11 ms·

Aviation industry tries to go green

35 points by dnetesn 7y ago

WalterBright 7y ago
The motivation for the 737MAX was it burns 15% less fuel.
- gpapilion 7y ago
  Fuel saving solutions are always attractive in the industry. Originally it was thought jet engines would fail due to their fuel consumption, but the reduced maintenance requirements made them more attractive.
  - WalterBright 7y ago
    Yup. Piston aircraft engines indeed need tons of maintenance. A huge number of moving parts coupled with trying to minimize the weight and maximize the power is the cause. In WW2 the Germans fitted aircraft engines to their tanks, which worked great when the engines ran, but too often they didn't due to battlefield conditions. (Germany was also terribly short of avgas, which crippled those tanks.)
    - newnewpdro 7y ago
      > In WW2 the Germans fitted aircraft engines to their tanks, which worked great when the engines ran, but too often they didn't due to battlefield conditions. (Germany was also terribly short of avgas, which crippled those tanks.) This sounded interesting so I skimmed the tanks mentioned in [0] and only found mention of prototypes exploring use of a turboshaft engine [1] from [2]. [1] explicitly states "none of these was fitted operationally", so I don't get the impression that these ever even encountered battlefield conditions before Panther II was canceled. [0] https://en.wikipedia.org/wiki/German_tanks_in_World_War_II https://en.wikipedia.org/wiki/German_tanks_in_World_War_II [1] https://en.wikipedia.org/wiki/GT_101 https://en.wikipedia.org/wiki/GT_101 [2] https://en.wikipedia.org/wiki/Panther_II_tank#Engine https://en.wikipedia.org/wiki/Panther_II_tank#Engine
      - zabzonk 7y ago
        Don't know about the Germans, but the British used modified aero engines quite extensively in tanks - https://www.wikiwand.com/en/Rolls-Royce_Meteor https://www.wikiwand.com/en/Rolls-Royce_Meteor
        newnewpdro 7y ago
        That's pretty smart, using de-tuned aviation engines. But unlike what WalterBright is describing, these were appropriately reconfigured to not require high-octane fuel.
        snovv_crash 7y ago
        Indeed, my grandfather was in one in Italy late in the war. From the stories he told, the crew one time got it up to 40MPH, then the crankshaft snapped.
      - WalterBright 7y ago
        I didn't mean a gas turbine engine, but a piston engine designed for aircraft. (Gas turbines don't run on avgas.) With a quick look I can't find a cite for my claim, just that the British did use Merlin aviation engines in some of their tanks.
        newnewpdro 7y ago
        I couldn't find mention of anything else aviation-related in the per-tank pages, and the Maybach WWII engines page [0] doesn't speak to it either. Do you have any good references we can check out? [0] https://en.wikipedia.org/wiki/List_of_WWII_Maybach_engines https://en.wikipedia.org/wiki/List_of_WWII_Maybach_engines
        WalterBright 7y ago
        I have a few hundred books on WW2, it's possible I'm mis-remembering it. I am ashamed :-(
    - redis_mlc 7y ago
      > Piston aircraft engines indeed need tons of maintenance. Modern small piston aircraft engines under 250 HP have average TBO of 2,000 hours and can be operated beyond that with oil analysis. That's fine for commercial use, and piston engines only use 1/3 to 1/2 the fuel of jet engines, though that may be because of the use of a propeller. So you trade fuel efficiency for engine maintenance, and I think they'd average out. DC-3 operators can maintain their piston engines just fine with one mechanic. (Large turbofan engines like the 737 MAX uses are basically resurrecting the propeller in terms of moving a large volume of air, rather that relying on only a jet of air.) I don't think there is a lot of data for larger piston engines. 1,000 HP engines and larger in WW2 had issues at the time, but that was 75 years ago. Metallurgy and production methods have improved since then. Also WW2 engines were boosted (supercharged and water/alcohol-injected) and the military didn't care about longevity as airliners do today. For example, the American supercharged P-38 was the fastest fighter of WW2, while the version sold to Britain wasn't, and was a dog. Source: commercially-rated pilot, WW2 student.
      - sgent 7y ago
        I don't know what the data is, but the DHC-8/Q-400 is a fairly popular regional airplane outside the US, and depending on the model goes from 1300 - 5000hp. https://www.pwc.ca/en/products-and-services/products/regional-aviation-engines/pw100-150 https://www.pwc.ca/en/products-and-services/products/regiona...
        redis_mlc 7y ago
        Both the DHC-8 and Q-400 are turbo-prop (ie. jet-engined) airplanes, not piston.
      - WalterBright 7y ago
        A Lockheed Constellation had 4 × Wright R-3350-DA3 Turbo Compound 18-cylinder supercharged radial engines, 3,250 hp (2,424 kW) each https://en.wikipedia.org/wiki/Lockheed_Constellation https://en.wikipedia.org/wiki/Lockheed_Constellation That's 72(!) cylinders. Then you've got the superchargers, variable pitch propellers, and on and on. It's a bit of a miracle one could get them all running at the same time :-/ BTW, Lindbergh flew the Atlantic on a single engine. He rejected multi-engine designs because the reliability would be halved. He selected the most reliable engine available at the time.
- himinlomax 7y ago
  Correction, the motivation for the 737MAX was that the Airbus A320neo burns 15% less fuel.
- yason 7y ago
  They don't seem to burn any fuel at all , as far as I can tell!
  - dredmorbius 7y ago
    In-flight fuel consumption was optimised by engineering a short flight profile and substituting bulk fuel consumption on ground following landing.
nradov 7y ago
