Last April, we dissected the worlds most advanced fighter jet, the F-35B Lightning II, in the pages of our annual How It Works issue. Now military contractor Lockheed Martin is firing up the jets 40,000-pound-thrust engine (the most powerful ever built for a fighter jet) in preparation for flight tests. The jet can soar at supersonic speeds (1,000 mph) and deflect radar signals, but by the end of the month, pilots are expected to show off its most highly anticipated feature: the ability to stop mid-flight and touch down virtually anywhere.

Graham Hawkes is best known for his radical winged submarines that "fly" under the sea like spiraling fighter jets. But the British-born engineer is also the inventor of the military's first robotic machine gun. He hit upon the idea after reading about a disastrous police shootout in Philadelphia in 1985. Here's what Hawkes, 57, had to say about how he brought it to life.

G-FORCE—WHAT IS IT?
You’ve seen us mention g-forces in articles about new jet aircraft and cars?many times with reference to their being a very serious obstacle to overcome when developing ever faster technology. But what are they? Gravitational force is the force of gravity pulling you toward the Earth. When you undergo a change in speed and direction, that force increases in proportion to the rate of change. To calculate the magnitude of the force you feel as g’s increase, multiply your weight by the number of g’s.