MIT Designs Aircraft That Uses 70% Less Fuel Than Conventional Planes

greenrainbow writes "Today a team of researchers at MIT unveiled their design for an airplane that uses 70% less fuel than conventional aircraft. The MIT design comes thanks to a NASA-funded initiative to increase fuel efficiency, lower emissions, and allow planes to take off on shorter runways. The team accomplished all of NASA's set goals with their innovative D-series plane, lovingly referred to as the 'double bubble,' which has thinner, longer wings and a smaller tail, and engine placement at the rear of the plane instead of on the wings."

Comments

hmmm

[meerling]

Looks like it's fuselage is also a lifting body.

Re:hmmm

[gyrogeerloose]

Looks like it's fuselage is also a lifting body.

On the larger one, yeah, it does.

Interestingly, TFA mentions that NASA was also soliciting new designs for a supersonic transport aircraft; given the reluctance of nations to allow those in their airspace and the resulting eventual demise of the Concorde (which, IIRC, never made a profit anyway), one has to wonder why.

Re:hmmm

[ircmaxell]

Well, it's possible to travel supersonic with a minimal or even no sonic boom (I remember someone came out with a design for a boom-less Learjet recently). IF they can do that reliably, perhaps the countries will open up their airspace to it... Or perhaps it's a losing battle. Either way, some good science should result from it (What NASA is ultimately, a science organization. It's not Airbus)...

Re:hmmm

[robot256]

Yeah...except it hasn't actually ended yet. Will Obama veto a budget with irrationally-mandated Constellation spending? Only time will tell.

Re:hmmm

[vtcodger]

***The faster you go, the less time you spend going.***

Of course. My understanding is that's why drag related fuel losses only increase with the square of velocity rather than the cube of velocity. Still, given likely future trends in fuel costs, I expect that we're more likely to see zeppelins return than supersonic airliners return.

Re:hmmm

[Grishnakh]

Who cares if there's a sonic boom? A large portion of long-distance air travel happens over the Atlantic and Pacific Oceans. As long as a SST plane slows to subsonic speed before crossing over land, which it'll probably need to do anyway because it's preparing to land, there shouldn't be a problem.

Think about it, most really long flights are going to be trips like LA to Tokyo, LA to Beijing, LA to Sydney, NYC to London, NYC to Paris, etc. The vast majority of the distance is over international waters, and these airports are mostly very close to the water. Obviously, trips over Western Europe will have to be subsonic, but it's really not that far from the Ocean to any airport in Western Europe so the subsonic leg shouldn't be a big deal. Trips over North America can be supersonic, since it's doubtful the American government will care about sonic booms. If they do, I'm sure a few "campaign donations" will fix that....

Even trips from LA to Western Europe shouldn't be a problem, since most of the journey is over the North Pole IIRC.

Re:hmmm

[shermo]

It's my understanding that drag increases as the square of velocity. This leads to fuel consumption per unit of distance increasing linearly.

Go twice as fast, use twice as much fuel getting there. Your rate of fuel consumption is four times higher, but you spend half the time getting there.

Re:hmmm

[cmiller173]

Dallas/Fort Worth - London Heathrow (looks like 50% over land and 50% over water give or take. http://gc.kls2.com/cgi-bin/gc?PATH=DFW-LHR&RANGE=&PATH-COLOR=&PATH-UNITS=mi&PATH-MINIMUM=&SPEED-GROUND=&SPEED-UNITS=kts&RANGE-STYLE=best&RANGE-COLOR=&MAP-STYLE=

Re:hmmm

[Anonymous Coward]

The "squared" "law" is not a law, the drag force can be greater or smaller.

Also, going twice as fast but using half as much fuel is only true from the drag perspective; most mechanical things become much more inefficient the faster and hotter you make them.

Re:hmmm

[Wyatt Earp]

Sonic booms are not legal over the majority of the United States and they don't routinely make them over urban areas, I lived in Portland for 14 years and there was never a sonic boom in the area there.

I've heard them, I lived near a high speed route for B-1Bs in the 1980s and they'd break the sound barrier on occasion.

http://www.aerospaceweb.org/question/planes/q0060b.shtml

http://www.kerncog.org/maps/MEAR_atlas/23MilitaryFlightOperationAreas.pdf

http://en.wikipedia.org/wiki/Oklahoma_City_sonic_boom_tests

Re:hmmm

[blueg3]

He didn't say it was a law. (It's not, it's a rule of thumb.)

I'm no aircraft engineer, but for cars, internal frictions are only significant at low speeds. At a respectable speed, all of your power is going to counteracting drag.

Re:hmmm

[daBass]

The larger the aircraft, the bigger the boom. A conventional 200 passenger airliner will create a very big boom.

I was surprised because the Mythbusters couldn't break any windows with an F-18 unless they were at tree-top level. But big booms from big airliners are real.

