The Future of Airliners? – Aurora D8


When we look back over the last century of
innovation in flight it’s sometimes hard to believe how far we have come. The Wright’s first flight in 1903 was at
best a proof of concept; only managing to fly 37 metres before falling ungracefully
from the sky. We often look back at this historic event
and see it as the spark that ignited a century of human flight, the truth is, the event barely
registered in national media and most questioned the legitimacy of the news. It took another 3 years of incremental improvements
and public test flights before the international community began to accept their achievements
and by that stage others had begun to catch up and even surpass their designs. By 1910, Louis Blériot had flown across the
English Channel, Georges Chavez soared over 2 kms to clear the Alps and Glenn Curtis began
to testing planes as a platform for weapons and his biplane became the first to take off
from the deck of a ship. This marked a trend for the next 35 years
of aviation history, which was dominated by war and by the time World War 2 came to a
close giant companies had been formed who were mass producing planes capable of transporting
humans across the world. These companies were not going to simply vanish
as the war ended and instead set their sights on building a new commercial civilian transport
industry. In the final year of World War 2 over 4 thousand
Douglas DC-3s had been built and many of these would go on to be converted for civilian use. The DC-3 is still the most produced airliner
in history with over 16,000 built and some are even still in service across the world,
but it’s slowly being caught up by the Boeing 737, which has sold so many units that at
any single point there is an average of 2000 737s in the air. The 737 made it’s debut in 1968 and it’s
design has essentially become the template for which most jet airliners have been built
on since. The initial design of the 737 had the engines
mounted on the tail, similar to the DC-9, which the 737 was competing with, but placing
the engines here reduced the amount of space available towards the rear of the cabin and
mounting the engine pods tight against the underside of the wing freed up space at the
back of the cabin for more passengers, which was important for this narrow and short body,
short haul plane. It also reduced the bending load on the wings,
counter-acting the upward bending load caused by lift. The success of this design has allowed the
737 to stay in service for over half a century with incremental improvements and today it’s
so popular that most budget airlines like Ryanair and Southwest airline use no other
plane. It’s engines have got gradually larger and
more powerful. It’s cabin got larger as traffic increased,
wingets were introduced to the wing to reduce induced drag and later this year the latest
iteration of the 737, which has already sold over 3400 units, will make it’s debut with
new split winglets, more efficient engines, an improved flight deck and the modern cabin
interior developed for the 787 dreamliner. This theme of incremental improvements in
the airline industry happens for a reason. Introducing a totally new plane design is
an incredibly risky business. We need to look no further than the failed
Concorde for proof of that, but even introducing a new plane series like Boeing’s 787 can
cause massive losses in revenue. The plane was plagued with delays, originally
slated to arrive in 2008, but actually made its first commercial flight in 2011 and only
recently has hit it’s stride in manufacturing and sales. New designs are simply a risky business decision
and in general companies will play it safe and not break the mold. On top of this a plane’s service life is
a huge part of its selling point. Airlines want to buy planes that maintain
their value over the years and can last them a significant amount of time with minimal
maintenance, so manufacturers have made effort to increase the service life of these planes,
which in turn has increased the cycle times between new iterations of planes. Making progress even slower again. With the current status quo of the airline
industry. We aren’t likely to see much change any
time soon, BUT what if a new industry disrupter emerged. One that could shake up the duopoly of Boeing
and Airbus to force competition and new designs? We have seen this happen in other industries
recently. The energy sector is being revolutionised
by cheap solar panels, Tesla was the first successful car start up in America in over
a century and composite materials are set to continue replacing metals in many every-day
applications. These disruptive technologies combined with
rising air traffic could raise the pressure to innovate. In this new series of videos I am going to
break down a number of future aircraft and the design challenges they need to overcome
to become a reality. Let’s first take a look at the D8, nicknamed
the Double Bubble, developed by Aurura, MIT and with the help of NASA. The current template of plane design at the
moment consists of a tubular fuselage. This shape is primarily there to resist the
internal pressurisation, allowing the fuselage to expand without creating dangerous stress
concentrations. As long as we pressurise the inside of our
planes this design aspect won’t change, but we can create fuselages with multiple
interconnecting tubular sections. This is exactly what the D8 does, with it’s
