I've always wondered why passenger aircraft don't use four smaller engines for take-offs only, then cut two of them for cruising and landing. Maybe even use retractable covers over the intakes of the two take-off engines to improve aerodynamics in flight. This would use less fuel and while it wouldn't improve the emissions during take off, it may be offset by fewer emissions during the flight itself.
I've heard of cargo planes (particularly C-130) being fitted with a system like that, except with rockets - and in one case, used to land and take off in the space of a football field.
The drawback is that the rockets need to be replaced after each use. With what you're talking about, the plane would only need more of the same fuel it uses anyway.
the reason is that engine not working in cruise is dead weight. Dead weight means less cargo and less money. So far the runways are sufficiently long.
Also, as Angry Penguin pointed out military transports used RATO - rocket assisted take-off. It works well, because the RATO engines are discarded after the take off, so they aren't a dead weight in cruise. On the other hand, I don't think that people living in the neighborhoods of airfield would like empty rockets with some fuel still remaining to fall on their houses.
@K5ING not only would two extra engines add weight (as per flame_can), they also add drag, and between the two, you'd have one totally uneconomical aircraft. That's before you factor in the cost of buying and maintaining two additional engines.
Why not make it a flying wing? You could carry more passengers that way. Why not put the engines above the wings? That way the noise would be reflected upwards instead of downwards towards peoples houses.
Good idea to reduce fuel consumption. How about using a Maglev bogie with 2 arms above which push behind both wings near the fuselage. The Maglev track bed would be invisible beneath the runway. Not sure if they could be used for landing..
Even though the miltary planes used to use rockets, the system is known as JATO, not RATO, for Fet Assisted Take-Off.
This plane looks suspiciously like the Sonic Cruiser Boeing unveiled in 2000.
As for a flying wing, that has been studied, but flying wings aren't currently able to use existinfg airport gates, jetways and other infrastructure, which would need to be heavily modified to accomodate them.
Why not try to use laser propulsion from the ground to the plane rather than a buggy?
@ Luke Beauchamp The flying wing is a decent idea the issue with it is airports don't have a good way of boarding them as they don't exactly work well with existing jet ways. Gizmag had an article on a sort of drive through airport not too long ago that might make something like that more feasible but not without issues. Other issues presented is a lack of window seats. Carbon fiber brings the possibility of windows on the roof, but that probably still isn't going to cut it for most people as the view is substantially less, unless flying at night. I think a more practical solution to that is to have LCD screens that let people use them as windows or whatever. These would naturally be more geared towards long haul flights so you could create a different class structure where you have the sleeper seats in the middle along with other amenities and try and keep the passengers to the outsides as best as possible.
Something else that I think would be interesting is the treadmill "myth" I still have some trouble wrapping my mind around it but they tested it on a prop plane for mythbusters, I'd be interested in seeing if i works for jets as well.
In regards to things brought up in the article, computer automated ATC's have been demoed to be far more efficient than humans with less errors. Big surprise. I think in the next 10-15 years we'll start seeing them be implemented. Not that there aren't obvious security concerns. V formation flying, it's about time. I guess they decided it was too much work for pilots to do this on commercial flights so they waited for computer control. The distances cited seems a little large to me but still cool. I know another thing that's being looked at is ground effect flying over the ocean. Again, not without safety concerns but has the potential for more fuel efficient flight. The eco climb idea is a great idea however I don't think it'll get them out of the expense/weight of having more powerful engines as you'd still need them for aborted landings where you suddenly need massive amounts of power to pull away. I'm a pilot myself and I've had to do this more times than I'd like (deer, another plane, ducks) This of course being the safety issue with glide in landings. If they can figure out a way to start the engines instantly while gliding in, then you may be in business. Or just carry on RATO for aborted landings. I don't know if the fuel savings would = the cost of of fuel used to carry the RATO. But assuming RATO works, you could save more money in fewer, lighter, smaller, more efficient, etc engines
Despite some "smart" comments your suggestion makes sense. In some 10 or 12 cylinder cars fuel is not injected in some of the cylinders unless you really need the power and this has reduced fuel use and emissions.
However, you want to have all four on when landing -- if you need to abort the landing you'll really need all the power you can get.
@ Passive Lead: using mag-lev doesn't require there to be any physical contact between craft and launchpad... if you can use the lorenz effect on superconductors to hover your vehicle, and chained sequential magnetic impulses to initiate forward momentum... the tricky part comes in timing when the pneumatic force of lift is enough that you no longer need the magnetic field and you have to dissipate the energy back into the system somehow without magnetically dragging the vehicle to the runway... the track would have to create a cascading magnetic field of declining strength exactly proportional to the increasing pneumatic lift created by the acellerated wedge... Some sort of wireless feedback system that would modulate the field strength in the correct proportions... Interesting idea, and using an electrical launch system would seriously reduce friction, and most obviously fuel consumption.
