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Scramjet Success in Australia
glengyron writes "Australia's ABC reports today that a University of Queensland team have successfully tested a supersonic scramjet (air-breathing supersonic combustion ramjet engine). Read more here or here. Great to see after previous problems. Does the future of air travel still include those breakfast egg-roll things?"
First the Metal Storm, now this!
Soon Australians will be able to fly up to anyone, anywhere in the world, within minutes, and then cut them to ribbons.
I wish I was Australian.
Marc Siry || interactive media professional, motorcycle enthusiast ||
I doubt it.
The donuts on a rope phenomenon has, to the best of my knowledge, not been fully explainet yet (i.e., nobody is fessing up as to what plane is making those contrails).
The most plausible explanations I can see for it require some sort of pulsejet engine. I'd expect scramjet engines to generate contrails similar to ramjet engines, since the shift to supersonic speeds doesn't turn any other supersonic engine's contrails into donuts on a rope.
A little more info from Encylopedia Astronautica. A scramjet is vastly more efficent than standard chemical rockets because only half the fuel has to be carried (hydrogen). Also scramjets have a greater ISP than most regular chemical engines and have no moving parts, unlike the hundreds of parts on moden rocket engines.
Taken from here
air/LH2 (scramjet) ISP=1,550
Space Shuttle Main Engines
ISP = 453
Obviously scramjets are vastly more efficent. Of course ION engines have ISP values of roughly 5,000-6,000 and fusion another magnitude greater, etc. Still lots of room for improvement.
Depends that you mean by high fuel consumption. They go fast, and this creates drag, thus fuel must be expended. It you mean low efficiency, then you are half right: No scramjet achieves good fuel efficiency at the moment. However, since there are not really any working scramjets that should come as no particular surprise.
Generally, Scramjets should work in the range Mach 6 to 20. I've never seen an upper limit on pulse detonation engine operation, but I can't remember ever seeing one that worked over Mach 8, even in theory.
Firstly, it is not really useful for passenger aircraft. The high G to get up to speed is not really sellable.
The main use is as a secondary engine for rocket propulsion. Since atmospheric air is used, the scramjet theoretically can lift more payload for a given engine weight, and it is hoped that this will translate into launch cost savings for light payloads (I've seen one estimate that put the saving at a factor of 10 for a 1-10 tonne payload), however nothing really beats rockets for very large payloads.
The biggest advantage, in a launch to orbit is that, since the engine will be going sideways to pick up speed, the cost difference between a polar and equatorial orbit is negligible.
"Donuts on a rope" is the characterisation given to the contrail of a secret US program thought to use pulsed detonation to achieve high mach.
"shock waves in the stream of a jet engine" are better known as shock diamonds and are the results of shock waves producing visible artifacts in the flaming exhaust of aircraft using afterburners.
Finally, as has already been stated in another post, the SR-71's engines fonction in both ramjet & turbojet modes. The inlet cone slows the air down to subsonic speeds so that it can be used in the ramjet part of the engine profile -- using hypersonic air is the definition of scramjet.
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