Business competition to get tourists into space is intensifying between two of the world’s biggest billionaires, Virgin Group founder Sir Richard Branson and former Amazon CEO Jeff Bezos. On Sunday, July 11, Branson traveled 80 km to reach the edge of space in his Virgin Galactic VSS Unity space plane. Bezos’ Blue Origin autonomous rocket was launched into space on July 20, marking the anniversary of the Apollo 11 moon landing.
These flights gave the opportunity for the very wealthy to reach outer space. On both trips, passengers enjoyed a brief ten-minute weightless flight and glimpse of Earth from space. Taking it a step further, Elon Musk’s SpaceX will complete four to five days of orbital travel with his Crew Dragon capsule later in 2021. Bezos says his Blue Origin rocket is better for the environment than Branson’s VSS Unity. Blue Engine 3 (BE-3) used liquid hydrogen and liquid oxygen propellants.
“Greenhouse gases and atmospheric pollutants are also produced”
VSS Unity used a hybrid propellant consisting of a carbon-based solid fuel, hydroxyl-terminated polybutadiene (HTPB) and a liquid oxidant, nitrous oxide (laughing gas). The SpaceX Falcon reusable rocket series will use liquid kerosene and liquid oxygen to propel Crew Dragon into orbit. The combustion of these thrusters provides the energy necessary to launch rockets into space while producing greenhouse gases and air pollutants. The combustion of the BE-3 thruster generates large amounts of water vapor, while the combustion of the VSS Unity and Falcon fuel 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 near Earth. About two-thirds of propellant exhaust gases are released into the stratosphere (12 km-50 km) and the mesosphere (50 km-85 km), where they can persist for at least two to three years. The very high temperatures during launch and re-entry (when the return vehicle’s protective hood is burning) also converts nitrogen fixed 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 by the breakdown of water vapor convert ozone into oxygen, depleting the ozone layer that protects life on Earth from harmful UV rays. Water vapor forms stratospheric clouds, which form a surface, causing this reaction at a faster rate than under normal conditions. Space tourism and climate change release heat into the atmosphere due to CO2 and soot emissions, which contribute to global warming.
Clouds made of emitted water vapor reflect light
The atmosphere can also cool, as clouds of emitted water vapor reflect sunlight back into space. A depleted ozone layer will also absorb less incoming sunlight and therefore heat the stratosphere less. To detail the global impact of rocket launches on the atmosphere would require detailed studies, to determine the impact of these complex processes and the presence of these pollutants in the upper atmosphere. Equally important is understanding how the space tourism industry will develop.
Virgin Galactic estimates that it will host 400 space flights each year for the privileged few who can afford it. Blue Origin and SpaceX have yet to announce their plans. But overall, rocket launches should not need to be increased beyond the current number of 100 each year to avoid its ill effects. When launched, the rockets could emit four to ten times more nitrogen oxides than Drax, the UK’s largest thermal power plant, over the same period.
The need to better understand the impact of billionaire astronauts
The CO2 emissions for forty tourists in space flight would be 50 to 100 times higher than those of one to three tonnes per passenger on a long-haul flight. As international regulators need to monitor this nascent industry and properly control its pollution, scientists need to better understand the impact of these billionaire astronauts on our planet’s atmosphere.
Author- Alois Marais, Lecturer in Physical Geography, UCL