“YesIMPLICITLY PUT, these tests are dangerous and we will not perform them”. So said Kamala Harris, vice president of the United States, in a speech on April 18 at Vandenberg Air Force Base in California. Ms Harris was announcing a US ban on complete testing of “direct ascent anti-satellite missiles”, ground-launched weapons designed to blow up satellites in orbit.
Four countries – the United States, China, India and Russia – have conducted such tests, most recently Russia in November last year. The danger Mrs. Harris fears is not so much the guns themselves, but the disorder they create. Space is already littered with junk: empty rocket stages, paint smudges, nuts and bolts, toothbrushes thrown away by careless astronauts, and the like. She can stay in the air for decades. At orbital speeds, even small objects can cause damage. The International Space Station (ISS) has to dodge pieces of junk about once a year. In June 2021, debris punched a jagged hole in one of her robotic arms.
Anti-satellite missiles, designed to blast satellites to pieces, make the problem much worse. A typical test could generate more than 100,000 pieces of debris, says Marlon Sorge of the Aerospace Corporation, a California-based nonprofit. Ms Harris noted that after a Chinese test in 2007, more than 2,500 pieces of debris large enough to track remain in orbit. There will be an unknown but much larger number of smaller bits.
Meanwhile, the number of satellites in orbit is increasing rapidly. SpaceX, an American company, has permission to launch around 12,000 satellites for its Starlink orbital internet service, more than have been launched since the space age began in 1957. Other companies like Planet and Maxar, which provide orbital images, they run fleets of their own. Armies rely on satellites for communication, weather forecasting, and even to provide early warning in the event of a nuclear attack.
At worst, a combination of more clutter and more stuff to hit could start a slow-motion chain reaction, with each collision producing more debris, making future collisions more likely. This Kessler syndrome, named for the POT scientist who first modeled the phenomenon in 1978—could render important orbits unusable for decades.
Since that would be bad for everyone, Ms. Harris hopes that other countries can copy US policy. Maybe. The timing of the initiative is inauspicious, to put it mildly. In addition to $2.5 billion in arms shipments, the United States is believed to be providing intelligence, including from satellites, to Ukraine’s military to help that country fight Russia’s invasion. Russian officials have complained about shipments of SpaceX satellite terminals to the Ukrainian military.
And while space debris is bad for everyone, it’s worse for some than others. More than half of all active satellites are American, meaning other countries have less to lose if parts of Earth’s orbit become too dangerous to use.
But there are also reasons for optimism. The US’s self-imposed ban pertains only to “destructive” missile tests, so nations that did the same would not have to give up their orbital weaponry altogether. Other methods of disabling satellites are being investigated, from blinding or jamming them to grabbing them with other satellites. And, says Robin Dickey, another analyst at the Aerospace Corporation, Ms Harris’s speech appears to focus more on building “norms of responsible behaviour” than formal arms control agreements, leaving other countries free to adopt bans without international pressure. .
Such rules, it seems, already have power. Countries conducting anti-satellite tests are clearly on the defensive. The United States justified one in 2008 on the dubious grounds that the target satellite, which was out of control, contained hundreds of kilograms of dangerous rocket fuel. After a test in India in 2019, the country’s Foreign Ministry claimed that by deliberately choosing a target in a relatively low orbit, the resulting debris would “break apart and fall back to Earth within weeks”. The battle, in other words, may already be half won. ■
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This article appeared in the science and technology section of the print edition under the headline “Launch break”