Making an extraordinary machine better: Mark Drela at TEDxNewEngland

[@joabarrera]

I am surprise how few likes, but the reasoning behind Drela's work is quite profound....maybe. I am just too much of a fan. A real pleasure is to understand him.

[@Triple_J.1]

I'm a huge fan of Dr. Mark Drela and his enormous contribution to Aviation, especially the open source, for the Everyman aerodynamicist xFoil and AVL. Which are powerful programs that are suprisingly accurate, offered at no charge. I'm obviously missing something here, as I understand where these efficiency gains are coming from, but there is a significant weight reduction for the same passenger load that has not been clearly explained. The fuselage generating aproximatly 7% of the total lift required accounts for a reduction in wing area, and therefore wing weight. - But the aspect ratio went way up which increases the wing weight, assuming the root chord Airfoil is constrained in thickness by Mach limitations, it will need a significantly stronger wing spar to support the new high aspect ratio, long span wing. Furthermore, you have removed the engines from the wings and relocated them to the aft fuselage, so there is no longer the engine weight counteracting the root-bending moment of the wings. Modern airliners place the engines as far outboard on the wings as possible to use their weight to relieve root-bending moment and therefore reduce wing weight. Engines would be mounted even farther outboard if not for the adverse single-engine operation effect that requires a larger vertical stabilizer to compensate, which would increase both drag and weight again. If you removed the wing mounted engines entirely from a modern aircraft, you would increase the root bending moment under G-load, as you would not have the mass of the engines pulling downward on the wings in opposition to the lift they are generating. By placing those same engines back onto the airframe on the fuselage, not only do you lose their beneficial effects from the wings, you exacerbate the issue by placing additional mass on the fuselage which the wings must support via the wing root. Drastically increasing the root-bending moment, requiring additional structure, and therefore more wing weight. Speaking of Engines: Up to this point engine placement has strived to avoid inadvertently ingesting the boundary layer. Almost all jet aircraft are designed to avoid this phenomenon, as there is often some turbulence in the airstream which was disturbed by the fuselage, the compressor blades will receive a rather more violent beating from ingesting this unstable air. - It can be done, no doubt. But at what cost? Simply stating that "new engines must be designed" that can function in an adverse environment is a tall order. Furthermore, in the landing phase, and during takeoff rotation to achieve the required Angle of Attack for slow flight to touchdown and/or initial climb to use available runways lengths at standard airports this Aircraft must be able to fly at relatively high angles of attack like other airliners do. This hight-Aoa is going to cause some instability in the airstream at the upper-aft end of the fuselage, possibly creating enough instability as to cause compressor surge or even compressor stalls of the engines. All jet aircraft that I know of which are intended to operate at relatively high AoA and high power settings have their inlets facing the freestream incoming air. Just look at fighter aircraft, their inlets even angle down and frontward to receive the incoming air at high AoA and this can be seen on the new 787 engine duct inlets also. There are a few exceptions among VLJs mounting their engines on the aft fuselage, but they protrude far enough above the cabin to receive clean airflow, except at potentially extreme (stalled) AoA. Placing the engines and their inlets much lower, and behind the sloping aft fuselage is asking for serious complications at high angles of attack and sideslip that will take a lot of resources both on the engine design front and the Aerodynanics side, costing countless millions of dollars in order to completely address for a seemingly small improvement in fuel savings that will take a long time to recoup: as this entire exercise was intended to accomplish. This design seemingly triples-down on costs and complexity, while also increasing weight by removing the engines from the wings, placing their mass on the fuselage, increasing the wingspan, and decreasing the wing root chord length therefore reduceing the absolute thickness at the root, as the thickness-chord ratio is always constrained by Mach number limitations. All of this requiring much heavier wing spars and therefore additional weight, not less. Though the design claims to be substantially less. (That entirely unaccounted-for weight saving would account for a significant reduction in induced drag and improved economy by itself). Also, that lifting fuselage cannot possibly have the same lift-to-drag ratio as a custom tailored Airfoil in the form of a moderate aspect-ratio wing, so whatever additional lift is gained by the lifting body will generate an inordinate amount of drag vs using a highly efficient Airfoil in the form of additional wing area. Speaking of the fuselage, there is a reason a perfect cylindrical tube is used on modern airliners, because it's the most efficient (lightest) means to contain pressurized gasses (air) for passengers to breath normally while cruising at 38,000'. Compressed air cylinders are always manufactured in this manner, from spray paint cans to welding gas cylinders; a cylinder is the lightest device to contain pressure. It's also Structurally efficient, a tube is a very lightweight design to transmit stabilizer forces from the aft tail of the airliner. A hollow tube is equally strong in Both yaw and pitch and any combination of the two, in fact hollow tubes are often used for control linkages and fuselage construction in small light aircraft for their efficient strength to weight ratio, in both bending and torsion. This fuselage abandons this concept, and it therefore will invariably weigh at least slightly more than comparable designs. You also open up the opportunity to develop fatigue cracks at the varied compound curve junctions. If not on the first flight pressurized cycle, maybe the 10,000th cycle. Testing and engineering will avoid any catastrophe, but at what cost in additional weight, and R&D? My point is, there is a finite amount of efficiency that can be gained and many ideas actually counteract what they are trying to accomplish. There are several methods to reduce fuel consumption: Fly slower. Not a lot slower, maybe 450mph vs 550mph. Drag increases with the square of speed, so slow down and drag and therefore fuel consumption per passenger mile comes down exponentially, to a point where induced-drag from lift begins to rise exponentially. Find the happy in between around 400-450mph at 35,000. Fly much much higher where the air is thinner and creates exponentially less drag. The only thing preventing this is regulatory bodies and their fear of cabin depressurization. (Rightly so, you won't live more than a few moments above 55,000'). And by designing aircraft to fly at very high lift coefficients, just below supersonic speed, and cruise in the "Coffin Corner" of their flight envelope. You can also reduce frontal area and pack more passengers in a line behind each other. Frontal area and drag go hand in hand, and a slight reduction in fuselage diameter results in near-exponential less frontal area. Though skin friction drag goes up, as does trim or fuselage lift related drag as airliners fly the first part of their trip at rather high cruising AoA which would likley be less efficient with a longer fuselage. From the standpoint of reducing greenhouse gas emissions, (Specifically Co2), a change to Nuclear Propulsion is in the works. Far safer than Anti-matter, (haha) as it's very well understood, it produces zero carbon dioxide, or any other atmosphere pollutant. And its power comes from rocks. Literally rocks. They say nuclear waste is hazardous, it is. But so is lava, which is melted by radioactive decay in the earths mantle. So just put in back down there with the other radioactive rocks. Send it down a four mile deep hole down near the lava to dispose of it. Nuclear power is the energy of the future. It's green. It's relevant. It's already invented. It doesn't kill four billion birds a year like the wind turbines, it works 24/7/365, unlike the sun which sets every evening. It doesn't block the coastline with wave actuated generators. It doesn't use fossil fuel, and it's the only energy source that's truely zero carbon, asside from the concrete and steel to built the plant. And the diesel to fuel the semi truck that brings the plutonium... Nuclear Propulsion or nuclear-electric propulsion, as seen on submarines and aircraft carriers, is sustainable and unlimited with at least 1 Billion more years worth of fuel available on this planet alone.

