Clinical psychologist Alain Brunet of McGill University in Montreal doesn’t usually torture his patients. But lately he has been pressing those with post-traumatic stress disorder, or PTSD, to relive emotionally scarring incidents. For some it’s rape, others battlefield trauma. When his patients get particularly upset—crying, shaking, blood pressure rising—he gives them a 25-year-old hypertension drug called propranolol. The idea, though, is not to lower their blood pressure.

NASA's Ion Engine

1. Charge the Fuel

Xenon is an inert gas, seemingly useless for rocketry. Before it’s used as fuel, the engine must convert it into an electrically charged gas, also called a plasma. An electron emitter fires electrons at the xenon gas. When an electron hits a xenon atom, it strips off an additional electron from the atom’s shell to create a positively charged xenon ion.