7 robots too expensive (or lethal) to own

Valkyrie is a one-of-a-kind marvel developed by NASA. It was designed to operate in dangerous environments, such as exploring the surface of other planets or performing external repairs at the International Space Station.

Valkyrie is semi-autonomous, meaning that she (yes, NASA assigned the robot a gender) receives commands from a human being, then performs those tasks. That includes walking, turning and twisting valves.

She weighs 275 pounds and is just as tall as Atlas. Cameras in the chest, forearms, knees and feet help scientists see what's going on. To analyze her surroundings, she emits lasers from her head and sonar from her abdomen. A massive battery in her back charges her body -- and the superhero glowing emblem in her chest.

This first model cost $7.6 million to build, but NASA expects future copies will cost $2.5 million a pop.