Radiative forcing caused by rocket engine emissions

Abstract

Space transportation plays an important and growing role in Earth's economic system. Rockets uniquely emit gases and particles directly into the middle and upper atmosphere where exhaust from hundreds of launches accumulates, changing atmospheric radiation patterns. The instantaneous radiative forcing (RF) caused by major rocket engine emissions CO 2 , H 2 O, black carbon (BC), and Al 2 O 3 (alumina) is estimated. Rocket CO 2 and H 2 O emissions do not produce significant RF. BC and alumina emissions, under some scenarios, have the potential to produce significant RF. Absorption of solar flux by BC is likely the main RF source from rocket launches. In a new finding, alumina particles, previously thought to cool the Earth by scattering solar flux back to space, absorb outgoing terrestrial longwave radiation, resulting in net positive RF. With the caveat that BC and alumina microphysics are poorly constrained, we find that the present-day RF from rocket launches equals 16 ± 8 mW m −2 . The relative contributions from BC, alumina, and H 2 O are 70%, 28%, and 2%. respectively. The pace of rocket launches is predicted to grow and space transport RF could become comparable to global aviation RF in coming decades. Improved understanding of rocket emission RF requires more sophisticated modeling and improved data describing particle microphysics.

Solar geoengineering using solid aerosol in the stratosphere

“…However, alumina has infrared absorption bands in the thermal infrared that will reduce its net radiative forcing and will cause some heating of the lower stratosphere (Ross and Sheaffer, 2014).…”

“…We examine diamond, but choose alumina as the primary example because there is a broad basis to examine alumina's potential environmental impacts. Unlike many other solid particles proposed for SRM, there is prior work examining alumina's impacts on stratospheric chemistry (Danilin et al, 2001;Jackman et al, 1998;Ross and Sheaffer, 2014), work that was produced from NASAfunded studies starting in the late 1970's motivated by concerns about the ozone impact of space shuttle launches (alumina is a major component of the shuttle's solid rocket exhaust plume). Moreover, alumina is a common industrial material with a high index of refraction for which there is substantial industrial experience with the production of nanoparticles (Hinklin et al, 2004;Tsuzuki and McCormick, 2004).…”

“…Our results for alumina are broadly consistent with the results of Ferraro et al (2011) for titania. Note, however, that Ross and Sheaffer (2014) conclude that the positive infrared radiative forcing from alumina can be larger than the negative radiative forcing from solar scattering by the same particles. We suspect that part of this discrepancy comes from the fact that Ferraro et al (2011) and this paper assume a narrow size distribution close to the optimal for solar scattering, whereas Ross and Sheaffer (2014) use a broad alumina size distribution.…”

Sub-micrometer refractory carbonaceous particles in the polar stratosphere

“…However, literature on particles emitted by rockets is sparse (e.g., Zolensky et al, 1989), and there areto the best of our knowledge -no studies available on carbonaceous particles by electron microscopy. According to Ross and Sheaffer (2014) (Strand et al, 1981;Zolensky et al, 1989;Cofer III et al, 1991) and can, thus, be excluded as the source of the carbonaceous particles encountered in the present study. Hydrocarbon-fired rockets are powered by kerosene or syntin and can be expected to emit soot.…”

Anthropogenic Sources of Nanoparticles

“…The large carbon black volume is caused by the incomplete fuel combustion, given the low oxygen concentration in the upper atmospheric layers [79][80][81].…”