[@chauhanabhisheksheshnath2640]

Hey Justin ,am Abhishek here an undergraduate mechanical engineer from India ur views are truly impactful and accounts for every possible condition if u don't mind may in know u....

[@mithrandir1313]

Awesome video!! Thanks to Mark Drela! (Fellow Airfoil Designer!! ;)

[@SoaringSimulator]

Dr M.Drela, are you taking into account the fuselage ice formation? Also the input will be slower, hot and turbulent.

[@azharcassim2795]

Doesn't look like this took off.. It's 11 years later. I think it comes down to what he said.. commercial aircraft manufacturers don't have much of an appetitite for wildly different designs that they dont fully understand. The safety reptutation in commercial aviation speaks for itself. You cannot disrupt that. And to really make it happen would probably end up costing wayy more than our estimations. Also, i dont buy the whole gate to gate metric. Nevertheless, I must take this opportunity to give a huge shoutout to Mr Drela for xfoil and AVL..

[@sergeyrink3003]

What can we do? To stage stratosphere hypersonic plane.

[@TheIndyspace]

Mark looks like Wilbur Wright..!

[@GrigoriZhukov]

I note, that totally ignores motorcycles. :) which can be viewed as 1, 2 or 3 passengers and at 50mpg :) set and match. Also way more fun that planes, trains or automobiles.

[@awuma]

Motorcycle fuel efficiency has not been a high priority, and with a few notable exceptions is no better than for the best small cars. My 500cc 1956 Triumph Tiger 100 had much the same mileage as modern bikes of similar size.

[@AlejandroIrausquin]

+Keith Schiffner, have you tried an AirBike or an autogyro?

[@girishnandgaonkar8303]

Sorry Mark, you're cheating a little there. A more legitimate comparison would be between the passenger jet and a train, not a personal automobile. Whats the P-mpg for Amtrak? Other than that, seems like promising work.

[@sergioortiz7222]

You are right. However, I think Mark uses the idea of how many P-mpgs are employed only as reference. It is always easier to realise about how big an scale is if we compare to items we are used to, like cars.

[@RaduB.]

Sergio Ortiz Right! I hope that it will come up to something out of this project...

[@awuma]

The trouble is that while jets are efficient in terms of fuel consumption, the exhaust is dumped high in the atmosphere, and furthermore contrails are created, which grow into extensive cirrus clouds. The importance of this was illustrated immediately after 9/11, when North American air travel was suspended, with a marked drop in temperatures in the absence of the contrail-induced cirrus clouds. The impact of jet travel on the climate is a big question mark.

[@THEfromkentucky]

Contrails are suspended ice crystals formed from the water vapor left by burned hydrocarbons. Cirrus clouds do apparently reflect infrared light back down to the surface, but considering they take up less than 1 hundredth of 1% of the sky, I'm hesitant to think it has a significantly measurable effect.

[@uggahh430]

wings and props old tech