A prototype of a spacecraft planned as a 'lifeboat' for crews on the International Space Station passed a major milestone. The wingless X-38, the first new U.S. spacecraft developed in more than 20 years, successfully made its maiden unpiloted flight test. The nine-minute flight of the atmospheric test vehicle took place at NASA's Dryden Flight Research Center in California. The vehicle dove from the wing of a B-52 bomber at 23,000 ft. A series of parachutes slowed its descent. Then a 5,500-sq-ft parafoil--a steerable parachute--billowed out. The X-38 floated to a touchdown on its skids. The craft is the first of several increasingly detailed X-38s being built to test technology for a six-person "crew return vehicle." The X-38 has no engines. It uses the aerodynamic shape of the vehicle to provide the lift that airplanes get from their wings. In 2000, a space shuttle will carry a larger version of the X-38 into orbit. From there it is to plunge back to Earth for a practice landing.
The choice between helical and spur gears in gearboxes may seem straightforward. But with planetary gearboxes, however, the choice between helical and spur gears requires some additional thought. Here’s what you need to know to make the right choice.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.