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PULSE DETONATION WAVE ENGINES
One option for a hypersonic vehicle might be four or six Pulse Detonation Wave Engines (PDWEs), fuelled with liquid methane. As air breathers, these PDWEs could theoretically propel a hypersonic aircraft towards Mach 10 at an altitude in excess of 180,000 feet. Used to power an trans-atmospheric vehicle, the same PDWEs might be capable of lifting the craft to the edge of space when switched to rocket mode.
Current theoretical operation of a PDWE Liquid methane or liquid hydrogen is ejected onto the fuselage, where the fuel mist is ignited, possibly by surface heating. The PDWE works by creating a liquid hydrogen detonation inside a specially designed chamber when the aircraft is traveling beyond the speed of sound. When traveling at such speeds, a thrust wall (the aircraft is traveling so fast that molecules in the air are rapidly pushed aside near the nose of the aircraft which in essence becomes a wall) is created in front of the aircraft. When the detonation takes place, the airplane's thrust wall is pushed forward. This process is continually repeated to propel the aircraft. From the ground the jet stream looks like "donuts-on-a-rope". Quoted below is a small description of how a PDWE would accelerate a vehicle towards the hypersonic regime. "...use a shock wave created in a detonation - an explosion that propagates supersonically- to compress a fuel-oxidizer mixture prior to combustion, similar to supersonic inlets that make use of external and internal shock wave for pressurization."
Not much is known about Pulse Detonation Wave technology, but there have been quite a few reports and sightings of mysterious aircraft using propulsion technology unlike any heard or seen before. On February 25, 26, and 27, 1992, there were night-time sightings of an unknown aircraft with a "diamond-pattern" of lights at Beale Air Force Base, which was thought to be the Aurora aircraft. The aircraft had a distinctive engine noise, described as "a very, very low rumble, like air rushing through a big tube." On the night of February 26, what was thought to be a ground test of Aurora's propulsion systems took place. A series of "booms" was heard and described as similiar to "artillery fire" and "deep bass notes, not like sonic booms." It was thought these were "light-off" tests of the engines. It was speculated that the aircraft was using Pulse Detonation Wave Engines. The noise and low frequency would, it was said, be consistent with PDWE technology. It has also been noted that despite the famous "Donuts-on-a-rope" air contrails not being consistent with Aurora's propulsion system, theses contrails can be produced by a PDWE operating outside of its specified parameters. |
