Seventy years ago, Earth had only one satellite: the Moon. Now it has more than 15,000 - about 10,000 of which are owned by Elon Musk's SpaceX. The world's first trillionaire plans to launch one million more satellites, each roughly 70 metres long and 20 metres wide, that would form a data centre megaconstellation.
But more satellites means more space junk , which is already threatening critical infrastructure we rely on every day.
Addressing this problem effectively requires work across three fronts: technology, policy and philosophy.
The race to the Moon and beyond is accelerating. Some say it's for the benefit of all humanity. But is it really? In this seven-part series , we explore what our future in space will look like, how we might travel and survive out there, and what's needed to stop a catastrophe from happening.
13 million cane toads worth of space junk
Space junk is everything in Earth orbit that doesn't have a purpose. It includes discarded rocket bodies, defunct and broken satellites, and fragments down to nanoparticle size. There are 36,000 pieces of junk larger than ten centimetres and tens of millions of smaller pieces and particles.
The estimated weight of all of this junk is 13,486 tonnes, the equivalent of 13 million adult cane toads . The United States, Russia (as well as the former USSR), and China are the biggest contributors.
Space junk is dangerous because it's orbiting at almost unimaginable speeds - 7 kilometres per second on average in low Earth orbit. A collision can break up a satellite and create even more space junk.
The worst case scenario is called Kessler syndrome . Each collision creates space junk which collides with other space junk, in an endless cascade. It could make regions of Earth orbit unusable, or possibly even cut Earth off from space.
Human spaceflight is already threatened by the debris around Earth. The International Space Station manoeuvres to avoid collision at least once a year.
The default solution is to let space junk get dragged into the atmosphere where it incinerates. For example, at least one Starlink satellite burns up in the atmosphere every day.
But this is now creating enough soot and alumina particles to have an impact on the ozone layer , which protects us from harmful ultraviolet radiation.
New technology can help
Technological solutions involve active debris removal , and strategic satellite and mission design.
Active debris removal gets rid of old spacecraft by tipping them into the atmosphere or pushing them into a "graveyard" orbit" which isn't used by functioning satellites. There's even a hit list of the 50 most dangerous spacecraft - mainly abandoned rocket bodies.
Debris removal technologies include nets , magnets , tethers , sails , slingshots , and harpoons . Very few have been successfully tested in space.
New satellites can be made from materials that are more durable, so they last longer - or more disposable, so they can be used and quickly de-orbited.
Japan has been testing wood as a spacecraft material. Other options include refuelling spacecraft to extend their life.
Better policies
Policies are also changing to focus more on satellite end-of-life disposal.
The old standard was that spacecraft should not remain in original mission orbits for more than 25 years. Now it's five years . The disadvantage to this policy is that more spacecraft will burn up in the atmosphere.
The European Space Agency is spearheading a zero debris policy , and the Inter-Agency Debris Co-ordination Committee issues debris mitigation guidelines . There's also an international standard for space debris mitigation.
Better international co-operation could be achieved through space traffic management . Space traffic management aims to establish "road rules" for avoiding congestion in orbit, by limiting debris creation, co-ordinating orbital activities and sharing information. However, a globally agreed space traffic management system doesn't yet exist.
All the same, satellite operators are starting to take their environmental responsibilities seriously. But is this enough?
Rethinking space
Old ways of thinking about space have not served humanity well.
The ideologies driving the space junk problem are competition for prestige and orbital resources , and the belief that there are no moral obligations to the space environment. Often, orbital space is not seen as an environment at all because it is without life.
These beliefs coincide in the "techbro" space, in which billionaires are competing to launch satellite megaconstellations. Research has shown caring for the environment is not seen as masculine .
Earth and space are no longer separate domains. Space junk should be managed as a more-than-planetary interconnected system extending from the spacecraft cemetery at the bottom of the ocean, through the atmosphere, to all Earth and lunar orbits. The Moon's surface is also being impacted by space junk.
Philosopher Val Plumwood's co-participation approach to environmental management provides a new perspective. We give the environment what it needs to flourish, instead of depleting it to the point of collapse.
The jury is still out on whether Kessler Syndrome will eventually cut us off from space. Perhaps new myths and stories will arise around the space junk people see burning through the atmosphere. Watching the skies for "cultural meteorites" is becoming part of the shared human experience.
Alice Gorman has received funding from the Australian Research Council to study the International Space Station. She is a Fellow of the Outer Space Institute and a Co-Chair of the Global Expert Group for Sustainable Lunar Activity.
