Bezos, Branson and Musk’s space travel emits greenhouse gases and pollutes the atmosphere
The business race to get tourists to space is intensifying between Virgin Group founder Sir Richard Branson and former Amazon CEO Jeff Bezos. On July 11, Branson traveled 50 miles to reach the edge of space in his pilot Virgin Galactic VSS Unit space plane. Bezos’ Blue Origin autonomous rocket launched on July 20, coinciding with the anniversary of the Apollo 11 moon landing.
Although Bezos lost to Branson in time, he reached higher altitudes – around about 69,000 feet. The launch demonstrated its offer to very wealthy tourists: the ability to truly reach outer space. Both sightseeing packages will provide passengers with a brief ten-minute weightless frenzy and glimpses of Earth from space. Not to be outdone, Elon Musk’s SpaceX will offer four to five days of orbital travel with its Crew Dragon capsule later in 2021.
What can be the environmental consequences of a space tourism industry? Bezos boasts that his Blue Origin rockets are greener than Branson’s VSS Unity. The Blue Engine 3 (BE-3) launch Bezos, his brother and two guests in space using liquid hydrogen and liquid oxygen propellants. VSS Unity used a hybrid propellant Composed of a solid carbon-based fuel, hydroxyl-terminated polybutadiene (HTPB) and a liquid oxidant, nitrous oxide (laughing gas). The SpaceX Falcon reusable rocket series will propel the Crew Dragon into orbit using liquid kerosene and liquid oxygen.
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The combustion of these thrusters provides the energy necessary to launch rockets into space while generating greenhouse gases and air pollutants. Large amounts of water vapor are produced by burning the BE-3 propellant, while the combustion of 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 Thruster exhaust gas is released into the stratosphere (up to just over 30 miles) and mesosphere (up to 53 miles), where it can persist for at least two to three years. The very high temperatures during launch and reentry (when the protective heat shields of return craft burn out) also convert stable nitrogen in the air to reactive nitrogen oxides.
These gases and particles have many negative effects on the atmosphere. In the stratosphere, nitrogen oxides and chemicals formed from the breakdown of water vapor convert ozone into oxygen, depleting the ozone layer that protects life on Earth from harmful UV rays. Water vapor also produces stratospheric clouds that provide a surface for this reaction to occur at a faster rate than it would otherwise.
CO₂ and soot exhaust gases trap heat in the atmosphere, contributing to global warming. Cooling of the atmosphere can also occur, as clouds formed from emitted water vapor reflect incoming sunlight back to space. A depleted ozone layer would also absorb less incoming sunlight, and therefore heat the stratosphere less.
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Determining the overall effect of rocket launches on the atmosphere will require detailed modeling, to account for these complex processes and the persistence of these pollutants in the upper atmosphere. Equally important is a clear understanding of how the space tourism industry will develop.
Virgin Galactic plans to offer 400 space flights each year to the privileged few who can afford it. Blue Origin and SpaceX have yet to announce their plans. But overall, rocket launches would not need to increase much from the current one. About a hundred produced each year induce harmful effects which are competitive with other sources, such as chlorofluorocarbons (CFCs) depleting the ozone layer and CO₂ from airplanes.
When launched, rockets can emit between four and ten times more nitrogen oxides than Drax, the largest thermal power station in the United Kingdom, over the same period. The CO₂ emissions of the four or so tourists in spaceflight will be between 50 and 100 times higher than one to three metric tons per passenger on a long-haul flight.
In order for international regulators to keep up with this nascent industry and properly control its pollution, scientists need to better understand the effect these billionaire astronauts will have on our planet’s atmosphere.
Eloise Marais is an associate professor of physical geography at UCL and originally wrote this article for The Conversation.