Space debris

1000-year simulation shows space debris will become ‘uncontrollable’

Image credit: Getty Images

Forward projections for space junk accumulation suggest that in a thousand years satellite launches could be almost untenable as the chances rise that they will suffer a fatal collision with other orbiting particles.

Researchers from the University of Southampton considered current mitigation guidelines that are in place such as the ‘25-year rule’ which stipulates that satellite operators should reduce the length of time their spacecraft spend in the protected region, dubbed Low Earth Orbit (LEO), after the end of their mission.

The LEO is a protected band below 2000km altitude that is considered highly important to spaceflight.

The researchers created long-term simulations where fewer than 20 satellites per year were placed into orbit at altitudes above 1000km. Only one or two of these were left there once the ’25-year rule’ had been applied to the others.

Professor Hugh Lewis, who worked on the project, said that even with these countermeasures in place, the amount of space debris is predicted to grow “uncontrollably”.

“The problem is that our best countermeasures slow the pace of the collision cascading to such an extent that it is impossible to observe in the current 200-year simulations. By extending them to 1000 years, the true and almost inevitable nature of the problem was revealed,” he said.

At the beginning of the simulation, catastrophic collisions above 1000km were occurring roughly every 50 years.

But this interval came down to just six years as time went on despite the fact that only one or two satellites had been added to this region each year.

To meet the ’25-year rule’, every satellite launched into LEO at altitudes above about 600km performed a manoeuvre at the end of their mission. These manoeuvres created additional traffic below 600km that led to a big increase in collisions.

“About one-quarter of all the catastrophic collisions seen in the simulations involved satellites that had successfully met the ’25-year rule’. If we just look at collisions involving whole, or intact, satellites then the number rises to two-thirds,” Lewis said.

The European Space Agency (ESA) is developing a plan to use tentacle-like mechanical arms to embrace dead satellites and bring them out of orbit.

Other options considered have included a net being cast over the object, using a robotic arm, or using a harpoon.

The head of the ESA's Space Debris Office, Holger Krag said: “The goal is to make these removal actions happen more frequently, and therefore they need to be cheap.

“The technology that we will most likely use now is actually consisting of some sort of arms, like tentacles, that embrace the object, because you can capture the object before you touch it.

“The dynamics in space are very interesting because if you touch the object on one side it will be dragged away – so you can basically embrace it before you touch it, and then you just embrace it closer as you dampen the tumbling motion.”

Currently, of the almost 4,500 satellites in orbit, only 1,500 are active.

Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.

Recent articles