Space "junk" becoming an increasing problem

Citation

(2002), "Space "junk" becoming an increasing problem", Aircraft Engineering and Aerospace Technology, Vol. 74 No. 5. https://doi.org/10.1108/aeat.2002.12774eaf.002

Space "junk" becoming an increasing problem

Keywords: Space travel, Environment, Safety

From tools lost by astronauts to abandoned launch vehicle parts and satellite fragments, near-Earth space is increasingly accumulating junk (more than 2,000,000kg within 2,000kg of Earth). That's what Dr Richard Crowther of QinetiQ recently reported in a leading science magazine, in the same week that the International Space Station had to be manoeuvred to avoid a potential collision with a discarded rocket body.

As Earth sweeps through space it encounters a flux of natural debris. Moving faster than 20k/s, these meteoritic bullets (some no larger than dust specs) can inflict severe damage on artificial satellites and spacecraft – which have to be designed to avoid or withstand such impacts. Thirty years into the space age, however, another population of debris has begun to have an impact on artificial satellites – unlike meteoroids, it is man-made in origin.

Space debris is divided into three distinct populations – risk population (objects smaller than 1 cm in diameter), lethal population (objects between 1 and 10cm in-diameter) and catalogued population (objects larger than 10cm in diameter). The latter of these makes up 99 per cent of the mass of debris in orbit and can be detected and tracked. They include payloads, rocket bodies, operational debris, and fragmentation debris.

The real danger comes from the smaller items of space debris because of the high collision velocities that are encountered. A small coin travelling at 10km/s through space will have the same impact energy as a small bus travelling at 100km/h on the ground! So, as these large objects break up they generate millions of fragments.

Several recent near-misses and one major collision involving the Cerise satellite and a fragment from an Ariane launch vehicle has alerted the community to the risks posed by this new environment, which is the direct consequence of previous launch and orbital operations.

"As we increasingly rely on space-based systems for remote sensing, communications, and navigation, we must understand the threat that space debris poses and the long-term financial consequences of ignoring it," says Dr Richard Crowther of QinetiQ. "Further, we must take appropriate steps to ensure the cost-effective and sustainable development of near-Earth space for generations to come."

Dr Crowther identifies two courses of action available to spacecraft operators to reduce the impact of space debris. The first is to manage the collision risk by accepting that the frequency of occurrences will increase but configuring systems to limit the consequences of such encounters. The second is to manage the collision hazard by limiting the likelihood of collision. Dr Crowther advocates the latter approach, stating that it is the only sustainable approach in the long term. He also outlines a series of measures to reduce the future production of space junk, ranging from boosting satellites away from crowded orbits through to expelling residual rocket fuel to avoid explosive fragmentation in orbit.

The importance of managing space debris is acknowledged by all space-faring nations as they recognise the long-term financial and legal implications of future collisions between high-value operational satellites, but to date no international agreement for regulating space debris exists.

The United Nations Committee for the Peaceful Uses of Outer Space has endorsed the action undertaken by the Inter-Agency Debris Co-ordination (IADC) Group, which comprises rocket and satellite experts from the majority of space agencies, to seek an international consensus on mitigation practices. Dr Crowther will present these guidelines on behalf of the IADC to the United Nations in 2003, and their subsequent endorsement will be a further step forward in ensuring safe and cost-effective access to space for future generations.

Details available from: Qinetiq. Tel: +44 1 252 394627.