The engines we are building. BTW, we do have powerful engines already, it's just not very reliable, due to a lack of experience and experimentation.
You know, this is the kind of ignorance of people not in the sciences. They think innovation is this magical thing, but it's really just development base on need and previous works. Though there are people that are almost alien, but even they didn't go from nothing to everything.
China will lead in science, you know why? Because riches creates needs, needs creates market, market creates wealth, and everyone wants that.
Just look at Japan, from Meiji to today, look at all of Europe, industrial revolution happened in England, and yet, today England is not the top technology nation, or look at England, she did once lead in science, but remember before that she was also a backwater occupied by farmers and hoarders.
Then there is China, India, Muslim Caliphs, Rome, Greece, technological leaders of their day. What do everyone have in common? Wealth.