Space Debris and Other Threats From Outer Space (2 page)

Historically, the creation rate of debris has outpaced the removal rate by a fairly wide margin. This is leading to a net growth in the debris population in LEO at an average rate of approximately 5 % per year. Although this may not sound like much, it means the amount of debris in orbit is now very substantial and based on past experience will likely continue to grow.

Although the low-Earth debris orbits in effect “spread out” as they orbit Earth they come much closer together over the North and South Polar Regions and thus serve to increase their chances of collision by a considerable degree.

To put the problem into a more accurate “visual perspective”, it important to note that because the scale used in Fig. 
1.4
is actually something like 10 million to one, the risk of collision is indeed much less than it would appear. It’s like when one looks in a rear view mirror and it says that “vehicles may be closer than they appear”. Recognize that the same is true here. The debris elements shown above, in fact, are 10 million times further apart and that the volumetric space of Earth and space within which the orbiting debris is depicted here is 10
²¹
times (or 1,000,000,000,000,000,000,000 larger).

A major contributor to the current debris population has been fragment generation via explosions of fuel tanks and more recently by collisions. It is hoped that future explosions can be minimized by venting of fuel prior to the operational end of life of satellites—as recommended by the current mitigation procedures. It may take a few decades for the practice to become implemented widely enough to reduce the explosion rate, which currently stands at about four per year.

Several environment projection studies conducted in recent years indicate that, with various assumed future launch rates, the debris populations at some altitudes in LEO will become perhaps completely compromised. In these projections collisions could take over as the dominant debris generation mechanism, and the debris generated will feed back into the space environment and induce more collisions—in short, an in-orbit cascade that creates more and more debris.

According to studies conducted by J-C Liou and N. L. Johnson, the most active and endangered LEO region is between the altitudes of 900 and 1,000 km, and, even without any new launches, this region is highly unstable. It is projected that the debris population (i.e., objects 10 cm and larger) in this “red zone” will approximately triple in the next 200 years, leading to an increase in collision probability among objects in this region by a factor of ten [9]. In reality, the future debris environment is likely to be worse than as suggested by Liou and Johnson, as satellites continue to be launched into space. In late June 2012 this author was at the Kennedy Space Center where the Delta IV Heavy vehicle launched a surveillance satellite into orbit and this satellite with on-board positioning fuel alone weighed some 30 tons.

The Liou and Johnson paper concludes that to better limit the growth of future debris populations, active debris removal (ADR) from space needs to be considered. The various technical and operational options that are being considered for such removal are discussed later in this book.

The problem of tracking debris, of course, becomes more difficult as one moves further away from Earth in higher orbits. In the geosynchronous geostationary orbit, for instance, the minimum size that can be tracked is 30 cm in contrast to about 10 cm in LEO. Among the tracked pieces of debris, there are about 200 satellites abandoned in geostationary geosynchronous orbits occupying or drifting through valuable orbital positions and posing a collision hazard for functional spacecraft. Fortunately, accurate tracking systems, charting of possible conjunctions that could result in high velocity collisions, and active collision avoidance maneuvers minimize these risks. The Satellite Data Association (SDA) that will be discussed later now plays a key role in this activity.

As noted earlier the survival time of the debris in orbit continues to changes with the higher orbits. Objects in 1,000-km orbits can exist for hundreds of years. At 1,500 km, the lifetime can go up to thousands of years. Objects in geosynchronous or super synchronous orbits can survive for millions of years.

And there are other realistic space threats that also need to be taken seriously. Although space debris has now become a top issue that must be dealt with in order to sustain useful access to space, this is just one of the “threats” that must be addressed. The harsh environment of space puts satellites, space stations, and even rocket launchers at risk. These risks include, micro-meteorites, solar flares, coronal mass ejections (CMEs), and cosmic radiation. These natural hazards can disable or totally destroy functioning satellites and spacecraft as proven by past events. These events are less under our control than space debris, but shielding and other protective actions can help protect against these types of hazards as well. Currently these natural threats pose a higher risk level than space debris, but over time space junk, unless aggressively attacked by Active Debris Removal (ADR), will become a higher level threat.