And it's not just the boom, it's also the engines. Hard to create a supersonic airliner using quiet high-bypass turbofans. Concorde used straight turbojet with after burners: very loud.

Right until the Paris crash, Concorde between London and NYC was full and making a lot of money for BA. (buying the aircraft for peanuts from the government helped) Ticket prices were barely more than 1st class going subsonic.

I would imagine a NYC-LAX service and between other hubs would be equally lucrative; there an aweful lot of very rich folks and companies!

That said: I agree the next SST will more than likely be a business jet.

How Fast?

[Bruiser80]

Long, thin wingspans taking off from shorter runways makes me think it's considerably slower.

However, TFA says it could replace the overseas market, so the range must be there. If it carries the same amount of fuel as a 777, it must fly faster than 30% of the speed of a 777 ;-)

Slower than current aircraft

[sunderland56]

One way they save fuel: flying slower than current aircraft. First, will customers accept that? And second, why not just fly current 737s a bit slower right now, to save on fuel?

Re:Slower than current aircraft

[h4rr4r]

They sure will. If you can give me a 30% reduction in ticket price but a 10 hour flight instead of an 8 hour one across the atlantic that would be fine by me.

Provided it is a nice European carrier like Lufthansa, who actually has free beer and back of the seat entertainment systems. Unlike American carriers who charge for beer and have 70s entertainment systems in the aircraft.

Re:Slower than current aircraft

[vlm]

They sure will. If you can give me a 30% reduction in ticket price but a 10 hour flight instead of an 8 hour one across the atlantic that would be fine by me.

Doesn't work exactly like that. Levitating a million pounds of aluminum costs a certain amount per unit time, no matter how slowly you move it. Also the hotel loads of pressurizing, electricity, air conditioning, hydraulics, all are mostly invariant. And cost of inflight food/entertainment increases linearly with flight duration.

The real killer, however, is financial.

To simplify, lets assume the plane instantly loads and departs and magically requires no maintenance nor cleaning. That means the 8 hour flightplan makes 3 trips per day. And the 10 hour flightplan (drumroll as slashdotters get out their HP-48 calculators) makes 2.4 flights per day.

So, your 10 hour flightplan, in addition to lowering revenue by 30%, lowers total DAILY revenue, just due to scheduling by (3-2.4)/3 = 20%. Now you can play games with percentages all day, but be careful adding them or applying one on top of another. Even worse, To continue shipping the same number of bodies around in their current cattle car style, they need 20% more planes. And 20% larger maintenance facilities to process 20% more planes. And 20% more management overhead to supervise the 20% increase in staff. And a 20% higher bond/rent payment to pay for those planes.

And some people simply don't enjoy sitting in a cattle car. So they'll spend a little more dough to avoid it.

I would casually estimate that slowing the planes down with that discount would lower revenues "about" 50% while increasing expenses across the board roughly 25%. Profit margins are low enough that its unlikely any airline could survive that.

If anything, to survive, an airline that slows down "to save the planet!" is going to have to increase ticket costs modestly.

Re:Slower than current aircraft

[LWATCDR]

Actually it is a lot more complex than that.
The higher you fly the less fuel you burn but the higher the stall speed as well as the speed that offers you the best lift to drag.
Also engines have an optimum power setting as well.
Also the higher you fly the more fuel you burn in climb so there is a function of distance, altitude, and airspeed where the plane gets the best efficiency.
The concept D looks like it is using the classic trick of increasing the aspect ratio of the wing. That increases climb rate and improves the lift to drag at a given speed.
My guess by looking at the pictures they are using engines that have a much lower disk loading than current turbofans and a wing that is optimized for cruise at a lowers speed.

The problem will be the increase in weight. When you increase the aspect ratio you increase the weight of the wing. If you decrease the disk loading of a turbo fan the weight goes up. It will be interesting to see if all the lines cross where they think they will.

Answered my own question

[Bruiser80]

NASA's link says the 777 design flies 10% slower. A pretty good return!

Wing length is a Really Big Deal

[PPalmgren]

I remember watching a documentary on the new Airbus plane. There are regulations on wing length, and that plane *has* to use the perpendicular tips at the end of its wings to help with lift, or its wings would be too long. If you require longer wings per pound, you will fit less passengers per plane to fit in regulation. They will have to find a way to collapse the wings without adding significant weight or complications to make this practical for larger planes. That is a very big hurdle, maybe they should focus on that next.

I can't remember why, but I remember them stating that the wing length regulations had very good reasons behind them (logistics of current airports being a major one if I recall). I don't think changing the regulations would be practical if that was the case.

Re:Wing length is a Really Big Deal

[dwye]

> The 70% savings in fuel cost will be sucked up somewhere,

The article mentioned that moving the engines to the rear increased stresses. Replacing engines will use up that savings; replacing airframes even more so. There is a reason that commercial jets have engines in separate nacelles, nowadays, despite the obvious benefits of locating them inside the wing or fusilage.

