Kairos power’s new test facility is on a parched site a few miles south of the Albuquerque, New Mexico, airport. Around it, desert stretches toward hazy mountains on the horizon. The building looks like a factory or a warehouse; nothing about it betrays the moonshot exercise happening within. There, digital readouts count down the minutes, T-minus style, until power begins flowing to a test unit simulating the blistering heat of a new kind of nuclear reactor. In this test run, electricity, not uranium, will furnish the energy; graphite-encased fuel pebbles, each about the size of a golf ball, will be dummies containing no radioactive material. But everything else will be true to life, including the molten fluoride salt that will flow through the device to cool it. If all goes according to plan, the system—never tried before—will control and regulate a simulated chain reaction. When I glance at a countdown clock behind the receptionist during a visit last May, it says 31 days, 8 hours, 9 minutes, and 22 seconds until the experiment begins.