double bubble fuselage. So let’s look at how they came up with this
design and the theory behind their design choices. To design this concept they actually started
off with a 737 and performed a morphing study by gradually introducing their design goals
to the current design. They started by first optimising the airframe
of the current 737-800 airframe with current generation improvements. They then changed the fuselage to feature
the double bubble. This shortened and widened the fuselage considerably. The wider body and shaped nose allows the
body of the aircraft to generate more lift, particularly at the nose. This allowed the wings to get thinner and
thus reduce the drag they generate, but it also meant that the tail wing could decrease
in size too. The primary purpose of the tail wing is to
generate downforce at the rear of the plane, which keeps the nose of the plane up, an important
stability characteristic, but when the nose generates it’s own lift, the importance
of the tail wing is diminished and it can decrease in size, which again reduces the
drag. They then reduced the cruise speed of the
plane from 0.80 mach to 0.76 mach, which may seem like a step backwards, but remember the
primary goal of this future design are to improve efficiency. This allowed the wing sweep of the plane to
decrease, if you don’t understand this go ahead and watch my “why are plane wings
angled backwards video”. In the next iteration they reduced the cruise
speed again to 0.72, essentially removing the wing sweep altogether. Reducing the speed of the plane reduces the
thrust requirements of the plane, which reduces it’s fuel consumption, reducing the sweep
reduces the wing area, which again reduces the drag. So reducing the speed by just 10% results
in a much larger percentage of in fuel savings. Consider that if you were flying on a 3 hour
flight this would increase your flight time by just 18 minutes and this increased transit
time would be even less of an issue when you factor in the reduced boarding times that
the double aisle configuration facilitates. The next design iteration moved engines from
under the wing to the rear of the plane and mounted the engines flush with the fuselage,
but this requires some future tech that isn’t quite ready. With the current configuration, engines are
placed far from the body of the plane and so the air entering them is undisturbed and
uniform. This is ideal for the engine designers because
each of the blades in the compressor experience the same air pressure and speed through each
cycle. But if we move the engines tight against the
back of the plane the engines have to ingest the boundary layer air-flow, which is the
slow moving layer of air that builds up on the surface of the plane. This type of engine is called a boundary layer
ingestion engine and it has been a topic of great interest for NASA and other aerospace
companies, because it reduces the loss of kinetic energy of the aircraft greatly. In a normal plane this boundary layer of slow
moving air simply rolls of the back of the plane and mixes with the fast moving air. This causes vortices and a low pressure zone
behind the plane, which creates drag. The idea behind the BLI engines is that they
take this slow moving air and speed it up and thus eliminate some of that drag. It’s a nice idea that is far from being
ready. The first problem we face is that non-uniform
air entering the engines. The air entering the engine furthest from
the fuselage of the plane is moving faster than the air entering the engine near the
surface. This creates a discontinuity of stress, as
discussed before in my dreamliner window video, cycling high and low stresses is VERY bad
for any part, as it results in fatigue of the part and when your part is rotating through
those high and low stresses a few thousand times per minute…your part isn’t going
to last very long and that’s just problem number one. The next big problem is stall. Airflow normally moves uniformly through a
jet engine, but when it’s distorted as it enters the engine, there’s a high risk of
compressor stall. Compressor stall works similarly stall on
a wing, where the speed and angle of attack of the wing can result in flow separation
behind the wing. This prevents the wing from generating lift
and thus stall occurs. Non-uniform, turbulent air makes this far
more likely to occur. When this happens in a compressor it can lead
to a chain reaction of stall, as the localised stagnated air travels with the blade it stalled
on, but lags behind slightly allowing it to come in contact with other blades, which then
stall too. Compressor stall may just result in localised
areas of stall that affect the engine’s performance or it can result in a complete flow reversal
where the incoming air is not being compressed enough to work against the previously compressed
air which results in an explosive flow reversal with air coming out the inlet of the engine. For these embedded engines to ever make their
way onto a commercial aircraft significant leaps in airflow prediction and engine design
& control will be needed. Although there are technical challenges, their
use could offer significant reduction in fuel consumption over the current generation of
podded engines. All of these technologies combined in the
D8 have been calculated to have a potential fuel savings of nearly 50% over conventional
technology and with the continual rise of fuel prices. This plane could be making it’s way to an
airport near you sooner than you may think.

