So much energy is expended on fast take-off and the need to decelerate quickly on landing. Why not make landing runways longer, giving gravity and inertia more time to work their magic?

Open rotor engines date from the late 70's. It is true they were noisy then, but it is far from clear that this would be need to be the case today, given much better sound modeling tools and a lower sound signature from the underlying turbines as well.

Propfans were not rejected, in any case, due to noise. They were abandoned as jet fuel costs declined in the 1980's because Airlines understood that any kind of prop would be seen as a return to "old" technology and would be hard to market.

In the design shown, the blades are placed between the twin tails of the aircraft. I suspect this is precisely an attempt at sound mitigation, so the designers are clearly aware of the issue.

The incandescent analogy is really poor. A 50% fuel saving is nothing to scoff at. Flying isn't going away any time soon.

If we go by the progress made with sound abatement in heliocopters, I think much quieter prop craft are possible than in the '70s.. I can barely hear the new helicopeters these days.

Re landing and takeoff:
Perhaps a catapult system similar to what aircraft carriers have would reduce the fuel costs. You could even recycle the energy from landing planes, by braking the planes with a wire connected to a generator or compressor. Maybe having 10 planes land would be enough to get one plane to take off free.

I expect that railguns will be the best way to launch aircraft and spaceships in the future. It uses a linear induction motor (like what propels a MagLev) with fast unloading flywheels to create the spike in energy needed.

I agree with what Alonso Perez said, and I would add this: I can think of no more effective way to sabotage the environmental movement than by invoking environmental limits to coerce people out of doing things that you oppose on other grounds. The quote from the article shows the issue clearly:

...lets keep doing what we are doing until this wonderful new technology makes it all better.

Back in the 70's, the idea being tossed around was building an airport on a hill, with the runways being inclined. When you landed, you were going uphill, which helped to reduce your speed just getting up to the gate. When you were taking off, you were going downhill, which helped speed you up without needing so much fuel. Nice double-purpose.

It doesn't appear to have gone anywhere.

The railgun/catapult idea isn't bad if you can have some kind of "tailhook" and a catch cable which gets dragged down a track in the runway. That way, a landing aircraft could put energy into the system. Another aircraft, accelerating for takeoff, could use the energy. In areas with electrified rail systems and either an overhead catenary or a "third rail," this is commonly used.

Airplanes bring their own unwanted byproducts into the environment and it's really time to do something about the emissions they make. New "green" planes would indeed contribute less to air pollution, but there's a drawback. For every new environmentaly friendly plane, there's almost always an old one that's lined up for dismantling. While most of the parts of these old planes are recycled, some only end up as unsightly junk which may or may not add toxic substances into the earth. Watch how an F-14 plane is methodically taken apart here: http://www.thenewsroom.com/details/460833/US?c_id=wom-bc-ar

- Alvin from The U.S. Desk at TheNewsRoom.com

I'd also like to add that fighter planes like the one shown being demolished have allowed enginners to design better and more efficient planes which can do do sometimes resemble flying vehicles from science-fiction films and television series like Star Trek. http://www.thenewsroom.com/details/460833/US?c_id=wom-bc-ar

- Alvin from The U.S. Desk at TheNewsRoom.com