Decluttering space

On November 15 last year, Russia destroyed one of its own defunct satellites in order to test its ‘direct ascent anti-satellite' system. The satellite, Cosmos 1408, launched in 1982, was supposed to be circling the earth at a height of around 650 km, but had since ‘decayed’ to about 490 km. The destroyed satellite broke into more than 1,500 large fragments, adding to the estimated 166 million pieces of space debris — each of which travels roughly ten times as fast as a bullet.

In the last 60-odd years, about 10,000 satellites have been launched. The launches have been increasing year after year and, tellingly, in 2020 alone about 1,000 were sent up. This number is projected to zoom to 12,000 by 2029, taking the number of satellites in orbit to 100,000. The space debris would have piled up to an estimated 100 billion pieces by then.

Now, satellites experience gravitational pulls from all celestial objects, no matter how far away they may be. To keep satellites in their designated orbits, navigation systems ‘nudge’ them back on track whenever they swerve, by firing one of the on-board motors. (Satellites need no fuel to orbit the earth, as gravity takes care of that. Fuel is needed only for course correction.)

This is an inefficient system — but it’s the only one we have — because once the fuel is exhausted, you lose the satellite and its valuable, well-working equipment. To delay this eventuality, more fuel is packed in the onboard motors, which increases the weight of the satellite and the cost of the launch.

The other, bigger headache is that a satellite that is out of control becomes a danger to the other satellites. Imagine, after a decade or so, having tens of thousands of defunct and footloose satellites endangering the functional ones! Collisions do happen and they may lead to thousands of fragments, or potential fast-moving ‘missiles’.

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Keeping space clean for future exploration

Space scientists are furiously engaged in finding a solution to this problem. Electric propulsion is one possible solution, but not good enough because it requires batteries recharged by solar panels, and these typically have limited recharge-discharge cycles.

The world, therefore, needs an entirely new deal. One such idea being toyed with is in-space refuelling. This seems to have caught the fancy of investors, too. A US start-up called Orbit Fab, which announced last month that it had won $12 million funding, offers US military satellites a system named RAFTI — ‘rapidly attachable fluid transfer interface’. The idea is to have a fuel tank in space that can be directed to attach itself to a satellite and refuel it through a port. An Indian start-up, Manastu Space, is working on similar lines.

Docking in space is not easy, but not impossible either. Space shuttles regularly dock with the international space station; you only have to find a way for satellites.

Once you master docking, you can use it beyond just refuelling. You can have a vehicle attach itself to a defunct satellite, for instance, and steer it out of harm’s way to wander off into space or fall into earth’s atmosphere and burn itself out safely.

This — known as deorbiting — and refuelling are among the in-space services that will be in demand in the space industry of the future.

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