Re: Best of Inventions 2002
Originally posted by medea
Times best of is out with the Inventions article, amazing stuff here this year, such as this Scramjet a rocket powered by oxygen instead of jet fuel.....
Ok, you probably know I'm a lawyer, but my undergraduate degree was in Aerospace Engineering. (I have a sweatshirt that says... "Why yes, I am a rocket scientist.")
Anyway, a lot of rockets are fueled by a mixture of oxygen and another material. Sometimes, it is a mix that gets ignited or sometimes, it ignites on its own (reactionary). Anyway, scramjets aren't revolutionary for using oxygen.
They ARE however revolutionary (or as revolutionary as something can be that's been studies ad nauseum for the last 20 years) because of the way the compression/combustion/expansion cycle takes place.
In a standard jet, the air comes in, gets compressed by a compressor, energy is added in the combustion tubes, and then the air expands through the turbine, and then sometimes through a nozzle (subsonic it can be directed through a funnel like shape, while supersonic, it is a reverse funnel)
Anyway, then you have RAM jets and scram jets which don't have moving parts. They compress the air using the shock waves coming off the inlet and then add energy and then the air expands out a nozzle generating thrust. The difference between a ram jet and a scram jet is that a ram jet compresses the air and slows it down to subsonic speeds, while the air in a scram jet is supersonic.
The biggest problem we had with scram jets was always how do you keep the combustion process in the engine? I mean, the air is moving so fast, that even using a very, very volitile fuel, the process of adding it to the air, igniting it, and it burning took far longer than it took the air to go from one end of the engine to the other. They had many tests fail, and it basically looked like a tube with a flame trailing behind it. The flame has to be in the engine to get any thrust!
Anyway, a scramjet that reliably works is impressive to me because of all the years of research that went into it.
On the other hand, a scramjet has extremely limited usefulness. I mean, what are you going to use it for other than perhaps comventional takeoff/landing aircraft that can travel to space. It's worthless for commercial travel. By the time you take off (with a different type of engine), get up to sufficient speed to use the scram jet, and then reach cruising speed, you're there, and have to slow down!