Comments 100

  • Had to make a small change to the video. I don't have my mic with me though so couldn't fix the "plane windows angled backwards" problem. Anywho….yeah thanks to http://squarespace.com/realengineering for supporting the channel. Please check them out or consider supporting the channel over on https://www.patreon.com/realengineering.

    Your support has allowed me to make my first part-time hire!

  • What if the engine intake went all the way around the fuselage? Then it would intake the boundary layer all the way around

  • The 737 max 8 deathliner

  • RIP 737 Max 8.
    Never return.

  • It is obvious that this video was made before the major flaws of the 737 Max became public due to the tragic and preventable loss of life

  • 2:35 I wonder what’s going to happen to that

  • Or… we can keep hanging improvements on existing airframes to the point where we need software to stop the plane from stalling… oops… now it nose dives… sorry… but this was cheaper.

  • Omg! Aurora D8 is THUNDERBIRD 2!!

  • Weird how they are shaped similarly to whales

  • wait what a d8 that is an airliner? a d8 is a flipping bulldozer !

  • I wouldn't call the concord a failed plane..lets count how many fell from the sky due to engineering issues and revisit that one.

  • they have to use vanes to fix that airflow
    1) stabilize turnulence
    2) even out the pressure
    As you pointed out they can not run an engine with varying loads across the circle

  • Slowly reinventing the grand zeppelin air-balloons of the past, what can be more efficient than that?

  • Or, you could save all the fuel by not going…

  • The Boeing 737 Max fiasco is a perfect example of what happens to a company that fires their well educated white engineers and replaces them with cheaper foreign immigrants, all in the name of "Diversity". All the relatives of those hundreds of people that lost their life are RACISTS for complaining! /s

  • Why not use a single large engine, effectively mounted behind the plane, with the rear of the plane shaped to make the boundary layer air hit the center of the compressor blades instead of the top or bottom

  • Concorde didn't fail…

  • Watching you talk about the max 8 like its a a wonder plane nowadays is just kinda funny

  • Why not divide the engine intake into two parts and put a choke on the inner intake section like a double barrelled gun's muzzle…

  • Why is the title and description not in English? I can’t find a setting for this so I suspect it’s the uploader that chooses this. Can you please remove it. Only people without a proper education prefers translated text.

  • Well let's hope this plane fixes the issues the 737 Max has.

  • Ya 737 max is real great

  • What about an air intake like a fighter jets?

  • the concord wasn't a failed project? the concord flew and did its job well, they just hit finical difficulties capped with the air France accident, concord itself is a sound design

  • He said "reduce" so many times

  • Regarding the d8 concept engines at the rear of the plane, would it be possible to have the intake within the nose of the plane leading back to the engines? just curious

  • Half the space of an airframe is dedicated to either plumbing or the carry through structure to support the weight of massive, thirsty, fan engine nacelles.  Another thirty percent supports the torsional loads of aerodynamic controls at either end and through the middle.  Rather than a triumph of multiple engineering disciplines, it's a suck squeeze blow go compressor/combustor/turbine powered catapult. 
    A genuine Rube Goldberg machine.

    If you want to see major efficiency changes, tell the airline companies to commit half their profits to a followon airframe design which has to burn half as much, go twice as fast and take off and land vertically.

    You will immediately see aircraft shapes begin shift as they use turbines (70% burn efficiency compared to ~23% for recips and ~40% for rotaries) purely for electrical generation and change their airframe volumetrics to BWB lifting bodies, solely to find internal volume and strength for large, heavy, field effect generators using quadripolar torsion field systems that take reaction:mass out of the propulsion:drag recovery equation and halve your fuel burn as a result.

    We are still thinking of flight as pushing a wedge through a fluid medium rather than changing the time:space suspension bubble laws through which it _slips_.  Pull the air aside and fall towards the gap.

