Despite the popular belief that space is peaceful, the military has always had a large, but often hidden, role. Today, however, space is far more crowded and more economically and militarily valuable. That means more diverging objectives, opposing interests, and even open conflicts. This is especially true when modern militaries depend on satellites to communicate with remote forces and target drone and smart bomb strikes. Defending that capability—and knocking out the military networks other nations depend upon—becomes essential.
On March 27, 2019, India tested an antisatellite weapon by destroying one of its own satellites. While a similar Chinese test in 2007 sparked widespread protests, the Indian exercise seems to have largely escaped front-page headlines.
Yet observers believe its aftermath will be debated for years to come and may eventually concern people who never think about such things. This is not just because it created a rapidly moving cloud of space junk that could threaten commercial satellites and ISS astronauts. Instead, they see it as another disturbing escalation in the slow advance toward war in space.
Despite the popular belief that space is peaceful, the military has always played a role in its exploration. The first rocket to breach the 100-kilometer-high Karman Line, which defines the beginning of outer space, was a German military V2 fired in 1944. The first satellite, Sputnik, soared into orbit atop a modified Soviet intercontinental ballistic missile (ICBM) in 1957.
NASA, founded one year later, established America's space program as strictly civilian. Still, the military went along for the ride. Its officers piloted most Mercury, Gemini, and Apollo spacecraft, which its rockets boosted into space. Behind the scenes, the Pentagon planned its own secret space missions, coordinated by an agency later renamed DARPA (Defense Advanced Research Projects Agency).
Yet space remained free of actual weapons during the Cold War. While military surveillance devices existed, most satellites were instruments of national prestige or scientific curiosity. With the United States and Soviet Union—the only nations with spaceflight capability—already confronting each other with nuclear-tipped ICBMs, extending arms into space seemed superfluous.
Today, however, space is far more crowded and more economically and militarily valuable. It is filled with vast constellations of satellites that link together communications and computer networks, monitor weather, search for natural resources, and provide GPS data for smartphones and navigation aids. There are also many more military satellites.
Nor is space the dominion of just two powers. More and more countries—and private corporations—have developed launch capabilities. Today, even a private company in Thailand can aspire to launch its own satellite aboard a 3D-printed rocket.
“The space environment has become increasingly congested, competitive and contested," Frank Rose, a senior fellow for security and strategy at the Brookings Institution and former assistant secretary of state for arms control, explained to Congress in March 2019.
That means more diverging objectives, opposing interests, and even open conflicts. This is especially true when modern militaries depend on satellites to communicate with remote forces and target drone and smart bomb strikes. Defending that capability—and knocking out the military networks other nations depend upon—becomes essential.
War has not yet invaded space, but it could.
From the start, the military rationale for space weapons was to control the high ground and shoot down enemies. Such an attack, generals and politicians argued, would be impossible to stop.
While such post-Sputnik ravings about “missile gaps” and Soviet satellites raining down H-bombs may have frightened voters, experts knew it was hogwash. As engineers perfected ICBMs, it became cheaper and far easier to attack another country’s territory from the ground instead of from space.
“Space-based weapons fare poorly when compared with other long-range means of attacking ground targets,” a 2005 study by the American Academy of Arts & Sciences concluded.
Yet as space began to fill with militarily (and economically) valuable missiles and satellites, militaries around the world pondered how to attack them from the ground and in space.
Both the United States and the Soviet Union have planned, tested, and even partially deployed various types of antiballistic missiles (ABM) and anti-satellite (ASAT) weapon systems for decades.
These range from ground-based missiles to rocket interceptors fired from high-altitude aircraft and space-based nuclear weapons.
At first glance, an antiballistic missile, like the U.S. SM-3 deployed against North Korea, seems an unlikely weapon to take out satellites. It is designed to destroy an incoming ICBM by crashing into it.
The same missile could also target some satellites, as the United States has already proved in tests. In fact, it is much easier to hit a satellite, which follows a known and predictable orbit, than a missile whose trajectory must be computed in real time.