OTOH, the super-wide bodies might be a real win, unless moving the fuel tanks from the wings decreases crash safety too much.

Can it fit into most airport's taxiways and gates?

[gront]

Sure, long thin wings, or a flying wing design are great, but widening aircraft past existing designs would be a nightmare for airports. There is a certain amount of space to fit airplanes while they are moving around on the ground, and wider planes = more of a hassle.

http://blog.flightstory.net/272/airbus-a380-hits-hangar-in-bangkok/

http://home.iwichita.com/rh1/hold/av/avhist/abs/a380flys.htm

Re:How to pressurize it?

[ThreeGigs]

It's actually two cylindical (or semi-cylindrical) cabins joined together lengthwise, with a stressed interior partition framework. Kinda like a number 8 laying on its side. Pressurization isn't difficult in that case, and the interior stressed partition can be a latticework. It's not a new idea, although it's never been done for reasons of practicality, just a lot simpler to make the body a long tapered tube and be done.

Both of TFA's linked sadly lacking in details

[Larson2042]

I'm disappointed in both of the linked articles. Some real substance about the design would have been nice, but as it is, I'm left with a lot of questions:
-70% less fuel? How much of that is aerodynamic savings and how much of that is engine efficiency savings?
-Did they do any wind tunnel testing of their model? How close were their CFD and tunnel test results?
-Are they using engines based closely off existing ones, or are they projecting fuel savings 25 years into the future (the 2035 time frame from the article)?
-What sort of structural weight-saving advances are they assuming, or projecting from?
-So they made the tail smaller, what makes up for the reduction in control authority there?
-Plus other more detailed questions based on the answers to those questions. Would it have been so hard for MIT to link a design document pdf or something? I guess not being a public university, they don't have to if they don't want to. Too bad.

Re:Great... insurance

[dltaylor]

It took FOREVER to get a composite commercial aircraft into production because the insurance companies had no data on hull integrity to do the underwriting. As a result, the proposed premiums were based on utter disaster.

It may have been the Beech Starship http://www.wingsoverkansas.com/legacy/article.asp?id=775 that provided some useful data. Although a turboprop, it is pressurized, and the more-frequent pressure cycling of a corporate hauler may have given them some idea that composites aren't highly more likely than conventional aluminum hulls to become convertibles (Aloha 737) in flight.

If the US gov't really wanted to help advance the aircraft industry, they'd create an insurance agency for new designs and materials.

I wonder which engines they used ...

[Aviation Pete]

So far, two thirds of efficiency improvement has been gained by the engine makers, not the airframe designers. If those planes are intended for 2035, I suspect that the guys at MIT extrapolated the current engine efficiency a quarter of a century into the future and had already half of the savings pocketed, without having to improve the airframe a bit. Attaching glider-like winks did the rest, easily.

Move along...

[Evtim]

You know, people, it is perhaps shameful to admit in front of this audience but despite working at the cutting edge of technology I only shrug at news like this one. Instead of all the exiting engineering/scientific thoughts that most of you exhibited and made the discussion interesting the only thing that crossed my mind was something like:

"So, we are going to save 70% of the fuel. What would happen in such "vacuum" Well, we will just build 70% more plains, fly even more people around, cheaper perhaps so the "gain" in efficiency will be quickly drowned by the increased volume of planes and passengers. Move along, nothing to see here..."

I don't want to rain on anybody's parade but every time when some new technological development frees us time, it is immediately filled with more work, not more recreation or hobbies or family life. When it comes to food and water it is even worst. Just consider the "green revolution" from the 70's. Population pressure due to the baby boom after the war. Solution - industrial agriculture which completely kills the taste of food (especially fruits and vegetables) but its efficient and easier to transport and preserve. When it was all over , did we wipe out the noble sweat and sat down to enjoy the fruits of our ingenuity (pun intended)?

No, because the population pressure was already pushing us again. We will never catch up with this. And as every scientist will tell you , every next step will require more energy and more effort to squeeze maximum yield from minimum volume. Asymptotic approach to use the proper term. Like trying to accelerate a mass to the speed of light. As long as we do not stop the geometrical progression of our multiplication we will never be able (most of us) to enjoy what the progress is all about - giving MORE time for ourselves and our personal development and personal life. Giving MORE and higher quality goods and services per person (population flat, but efficiency increases).

Globally as humans we experience what we people in the west experience with the constant inflation - you have to run ever harder just to stand still. Miss one year's promotion or a raise and your buying power goes down. The effect of missing one year only is accumulative like compound interest. I am sick to the teeth that I have to run like a mouse on an endless tread just to stand still. Just to exists. And being told all the time how good I have it.