    There is a massive difference, literally, in everything from fuel fraction to control forces and aerodynamic flight profiles.  Until we start to think beyond the box of Newtonian physics (Hello NASA, what are you, a tourist agency or a subdivision of the Smithsonian?) we will not change the SOA in any major way.

    Stop repelling the earth and start pulling the sky.

  • If you ask me,it Looks like THUNDERBIRD 2

  • If they don't call it the Blue Whale I'm going to be disappointed

  • 737 Max may bankrupt Boeing yet.

  • Boundary-Layer Ingestion can be solved by inlet adjustable stationary blades redirecting the intake flow. Steam turbines also have had similar problems with what is called partial throttling which steam is directed on part of the arc 1/8 or 1/4 around the circle as flow increases to reduce throttling losses. Some studies on adjustable stationary blades were looked into to reduce cycling fatigue though never implemented because the cost would not benefit turbine efficiency increases. In aircraft, I think it could pay for itself especially with modern controls that are much more sophisticated than what we had in the 1990s.

  • You should do something on the Delft University-KLM project of a V body jet aircraft which turns almost all of the passenger spaces into a lifting body requiring even smaller flight control and lifting surfaces. https://www.travelweekly.com/Travel-News/Airline-News/KLM-working-on-V-shaped-plane

  • 737 Max Excuses, tell that to the Engineers. Not the Victims.

  • Aurora this is sunbeam

  • D8 has a whale shape when looked at from sideways.

  • It's about the past of airliners until about 4:14

  • Don't the MD planes had issues with boundary layer airflow with their fuselage mounted engines? If not (because they're actually off the fuselage) then why can't these engines be mounted far enough off to get the same effect?

  • Thunderbirds are go!

  • 7:56 I wonder if there could be a preturbine that could blend the high and low pressures before it arrives at the jet engine as a way to minimize the high and low pressure extremes?

  • Also BOeing in 737 MAX introduced new, dive down to grown flight set up onfiguration… what an achievement Boeing !!!

  • Won't be coming any time soon…. These may show up to a airport sooner than you think??? Wat

  • Why not mount the air intake at the nose instead and have ducts that lead to the engines to fix this problem? Something like the MiG-21 or the F-86.

  • Why not make a floating plane like ekranoplan glides on the water for transatlantic flights

  • they can reduce the speed to 10knots as well. it is called a sailboat and moves around with no fuel.

  • 1:31

    Thanks to Ryanair 😛

  • You irish mate?
    Me too

  • The write brothers wasn't the first motorized fight but we've only recently discovered this. It was all media bs

  • Love your videos bro

  • I thought I clicked on a trap beat because of your intro

  • I am from the future, Boeing shouldn’t have put the engine so high up on the wing.

  • What about if you separate the boundary layer by adding something on the fuzelage before the engine to separate the boundary layer in two and thus spread the stress on the engine?

  • At any given moment over the USA there are 5000 planes in the air.

  • d8 engine will also hold water in it so its a bad idea

  • If double bubble is a thing then I think Americans are going backwards in progress rather then forwards. Double bubble was considered by Airbus for A-380 but the it was found that the increase in half the surface area doubled the drag and the plane wouldnt be as fuel efficient. What not consider their study into consideration rather then starting from scratch.

  • Look at the intakes of F-4phantom, F-5, Su-27, Mig-29, concorde, etc. Their intakes arent flush with the rest of the fuselage of the plane but separated by a small gap which reduces the effects of boundary layer air flow.

  • I would trade more flight time for less time in the frustrating airport/shopping mall any day.

  • So air travel is about to get slower instead of faster…
    Can we stick with current designs, please?

  • It is notable how the new fuselage design resembles that of a whale… It is not the first observation of how often aerodynamic designs mirror those of birds and fish… lol – One wonders if the designers saw this emerging from their design evolution by chance or perhaps did this on purpose…

  • 737 max is the future! It s 2018 am i am putting all my life savings in Boeing stocks 😊

  • How to fall gracefully? Get all the Grace's, put them in the plane and then let it fall, there you go now you falling gracefully.