“Missile defense interceptors make excellent antisatellite weapons, at least hit-to-kill ones do,” said Jeffrey Lewis of the James Martin Center for Nonproliferation Studies.
This functional dichotomy causes enormous practical, political, and military complications. An antiballistic missile is defensive by definition, used only against incoming ICBMs. But an anti-satellite weapon is primarily offensive when used to attack an enemy’s satellite. If the same system can defend and attack, how can a potential adversary gauge your intentions?
“Due to the dual-use nature of many space technologies, even benign space capabilities can be viewed by others as counter-space weapons,” a 2018 report from the Center for Strategic & International Studies noted.
Indeed, one does not even need an actual antiballistic missile to take out satellites.
“If you’re a nation that has the capability of routinely launching satellites, then you also have the ability to destroy satellites,” said Ted Postol, an MIT emeritus professor of physics and former Pentagon nuclear security expert.
While antiballistic missiles attack by direct assent, launching from ground or near ground-level into space, antisatellite weapons can strike by co-orbiting, which is sneakier and, in some ways, simpler.
“The problem with direct ascent is you have to be able to see your target at significant range and line yourself up to hit it,” Postol explained. “When you co-orbit, you can just sort of cozy up to your target. You don’t have the problem with acquiring your target and precisely positioning yourself until you get close to it.”
A co-orbiting ASAT simply moves in and either hits the target or explodes next to it.
Both antiballistic missiles and co-orbiting antisatellite weapons use kinetic attacks that apply physical force to disable or destroy a satellite. They are far from the only options in the counter-space arsenal.
Nonkinetic approaches were studied intensively since the early 1960’s and then revived during President Ronald Reagan’s Strategic Defense Initiative in the 1980s. They seek to disable or destroy vital components or sensors with lasers, particle beams, or high-powered microwaves, either from space or ground stations. Such methods are difficult, expensive, and require great amounts of power, but the United States and other nations have tested them.
A more subtle—and perhaps more deniable—nonkinetic approach might involve electronic warfare. This might range from such time-honored techniques as jamming or spoofing an adversary’s satellite communications to cyberwarfare that targets computer systems that control satellites or process their data.
Nonkinetic weapons also avoid orbital debris. The 2007 Chinese test, for example, produced a rapidly moving cloud of thousands of razor-sharp fragments in a highly-traveled high orbital zone. Those fragments will remain in orbit for decades before decaying and burning up in Earth’s atmosphere. The Indian government claims its recent test created less debris in a lower orbit that will burn up faster, but it is still high enough to possibly threaten the International Space Station and its crew.
Even random orbital debris created unintentionally from decades of space activities is a danger, especially with no available means of cleaning it all up. Intentionally adding to it with kinetic weapons would only make the situation worse and endanger an aggressor’s own satellites.
So far, only the United States, Russia, China, and now India have demonstrated any sort of viable anti-satellite capabilities. The United States maintains a firm—but by no means unchallenged—technological lead, thanks to its commanding advantage in sensors to detect, acquire, and home in on targets, MIT’s Postol said.
Take, for example, light sensors. Antisatellite systems that rely on visible light cannot attack in the dark, a big problem when satellites spend half their time in Earth’s shadow. U.S. engineers have developed mercury-cadmium-telluride arrays and other advanced devices, which they can tune precisely to detect specific infrared wavelengths.
“It’s very closely guarded technology that allows you to home in at long range with an interceptor,” Postol said. “You can’t use radar because you can’t put a giant radar on top of a small interceptor. So it must be something like an infrared homing device.”
Such technologies no doubt fuel U.S. military dreams of “space superiority” or “counter-space dominance.” Judging by their own publications and statements, Russian and Chinese strategists clearly share such reveries. Nascent space powers like India and North Korea may do so as well.
Yet technology advantages often prove fleeting. After all, the U.S. military once had an exclusive hold on atomic weapons, jet aircraft, ICBMs, semiconductors, cyberwarfare, and artificial intelligence. It may still lead in those fields, but it is clearly no longer alone.
Besides, space, by its very nature, will be hard to transform into just another theater of military operations.