What is often not mentioned is that these natural debris and natural phenomena could actually pose threats even to people on the ground. Solar flares, coronal mass ejections, cosmic radiation, meteorites, asteroids and comets, and yes, even space debris can pose risks to people on the ground. These risks to people right here on Earth’s surface will be addressed in later chapters of this book. Most of these risks would involve only a limited number of people.

But there is one type of natural hazard that not only threaten astronauts and spacecraft but could indeed threaten life on Earth in a big way. This threat is known as Potentially Hazardous Asteroids (PHAs), and this is in no way just a “theoretical” risk. Actually this is something to be taken quite seriously. It is believed that an asteroid, rich in the poisonous substance iridium and perhaps 10 kilometers in diameter, plunged into Earth some 65 million years. When it impacted Earth it created a huge cloud around Earth that blocked out the Sun for several years. As a result the dinosaurs and well over a third of all life-forms on the planet died off. Another asteroid or large comet could do equal damage to humans and other life forms if it were to hit Earth in future years.

Even a smaller asteroid such as Apophis, which is about 300 m in diameter, if it were to hit in an ocean near a large city could bring death to tens of millions of people, and if it were to hit in, say, the United States it could possibly wipe out an entire state. Fortunately Apophis is scheduled to fly by in 2029 and 2036 and then be on its way [10]. This very real subject of “killer asteroids and comets” and what we are doing to be ready for them, will also be addressed in later chapters.

In short after addressing the problem of growing amounts of space junk the discussion will turn to various types of natural threats in and from space and even potential threats to people here on the planet’s surface. In all cases the discussion will go beyond identifying risks to explore protective actions. It is not enough to just explain that there are threats. There are indeed a number of actions being taken to protect the billions of dollars in space assets from both space debris and natural space hazards. In fact, military satellites deployed in strategic regions are even hardened against nuclear weapon explosions, electronic magnetic pulses (EMPs) and cosmic radiation. As new techniques are developed to protect space assets and extend space situational awareness, these solutions can presumably be applied to help protect people here on Earth as well.

The purpose of this book is to provide a good overall understanding of the nature of the various space threats and what techniques, new technologies and strategies can be developed to cope with these various hazards.

In addition there are programs operated by space agencies and research centers around the world related to protection of humanity against natural threats from space. These include:

Despite all of these activities, there is evidence that what is being done may well not be enough.

The structure of this book is to first introduce the nature of the problem of space threats and to note that the methodological approach to the subject is completely multi-disciplinary. Thus the technical, operational, economic and financial, and legal aspects of the problems related to space threats will be addressed along with possible solutions in each of these areas. In some cases an interdisciplinary approach is used simply because the solution may require new technology, new international legal regulations and financial incentives or penalties if corrective action is not taken.

Four chapters of the book provide a good deal more information about the various problems associated with space debris. These chapters address the technical, operational, institutional and even financial and regulatory arrangements associated with attempts to address and mitigate this growing and increasingly very real problem. The remaining chapters of the book address the very real threats that exist in space that come from natural space phenomena, including coronal mass ejections, solar flares, solar and cosmic radiation, and finally potentially hazardous near-Earth objects (NEOs), including comets and asteroids. Here is a quick recap with some key highlights.

Chapter 2
will address in depth why the threat of space debris and the Kessler Syndrome is increasing. This chapter explains that even if there were to be no new space debris created from new launches that the problem would still keep increasing for decades to come just from the space debris that is already out there.
Chapter 2
also seeks to provide a general understanding as to how and why the problem of space debris will increase over time. This analysis notes we need to develop not only new technical and operational solutions, but also new regulatory, institutional and financial mechanisms and procedures as well.

Chapter 3
addresses the nature of the space debris problem and possible solutions that actually vary fairly widely in terms of the various orbits. The biggest and most urgent problem involves LEO and Sun-synchronous polar orbiting satellites as the top priority. Despite the fact that there is a critical need to get large space junk out of LEO, we should not lose sight of the need to clean up all the space around Earth in all the orbits. In short, solutions and corrective actions for all types of orbits from LEO out to geosynchronous orbit must be eventually found and implemented.

Chapter 4
addresses the institutional and regulatory issues. In particular, this chapter presents the specific efforts of the Inter Agency Space Debris Coordinating Committee (IADC) and the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS). These international bodies have been seeking for some time to address the problems of space debris and the longer-term sustainability of space. So far they have evolved to the point of “voluntary guidelines” to minimize orbital debris. But we need to go much further. In addition to these two key international bodies there are other organizations and activities that are helping to develop improved space situational awareness and to coordinate activities among space system operators to avoid possible collisions. Two examples of such organizations are the Space Data Association and the U.S. Air Force Space Command that provides the prime space tracking capability.

The longer-term sustainability of space currently starts with the development of improved tracking capabilities. But this is only the start of the process. There are a series of legal, regulatory and liability issues related to orbital debris and space operation concerns that applies to all current and future space faring nations. The current international liability provisions related to spacecraft and orbital debris, unfortunately, do not help with efforts to remove orbital debris from orbit. In fact, the current international liability convention might well be considered a barrier to this process. Indeed that is the opinion of most space legal experts that have addressed this problem. Most recently the COPUOS in 2011 established a Working Group on the Longer Term Sustainability of Space that examines the various issues related to making sure that all nations have the future ability to use space in a productive and effective way. This working group is addressing all of the technical, operational, and legal matters that are involved.

Chapter 5
addresses space debris remediation processes and the current status of space technology and related ground systems that might be employed to undertake space debris removal. In general, none of the technologies are really mature. Even if these various methods could be brought to technical and operational maturity they do not currently constitute cost-effective means to accomplish the task. In short a great deal of future research is needed in these areas to develop effective, cost-efficient methods for orbital space debris mitigation and also to avoid anything that might seem to be employing the use of “space weapons”. In fact, finding ways to accomplish space debris removal with technology that would not be considered as a space weapon is one of the key challenges to overcome.

We next move on from space debris related issues to the very real concerns of natural space hazards and the problems and issues related to the so-called phenomena known as “space weather,” cosmic radiation and potential collision with asteroids or comets. Here we explore the fact that the ‘natural threats’ from space endanger both our spacecraft in orbit and actually can endanger us here on Earth as well.

These natural space phenomena certainly include hazards to spacecraft and space operations. Satellites must be designed to withstand the very real difficulty of long-term operation in the very harsh space environment, where in-orbit repair or refurbishment is generally not an option. But the hazards involve more than just designing satellites to withstand the rigors of space and thus we will explore why and how we need to protect modern electronic infrastructure from space hazards as well. Although space debris is a very real threat to the long-term sustainability of space-related activities, it is important to understand that there are a number of very real natural space threats as well.

The hazards addressed in the later chapters actually could represent a much larger threat to humanity than space debris—and by several orders of magnitude. But fortunately that is not the whole story. Although the threat levels are high, the chances of many of the most hazardous events actually occurring—as triggered by natural space phenomena—are quite small. One of the great challenges for space scientists today is how to deal with threats that are very large, but with their chance of occurring being quite small.

Fortunately the protective shield of the Van Allen Belts, the ozone layer, Earth’s atmosphere and especially Earth’s geo-magnetosphere provide us critical life-saving protection. There are, however, currently two emerging problems in terms of Earth’s protective system against threats from space. One problem is that Earth’s geo-magnetic field seems to be developing “cracks” that could let highly destructive radiation and ionic particles as well as poisonous gases through with deadly effect. This is a problem being studied by space probes with some urgency. The other problem is what to do if Earth’s protective atmosphere begins to rise to unacceptably high temperatures as the result of climate change. If the atmosphere that protects us should grow too hot, it would raise an entirely new danger that may raise new issues about humanity’s longer-term survival. There is real concern that this heating process, if it should go up on a global average by two or three degrees Celsius, might reach a “tipping point” where reversal of this gradual process might become irreversible. This is, of course, unless some totally new technological solution might be found. Fortunately humans are often clever in finding survival technologies.

Unless one is flying in space above the Van Allen Belts the threats from natural space hazards today remain quite small. These various hazards include so-called solar flares and coronal mass ejections that coincide with the 11-year solar cycle that varies from solar minimum to solar maximum. Most of the times we are quite safe here on Earth, but every 11 years there is a risk that our electrical grids and electronic systems could be zapped big time. We know from The Carrington Event of 1859 and the more recent massive coronal mass ejection of 1989 that these are dangers that cannot be ignored and must be taken seriously [11]. We will also consider the hazards that come from cosmic and solar ultraviolet radiation that is a threat to astronauts and cosmonauts as well as an increasing threat to people in the extreme latitudes near the Polar Regions where the ozone holes now exist.

