The Real Problem With Space Junk

In an exclusive interview for Silicon Luxembourg, Dr Carol Martinez, robotics and automation researcher at the SpaceR group of the SnT talked to us about space debris and how to use robotics to remove it.

In 2020, Dr Carol Martinez joined the Space Robotics Research Group (SpaceR) at SnT, where she coordinates the orbital robotics activities, including the two SnT partnerships in active space debris removal and autonomous manipulation for on-orbit servicing. Her current research focuses on perceptions for multi-purpose manipulation tasks for autonomous planetary and orbital robotics applications.

“One of the projects that I coordinate comes from an SnT partnership program with the company Spacety. We started the 4-years partnership project in April, and we will conduct R&D in active space debris removal (ASDR) technology. Right now, we are designing a capturing mechanism for ASDR,” she tells us, also mentioning her colleagues Dr Baris Can Yalcin, Maxime Hubert Delisle and the head of the program, Prof. Miguel Olivares Mendez.

What is space debris and where does it come from?

Space debris is caused by millions of non-functional human-made objects left in space with varying geometry, size, and weight, such as spacecraft, construction materials from the ISS, collision fragments, part of rockets, satellites, mission-related debris. It also includes tiny paint flecks that have fallen off a rocket, among others.

More than 27,000 pieces of orbital debris, or “space junk,” are tracked by the Department of Defense’s global Space Surveillance Network (SSN). Is there more out there?

Millions. Some are defunct military satellites that are not publicly shared, and many are small pieces that are difficult to track by the tracking systems. You can find the current estimations here.

Are they “floating” in the Earth’s atmosphere (one of the five layers) or higher?

Most of them are in LEO or low Earth orbit, but there are also in the other earth orbits (MEO, GEO, HEO). There is also debris left on the moon and mars.

Why do they represent such a problem and a growing one at that?

First, the main problem is that currently, operators rely on tracking systems that tell you where debris is approaching. Then, they conduct collision avoidance manoeuvres to avoid the debris object. But, as you mentioned above, and based on the estimated data provided by ESA only a few are tracked. Millions of space debris objects are not tracked by those systems.

On the other hand, we are starting the second space era, launching more satellites than ever before (e.g., Starlink mega constellation), more operations, and more objects orbiting around the earth that must conduct collision avoidance manoeuvres. These objects later will become more debris as well. There will be a point at which we cannot operate safely.

If the orbits are crowded, it will be more challenging to conduct collision avoidance manoeuvres.

Suppose the orbits are crowded and one satellite crashes with an untracked piece of debris (as happened this year with a Chinese satellite). In that case, the risk of a chain reaction (Kessler syndrome) is much higher: collisions generate more fragments that can collide with functional satellites and will be responsible for causing more collisions, i.e., a chain reaction—making certain orbits not safe anymore and spaceflight too hazardous to be conducted.

How would one go about cleaning up this space debris?

There are different ways to mitigate the problem. But apart from that, there are also initiatives to clean space by actively removing space debris. Right now, no one wants to assume the cost of removing any piece of space debris. A mission is too expensive and creating one only for removing small pieces of debris is not an economically viable solution now.

We want to develop a low-cost piggyback payload to be used as a protection device or to provide a service mission to customers. The system will capture, stabilize (in case it is tumbling) and de-orbit space debris.

Many people think that junk will just “float” off to space or disintegrate – why doesn’t that happen?

That is the big problem that people are not aware of the real problem. We are not aware of the number of debris that is orbiting around earth or the debris that has been left on mars or the moon, and the real problem is that if we do not act on time, then there will be a point where it will be too late to contain the situation. The floating objects to disintegrate need to reenter the atmosphere. Depending on the altitude, floating objects can take many years to reenter, hundreds, or thousands of years.

What is the “worst case scenario” for the future, and how to prevent it?

Astronauts conducting spacewalks to maintain the ISS could be affected. A chain reaction (the Kessler syndrome), or orbits that can no longer be used due to the accumulated debris. To prevent it, it is a very complex problem. On the one hand, the incursion of the private sector is accelerating space exploration, something that is good because it will contribute to bringing answers to questions about the origin of life, provide information about our planet, and make the general public aware of what is happening in space.

To prevent it, as with any new technology, we need clear rules and policies and entities that aim to supervise the sector without any interest involved. Of course, targeting the problem from the source, i.e., every new object launched, should count with a system that ensures it is deorbited at the end of its life. But it is also needed to do something with the debris that is already out there.

There was an idea of dumping our Earth trash into deeper space – is that realistic?

Graveyard orbit can be used, but it depends on the altitude of each debris case for being or not a feasible solution. However, that does not solve the problem. The debris will still be there, which is not sustainable. That will be a temporary solution that will require another solution in the future, i.e., we will be passing the problem to future generations. Something like what happened here on earth a long time ago with our way to manage our waste. We did not see it as a problem, and now that the planet is overpopulated, we realise that our waste management is unsustainable.

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