In the 21st century, humanity will see many technological developments, but also increased risks of confrontation. And the place where this confrontation is likely to be exacerbated will be in space, probably during the conquest of the Moon or Mars. On July 9, 1962, the night sky above the Pacific Ocean, from Hawaii to New Zealand, suddenly became illuminated by brilliant light, as if it were the middle of the day. A stunning artificial aurora appeared, creating a glow of green, yellow, and red, which lingered for less than an hour. Then came the blackouts. The streets of Hawaii became unlit, telephone service was disrupted, burglar alarms went off. What looked like a beautiful light show from Earth was the result of the biggest nuclear bomb ever detonated in space. From a tiny island in the middle of the North Pacific Ocean, the U.S. had launched a 1.4-megaton nuclear warhead, a weapon test and a display of power during a particularly tense period of the Cold War. The experiment, dubbed Starfish Prime, generated an electromagnetic pulse, releasing a massive burst of energy 250 miles above the ground, which fried about one third of all active satellites at that point and turned out to be more destructive than anyone expected.

Then, on October 22 of the same year, the U.S.S.R. conducted its own high-altitude experiments, including the Project K nuclear tests. The Soviets launched and detonated a 300-kiloton warhead some 180 miles above central Kazakhstan. The smaller yet lower and therefore more destructive blast also affected infrastructure on the ground, frying overhead telephone lines and causing the fuses to blow on their overvoltage protectors, shutting off underground power cables and knocking out a power plant. Nukes in the sky don’t stay only in the sky: With their electromagnetic radiation, they’re a threat to any technology or device that can carry a charge, and they can destroy satellites, immediately disrupting key functions that those spacecraft provide. From these tests, the world learned the danger of a nuclear weapon exploding in space; but today, the risks are far greater. That’s why on February 14, 2024, lawmakers were startled when Ohio congressman Mike Turner warned of a « serious national security threat. » The House Intelligence Committee chief offered no details, perhaps because key information remained classified, though the statement was quickly linked to the possibility of a Russian nuclear space weapon. Speculation immediately swirled. It was like a terrifying Mad Libs, as experts imagined ways to combine « Russia, » « space, » and « nuclear. » Was it an actual nuke or just nuclear-powered? Was it an orbiting bomb or an antisatellite missile? Was it a worrisome weapons program being advanced, was it just bluster, or was it a cynical ploy to boost calls for more U.S. military aid to Ukraine? The following day, officials said little, likely because intelligence was still being collected. « It is not an active capability and it has not yet been deployed, » said National Security Communications Advisor John Kirby at a White House briefing. Few experts offered much insight. « There’s not a lot of information out there, » said Victoria Samson, a space policy expert at the Secure World Foundation in Broomfield, Colorado, a nongovernmental organization that supports peaceful uses of space and promotes space diplomacy. However, based on information available to her, Russia’s space military appears to be engaged in research and development on some sort of nuclear-armed space weapon that could be deployed and used in orbit.

Days later, Russian President Vladimir Putin denied claims that the country is developing a nuclear capability for space. But during a House Armed Services Committee hearing on May 1, a Pentagon official dismissed his denial, citing a Russian veto of a United Nations resolution from April that would have reinforced the ban on nukes in space by the Outer Space Treaty from 1967. Russia’s government hasn’t shied away from nuclear threats—at least not on the ground—and Russia, like the U.S., maintains a vast nuclear arsenal on hair-trigger alert and hasn’t ruled out a first-use policy.

Russia’s potential space nuke—or whatever it is—is just the latest military technology countries have been developing that could be used to trick, damage, or destroy rivals’ spacecraft. And Russia is not the only potential threat: The Pentagon is closely watching China’s nuclear ambitions, as its arsenal is on its way toward rivaling those of the U.S. and Russia. Nearly 70 years after the first space race began, we’re in the midst of a new, more complex one, where security concerns and goals are paramount, often trumping science and exploration. After all, the Space Force’s budget has already surpassed NASA’s, and China and Russia also spend enormous sums annually on their space militaries. As tensions intensify between these big three powers, we could be advancing toward a new arms race, in space. Killer satellites, blinding lasers, sophisticated jammers: the world’s military powers are quietly readying for a war in outer space—at the risk of fueling a dangerous new arms race. US military officials have in recent years sounded growing alarm about the potential vulnerabilities of their satellites, which underpin US military power. Initially, the reserve of the United States and the Soviet Union, space has now become accessible to an ever-expanding multitude of nations and private firms. And Moscow and Beijing are keen to show off their space-attack capabilities, a deep worry for US strategists. For the Pentagon and many US experts, it is clear America should speed up military efforts in space, and prevent its communications network from becoming the armed forces’ Achilles heel. But other experts say the United States should show restraint, noting the Pentagon may already have some of the offensive capabilities that China and Russia are hoping to acquire. The United States has since 2004 possessed a mobile jamming station which, from the ground, can block satellite communications. America has already tested using a missile to blow up a satellite, and has recently acquired satellites that can maneuver in orbit and inspect or monitor other space objects. Space war could be devastating for humans, as a single exploded satellite would leave a trail of debris that in turn could damage other satellites in a chain reaction of destruction.

We are at a very dangerous place right now: if we actually ever fought a war that would involve anti-satellite weapon, we would damage the space environment to such an extent that it would make it very difficult to have the benefits that satellites provide to society. Now, some believe that a new space race has begun with the United States pitted against superpowers such as China and India, as well as old rival Russia. The world is much more complex today than it was during the Cold War when two major superpowers vied for dominance. Now, private companies, such as Elon Musk’s SpaceX and Jeff Bezos’ Blue Origin, have joined in a new contest to show off their spaceflight capabilities. While there are some competitive aspects, such as the potential for fights over limited lunar resources, tomorrow’s space races will involve a greater number of actors and more muddled win-lose scenarios than before. The dominant power of this century will also be the one that masters space resources.