Call Us: US - +1 845 478 5244 | UK - +44 20 7193 7850 | AUS - +61 2 8005 4826

meteorology: Science of the Atmosphere

In the Chinese science fiction film The Wandering Earth, recently released on Netflix, humanity attempts to change the Earth’s orbit using enormous thrusters in order to escape the expanding sun — and prevent a collision with Jupiter.

The scenario may one day come true. In five billion years, the sun will run out of fuel and expand, most likely engulfing the Earth. A more immediate threat is a global warming apocalypse. Moving the Earth to a wider orbit could be a solution — and it is possible in theory.

But how could we go about it and what are the engineering challenges? For the sake of argument, let us assume that we aim to move the Earth from its current orbit to an orbit 50% further from the sun, similar to Mars’.

We have been devising techniques to move small bodies — asteroids — from their orbit for many years, mainly to protect our planet from impacts. Some are based on an impulsive, and often destructive, action: a nuclear blast near or on the surface of the asteroid, or a “kineticimpactor“, for example a spacecraft colliding with the asteroid at high velocity. These are clearly not applicable to Earth due to their destructive nature.

Other techniques instead involve a very gentle, continuous push over a long time, provided by a tugboat docked on the surface of the asteroid, or a spacecraft hovering near it (pushing through gravity or other methods). But this would be impossible for the Earth as its mass is enormous compared to even the largest asteroids.

Electric thrusters

We have actually already been moving the Earth from its orbit. Every time a probe leaves the Earth for another planet, it imparts a small impulse to the Earth in the opposite direction, similar to the recoil of a gun. Luckily for us — but unfortunately for the purpose of moving the Earth — this effect is incredibly small.

SpaceX’s Falcon Heavy is the most capable launch vehicle today. We would need 300 billion billion launches at full capacity in order to achieve the orbit change to Mars. The material making up all these rockets would be equivalent to 85% of the Earth, leaving only 15% of Earth in Mars orbit.

An electric thruster is a much more efficient way to accelerate mass — in particular ion drives, which work by firing out a stream of charged particles that propel the vessel forward. We could point and fire an electric thruster in the trailing direction of Earth’s orbit.

The oversized thruster should be 1,000 kilometres above sea level, beyond Earth’s atmosphere, but still solidly attached to the Earth with a rigid beam, to transmit the pushing force. With an ion beam fired at 40 kilometres per second in the right direction, we would still need to eject the equivalent of 13% of the mass of the Earth in ions to move the remaining 87%.