• Otávio Santiago

The jaw-droppingly high, out-of-this-world carbon footprint of space tourism

The commercial race to get tourists to space is heating up between Virgin Group founder Sir Richard Branson and former Amazon CEO Jeff Bezos. On July 11, Branson ascended 80 km (49 miles) to reach the edge of space in his piloted Virgin Galactic VSS Unity spaceplane, while Bezos’ autonomous Blue Origin rocket launched today on July 20, coinciding with the anniversary of the Apollo 11 Moon landing. Although Bezos launched later than Branson, he set out to reach higher altitudes — about 120 km, or 74 miles.

The launch demonstrates a new type of offering to very wealthy tourists: The opportunity to truly reach outer space. Tour packages will provide passengers with a brief 10-minute frolic in zero gravity and glimpses of Earth from space. Not to be outdone, later in 2021, Elon Musk’s SpaceX will provide four to five days of orbital travel with its Crew Dragon capsule.

What are the environmental consequences of a space tourism industry likely to be? Bezos boasts that his Blue Origin rockets are greener than Branson’s VSS Unity. The Blue Engine 3 (BE-3) launched Bezos, his brother and two guests into space using liquid hydrogen and liquid oxygen propellants.

VSS Unity, on the other hand, used a hybrid propellant comprised of a solid carbon-based fuel, hydroxyl-terminated polybutadiene (HTPB), and nitrous oxide (or laughing gas), while the SpaceX Falcon series of reusable rockets will propel the Crew Dragon into orbit using liquid kerosene and liquid oxygen.

Burning these propellants provides the energy needed to launch rockets into space — but it simultaneously generates greenhouse gases and air pollutants. Large quantities of water vapor are also produced by burning the BE-3 propellant, while combustion of both the VSS Unity and Falcon fuels produces CO2, soot and some water vapor. The nitrogen-based oxidant used by VSS Unity also generates nitrogen oxides, compounds that contribute to air pollution closer to Earth. Roughly two-thirds of this propellant exhaust is released into the stratosphere (12 km-50 km) and mesosphere (50 km-85 km), where it can persist for at least two to three years.

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