Each time we shoot a fuel target with the laser, it produces energy. But power isn’t just energy – it’s energy over time. So, to create electricity, we have to continually produce energy. That means we shoot the target ten times a second – or 10 Hz.

This is similar to what happens in a conventional car engine. Fuel is injected and ignited, releases energy, and then repeats hundreds of times per minute. Why 10 times per second? Math mostly: If each shot produces 450 MJ (450 million joules of energy), then repeating that 10 times per second nets 4500 MW of power or 4.5 GW (4.5 gigawatts). If you lose a little more than half of the power in the conversion from heat to electricity, you get a touch more than 2 GW of electricity.

But the laser itself takes about 500 MW of power – leaving 1.5 GW of electricity for grid production. This is the size of the very largest coal or nuclear power stations today (enough to power a large city throughout the year).

As may be apparent, there is a tradeoff between how much energy each shot produces, and how many shots per second you need to generate a given amount of power. If each shot produces more, you need fewer shots. For example, if each shot has twice as much energy, say 1 GJ, then you could create the same amount of electricity with half as many shots.

However, we don’t think maximizing energy output and minimizing shot frequency is the right optimization. Higher energy output per shot means we have to put the chamber walls further away, meaning a much larger (and more expensive) power plant. Second, once you develop systems to hit a target multiple times per second, the exact number of times isn’t that important. Hitting a target 10 times a second isn’t really any harder than hitting a target 5 times per second. So, all things considered, a yield of 50x and a repetition rate of 10 Hz strikes a good balance.