Operation star shot is a go.
"Starchips" would be carried on light sails propelled by Earth-based lasers in just 20 years, by travelling at a fifth the speed of light.
¡°Today, we commit to this next great leap into the cosmos,¡± Hawking added at the announcement. ¡°Because we are human, and our nature is to fly.¡±
The most astounding part of this idea is that it¡¯s actually feasible. That¡¯s not to say it¡¯s easy ¨C or even sensible ¨C but we may well see it happen, based on existing or extrapolated technology in the coming decade.
The target star system, Alpha Centauri, is around 4.4 light-years away. This means, if a spacecraft travelled at the speed of light, it would take 4.4 years to arrive.
We're nowhere near accelerating a probe to those speeds. Instead, a fifth the speed of light should get a craft across in 20 years or so. But this calls for a dramatic change in design philosophy for a spacecraft.
To date, they carry fuel or propellant that is expelled from rockets (thanks to Newton¡¯s third law, this gives an opposite and equal force in the forward direction).
To go faster you need more fuel. That fuel, though, adds mass to the spaceship, and so it snowballs: you need to carry more fuel to move both it and the spaceship.
Instead, you can use a light sail to reflect a ¡°wind¡± of photons (particles of light) that bounce off and transfer momentum.
The idea that light can push a spacecraft, much less to 60 million metres a second, seems fanciful. You need to boost the power of the light source to brighter than the Sun and shrink the mass of the spacecraft.
Sure enough, these are the next steps.
Perhaps the most challenging idea of Starshot is constructing a laser powerful enough to focus enough photons on the light sail, so the spacecraft can be accelerated to 20% the speed of light.
Can we build a laser powerful enough to rapidly accelerate the sail to that speed? Starshot suggests an array of lasers, stretching a kilometre across, of total power 100 gigawatts ¨C akin to a blinding billion 100-watt globes ¨C which will act as a giant light ¡°fan¡± to the light sail.