Hi.. That’s a good question ! There are 2 main ways of doing fusion, one which uses magnets to trap the plasma and another that uses lasers. I’ll go through both:
– I study magnetic fusion (there’s more info about this on my profile). The next big step for magnetic fusion is ITER, a massive tokamak that will be switched on in 2019. If ITER works as predicted and produces 10 times more energy than it uses, then we should be building test fusion power stations in the 2030s and putting electricity onto the national grid by the 2040s. The exact timing depends on how much money is spent. At the moment, nearly all fusion research is funded by governments because private companies don’t want to gamble on fusion working. If ITER works then we think private companies will start spending more money on fusion research and we should have a power station much more quickly.
– Laser fusion works by imploding tiny pellets of fuel with loads of huge lasers. The big laser fusion experiment at the moment is called NIF (the National Ignition Facility) in America. NIF should be producing more energy than it uses at some point in the next year or so. This will be a really big step for fusion in general (for both magnet people and laser people !). One problem with laser fusion is that to make a power station viable you have to implode 10 fuel pellets a second. If they can work out how to do that then it’s sorted!
Overall, it’s a bit uncertain, but we’ve made lots of advances over the last 30 years and we’re definitely headed in the right direction. Hope that answers the question
I forgot to say .. the design for ITER started in the late 1980s – so we’ve known how to build this thing for aaages. The reason it took so long to build is that we’re doing it as part of a massive team (European Union (EU), India, Japan, the People’s Republic of China, Russia, South Korea and the United States – it’s the biggest international science project ever!). So getting an agreement on something simple like ‘Where are we going to build it?’ can take a decade or so.
So it isn’t just difficult science that has slowed fusion down – it’s also politics!