fterh wrote:Guys I got an idea. Is it possible to have a powerful fan that forces air in, and one it starts the fan will keep on spinning (faster and faster every second) due to the thrust? What I plan to do is:
Have a long heat-resistant rod to go through the center of the ramjet, connecting two fans: One to blast air in and one at the back (obviously it gotta be heat-resistant). Run the fan off a battery until the ramjet starts, once it starts up the battery can be disconnected. Air will enter the ramjet at x velocity and exit at x+y velocity (due to the fuel exploding and creating a faster-velocity stream of air). The x+y velocity thrust will spin the fan at the back which will in turn increase the RPM of the one in front (because they're connected by the rod).
Will it work?
Well, that's a primitive turbojet. It probably won't work because of the inefficiencies of simple sheet metal fans. You won't get enough power from the turbine (rear fan) to drive the compressor (front fan) hard enough to mean anything. Amateurs can make their own turbojets, but it takes a LOT of engineering skill to design, and a LOT of technical skill to build. Just browse the Turbojet Forum (EDIT: I mean, the Gas Turbine Forum, of course ;-)
a while and take a look at how it's done. Anything much simpler than that just won't work well (and maybe not at all), because it's so hard to get the necessary efficiencies. The "losses" have to be extremely low, and you cannot get by without high precision machining, not to mention many other potential problems that come up along the way.
If such an idea was easy and effective, everyone would be doing it.
Please understand, I'm not trying to discourage you from inventing. Just trying to frame this particular question in some harsh realities ;-)