Space Flight and the Environment
Are space travel, and space exploration something that the planet can afford for us to do? ross Clifton discusses the importance of space flight, its environmental impacts, and how we can act to mitigate them.
Illustration by Nathalie Dickson.
How Rockets Work
A common misconception about space flight is that rockets only have to go up to get to space. While this is in essence true, it is only half the story. For something to go to space and remain there it must achieve a stable orbit, which means as well as going up, it must also go sideways. At 160 kilometres in altitude, just above the atmosphere, a spacecraft must have a sideways velocity of around 7.8 kilometres per second (17,400 miles per hour). The amount of energy this requires (forgive the pun) is astronomical. For example, the Space Shuttle had a mass of around 110,000 kilograms and needed about 3,120,500,000,000 joules to reach orbit. This is around the amount of energy it would take to power 800 homes for a year. This energy was delivered to the shuttle by burning 500 tonnes of solid fuel alongside 720 tonnes of liquid fuel, all in about 8 minutes. In fact, the fuel in most rockets makes up around 90% of their mass at take-off, with most of it being burned during the early stages of the flight while the rocket is still in the atmosphere.
With our current technology, there is no better way to get any meaningful amount of payload to orbit than with a rocket. Unfortunately, in the meantime, before future technology can take over, this means we will need to continue using the vast amounts of fuel it requires to fly rockets to space.
SpaceX Bangabandhu Satellite-1 Mission. Image from SpaceX, Unsplash.
Is space flight important?
A familiar sentiment around space flight is that it is a huge investment with little consequence for the average person down on Earth. This is often summed up in the phrase “why don’t we focus on our problems down here, before we focus on up there?” However, there are diverse and far-reaching benefits derived from space flight. Some things are planned to provide a service from the start, but there have also been unexpected outcomes from having people spend time in space or from adapting technology made for space, for use on Earth.
Astronauts are put in very different circumstances from what we experience on Earth, and how their bodies change while in microgravity has provided insight into various medical conditions. For example, while in space there is almost no stress put on an astronaut’s skeleton, so the body attempts to adapt to this new environment by reducing the density of bone. Of course, while in space this is of little consequence, but upon returning to Earth, astronauts are at higher risk of bone breaks and deformation. Research into preventing bone density loss in astronauts is also applicable to people suffering from osteoporosis and other osteodegenerative conditions. This is not to say that research into bone density loss prevention would not have happened otherwise, but extra funding and effort is coming from the space industry to bolster medical research.
Some more direct benefits include the services provided by satellites. Global positioning systems, climate change and weather monitoring, communications and the internet are all things that are currently available or improved by using satellites. Without satellites, many of these technologies would require immense infrastructure which would be costly to build and maintain, and likely be a detriment to their local environment. SpaceX is currently building a network of satellites called Starlink to provide worldwide internet services. They have already demonstrated their capability of providing high speed, low latency connections to extremely remote places, which will have huge positive implications, especially for less developed countries.
The Starlink 3 train rides across the early morning sky, accompanied by a handful of other satellites Image by Forest Katsch, Unsplash.
Environmental impacts of rocket launches
Perhaps the most alarming thing about launching rockets is the amount of fuel they use and therefore, the emissions they produce. Rocket fuels can generally be split into two categories, solids and liquids. Solid fuels, which emit inorganic chlorine and aluminium oxide, are usually burnt while in the lowest part of the atmosphere, but the emitted gases that make it to higher altitudes can deplete ozone. Liquid fuels, like methane and hydrogen, produce carbon dioxide (CO2), water vapour (H20), carbon soot and various oxides of nitrogen (NOx), all but one of which are greenhouse gases (carbon soot is not a gas but can still have a greenhouse gas-like effect). Currently, the most launched rocket is SpaceX’s Falcon 9, with 26 launches in 2020 and 31 planned for 2021. It emits around 425 tonnes of CO2, 152 tonnes of H20, 30 tonnes of soot and 1 tonne of NOx per launch, the equivalent of 92 average cars per year. This is obviously a huge amount of pollution, the effect of which can be amplified by the altitude that it is released at since higher altitude pollutants remain in the atmosphere for longer.
NASA’s launch site in Florida is located on Merritt Island, and due to the dangers associated with rocket launches, this meant that a large area surrounding the launch site could not be developed. This land was therefore designated as a Wildlife Refuge and boasts a very high degree of biodiversity, including 21 endangered species. This is a bittersweet situation; on one hand, a wildlife refuge exists and provides habitat for a huge number of species, on the other, there is a risk that rocket operations may be having detrimental effects on the wildlife in the area. One concern is the amount of noise rockets produce, which can be up to 200 decibels. At this level, the waves produced are more like shock waves than sound waves and can be fatal to anything nearby and at the very least could be a source of disturbance. With the launch cadence in Florida increasing, wildlife will be subjected to rocket noise more and more frequently, potentially reaching a threshold where the biodiversity in the area is damaged.
Merritt Island, Florida, USA. Image by Jill Bazeley, Flickr.
Mitigation
It is worth noting that compared to other industries, rocket launch emissions make up a small percentage of global emissions. For example, in 2018, there were around 37,800,000 commercial flights emitted a total of 918,000,000 tonnes of CO2. In the same year, there were only 114 orbital launches which emitted around 22,780 tonnes of CO2. However, with the advent of reusable rockets, launches are becoming far cheaper and therefore more frequent. There is still a long way to go before rocket emissions are as high as emissions from other industries, but there is concern that in the future the problem will grow. However small the relative detrimental effects of rocket launches seem, they are still detrimental, and efforts should be made to mitigate them.
For rockets that use either RP-1 (a highly refined kerosene) or methane, carbon capture technology could be used to provide synthetic fuel, which could help rocketry move towards carbon neutrality. The processes to remove carbon from the atmosphere and then to create fuel with it are currently novel and not very efficient, resulting in an added expense. This technology does not exist at the required scale yet, but there is promise. Hydrogen may also be able to be created sustainably as well, making use of electrolysis - a process that uses an electric current to split water molecules into hydrogen and oxygen which can be used to fuel rockets. This process is also inefficient and requires a large power input, so for it to be sustainable, the power would have to come from a sustainable source.
Other methods of getting to space, which use a smaller amount of fuel, have been proposed. These include space planes like Skylon, which uses air-breathing engines and the lift produced by wings to get as high and fast as possible in the atmosphere before switching the engines over to rocket mode for the final push into space. This allows the vehicle to avoid carrying its own oxidiser for use in the early portion of the flight which could save a tremendous amount of weight and greatly improve fuel efficiency. This concept is still in its infancy, with many engineering problems to overcome before we see a flight.
It may also be possible one day to use rockets to move heavy industry into space, this would allow factories and mines to operate outside of the atmosphere and Earth’s ecosystems, where they will have very little effect on the planet.
Space flight can seem to be a useless endeavour, but in reality, it can provide huge benefits for our planet and its inhabitants. With the number of rocket launches increasing every year, and the potential harm they can bring, the industry must find ways to mitigate their detrimental impact. Work is being done in this area and concepts have been proposed which could allow space flight to continue in a more environmentally friendly way.
Thank you to Nathalie Dickson for her beautiful illustration. You can find more of her work on her Instagram @nathalied_art.
Ross Clifton
Ross is an MSc and BSc (Hons) Conservation graduate from the University of Exeter, and is currently based in Cornwall. He is an avid homebrewer and cook and enjoys making new things as it is an opportunity for him to learn and share with others. He is a firm believer in pragmatic sustainability and has a strong interest in wildlife conservation, aspiring to work in this field in future.