The environmental and moral implications of human space travel.

Humans have long dreamed of traveling to space. In response to the recent increase in commercial space flight, this paper evaluates environmental impacts of human space travel, both past and present, to shed light on the large environmental footprint of such activities. This environmental impact also has a moral component, since most of the global population will never be able to participate in such activities, yet still must bear the cost. Ironically, instead of a space future acting as a relief valve on Earth's resources, few activities exact a heavier burden on our planet's resources than the space pursuit, for the number of people it serves. This analysis utilized the structure of life cycle assessment. Data on launch vehicles mass and propellant type and mass was taken from public sources. Combustion emission results were calculated using combustion analysis software. These data were then combined with data from life cycle inventory databases and impact assessment methods to evaluate midpoint impact indicators. The hourly impact from sustaining humans in space over 1500 kg CO2-eq per hour. To put this into context, this is 2000 times greater than the emission rate of the average person on the globe, which we term global citizen equivalents (GCE). This global warming impact is also 650 times greater than the average person in the U.S. In terms of familiar activities, this is equivalent to continuously supplying at least 4 MW of electricity from the U.S. grid; simultaneously driving over sixty diesel buses; or occupying twenty seats on a Boeing 747 that never lands. Clearly such impacts raise questions not only to the sustainability of such activities, but also to the moral and ethical implications where such travel is limited to only the very wealthiest, but the costs are borne by all with few benefits to show from the endeavour.