http://www.nasa.gov/missions/research/x43-main.html The X-43A is a tiny unmanned skimmer about ten feet long but the SCRAMjet concept needed further validation, and the X-43A was the craft with that mission. Here is a short description of the differences between RAMjet and SCRAMjet engines, the former of which has been around since World War Two. Basically, the ability of a SCRAMjet to achieve combustion above the speed of sound means that its exhaust can move a lot faster, and thanks to Newton's second law of motion, that means the craft it's propelling can too. This technology has AMAZING implications: http://apnews.myway.com/article/20041117/D86DA1MG0.html This same advantage will also apply to a new generation of SSTs that will make the Concorde a slug, and cheap, reuseable, SSTO launch vehicles for satellites and spacecraft. The X-43A has finally dethroned the X-15, which held the atmospheric speed record of Mach 6.7 since 1967. In other news: Europe's SMART-1 probe has nudged itself into Lunar orbit. This is special, because SMART-1 uses an ion engine for propulsion, rather than chemical thrusters. Ion drives are low-thrust electric engines and have been used on communication satellites for orbital station keeping since the 1970s, but propulsion is another matter entirely. Once we get nuclear reactors in space (thank you Project Prometheus), we'll have enough power to make one with enough thrust to move a spacecraft of substantial size. This is what could ultimately get us to Mars in three months via direct flight, rather than a nine month slingshot around Venus for a gravity-assist. Airborne Laser achieves First Light. In case you don't know, the Airborne Laser is a Boeing 747-400 freighter that will be outfitted with a chemical laser with an output of around five million watts. It will orbit around a ballistic missile threat like North Korea at high altitude (40,000 feet or so) above roughly 90% of the Earth's atmospheric contaminants that normally occlude the beam path. When a ballistic missile launch is detected, the ABL tracks and engages the missile during its boost phase when it's slow-moving, throwing out lots of heat, and largest due to all its engine stages still being attached. A few seconds of lasing later, the missile is rendered functionally dead. One ABL aircraft will have a lateral engagement radius of around 300 nautical miles. As far as this "First Light" is concerned, that means that the laser and directing optics have been operated while connected for the first time. The laser itself had been tested but never while connected to the beam shaping optics that will be used to direct it against a target. The optics are pretty complex - gasdynamic lenses that shape the beam using a few layers of Helium moving at supersonic velocity to keep from overheating, and a directing mirror composed of 768 parasitic subreflectors, each capable of changing shape at 1,000 times per second to continually adjust the beam on the target for the few seconds of illumination necessary to kill it. The COIL laser used in the ABL has been around since the mid-1980s (it was originally conceived for use in the SDI) but beam direction is a much finer art than that, and is by far the most technically daunting aspect of any laser weapon system.