Mind you, the strength of magnetic field required to launch a large enough vehicle to be commercially feasable would likely play serious havoc with onboard instrumentation and communications... ;)
@Passive Leads, if you mess up the magnetic rail for whatever reason (Heavy gust, reliability or else), the runway or the A/c might simply be un-usable ? Using a buggy could allow you to swap when one is out of use.
Thinking about it, assuming you can take off and land on a vehicle, could you simply get rid of the Landing gears ? ... 15 tons of weight saving on each A/C and for each flight, represents quite a huge fuel saving in the end .
@K5ING and Sidarth, the B-36 Pacemaker is worth a look. It was prop driven, but it had 4 temporary-duty turbojets for enhanced take-offs performance and high-altitude dash speed, but they were usually not running in cruise, which saved some fuel exactly as you suggest.
But engine technology has improved since then, and most modern turbofans are generally overpowered for a given take-off, for instance when a Boeing 777 is climbing out it's generally using de-rated thrust unless it's taking off at max gross weight on a hot day out of Denver or Mexico City.
I like the idea of a Maglev-assisted take-off though, then you could de-rate engines even more, saving fuel and reducing noise, and you could even improve the safety margins by allowing an aircraft to reach V1 much more quickly, and have a greater margin to stop the aircaft without needing any brakes.
If these pictures represent the new type of Airbus, I seriously doubt that this would work. The engines are located at the back and require the wings to be mounted further aft. The Center of Gravity (CG) is way back, a la B727, DC-9, L1011, DC-10, VC-10. The pictures shows the engines are pointed downwards. So if the plane is trimmed wing level, these airplanes would fly into the ground. In order to trim these planes to fly, the fuselage would not be level and the noses need to point up at a steep angle. I do not think the flight attendants would have the strength to push the service carts towards the front of the planes. Trimmed with such a nose up configuration, it would not be even aerodynamic. Any Pilot or Aerospace Engineer could tell these planes in these pictures would not work.
I am a Pilot and an Aerospace Engineer and can tell these planes will work. Engines can be ducted so that the airflow is not always in a straight line. The thrust vector of the engine depends on the orientation of the exhaust nozzle but not that of the orientation of the engine center-line. The exhaust end of the nozzle of this design is also cut at an angle which does not reflect the actual orientation of the center-line of the exhaust flow. Have a little faith in the propulsion engineers at a company with combined years of experience greatly in excess of yours. It often amazes me how little experience some commemorators actually have but don't realize. Keep studying.
Hey Rohn one of the best things about Gizmag is that any opinionated git (like me) can throw their two bobs worth in and the reaction can be gauged. Most readers are not scientists or engineers but I hope there are lots of them lurking and getting an idea of what the average dude is thinking about technology.
FWIW I see that there is now so much reliance on the tourism dollar especially by those developing nations which have nothing to offer the global economy except pretty scenery and quaint culture that something will have to change because lets face it aircraft are heavy resource consumers and prodigious polluters.
Couldn't the problem with flying wings (the doors not being on the sides) be solved by having them taxi sideways? If the door can be on the front, the aircraft could move sideways to fit into the boarding area.
...or something. My engineering experience consists of playing with Legos.
Build that Mach 3 plane so we don't have to endure hours on end acting like a sardine.
And for this plane, launch it with a big rubber band.
I am an aerospace engineer. I am well aware of Vector thrust would work but at what efficiency? The plane as show in these pictures would fly but not efficiently. If the inlet is not pointed at the direction of the airflow, when it pitches the angle would be worst. This might impact the amount of air going in and there is a chance of flame out.
@Angry Penguin So I think you're suggesting to taxi the plane in sideways such that the wings don't get in the way of other terminals. This is a good idea but would still likely require a longer jetway as I assume you were having people board below the cockpit. The other (easier) option have everyone walk to the plane. Could use the wing as cover from the elements if the engines are in the wing or over the wing.
@ everyone else on maglevs: EMALS http://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launch_System
I encourage creative minds to pursue these innovations. The "eco-climb" concept would have to overcome the following challenges: It only assists on the runway. The jet engines would have to be running during takeoff to make sure they are ready to take over once the effect of the catapult is ended probably approximately at 1000 feet distance after takeoff. Then to climb from 100 feet to cruise flight level, the engines still have to work, so the fuel savings are limited. There would be a safety risk of not turning on the jet engines until the aircraft is in the air. What if the engines do not turn on right away, or take longer than expected to come on? That's a safety risk. The biggest benefit to this may be increasing airport capacity by allowing larger aircraft to use shorter runways, plus a slight reduction in local noise and emissions locally around the airport. Although total noise and emissions could go either way, it would be ambiguously lower on a per-passenger basis. Another challenge is to modify the landing gear so that it can take forces from the rear. Landing gear are currently designed to take forces from the front upon landing. Also imparting acceleration forces on the wheels is further away from the center of gravity of the airplane, and would impart rotational forces--especially the last few seconds with the nose off the ground.