Satellites and spacecraft are at risk in orbit
(source: ESA Space Debris Brochure)
Garbage is big business. In fact, collecting and processing our discarded items here on Earth is a multi-billion dollar industry around the world. But what about space junk? It’s not like you can just back up a truck, or more specifically a spacecraft, load in the refuse, and take it away to be discarded in another location. But space junk is becoming a growing problem, particularly as more and more countries launch satellites and enter the global space economy.
According to the NASA Orbital Debris Program Office there are more than 21,000 debris objects larger than 10cm, approximately 500,000 objects from 1-10cm, and more than 100 million objects less than 1cm. This includes significant amounts of debris in low Earth orbit, where satellites such as Landsat and WorldView-2 reside, as well as debris in geosynchronous orbit, where instruments such as the GOES and Meteosat weather satellites reside. In total it’s a lot of debris to take into account with respect to current satellite operations and future launches.
So where does space junk come from? Sources of debris, according to NASA, include “derelict spacecraft and upper stages of launch vehicles, carriers for multiple payloads, debris intentionally released during spacecraft separation from its launch vehicle or during mission operations, debris created as a result of spacecraft or upper stage explosions or collisions, solid rocket motor effluents, and tiny flecks of paint released by thermal stress or small particle impacts.”
The obvious danger of space debris is the potential for collisions, which result in at best minor surface pitting and at worst catastrophic destruction. And such destruction only leads to more debris. To mitigate this eventuality, the U.S. Space Surveillance Network and a number of other national and international organizations, routinely monitor space debris distribution. However, tracking individual debris items is limited to only the largest of objects, typically those > 10cm.
To avoid collisions, satellites with maneuverability, such as the International Space Station, can adjust their orbit accordingly. Additionally, shielding can be used to protect spacecraft from impacts of smaller debris items. Unfortunately, not all debris is explicitly tracked, not all satellites are maneuverable and not all components can be sufficiently shielded, resulting in a certain level of ‘space roulette’ for any given spacecraft.
So what are some of the solutions? The U.S. Government and a number of other spacefaring countries, including Japan, France and the ESA, have established orbital debris mitigation guidelines to reduce the creation of new debris. This includes ‘end-of-life’ disposal plans for spacecraft and used orbital stages to either re-enter the Earth’s atmosphere or be re-orbited to an unusable ‘graveyard orbit’. Spacecraft are now also designed and operated to avoid unnecessary debris release and to reduce risks of accidental post-mission explosions from unspent energy reserves.
This still leaves the question unanswered on how to remove the significant amounts of existing debris. Referred to by NASA as active debris removal, “many different methods for remediation of the orbital debris environment have been proposed over the years. These include the use of lasers, electro-dynamic or momentum exchange tethers, tugs, drag enhancement devices, and other, more exotic methods.” A workable, technically sound, economically viable solution, however, is yet to be achieved.
What’s your idea? Perhaps a unique method for capturing and combining numerous small debris items into larger objects that can be safely de-orbited, or perhaps an orbiting recycling center that puts the debris to good use? Whatever the solution, something needs to be done soon. It’s getting crowded up there.
For more on space debris, view “The Space Debris Story” video produced by the ESA.