This article originally appeared on Talk. The publication posted the article on Space.com. Expert Voices: Commentary and Insights…
Eloise Marais, Associate Professor, Department of Physical Geography, UCL
The commercial race to attract tourists to space is raging between Virgin Group founder Sir Richard Branson and former Amazon CEO Jeff Bezos. On Sunday, July 11, Branson climbed 80 km to reach the edge of space in his Virgin Galactic VSS Unity manned spacecraft. The Blue Origin autonomous Bezos rocket was launched on July 20 on the anniversary of the Apollo 11 moon landing.
Although Bezos loses to Branson in time, he is going to climb to a great height (about 120 km). The launch will showcase his offer to very wealthy tourists: the opportunity to truly experience space. Both tour packages will provide passengers with a short ten-minute zero-gravity agility and views of Earth from space. Not to be outdone, Elon Musk’s SpaceX will provide four to five days of orbital travel with the Crew Dragon capsule later in 2021.
What are the likely environmental impacts of the space tourism industry? Bezos brags that his rockets are Blue Origin greener than Branson’s VSS Unity. Blue Engine 3 (BE-3) will launch Bezos, his brother and two guests into space using liquid hydrogen and liquid oxygen fuel. VSS Unity used a hybrid fuel consisting of a carbon-based solid fuel, hydroxyl-terminated polybutadiene (HTPB) and a liquid oxidizer, nitrous oxide (laughing gas). SpaceX’s Falcon series of reusable rockets will launch Crew Dragon into orbit using liquid kerosene and liquid oxygen.
Our maiden flight on Tuesday will mark the 16th flight in # NewShepard history. Learn about the meticulous and meticulous startup program that led us to this first step. Watch the launch live at https://t.co/7Y4TherpLr starting at 6:30 CDT / 11:30 UTC. #NSFirstHumanFlight pic.twitter.com/xWQRYLikZdJul 18, 2021
Burning this fuel provides the energy needed to launch rockets into space and also generates greenhouse gases and air pollutants. The combustion of BE-3 fuels generates a large amount of water vapor, while the combustion of VSS Unity and Falcon fuels produces CO, soot and some water vapor. The nitrogen-based oxidizer used by VSS Unity also generates nitrogen oxides, compounds that contribute to air pollution closer to Earth.
About two thirds of exhaust gases are emitted into the stratosphere (12-50 km) and the mesosphere (50-85 km), where they can persist for at least two to three years. The very high temperatures during launch and re-entry (when the protective heat shields of the returning ships burn) 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 from the decomposition of water vapor convert ozone to oxygen, depleting the ozone layer that protects life on Earth from harmful ultraviolet radiation. Water vapor also creates stratospheric clouds, which provide the surface for this reaction to occur at a faster rate than otherwise.
Space tourism and climate change
CO and soot emissions in exhaust gases trap heat in the atmosphere, contributing to global warming. Cooling of the atmosphere can also occur as clouds formed from the emitted water vapor reflect incoming sunlight back into space. A depleted ozone layer will also absorb less incoming sunlight and thus heat up the stratosphere less.
Identifying the overall impact 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 expects to offer 400 space flights annually to a select few who can afford it. Blue Origin and SpaceX have yet to announce their plans. But globally, the number of rocket launches should not increase significantly over the current 100 launches every year to cause harmful effects that rival other sources such as ozone-depleting chlorofluorocarbons (CFCs) and CO₂ from aircraft.
During launch, rockets can emit four to ten times more nitrogen oxides than Drax, the largest thermal power plant in the UK, over the same period. CO₂ emissions for four or so tourists on space travel will be 50 to 100 times more than one to three tons per passenger on a long-haul flight.
For international regulators to keep pace with this nascent industry and properly control its pollution, scientists need to better understand the impact of these billionaire astronauts on our planet’s atmosphere.
This article is reprinted from The Conversation under a Creative Commons license. Read the original article.
Follow all Expert Voices issues and discussions – and participate in discussions – on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher.