by Les Johnson
Gravity was a fun movie that didn’t seem to care if it got the science "right." In portraying the very real threat of space junk destroying our satellites and space stations, Gravity was conceptually correct, but the timeline in which such destruction might occur was extremely compressed. Unfortunately, the threat posed by space junk is real and it isn’t the only reason we might have to learn to live without satellites…
Time Zero
Somewhere in Low Earth Orbit, a few hundred miles above the Earth
The weather satellite was old. It was launched into space in 1972 and had done its job well until it was turned off in 1983 as its replacement was finally finished and lofted into orbit to replace it. Having long outlived its useful life, the once state-of-the-art satellite, weighing 1580 pounds, was now just a dead piece of metal orbiting the Earth at 17,500 miles per hour. Nothing much had happened near the old satellite since the rocket that carried it into space those many years before had sent it on its way to circle the globe every ninety minutes. Since it was launched, it had orbited the Earth nearly 250,000 times – traveling over nine billion miles.
The weather satellite’s orbit crossed that of many other satellites and many more pieces of orbital debris, but the probability of it being in the same place at the same time as anything else was rather small. After all, space is big. Space is very big and, compared to the volume of space around the Earth, the volume occupied by the weather satellite was very small. The probably of it colliding with another object in space on any given orbit was small, but, unfortunately, the laws of probability finally caught up with the weather satellite. After more than a quarter of a million orbits, even a low probability event might actually happen. And happen it did.
An old Soviet-era rocket booster was orbiting the Earth at the same altitude but at a slightly different inclination. (Orbital inclination is simply another way of saying at what angle the orbit makes compared to the equator.) Their orbits crossed in two places and it was at one of these crossing points that the unlikely event occurred.
The rocket booster had launched a Cold War era spy satellite that was lofted into space by the Soviet Union. The booster was out of fuel and had no way to propel itself back into the atmosphere to burn up, so its masters had simply cataloged its orbital location and forgot about it. After all, the country that launched it into space didn’t exist anymore. The booster also circled the Earth every ninety minutes at 17,500 miles per hour.
The two objects approached the same physical location in space at a relative velocity of over 30,000 miles per hour. When the weather satellite collided with the old rocket stage there was no sound – there was no air to carry any sound - but there was a flash. Given that the satellite and the rocket stage were each traveling at least twenty times faster than a bullet, both were totally destroyed. The resulting debris cloud consisted of more than ten thousand pieces. Each piece was moving at over 17,000 miles per hour and, as a result of the collision, most were thrown into new orbits threatening additional satellites. The amount of junk had just grown past the tipping point, raising the probability that a piece of debris would then hit another satellite, destroying it and creating yet more debris, etc. etc. etc.
The United State Space Surveillance Center, Cheyenne Mountain, Colorado
Months before, using computer simulations, the US Space Surveillance Network had predicted that these two satellites would collide. Sophisticated radars around the world kept constant watch on the myriad of objects now circling the Earth and equally sophisticated computer models predicted with high accuracy when such collisions were likely to occur. They got this one right.
A team of engineers was watching the display and anxiously waiting on the radar results to provide an estimate of how bad the collision was. After just a few orbits, they had their preliminary answer – pretty bad. According to their models, the debris created in this latest collision was just enough to initiate the Kessler Syndrome. The Kessler Syndrome, named after the engineer who predicted it, says there will be a time when there are enough pieces of debris in space to create a cascading series of collisions that may ultimately render Low Earth Orbit (LEO) unusable. Any satellite in LEO after that time will have a high probability of being hit by debris and destroyed.
The team lead, with data in hand, contacted his superior and informed him of the latest predictions. Not wanting to be alarmist, his supervisor asked for more information, including when the next collision was likely to occur if predictions of a runaway Kessler Syndrome were accurate.
The next impacts would occur in no more than six months.
Time Zero Plus 6 Months
The computer models were correct. Six months later, a two inch piece of aluminum, still traveling twenty times faster than a bullet, collided with a functioning Global Positioning System (GPS) satellite and destroyed it. The collision created another five thousand pieces of debris that quickly spread out into several different orbits.
Shortly thereafter, yet another piece impacted a European science satellite, creating still more debris.
The Kessler Syndrome had begun.
Time Zero Plus 18 Months
The six astronauts on the International Space Station were aware of the orbital debris problem. They’d learned about it during their extensive training and they had contingency plans in place should there be a debris threat to the 660,000 pound orbiting laboratory. Bigger than a football field, the station was a large target for debris. Fortunately, under normal circumstances, any debris object large enough to pose a serious threat to the space station was tracked on radar, allowing ample warning of any potential collision risk. In fact, the station performed adjustments to its orbit several times each year to reduce the likelihood of an impact with a closely passing piece of junk.
But these were not normal circumstances. The astronauts had been warned of the potential runaway Kessler Syndrome and were in the process of abandoning ship and returning to Earth in the emergency crew escape vehicle when the entire station shuddered from a debris impact somewhere in the Destiny, America’s Laboratory Module. Fortunately, they were in the process of leaving and they were quickly able to get in the escape vehicle. Moments after they separated from the space station and began their return to Earth, the thirty billion dollars orbiting laboratory lost its entire atmosphere and began tumbling out of control. As in the movie
Time Zero Plus 3 Years
Ten satellites and the International Space Station were now lost and the number of collisions was increasing.
The United States, Russia, and China were now on high military alert. Among the ten lost satellites were super-secret and super-sophisticated spy satellites. Since the Cold War, the world’s major nuclear powers had placed into space spy satellites capable of providing early warning of an attack. These satellites could detect the launch of an adversary’s missiles with sufficient time to trigger a punishing counter attack before the first hostile bomb could fall on one of their cities. The doctrine of Mutual Assured Destruction, or MAD, had worked to keep the peace for decades due to the vantage point provided by these eyes in the sky. As the satellites began to go down, defense planners got nervous and increased their state of readiness, regrettably also increasing the chance of a miscalculation causing a devastating war.
In both the United States and in Russia, forces were placed on high alert. Fortunately, both countries maintained a significant array of radar installations that could detect missiles in flight shortly after launch. Without satellites, these radars would provide the only warning that an attack had begun. Not since the Cold War had either country’s nuclear forces been on such a high state of alert.
Time Zero Plus 5 Years
The total number of satellite collisions totaled over twenty-five. The world’s spacefaring nations were now acutely aware of the problem and working to find a solution. Unfortunately, any solution would require building a series of complex and expensive spacecraft to either remove large debris objects or de-orbit small ones. The first of the satellites to try and reverse the Kessler Syndrome would not be launched for another three years – the total number of damaged satellites at that time was projected to be near fifty…
The disaster might play out very differently than the previous scenario. It might begin with a blast of radiation coming from the Sun impacting the Earth, zapping with spacecraft electronics and causing many of our satellites to die or become uncontrollable. It might also be caused deliberately, as an act of international terrorism, with a small country launching a rocket filled with ball bearings into an orbital region occupied by numerous commercial satellites, kickstarting the Kessler Syndrome. Any country with access to space can wreak all sorts of havoc on the largely fragile and unprotected satellites that freely circle the globe.
There are already over half a million pieces of debris in Earth orbit (Figure 1). Debris was probably placed in space with the launch of our first satellites in the late 1950s. Flecks of paint, screws and bolts from early rockets, bits of insulation, and even ice crystals discarded from orbiting space stations are among the debris that will likely remain in Earth orbit for thousands of years until their orbits naturally change and decay or until we go out and get them. Until recently, when a satellite was launched into space, no thought was given to what would happen to it after it completed its mission or ceased functioning. As a result, long-dead satellites are still out there, whizzing through space, becoming debris for some future satellite to crash into. Sometimes these old satellites still have residual propellant in pressurized onboard tanks or high energy batteries. Over time these tanks and batteries fail, causing a relatively large spacecraft to explode and create its own small debris cloud consisting of hundreds or thousands of pieces. Creating orbital debris wasn’t intentional; it happened due to a lack of foresight and planning.
Figure 1: Earth is surrounded by a cloud of spacecraft and debris that number in hundreds of thousands. (Image courtesy of NASA.)
No matter the cause, once the cascade of collisions begins, the result may be the same: a debris cloud of increasing size will encircle the globe. The cloud will consist of thousands of debris objects, each traveling at over five miles per second. These objects will circle the globe every ninety minutes and on every orbit, each piece will have a small, but very real, probability of colliding with a functioning spacecraft. When these inevitable secondary collisions occur, more debris will be added to the cloud, increasing yet again the probability of future collisions. Like a nuclear chain reaction, the cascade of collisions will continue until the count of debris objects numbers in the millions. There are now nearly half a million pieces of debris with diameters of a few centimeters or more. Most of these objects are in orbits too high for them to naturally decay, enter the Earth’s atmosphere, and burn up. Once the cascade begins and the tipping point is crossed, no satellite will be completely safe. Is this inevitable? No. But unless we begin to take steps to clean up the existing debris, limit the creation of future debris, and harden our commercial satellites against extreme solar storms, then this frightening scenario may become a reality.
Some may be wondering why I call this scenario “frightening.” After all, space is out there and we’re down here. How can the loss of space satellites, things that didn’t exist in any significant number until the 1960s, possibly have any meaningful impact on our lives here on Earth? Most people don’t realize how their lives are affected by space technology and space satellites. When they think of space exploration, they think of the International Space Station, Apollo and sending people to Mars. What they should also be thinking about are the Global Positioning System (GPS), communications satellites, spy satellites and weather forecasting – among many other things.
GPS was developed first and foremost to support the needs of the U.S. military. It consists of a network of between 24 – 32 satellites that provide line-of-sight access for receivers on the ground from virtually any place on planet Earth. A receiver uses the signals from multiple satellites simultaneously, and the amount of time it took each signal to reach it (knowing that the signal travels at the speed of light), to calculate its position on the ground with very high accuracy. Since the early 1990s, GPS has allowed our armed forces to navigate and coordinate with precision unequaled in the history of warfare. GPS signals are used to navigate drones for reconnaissance and combat, soldiers on battlefields, ships at sea, and planes in the air. GPS allows precise navigation anywhere on the globe and under varied weather conditions including rain, fog and sand storms. A sudden loss of GPS for the modern warfighter would be akin to someone losing one of their primary senses – sight, sound, smell or touch. It would not necessarily be fatal, but it would certainly be debilitating.
It is so useful that other countries are building their own systems so as to not be dependent upon the US should we decide to turn off GPS signals. After all, if we can use it, so can our adversaries. The Global Navigation Satellite System (GLONASS) is Russia’s answer to GPS. Europe is building and deploying their Galileo positioning system and countries like India and China are building their own regional systems to provide comparable capability under their own control. Who can blame them?
Shortly after becoming operational, GPS entered the civilian economy like a tidal wave. Commercial electronics companies began selling portable GPS receivers for cars and trucks. Cell phone manufactures now have them embedded in virtually every cell phone produced. Google Maps changed the nature of mapping and how we travel, both in our cars and on foot. Local emergency personnel adopted the technology for E-911 services and for navigation. Cities have mapped the locations of fire hydrants and can direct emergency responders to the nearest one should the need arise.
Have you ever heard of Positive Train Control? In 2008, the U.S. Congress mandated that the nation’s rail system use GPS tracking to improve safety and reduce the risk of accidental collisions. Our rail system, which moves goods across the continent, is now dependent on GPS to function. And, as goes the rail system, so go the airlines. By 2025, U.S. air traffic control will move from ground-based beacons to space-based GPS tracking and navigation. Touted to increase the efficiency of air travel, with ever-increasing number of commercial airline flights, the Next Generation Air Transportation System will also be dependent upon satellites for routing planes and handling the complex traffic control near the nation’s airports.
Ships at sea already use GPS for navigation, with the thousands of cargo ships carrying everything from cars and electronics to food and diapers moving from country to country as international trade becomes increasingly globalized. Few countries make all the goods their citizens need within their own borders and GPS is one of the technologies that helped make massive international trade affordable.
The retail industry has embraced GPS for moving goods in a timely manner from warehouses to store shelves. Knowing where a particular shipment is located on its journey allows just in time manufacturing and inventory control, reducing costs and warehousing expenses. Retail companies also makes use of satellite technology in other ways. Credit card companies often use secure satellite links for card and check approvals at retail stores, bypassing the increasingly insecure Internet for transmitting financial data. The satellite dishes on the roofs of your favorite stores are not there for employees to watch DirecTV in the break room. They are likely VSAT (Very Small Aperture Terminal) antennas that are humming with the financial and inventory data needed for the store to keep its doors open and its shelves stocked. Some banks now use VSATs to transfer funds from one to the other, making them a part of the global financial infrastructure.
Cable television doesn’t originate at your local cable company and then get piped into your home. Instead, the myriad of channels conveniently aggregated into whatever bundle to which you happen to subscribe come to your local cable provider by satellite relay. Without satellites, news of what’s happening in Russia, China and other parts of the globe cannot otherwise make it into the daily newsfeed. Your favorite football team playing a game in another state this Monday night likely cannot be broadcast without going through a satellite relay. If our communications satellites are lost, your televisions and, to the extent that they play to a national audience, your radios, will become purveyors of only what’s happening locally.
We shouldn’t forget weather forecasting. A network of satellites provides critical data for forecasting the weather, particularly the outlook for several days in the future. Figure 2 shows a satellite image of Hurricane Ivan approaching Alabama’s gulf coast in 2004. This type of data saves lives and, almost as importantly, helps people and businesses determine if they are in the path of a storm and how to react appropriately. The vantage point of space allows the precise evacuation of the communities likely to be most affected and those that are not in the line of fire to know that they can remain in place, saving lives and millions of dollars.
Figure 2: Hurricane Ivan made landfall at Gulf Shores, Alabama on September 16, 2004. (Image Courtesy of NOAA)
Satellite imagery is used by the military and our political leaders to maintain the peace. When your potential adversaries can’t hide what they’re doing, where their armies are moving and what they are doing with their civilian and military infrastructure, then the danger of surprise attack is diminished. In our nuclear age with instant death only minutes away by missile attack, the doctrine of Mutual Assured Destruction (MAD) only works if both sides know whether or not they are being attacked. The launch of missiles or a bomber fleet can easily be seen from space far in advance of either reaching their potential targets halfway around the globe. The danger of surprise attack is therefore small, making an accidental war far less likely.
So what does all this mean? And what do we do about it?
First of all, it means that the advocates of space development, exploration and commercialization have succeeded far beyond their initial expectations and dreams. The economies and security of countries in the developed world are now dependent on space satellites. We space advocates should celebrate our success and be terrified of it at the same time. Should we lose these fragile assets in space, our economy would experience a disruption like no other: ship, air and train travel would stop and only restart/operate in a much-reduced capacity for years (GPS loss). Many banking and retail transactions would cease (VSAT loss). Distribution of news and vital national information would be crippled (communications satellite loss). Lives would be put at risk and the productivity of our farming would dramatically decrease (weather satellite loss). The risk of war, including nuclear war, would increase (loss of spy satellites) and our military’s ability to react to crises would be significantly reduced (loss of military logistics and intelligence gathering satellites).
It doesn’t have to be this way. We can change how we view the space environment and do things to clean it up and prevent it from becoming increasingly trashed.
Most spacefaring nations now require spacecraft to deorbit within twenty-five years of their anticipated end of life. This will prevent the accumulation of old satellites in space and go a long way toward reducing the chance of future dead satellite explosions creating new debris fields. Most countries now also require their rockets to minimize the creation of new debris in the launch process. During virtually all phases of flight, rockets are now designed to not contribute to the buildup of space debris.
We can come up with a way to collect or destroy the nearly half million pieces of space debris already circling the planet. This won’t be easy. The junk is traveling at orbital velocities and will be difficult to find, catch and remove. The cost of creating a space garbage collection program could run into the billions of dollars.
We can stop testing satellite destroying technologies in space. In 2007, China wanted to show the world that they, like the US and Russia, could target and destroy a satellite in space. They used a missile to destroy one of their own old weather satellites, creating an estimated 2,600 pieces of new debris –having the dubious honor of causing the single largest debris-generating event in human history. Figure 3 shows the growth of orbital debris over time and the huge impact of this Chinese test. It must be noted that shortly after the Chinese test, the US conducted a similar test. The US targeted a satellite in a very low orbit for destruction; the debris created thus didn’t remain in orbit very long and it did not add to the overall debris accumulation problem.
Figure 3: The graph shows the dramatic increase in the number of cataloged orbital debris objects following the Chinese antisatellite test of 2007 and the Iridium/Cosmos spacecraft collision in 2009. The chart shows only those objects that are actively tracked and cataloged. It is estimated that there are approximately 500,000 smaller debris objects in orbit today. (Image courtesy of NASA.)
To protect against solar storms we should add significant shielding to our satellites, making them more resistant to the radiation that might someday otherwise overwhelm them. Most military satellites are designed to survive a space nuclear war and the increased radiation that would result. Civilian satellites are not, making them vulnerable to solar storms that do occasionally strike the Earth. Fortunately, we haven’t experienced a solar storm large enough to destroy our satellites since the dawn of the modern space age. But they do happen, we’ve just been lucky that they missed the Earth as they blew outward into the solar system.
We need to be aware of the risks we’ve accepted by becoming a space-dependent nation and civilization. With foresight and planning, none of these disaster scenarios need become real. Let’s have the dialog, make plans, and do what it takes to make sure that they remain in the realm of fiction.
Copyright © 2014 by Les Johnson
Les Johnson is a Baen science fiction author, popular science writer, and NASA technologist. His most recent science fiction novel, Rescue Mode, coauthored with Ben Bova, was published by Baen in June 2014. To learn more about how we might lose our satellites and what the effects might be from such a loss, check out his nonfiction book on this topic from Springer Books, Sky Alert: When Satellites Fail.