Space debris falling back to Earth has hit the headlines several times in the last month, which is not surprising given the sheer scale of the orbital debris problem. According to the ESA, there are currently 36,500 space debris objects being tracked that are greater than 10cm in diameter, and a further 1 million objects being tracked that are between 1cm and 10cm in diameter. Space debris is having a significant impact on space safety and sustainability.
The space industry is growing rapidly, most notably within LEO where, in recent years, there has been a big increase in commercial satellite constellations. As the Earth’s orbit becomes more congested, the need to tackle the problem of space debris has increased. In this blog, we’ll explore which strategies and initiatives are having the biggest impact.
Sources of space debris
Earth’s orbit could be likened to a graveyard for rockets and satellites of yesteryear. In fact, many of the dangerous objects orbiting Earth are from rockets and satellites launched decades ago, before the publication of guidelines on mitigating space debris. According to ESA, since the start of the space age in 1957, there have been approximately 6250 successful rocket launches which have resulted in about 13630 satellites being placed into Earth’s orbit. Of these, 8840 are still in space, and only 6200 are still functioning.
Space debris is caused by non-operational satellites, spent upper stages and mission related objects such as launch adapters and lens covers, fragmentation events such as explosions of satellite and rocket bodies, anti-satellite testing, and non-fragmentation debris such as reactor cores and copper wiring released during space missions. The concern among some experts is that the accumulation of space debris at certain altitudes will eventually cause a cascade effect called the Kessler Syndrome, at which point, travel into space will become impossible because of a chain reaction of uncontrolled collisions.
Clean up and removal initiatives
There is always the likelihood of large objects breaking apart into many smaller objects so the focus has been on removing larger objects before that can happen. Clearspace-1, launching in 2026, is a mission to do just that by rendezvousing with, then capturing a specific object (a piece of debris left by a rocket in 2013). It will bring it down for a safe atmospheric re-entry, where both spacecraft and debris will burn up. Other removal concepts include remote energy impact (laser or ion flow), full or partial recycling, capture and tug by another spacecraft, and methods of slowing down and deorbiting the debris. Although there has been a number of concepts and methods suggested for removing space debris, to date, there hasn’t been a great deal of progress made in actual physical removal of the debris.
The lack of progress is perhaps unsurprising given that debris removal is extremely expensive and is not a profitable activity. Although there have been no clear commitments from governments yet, it seems clear that the only way forward is for the removal of space debris to be publicly funded.
This is why it is absolutely critical that effective measures are in place to prevent any further debris from being created that add to the existing problem.
Preventing creation of additional debris
In-orbit collisions cause damage to satellites and spacecraft, potentially causing fragmentation events that result in the generation of additional space debris. Having fit for purpose Space Situational Awareness (SSA) systems in place to prevent in-orbit collisions is an important part of the strategy to avoid creating more debris. As discussed in a previous blog, a reliable and accurate SSA system requires effective data sharing, and a public, coordinated, and internationally funded approach.
Another strategy to prevent the generation of new space debris is to ensure that satellites are managed carefully throughout their entire life cycle, from the launch phase, to the end of life when they are decommissioned. Fortunately, the launch process is managed much more sustainably now than in the past. Generally, the rockets used for launching satellites are either burned up during a process of controlled re-entry into the Earth’s atmosphere, are placed in orbit to naturally decay within a set time period, or are partially recovered as happens with SpaceX stage 1 boosters. Generally, most satellite manufacturers now aim to design their satellites in such a way to minimize the debris generation during the satellite life cycle. Unfortunately, decommissioning satellites at the end of their life is not managed quite so responsibly. Not all disposal attempts are successful, and all too often, no attempt is made to remove and dispose of the spent satellite at all.
It is also important that spacecraft are disposed of safely at the end of their mission, as per space debris mitigation guidelines published by the Inter-Agency Debris Coordination Committee.
Getting it right
While the need for a two-pronged approach to deal with existing space debris as well as preventing any new debris from being created is clear, techniques to remove debris are yet to have any impact. The priority therefore, must be to stop, as a matter of urgency, any activity that is adding to the problem, such as anti-satellite testing, and the launch of small LEO satellites that fail to meet the re-entry requirement.
Tackling the problem of space debris is not a final destination, but instead, is definitely much more of an ongoing journey which will require significant attention and resources as we move forward. Our ability to avoid a future scenario where space use becomes unsafe because of debris, is dependent on us tackling the issue now, and getting it right.