Its not Elon Musks SpaceX rocket thats going to hit the moon, but space junk is a real th – iNews

We cant, as it turns out, pin this one on Elon Musk. Part of an old spacecraft is going to crash into the moon early next month, and initial reports suggested that it was the second stage of a Falcon 9 rocket, built by Musks company SpaceX to launch a climate-monitoring satellite in 2015.

This made a lot of people very angry. (One well-known UK Twitter account suggested that Nasa should crash the International Space Station into Musk, rather than the Pacific Ocean as planned, when it reaches the end of its life.)

Unfortunately for Musks many detractors, it turns out that the rocket was not built by SpaceX but by the Chinese government. The confusion arose because tracking small objects (and a four-ton, 15ft-long rocket counts as small in space) is really difficult.

The story does matter, though. The fundamental point is that putting things in space is important. There are probably 5,000 working satellites in orbit right now, says Jacob Geer, head of space surveillance and tracking at the UK Space Agency. They provide navigation for phones and cars, communications, banking. An awful lot of modern life involves satellite data.

Unfortunately, as well as those 5,000 or so working satellites, there are also millions of pieces of debris. As well as huge chunks like the old Chinese rocket booster, Nasa estimates that there are 23,000 the size of a softball or larger, but half a million the size of a marble, and hundreds of millions of tiny ones a bit larger than a grain of sand.

And because each of them is travelling at around 25,000mph, even the smallest can be devastating. Even a piece of debris 1cm across could destroy a satellite, says Don Pollacco, director of Warwick Universitys Centre for Space Domain Awareness. A head-on collision at a closing speed of 50,000mph would be like a grenade.

Its a growing problem, for two reasons. One is that the number of satellites goes up monthly. The British space company OneWeb is launching 30 or more microsatellites every month; Musks Starlink satellites are going up at a rate of 50 or so a month. And the other is that the number of pieces of debris in orbit is going up too, as bigger bits fragment.

We think space is infinite, so historically we havent cared about it that much, says Pollacco. Nowadays rocket boosters are given less energy so they fall back to Earth, but in the past, those boosters went into orbit. There are thousands of tonnes of old boosters sitting in orbit, just dumped, full of fuel, and sometimes they have a collision or explode and create more debris.

Even worse, every so often a country blows up a satellite with a missile to show off its military prowess. Russia famously did it last year, creating a cloud of satellite-bits. But, says Pollacco, the Americans have done it, the Chinese have done it, the Indians.

As a result, there are near misses every day. Geer says that in the UK, a team of military and civilian analysts are tracking debris using radar and telescopes, and have to warn British satellite operators about 1,500 times a month that theyre at risk of collision, so they can get out of the way. And there have been collisions, most famously in 2009 when an active communications satellite was hit by a derelict Russian military one, and many smaller-scale ones.

There are reasons to be optimistic. One is that there is growing international awareness of the problem. There are internationally agreed guidelines, and although some countries notably Russia and China are less than fastidious about them, others are putting them into law: the UKs Space Industry Act makes sustainable use of space a legal requirement.

Another is that there are efforts notably by UK organisations, backed by the Government to capture defunct British satellites and decelerate them so they burn up in the atmosphere.

But thats only feasible with large objects: you cant send a satellite up to capture hundreds of thousands of marble-sized fragments. For that, you need tracking, and while we do have some facilities, Pollacco says we are underinvesting. What annoys me is satellite missions cost hundreds of millions, he says. We rely on the military, using radars designed to look for missiles not optimal, because theyre meant for looking at lower altitudes.

That means that the warnings of impending collisions are very imprecise a piece of debris could miss by several miles and because its expensive to move a satellite, often operators dont bother and take the gamble.

But for, he says, a few tens of millions of pounds, we could build a system of optical telescopes that could monitor everything in an orbit above about 400 miles high. You dont even need big telescopes, he says. You just need to use them in clever ways, to detect moving objects, track their orbits and predict them. His team at Warwick is working on projects that could do that even with small objects. With more precise warnings, operators could move their satellites only when necessary, and not take the risk of sudden destruction.

The moon-crashing rocket may not have been Musks and, in fact, says Pollacco, old Apollo spacecraft and other things crash into the moon all the time: its not that unusual. And Musks Starlink enterprise showed an admirable commitment to avoiding space junk, by launching them so low that they will automatically de-orbit if they go wrong. (Last time, 40 of them got taken out by the Earths atmosphere expanding during a solar storm.)

But Starlink, and the many other groups putting large numbers of small satellites out there, are filling the sky with metal. Thats a good thing the metal is up there to do useful things for us but keeping it up there is starting to get difficult.

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Its not Elon Musks SpaceX rocket thats going to hit the moon, but space junk is a real th - iNews