Cleaning Up the Orbital Neighborhood
I received some pretty interesting answers to the question from the first article, some of which revealed biases that I had never encountered before, but the one I had in mind is that on average, a woman requires only about 75% of the resources (food, air, water) to sustain good health that the average man does. Thus having a woman-only crew would produce substantial savings for the life support system over the one needed for an all-male or mixed crew.
Over the nine previous years of Space Week, there are more than a few instances in which I have addressed the same topic more than once, usually because recent developments or new information warrant another look at it, and today’s topic of space debris falls squarely in that category. Think back for a moment to the popular 2008 animated feature Wall-E. In it we see the Earth depicted as a deserted wasteland, filled to overcapacity with the mostly useless junk left behind by the former human inhabitants, who have now fled to the stars in vast spaceships where their consumptive ways continue unabated. In this bleak scenario, not only is the Earth’s surface choked with humanity’s detritus, but its orbital space as well. We see this first in the opening zoom-in shot and again when the title character stows away on the robotic reconnaissance ship as it leaves Earth to report back to its human masters. In the film, this cloud of debris is navigated with minimal difficulty and is used for comic effect (including a satellite looking an awful lot like Sputnik, now long since fallen to Earth), but in real life, the journey would be perilous beyond measure.
Space debris of the man-made variety has been around ever since the first rocket launches in the late 1950s, but it was not until the end of the Cold War that the major space-faring nations began to see the growing number of leftover objects still in orbit from previous space missions as a concern. Types of debris range from entire derelict satellites to spent rocket booster stages to square-inch-sized flecks of paint that have fallen off spacecraft by the millions, but regardless of size, any piece of debris carries the risk of colliding with something we would prefer remained intact, such as a working satellite or the International Space Station.
In the early years of space exploration, there were no protocols against generating debris mainly because the odds of a potential collision were very low. Since the one main thing about space is that there is just so much of it, it can be difficult to envision how it could all be filled up. But while space is vast, the fact is that some space is better than other space, especially when it comes to objects like communication satellites or for conducting certain types of scientific observations. For example, the geostationary orbit, which is the altitude where a satellite will orbit at the exact same speed as the Earth itself (thus appearing stationary to an observer on the ground) has long been well-populated. The five Lagrangian points (areas of stable gravitational influence) of the Earth-Moon or Earth-Sun systems are also potentially valuable and the privilege to occupy them may generate fierce competition as space activity continues to increase.
This growing crowd of objects, especially in high-demand orbits, is one factor that enhances the risk of debris-creating collisions. Another factor comes from a basic feature of orbital physics that stipulates that, except in the case of the Lagrangian points mentioned above, for an object to remain in a stable orbit for any useful length of time, it must be periodically boosted to counteract the effect of Earth’s gravity. This orbital maintenance requires an onboard, therefore finite, store of fuel that will eventually be exhausted. Since weight is money when a space launch is concerned (currently the average is several thousand dollars per pound), there is an incentive to push this fuel store down to the minimum that is necessary to keep the object’s orbit from decaying during its planned operational lifetime. That incentive creates two distinct sources of risk: one is that the amount of fuel available to make emergency course corrections, such as ones needed to avoid a collision, is minimal; the other is that once the fuel is exhausted and the object is no longer operational, it becomes a potential risk to objects that are, especially if the launching nation or company did not take steps to de-orbit it prior to that point.
While responsible space-faring nations are making de-orbit plans a standard feature of launches today, there are hundreds, possibly thousands of derelict objects still around from the time before this need was recognized. These factors combine to create a recipe for eventual chaos in the orbital arena, which if left unchecked, could render wide regions of Earth’s orbital space effectively unusable for decades or even centuries. For while debris generated from objects in low Earth orbit (usually defined as orbits 1,250 miles or less from the Earth’s surface), such as an astronaut’s lost toolbox from a recent shuttle EVA, will fall back to Earth in the space of a few months or years, the orbital decay of debris from higher altitudes may take up to thousands of years depending on its size, speed, and initial orbit. The problem will thus not clear up on its own anytime soon.
Furthermore, there exists the possibility of what is known as a Kessler Syndrome cascade (named for the NASA scientist who first described it in 1978). The dynamics are similar to those of a nuclear chain reaction: once enough material exists, the debris created by any initial collision will go on to trigger a cascade of further collisions that create even more debris. The process continues until there is a cloud of debris around the Earth so thick that it becomes virtually impossible to launch any new satellite without it being chewed to pieces by existing debris in relatively short order and in turn providing fodder for yet more collisions.
The prospect of the orbital space around Earth becoming filled with hazardous debris is thus no longer simply a remote science fiction scenario but has the potential to become reality in relatively short order. Indeed, on February 10th, 2009, the first known collision between two intact satellites took place in orbit above Siberia, an event which nearly doubled the amount of known space debris and created perhaps thousands of small, but still dangerous, objects that are too difficult to track. Later that month, there were two incidents that occurred within a week of each other in which the crew of the International Space Station had to take refuge in anticipation of a possible collision with a golf-ball-size or smaller object. Thankfully, neither potential collision actually took place, but those two close calls and the satellite collision have put the danger of space debris in stark relief.
While individual nations and groups such as the European Union have developed protocols for cutting down on the creation of new space debris, there is currently no comprehensive international framework or set of rules to manage the Earth’s critical orbital space. Some steps have been made in this direction by the UN Committee on the Peaceful Uses of Outer Space (COPUOS), but nothing concrete has been established. In my opinion, it will have to be an international body that sets up and enforces any new orbital management system, and I look to the model of the international unions that emerged in the 19th century to solve previous coordination issues between national governments as well as private businesses. One of them, the International Telecommunications Union (ITU) already manages some aspects of the geostationary orbit, but its mandate is limited to issues dealing with the use of various spectrum resources and does not address the physical issues that crowding creates.
Thus I think we need a new international union, free of the control of any other government, to manage the allocation of orbits and deal with the problem of space debris. This union should have the authority to charge rents for the use of high-demand orbits, impose fines on nations or companies that violate regulations (intentional destruction of satellites, such as China’s action in late 2007, would certainly be prohibited), and require collision insurance for any object launched into space for reasons similar to the reasons why most US states require all drivers to have auto insurance.
Of course, even any new regulatory regime will not be able to completely stop the creation of new space debris, as accidents will happen and some people will try to circumvent the system. Nor will it deal much with the debris that is already there. One policy, already in use, is requiring satellites to be moved to a designated “graveyard orbit” once they have reached the end of their useful lifetime. This takes them out of the way of working satellites and puts them high enough up that they will not pose a danger anytime soon. While some other nifty technical solutions have been proposed, such as pointing lasers at debris to make them fall to Earth faster, they all fail the cost effectiveness test by requiring expensive new architecture for their support. Depending on how soon we can get a new international union or other regulatory framework in place, such technical fixes may become necessary, but for now we still have some breathing room, and making sure no new debris is created should be our top priority.
IMDB page for Wall-E
The Kessler Syndrome
Recent news articles on space debris:
The Economist: Flying blind
Space.com: Space Junk Around Earth on the Rise, Experts Say
ABC News: Space Junk Threatens Atlantis’ Hubble Repair Mission
Question: What other animated production features an Earth surrounded by a cloud of debris, and actually deals (somewhat) realistically with the danger it poses? (Major geek points if you know this one.)
Norman Barrett Wiik as a current graduate student in public policy, a board member for Camp Quest of Minnesota and Camp Quest Inc., and a lifelong enthusiast of space exploration.
This entry was posted on Sunday, October 11th, 2009 at 7:51 pm and is filed under Features, Science. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.