Two cool engines

In the news this week are two really neat new propulsion systems.

First, there is the scramjet powering NASA's hypersonic X-43A test place. The latest flight achieved Mach 9.6 breaking the world record for speed. The engine is cool in that it scoops oxygen from the air instead carrying it in a tank like other rocket engines. This saves a lot of weight. Of course, the engine only works at supersonic speeds, so it needs a rocket engine to get it started.

The second engine is, IMHO, even cooler. That's the ION drive used on the European Space Agency's SMART-1 probe that just entered lunar orbit. Solar panels generate electricity that ionizes the atoms of the xenon fuel. These xenon ions are then shot out the back of the craft, creating a very gentle push. The force is almost imperceptable, but unlike a rocket engine, it is also continuous. So the craft keeps moving faster and farther, until suddenly, you're at the moon. Even cooler is the fuel economy: 5,000,000 miles a gallon!