  • The american engineer solution: bigger, slower old technology and a bit of help from the government 😉

  • So, what are the other videos in this series. There's no playlist, or videos obviously distinct by name.

  • Curious why he didn't explore over wing mounting of engines, and exclusively looked at rear mounted… also, an aft mounting would work better if it was fully shrouded/ducted so as to reduce the boundary layer velocity differential. ( Like the F-15, F-16, F-35 ). Maybe the best of both worlds, have a tri propulsion arrangement , where smaller electric forward mount fans/swept props are intended only for takeoff/climbing, and the aft engines are to sustain cruising speeds ?

  • We want to make Concorde great again !

  • I can fly

  • Meh, by then large scale electric planes will be flying.

  • Still no vtol planes that eliminates a lot of problems old and new ones

  • What utter nonsense.
    The Concorde was no failure.
    What an absolute juvenile comment.

  • looks like a whale

  • The Wright flyer, when it was brought over to France, blew everyone away. They'd never seen a flying machine that was completely controlled by its pilot. Until then, machines had flown, but the pilots were pretty much along for the ride as they were barely controllable. The Wiright flyer literally flew circles around its peers.

  • thicc

  • Might mixing the slow and fast moving air fix the problem? Like, add some sort of small wing in front of the engine to merg the air speeds into one consistent air flow? Or will this introduce to much drag again?

  • What? Notwithstanding the double-bubble fuselage, you just made a bigger C-130 Hercules.

  • Why not make the engine like the b-2 spirit bomber but still have the same design with the engines at the aft of the plane

  • Look at Lilium (its a startup in Germany).

  • How do military jets with in-board engines get around the boundary layer issue? Could military tech be somewhat easily applied to commercial airliners?

  • I hope we can have faster international travelling in the future… crumbling yourself in the economy class seats for 12 hours is absolutely terrible! Now, before they step back from turbofan to turboprop, I hope the commercial BFR flights are ready…

  • 2:33 … it crashed twice xD

  • After flying for 24 hours over 4 consecutice flights to get to Bora Bora this spring, a slower airplane is exactly what I was looking for…

  • one question: how so, that civilians still use half century old design, while military… 5th – 6th generation?

  • Without wars would these planes have been developed?

  • https://youtu.be/H7Z04Tl1-1Q?t=163 "..flight deck with multiple new advanced functions like the MCAS system" 🙂

  • I'm sick of watching stupid videos that put the Whright brothers as the 1st to "fly" on a plane! This is a grotesque and unreasonable lie, a phobic and ridiculous Americanism as these 2 picks only catapulted something that was unable to fly by their own means! According to the rest of the world the first human to take off, fly and land a device heavier than air with wings and an engine was the Brazilian Santos Dumont and period!

  • 90'$ TAIL SPIN

  • Okay why the inlet of the engines just dont take air from the bottom of the aircraft, there will be much more air because its compressed under the air craft. I dont understand why the inlet have to be on the top. Can someone explain?

  • I love music by Maeson… Also Dekobe, Lakey Inspired, Engelwood, Poldoore, Tom Misch, Llindecis. My go to travelling music, couldn't live without it!

  • looks dumb no thanks

  • The new airplane body looks more like a humpback whale in profile.

  • Ohio gang!! We made flight, bitches!

  • Is there anyone planning on building the Aurora d8?

  • The 737 Max will make its debut by smashing into the ground

  • Cars should be made with the same maximized service life, minimal maintenance required principles as these planes. Or at least an "as close as is possible" approximation of these principles…. and preferably with out the massive brand name mark up of say Toyota…..

  • It might be worth taking thus video down as it's hopelessly inaccurate.

  • I love incremental improvements!!!

  • The double bubble is great but it's going to be expensive cos you have to pay twice the amount by next week

  • maybe mixing upper low pressure air with lower high pressure air before entering the engine could balance the engine at back of the airplane

  • 50 years in less than 1 generation all the cheep crude oil will be gone. No trains No 18 whellers No Aircraft.

    I not sure what our future will be but I do know it will be dark and cold.

  • That Aurora is one ugly mofo lol. Though it is amusing to learn why they are doing what they are doing.

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