“SIMPLIED PUT, these tests are dangerous and we will not perform them. So said Kamala Harris, US Vice President, in a speech on April 18 at Vandenberg Air Force Base in California. Ms Harris was announcing a full US test ban on “direct-ascent anti-satellite missiles” – ground-launched weapons designed to blast orbiting satellites.
Four countries – America, China, India and Russia – have carried out such tests, most recently Russia in November last year. The danger Ms. Harris fears is not so much the weapons themselves, but the mess they create. Space is already filled with junk: empty rocket stages, paint stains, nuts and bolts, toothbrushes dropped by careless astronauts, etc. It can stay in the air for decades. At orbital speeds, even small objects can cause damage. The International Space Station (ISS) has to dodge bric-a-brac about once a year. In June 2021, debris punched a jagged hole in one of its robotic arms.
Anti-satellite missiles, designed to blast satellites to smithereens, further compound the problem. A typical test can 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 growing 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 start of the space age in 1957. Other companies such as Planet and Maxar, which provide orbital imagery, maintain fleets of their own. Armies rely on satellites for communications, weather forecasts and even to provide early warning of nuclear attack.
In the worst case, a combination of more clutter and more things to hit could set off a chain reaction in slow motion, in which each collision produces more debris, making future collisions more likely. This Kessler syndrome, named after the Nasa scientist who first modeled the phenomenon in 1978 – could leave important orbits unusable for decades.
As that would be bad for everyone, Ms Harris hopes other countries could copy US policy. Perhaps. The timing of the initiative is a bad omen, to put it mildly. In addition to $2.5 billion in arms shipments, America would provide intelligence, including from satellites, to the Ukrainian military to help that country fight the Russian invasion. Russian officials have complained about deliveries of satellite terminals by SpaceX to the Ukrainian armed forces.
And while space junk is bad for everyone, it’s worse for some than others. More than half of all active satellites are American, meaning other countries would have less to lose if parts of Earth’s orbit became too dangerous to use.
But there are also reasons for optimism. America’s self-imposed ban only applies to “destructive” missile testing, so nations that followed suit wouldn’t have to give up orbital weaponry entirely. Other methods of disabling satellites are being explored, ranging from blinding or jamming them to catching them with other satellites. And, says Robin Dickey, another Aerospace Corporation analyst, Ms. Harris’s rhetoric appears to be more focused on building “standards of responsible behavior” than formal arms control agreements, leaving other countries free to enact bans without international pressure.
Such standards, it seems, already have power. Countries conducting anti-satellite tests are clearly defensive about them. America justified one in 2008 on the dubious grounds that the targeted satellite, which was out of control, contained hundreds of kilograms of dangerous rocket fuel. After an Indian test in 2019, the country’s foreign ministry claimed that by deliberately choosing a target in relatively low orbit, the resulting debris would “break down 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 & Technology section of the print edition under the title “Launch break”