07 May 2010
New Scientist has an update on the Boeing WaveRider X-51. I don't know what it is about Rocketdyne...maybe the cool comic book sounding name or the fact that they make the most badass motors on the planet, but they keep popping up in my reading. The latest pin-your-eyeballs-to-the-back-of-your-skull toy is the X-51 WaveRider scramjet powered aircraft. Click here to see the complete hypersonic propulsion system company brochure.
The recent testing is looking for speeds of Mach 6, but scramjets have been flow at speeds of Mach 10, though they typically only fly at those speeds for very short periods. The Airforce is hoping for flight times of 300 seconds. In case you suck at math, that's 5 minutes of flight time. Now consider how far you can travel going Mach 6 in five minutes: Mach 6 is about 4,400 mph (the density of the air causes variations in what Mach 6 actually is), so you could cover 367 miles in 5 minutes. Consider at Mach 10, you could fly from Sydney to London in about 2 hours, currently it takes about 22 to 23 hours.
At Mach 6, the temperature of the nose cone will reach temperatures of almost 1500 degrees Celsius [Aluminum melts at 660]. It is expected the engine will be reusable, due to its advanced cooling systems, though the Boeing program manager indicates they won't be recovering the 4 meter long aircraft from the ocean. A scramjet works in a similar fashion to a rocket, but rather than carry the oxidizer for fuel on the aircraft, the scramjet uses oxygen from the atmosphere as the oxidizer, unfortunately, to gather [i.e. compress] enough oxygen the scramjet must be travelling at velocities approaching Mach 5 to even "start" the motor, thus the WaveRider has a conventional chemical rocket assist to get it moving. NASA's hope is that you can reduce the cost of launches by reducing the mass of oxidizer carried by a launch vehicle with the inclusion of scramjets for propulsion. Consider the escape velocity to exit Earth orbit is Mach 34. Mind boggling. The Rockstar Alchemist loves it!