MIT proposes to Reinvent the 737 for 70% greater fuel efficiency | Hacker News Reader

MIT proposes to Reinvent the 737 for 70% greater fuel efficiency

nextbigfuture.com

36 pointscwan21 comments

From browsing http://aviationweek.typepad.com/files/mit_n3_final_presentat... …

• It's all about radically different fuselage design.

• 10% slower than current, think they might pick it up by saving 15 minutes on load and unload because of multiple aisles.

• The 777 model has no windows in economy class, and apparently no doors visible either. They are 9 row deep pods with 3/2 seats and a lateral aisle at the front. That is going to take some getting used to.

• There is a slide that says the N+3 numbers are reached with "advanced technology insertion". I am reminded of a Sidney Harris cartoon: http://avionod.wordpress.com/2009/04/06/and-then-a-miracle-h...

• They will fly higher, 40k feet and 45k feet. No word on how that changes turbulence, I presume it helps.

Emergency passenger evacuations for the 777 model could be interesting...

This is all missing the point. And is a typical case of solving the problem with a "bigger hammer".

China is building a national rail network running at 350km/h to with the goal of putting any city within an 8 hour travel radius of Beijing. http://www.globalissues.org/news/2010/09/30/7114

Kind of makes domestic air travel somewhat obsolete and really quite unnecessary.

Why is rail travel inherently superior to air? Every spot in the continental U.S. is already well within 8 hours of...everywhere.

Ah... you can get up and go to the bathroom during "take-off" is one of the main reasons that come to mind.

But, there are may others relating to carbon footprint per tonne.km traveled, which have greater relevance.

for short to medium distances it is:

1. Much more comfortable (wider seats, more luggage space, etc)

2. A lot more convenient. No taking off shoes, check points and lines. Plus the chances are a train station would be a lot closer to the center of the city, rather than an airport.

3. Cheaper and less pollution.

E.g. If the CA High Speed Rail got build, it would take about 2.5 hrs. from downtown SF, to downtown LA. By plane it is about 50mins. BUT, you should add the time it takes for check in check out (at least 45mins), then the time to travel to the airport themselves (30 mins with Bart, if you live in SF), etc. If High Speed Rail would have been implemented throughout most of the major cities of US, It just wouldn't make sense to fly for short and medium distances. Coast to Coast, yes, coast to Midwest yes, SF to LA or LV, probably not.

"2. A lot more convenient. No taking off shoes, check points and lines. Plus the chances are a train station would be a lot closer to the center of the city, rather than an airport."

I would imagine that the first part would change as rail became a more traveled medium, thus making it a more attractive target for terror attacks.

However, having train stations closer to the city centers than out in the suburbs would be great.

There have already been terrorist bombing attacks on high speed rail: http://en.wikipedia.org/wiki/TGV_accidents

It turns out that high speed trains are a lot more robust than planes: the failure mode is usually "soft", i.e. the train comes to a halt safely and damage is confined to one carriage (unlike an airliner). To inflict mass casualties (e.g. 7/7, Madrid) attackers target either busy subway systems at rush hour (7/7) or busy transport terminals with lots of people (Madrid). It's worth noting that both 7/7 and the Madrid bombings involved large suicide teams and multiple bombs -- but killed fewer people than a typical airliner bombing.

The article claims a 70% fuel efficiency increase, and another quoted part claims a 70% reduction in fuel use. Which is it?

Journalists typically don't "get" percentages, so they just throw them around and hope it's correct.

Other examples:

"Crime rate drops with 8%!" ... compared to what and when?

"Inflation now 2% higher" ... does that mean inflation went from 1% to 1.02% or to 3%?

The mere notion that you can express change of a metric (expressed as percentage), as a percentage would probably destroy the average journalist's brain.

Isn't the really interesting thing that they're proposing fuselage and wing shapes that you can't design without using "modern" (developed after 1965) methods? The cylindrical fuselage standard passenger jet design is something you can design using a slide rule or pocket calculator and a copy of "Roark's Formulas for Stress and Strain".

I am very happy flying in things that could be designed with a slide-rule. If the computer program that analyzed the fuselage is wrong and I can't spot the error because the result is too complex for a human to have a clue, I'll die anyway, regardless of what the computer said.

I like what a test-pilot once told me: We don't need milestones. We need inchstones.

A common problem with this wide body design is that it makes turning the plane harder. Because people are further from center they will feel the dips of the wings more as the plane banks for a turn. The pilot would have to make wider & shallower turns to compensate so people don't get sick.

5% saving with better aerodynamics - at huge cost in changing every runway, taxiway, jetbridge, hanger and terminal to handle the new shape/size/layout

65% saving from new engine design based on unobtanium

Is that so? I'm struggling to understand how the 70% fuel usage reduction is supposed to occur just by feeding in slower-moving air. Anyone have any insight here?

I don't think that is what they mean to say. The slide on page 128 of http://aviationweek.typepad.com/files/mit_n3_final_presentat... for instance breaks down the fuel savings by various changes:

  D8.1 configuration (double bubble)   49%
  Airframe Advanced Materials           8%
  High BPR Engines                      4%
  .. and a long tail that might be 8% more for the engines.

Now maybe the D8.1 configuration is only possible with impossible engines. I can not say.

"Reinvent the 737" is a horrible way of putting this. They used the 737 and 777 has baselines/references of their design goals. Perhaps they based some of the fuselage/wing work on the existing planes, but they are so different, you could say they reinvented any two engine passenger liner built since the 737.

These designs also rely on some very advance (for commercial jets) engines. PW was involved in the engine redesign of this project, so I imagine the numbers they pulled out for increases in efficiency, while optimistic, are not pulled out of their ass, and definitely achievable. One of the things they're trying to to shift towards lean burning (so more oxygen than required for "complete" combustion), to reduce pollutants. They also want to use thrust vectoring in their hybrid wing concept, which I guess would do wonders for runway length requirements.

Regardless of how feasible actually getting these into production (imagine Boeing actually redesigning one of their planes based on what some outside source came up with... at the very least, it would be completely reinvented in house at Boeing... well, that's my guess anyways), it's nice to see how much detail they put into this. They even went to try to reduce vortices at takeoff/landing so you could cycle planes faster through a runway.

Some of this savings has to be from by going 10% slower? Since drag is quadratic, doesn't that mean a 20% reduction in drag alone?

Sure, but presumably the 737 would not be getting its optimal fuel efficiency if it went slower (every vehicle has some sort of a target speed that it's optimized for.)

I thought a 737 was a specific model of plane, no? Wouldn't this be a completely different model? Can someone explain what makes a 737 a 737 and why you would still call something with as much change as this a 737 still?

Two ideas: they are using 737 as synonymous with small-to-midsize passenger jet. They could as well use Airbus 318/319/320, but Boeing wouldn't like it.

They are implying this will be a commercial hit of the same size as the 737, so it's worth of government funding (because if they don't develop it, Airbus will).

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