Wingnuts and FlyboysFollow

Kao, you're into aerospace engineering...is there any way to make an aircraft power itself by its own airspeed? My thoughts were that a fuselage-based wind turbine could be used to power dual props. A system like this would be perfect for small, lightweight craft like reconnaissance and spy UAVs. This is probably infeasible due to power limitations but it has been intriguing me for some time, and wondered if anyone might have heard anything like that.

No the energy transfer loss would mean you wouldn't have enough power to sustain flight.

I know nothing about engineering and just made that up.

What, you don't believe in perpetual motion machines??

The problem with ramjets isn't their basic design, but our current knowledge of chemistry and technological constraints. We are not able to convert the air into a direct fuel source yet. There is no way for an aircraft to power itself by its own velocity through purely mechanical means.

Edited, Oct 29th 2008 8:09pm by Allegory

You could power a turbine if the aircraft was already at altitude by letting gravity do the work, but you would never reclaim the amount of energy you put into the aircraft to get it to that altitude. Plus you have to then carry the mass of the generator you are using. Even if you had an airplane at speed in level flight, the drag coefficient on the wind turbine would decrease the amount of force you could apply on your propulsion system. Plus the propulsion system turning through the air would also experiance drag. Even if your conversion mechanisms were 100% efficient you still would experiance a net loss because you wouldn't be imparting additional energy intot he system

Think of it this way. if you start a non powered airplane off at 10,000 feet, put it into a perfect parabolic dive, the airplane will only be able to climb to 9,000 or so feet because of drag on the wing and fusalage. (ignoring thermals and sailplanes for the moment)

There are several proposals out there for an electric or electric hybrid passenger aircraft. Composite fusalage, electric propellers, solar cells over the entire fusalage and wing area. It wouldn't be as fast as a jet, but it theoretically would be much cheaper. They already have some long duration UAV prototypes in the works along those lines, but the main limitation at this point is our reliivly inefficient solar cells. Give things another 5 years, and if solar cell efficiency goes up significantly (which it is looking like it might, with things like the recently discovered black silicon, etc) then I would expect to see design work start on a hybrid solar aircraft. Probably somethign in the short haul class to start.


I personally would like to see a return of the semi rigid airships such as those that the new zepplin company is making, only larger, for domestic cargo delivery. You could coat the top of one of them with solar cell cloth, and if you didn't mind a slower transit you wouldn't have any fuel costs. since a large blimp would have more than enough surface area to power engines.

One thing I remember seeing on live TV which I thought was extremely interesting as a teenager:

They proposed using large lines suspended from orbiting objects to generate electricity. As you move a conductive wire through a magnetic field, it causes current to flow.

I remember probably about 6-8 years ago they tested this. And they showed the footage from the surface of the Earth on live TV. It created generated even more energy than expected and almost instantly incinerated the cable.

After this test though, I never heard anything more of it. It seemed very interesting.


Edit:
Sorry, energy is not created.

Edited, Oct 29th 2008 9:36pm by TirithRR

You really need a hybrid ramjet with a turbine in front of the ramjet, which would convert in flight. Most ramjets are either cylenders or rectangular, but you could easily make them in a curved configuration and then place them in an array around a turbine. Once you hit ideal ramjet speeds, you would have to kill the turbine jet, close it over with an airflow diverter panel of some sort, then open up panels over the ramjet and ignite them. Ramjets aren't very heavy so they wouldn't be a really insurmountable weight issue. They eat fuel way to fast though.

Like the Earth really needs angular momentum...

It sounded real smart. If you were more patriotic you could run for VP.

Well, yes... but that is not exactly powering the aircraft through its own velocity.

Neither is running it off hydrogen...

I believe the penultimate method for testing such an aircraft would require a giant treadmill. The ultimate method would involve a tiny plane and a regular-sized treadmill.

Yes, which is what I said earlier.