The U.S. space agency will aim to send a nuclear-powered spacecraft to Mars—a first—in a bid to show that nuclear propulsion ...

Add Yahoo as a preferred source to see more of our stories on Google. The 175-foot-tall concrete exhaust stack at the Hanford nuclear site’s defunct K West Reactor came crashing down Friday afternoon.

Moving an object in space is very energy-consuming, even once a spacecraft has escaped the gravity well of a planet. This is ...