“The most important thing to keep in mind about space is that it’s a commons,” said Martin Nonproliferation Center’s Lewis.
Space, he explained, is a shared domain. Land can be fenced in and guarded and shorelines, sea lanes, and airspace patrolled. But space has no natural boundaries or regions that can be marked off and claimed by anyone. Any orbiting object can move anywhere. The space debris issue underscores this commonality and the need for a common approach.
“We need the cooperation of all spacefaring countries to reduce the amount of debris and to help mitigate it,” Lewis said. “The biggest threat to [satellites] right now is getting hit by a piece of debris. We can’t use threats of force to deter countries from creating debris, we actually have to actively engage with them.”
The commons of space also creates another show-stopper: There’s no place to hide.
“Satellites are easy to attack,” Postol said. “They’re in known orbits, so acquiring them with a visible light sensor is doable, although you may have to be restricted when you can attack them.
“But to defend them is essentially not possible for all practical purposes. The obvious ways you defend things is to use armor, which is not viable because it costs so much to lift anything into space,” Postol said.
Nor is it easy to evade an attack: “If you have a satellite that’s important, its lifetime in space is usually determined by the fuel it carries,” Postol said. “You need propellant [to keep an orbit from decaying]. And if you have to expend that propellant trying to evade attacking interceptors, your satellite is going to become useless very fast.”
Even the United States, which boasts the world’s most sophisticated space surveillance and tracking capabilities, cannot get around such problems.
“The U.S. has the advantage of the best sensors that modern engineering can produce, which work near the limits of what science says can happen,” Postol said. “We also have a lot of allies who let us put facilities on their soil so we can track things. We get to look at things from all different locations, using different kinds of sensors. So we’re in a much better position to know we’re under attack if things get bad. But we can’t do much about it.”
The Union of Concerned Scientists agrees. As it observed, “No foreseeable space-based technologies would allow one country to prevent another from deploying space weapons or would allow it to reliably protect its satellites.”
That’s why Postol claims anyone “with two neurons to rub together” would support the international effort to make space a sanctuary against weapons.
In fact, efforts to keep space a weapons-free zone dates back to the Outer Space Treaty of 1967. Among other things, it prohibited weapons of mass destruction and the establishment of military bases in space or on any celestial body.
Yet—perhaps because there were so few orbital targets in 1967—the treaty permitted conventional weapons, such as antisatellite weapons. Subsequent arms control treaties, such as SALT and START, forbade interference with surveillance satellites used for treaty verification, but did not cover communications and global positioning satellites.
Plugging such loopholes will require new diplomatic efforts to address space infrastructure issues that barely existed decades ago. New treaties may limit space weapons, but they will also have to improve international cooperation.
“When people start the conversation about protecting space assets by assuming that the main threat is someone attacking them, they’re missing 90 percent of the problem,” Lewis said.
“There are all kinds of real challenges—allocating slots for communications satellites in geostationary orbit, deconflicting frequencies so that they don’t inadvertently jam one another, and mitigating debris—that require cooperation.”
Postol argues that any agreement could be verified: “The United States is certainly in a position to provide the data. You can have a treaty regime that is very solid and all of the countries involved have a big incentive to follow it.”
Yet today’s international climate seems less welcoming for intensive diplomatic negotiations and new international treaties. Some organizations, such as the Stimson Center and the Union of Concerned Scientists, have drafted codes of conduct and proposals for spacefaring nations to avoid space conflict. Even if nations adopt them, they do not carry the same force as a binding treaty.
As the technologies of space warfare continue to become ever more sophisticated, the Earth seems trapped in a slow spiral of escalation toward open conflict in space. In some ways, it seems like a rerun of the Cold War, but with more players and less predictability. In this realm of move and countermove, India’s recent antisatellite exercise is merely the latest symptom.
“We need to do everything we can to reduce the fear that we’re going to use these weapons against other countries’ satellites, because that fear is what’s generating a reaction,” Postol asserted. “This is nuclear deterrence without the nuclear weapons.”