Chapter 6
addresses the threats posed by solar flares and coronal mass ejections (CMEs). So called “space weather” from the Sun and the cosmos occurs all the time. There are solar eruptions that occur periodically, and during so-called solar max these threatening events are about 15 times more likely to occur than at solar minimum. So-called CME events are characterized by the release of massive amounts of super charged ions that are ejected from the Sun’s corona, which is a raging mass of super-heated plasma that reaches one million degrees Celsius. As a result of these periodic solar events a highly destructive mass of ions are released. These ions and charged particles travel at millions of miles an hour and actually pose a major threat to satellites and spacecraft in space. A number of protective measures need to be employed to protect satellites and orbital spacecraft from these occasional blasts, some of which are violent enough to threaten not only not only satellites in orbit but as noted earlier electrical grids, electronic equipment, and facilities on the ground. In short, CMEs, in the most severe cases, can endanger much of the modern infrastructure on Earth. This means not only power grids but pipeline systems and highly distributed computers and telecommunications networks as well. Just think of the consequences if all the microprocessors on all the vehicles and aircraft in the world were to be blown out by a super-massive solar eruption.

Chapter 7
will focus on solar and cosmic radiation and can likewise present hazards to space assets as well as people right here on Planet Earth as well. Widening holes in the ozone layer allow through truly harmful X-ray radiation in the Polar Regions. Solar and cosmic ultraviolet radiation travels essentially at the speed of light or close to 300,000 km/second or 186,000 miles/second. Solar eruptions that contain super charged electron ions as well as alpha and beta particles travel at huge velocities. Despite this great speed these eruptions nevertheless travel on the order of a 100 times slower than the speed of light or energetic gamma rays. This is indeed fortunate. The speed differential allows solar flares and CMEs to be detected via solar observatories and space-based sensors so that satellites and key facilities can be powered down and electrical systems switched off to protect against the “big hits” from these solar storms or super space weather events. Without this type of warning system hundreds of orbiting spacecraft worth hundreds of billions of dollars could be at risk and essential satellite operations lost for communications, navigation, remote sensing, weather forecasting, and military-related services.

Chapter 8
examines how potentially hazardous asteroids (PHAs) and comets pose an ongoing risk to humans, and
Chap. 9
addresses what is currently being done to address and forestall these potentially calamitous events. These NEOs are rarely of large enough size to actually pose a major threat, but on average—about every 50–100 million years—these natural orbital debris can truly clobber Earth and its inhabitants. The good news is that we believe that we have identified some 90 % of the potentially hazardous asteroids that are 1,000 m or more in diameter and might come within 9 million miles (or 14.4 million km) of Earth. The bad news is that it is estimated that there are another 10 % of these large threats still to be identified and some 80 % of such asteroids some 100–1,000 m in size to be cataloged. An asteroid of this smaller size could still hit us with the force of tens of thousands of atomic bombs. What is perhaps most important of all is to understand that impacts of objects in this size range are much more frequent than every million years. In fact the chance of a Tunguska-size impact this century is in the order of 1 in 10 to 1 in 5. Later in this book we address the so-called Torino Scale, that is sort of like the Richter Scale for potentially hazardous asteroids. This chart indicates both the likelihood of strikes and the type of damage various-sized NEOs might cause if they hit Earth.

And there are also a large number of potentially hazard comets still to be detected as well. Currently the odds seem to be in our favor, but there are a number of specific asteroids we are tracking with particular concern.

In the short term a much more serious threat for spacecraft are the millions of meteorites and micro-meteorites that can strike and disable a spacecraft. There are a series of recurring meteor showers that pose high levels of risk, but damage from a meteor or even a meteorite can occur at any time. Indeed it is estimated that about 15 % of the strikes on satellites today are from micro-meteorites and not miniscule space junk.

Chapter 10
recaps the major points from the book. Thus this chapter seeks to provide a synoptic overview of the various types of space threats to space assets and even to people residing on Earth or flying through Earth’s atmosphere. The strategies and technologies that address these various hazards are summarized as the “Top Ten Things to Know about Space Threats”.