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Removing junk from Space
Read more on - Polity | Economy | Schemes | S&T | Environment
- The problem in space: Humans tend to leave rubbish behind them wherever they go, to expect someone else to clear that rubbish up! This is true even in outer space. The problem of orbiting debris, and the concomitant risk of it colliding with and damaging an active and probably expensive satellite, has been around for a while. But it is rapidly getting worse.
- Lots and lots of them: There may now be as many as 1 million bits of debris measuring 1 cm or more across in orbit. Of larger objects, more than 20,000 are being actively tracked from Earth. The past three years have seen a doubling of the number of times that bits of junk have almost hit operating satellites. In the short term, satellite owners can, literally, dodge the problem—as long as their craft are fitted with appropriate thrusters. There exist software which helps satellite operators sidestep such collisions. In the longer term, however, more radical action will be needed.
- More launches: Part of the problem is the growing number of launches taking place. Also, every year, a dozen or so sizeable chunks of debris orbiting Earth break up. Around half of these explosions are caused by things like the ignition of leftover rocket fuel and the bursting of old batteries and pressurised tanks. The rest are the result of collisions.
- Accelerating: The upshot is a chain reaction of impacts in orbit, as captured nicely in “Gravity”, a film released in 2013. But the real problem is accelerating only slowly, so there is still time to curtail it. If action is not taken soon, insurance premiums for satellites will rise, spending on tracking and collision-avoidance systems will have to increase, and certain orbits eventually risk becoming unusable.
- Burn them up: Stopping this orbital-junk-generating chain reaction means casting part of the superfluous tonnage in space down into Earth’s atmosphere, where the frictional heat of re-entry will burn it up. A clean sweep is not necessary. Removing a handful of the larger derelicts every year would be enough. Japan’s space agency, JAXA, estimates somewhere between three and seven.
- How to do it: Projects are being planned to do this. A mission dubbed ELSA-d, consisting of a 175kg mother ship called a servicer, and a 17kg pod fitted with a ferrous docking plate to act as a dummy target, will eject and recover the pod three times, in successively harder trial runs, before thrusters push the whole kaboodle to fiery doom in the atmosphere below. For all the technological prowess these tests will require, however, real derelicts pose a greater challenge than dummy ones. For one thing, few spacecraft have been designed to expedite their own removal. Those objects which most need removing are dangerously heavy.
- How to capture: Magnets will not be too useful, as normal spacecraft have no iron in them. Using a harpoon to capture such an object might be feasible, though. That panelling was attached to a boom extending from the satellite, so this was but the most preliminary of experiments. A harpoon can miss, ricochet or—worse—break off parts of the target which will then contribute yet more objects to the celestial junkyard. Another option is to shoot a net. Airbus tested this idea in 2018. That test successfully enveloped a small “cubesat” which had been pushed seven metres away from the net-throwing craft—though this net was not tethered to the mother ship.
- ESA: As to the first clearance of actual orbiting debris, that is likely to be a European affair, for, in 2019, the European Space Agency awarded a contract to ClearSpace, a Swiss firm, to grab a 100kg piece of rocket debris that has been looping Earth since 2013. This mission is scheduled for 2025.
- Some time away: An era of serious cleanup in space is still some way off. Besides the technological obstacles, removing junk will be expensive. The controlled re-entry of an object requires fuel, big thrusters and close attention from a ground controller. These things can tack millions of dollars—perhaps more than $20m—onto a deorbiting operation’s price tag. ClearSpace’s mission, for example, may cost as much as €100m ($122m), though Mr Piguet hopes subsequent jobs will be cheaper.
- Tax it: The solutions to tragedies of the commons usually have to be imposed from outside, often by governments. One idea is a special launch tax, with the proceeds hypothecated to pay for cleanup operations.
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