relies on a “liquid oxygen/liquid methane combination expected to be less harmful than kerosene,” but it is unclear whether this switch will be offset by the significant associated increase in launch rate. Id. at 7.

[28] See Miraux, supra note 2 at 7; Marais, supra note 4.

[29] See Marais, supra note 4.

[30] It should be noted that while Blue Origin’s BE-3 propellant produces zero carbon emissions during launch, it will produce carbon-based emissions in the production of liquid hydrogen. A potential answer to the reduction of carbon emissions from Blue Origin’s BE-3 propellant may be in green hydrogen technology. See generally, Jon Greenberg, How much CO2 did Bezos’ Rocket Ride Release? Close to Zero, POLITIFACT (July 20, 2021), https://www.politifact.com/factchecks/2021/jul/20/tweets/how-much-co2-did-bezos-rocket-ride-release-close-z/.

[31] Miraux, supra note 2 at 6.

[32] Id. at 7 (referencing study described in Ross & Toohey, Potential climate impact of black carbon emitted by

rockets, 37 Geophysical Res. Letters, 24 (2010)).

[33] Miraux, supra note 2 at 6 (referencing study described in Ross et al., supra note 18).

[34] See Miraux, supra note 2 at 6.

[35] See Marais, supra note 4.

[36] See Durrieu et al., supra note 14 at 242.

[37] See Id.

[38] See Greenberg, supra note 32.

[39] See Durrieu et al., supra note 14 at 242.

[40] Miraux, supra note 2 at 6 (referencing study described in Ross et al. supra note 34).

[41] Miraux, supra note 2 at 6 (referencing study described in Ross et al. supra note 13).

[42] Durrieu et al., supra note 14 at 242.

[43] Ozone-depleting Substance (ODS) is a compound that contributes to stratospheric ozone depletion recognized under the Montreal Protocol including “chlorofluorocarbons, hydrochlorofluorocarbons, halons, methyl, bromide, carbon tetrachloride, hydrobromofluorocarbons, chlorobromomethane, and methyl chloroform”. Ozone-Depleting Substances, EPA (last visited Jan 19, 2022) https://www.epa.gov/ozone-layer-protection/ozone-depleting-substances.

[44] Miraux, supra note 2 at 6 (referencing study described in Ross et al., supra note 13).

[45] See Marais, supra note 4.

[46] See generally Draft Environmental Impact Statement for the Mars 2020 Mission.

[47] See generally Id.

[48] See 14 C.F.R. § 420.15(b)(2) (2000).

[49] See Marais, supra note 4.

[50] See Miraux, supra note 2 at 6.

[51] See Letter from John S. Seitz, EPA Dir., Off. Quality Planning & Standards, to Pat Ladner, Exec. Dir., AK Aerospace Dev. Corp. (Jan. 12, 2000), https://www.epa.gov/sites/production/files/2015-08/documents/rocket.pdf.

[52] Id.

[53] See Massachusetts v. EPA, 549 U.S. 497, 528–29 (2007).

[54] See Regulating for Greenhouse Gas Emissions From Aircraft, EPA (last visited Jan. 16, 2022), https://www.epa.gov/regulations-emissions-vehicles-and-engines/regulations-greenhouse-gas-emissions-aircraft; See also Ashima Talwar, One Small Step for the EPA, One Giant Leap for the Environment: A Hybrid Proposal for Regulating Rocket Emissions Due to the Rising Commercial Space Industry, Geo. Wash. J. of Energy & Env. L. 87, 92 (2018).

[55] Ozone Layer Protection Milestones of the Clean Air Act, EPA (last visited Jan. 16, 2022) https://www.epa.gov/ozone-layer-protection-milestones-clean-air-act#MVAC.