There are a number of other initiatives underway to reduce greenhouse gas emissions from commercial aviation. Synthetic kerosene can be manufactured using power and heat from renewable energy sources. Electric motors can be used for taxiing so that the turbines only have to be started immediately before takeoff. The electromagnetic catapults used on the latest Navy aircraft carriers can be scaled up to launch redesigned airliners from runways on land with lower accelerations. But it will probably take many years until any of these innovations are widely deployed.
- chrisseaton 7y ago
  > Electric motors can be used for taxiing so that the turbines only have to be started immediately before takeoff. I thought that this was pointless because the engines needed that time during taxiing to warm up properly anyway? If you moved them to the runway electrically they'd then just need to sit there burning fuel for five minutes to warm up. Naval jet fighters, which launch through steam or electronically and don't need to taxi further than a few metres, still sit there for ages warming up. They don't just turn on and go.
  - WalterBright 7y ago
    I know that for piston engine aircraft, it is critical that the engine be properly warmed up before takeoff. Otherwise, the engine would likely stall shortly after liftoff, leading inevitably to a crash. This is a common cause of accidents. I don't know specifically about jet engines, but as the engine is designed to run while hot, and metal expands when hot, I'd be quite surprised if it wasn't necessary to warm them up before full power, too. Drag racing engines will often be warmed up using some sort of electric blanket. Even for your car, it's a bad idea to floor it while the engine is cold.
    - imsofuture 7y ago
      I know that for piston engine aircraft, it is critical that the engine be properly warmed up before takeoff. Otherwise, the engine would likely stall shortly after liftoff, leading inevitably to a crash. This is a common cause of accidents. This is not true. Engine start to takeoff is usually at least a few minutes, but there is no critical temperature factor for the engine (barring extreme heat or cold). It's a lot like a car, you don't want to overly stress by flooring it when cold, before oil is circulating comfortable -- but running for 10s of seconds is plenty to get going.
cgrealy 7y ago
The big win would obviously be electric aircraft, but I doubt we'll see that in my lifetime (barring a massive breakthrough in battery technology). The problem is even the best batteries have a much lower energy density compared with traditional fuels. Also, a battery that weighs 100kg when full weighs pretty much 100kg when empty. Real Engineering did a pretty good video on the topic https://www.youtube.com/watch?v=VNvzZfsC13o https://www.youtube.com/watch?v=VNvzZfsC13o
- moltar 7y ago
  World's first fully electric commercial aircraft takes flight in Canada https://www.theguardian.com/world/2019/dec/11/worlds-first-fully-electric-commercial-aircraft-takes-flight-in-canada https://www.theguardian.com/world/2019/dec/11/worlds-first-f... Of course far from intercontinental jet, but it’s a start :)
  - cgrealy 7y ago
    Did you watch the video I posted? It specifically talks about converting a small aircraft and says you could get "about 20 minutes". Building an actually useful commercial plane (i.e. something along the lines of 737 or A320) is an order of magnitude more difficult, in fact, basically impossible with current battery technology.
    - benhurmarcel 7y ago
      For electric airliners, most promising research centers on hydrogen fuel cells, not batteries. It brings a lot of issues (mainly volume and cooling), but still it's being seriously considered.
      - anovikov 7y ago
        Why not just liquid hydrogen, burned in a jet engine? Yes it has density about 12x lower then kerosene, but specific energy is about 3x higher so for the same fuel volume, we get 4x less range. In fact better than that, because of much lower weight and about 2/3 power ratio of fuel burn to aircraft weight and about 40% of weight of a typical plane being fuel, it being gradually burned during flight... it adds about 11% of range, so like 28% of the kerosene-powered range for the same fuel tank volume. So about 4500-5000km, with added benefit of fantastic takeoff performance (low weight). Enough for cross-USA travel, and non-Arctic cross-Atlantic flights (anywhere in CONUS->Bangor, Maine->Shannon, Ireland->Anywhere in EU)... solves the problem as i see it?
justlexi93 7y ago
It is definitely a good idea. The environment changes and we need to do something about it.
animalnewbie 7y ago
Serious question, pardon my ignorance. How much is the per capita fuel consumption compared to a petrol car? Small steps are good too but I sincerely hope we can spend that effort in safety and perhaps speed. Societies progress as distances get shorter.
- jcampbell1 7y ago
  Airlines get about 40-60 passenger miles per gallon. Not sure if that answers your question.
  - animalnewbie 7y ago
    It does exactly. Thank you. This is 4 times that of a singly occupied car. Probably more effort should go towards car pooling. And maybe electric scooters.
    - zdragnar 7y ago
      That's not outside the range of most hybrids, and even 40 isn't much far off from, say, a kia optima at all freeway miles. Even low efficiency crossover SUV types get at least half, if not better. As the sector transitions to battery over gas, the situation will only continue to improve, as it has been for years. That's not to say that proper incentives for car pooling are bad, but it's also no reason to exclude looking at improving the efficiency of planes- especially since fuel costs are so large a portion of their operating costs.
    - upofadown 7y ago
      That's only a meaningful comparison if you drive across oceans to different continents. People tend to fly much much longer distances than they drive. Supposedly a single long over ocean flight costs something the same as a whole year of driving in terms of carbon emission.
      - maccard 7y ago
        > That's only a meaningful comparison if you drive across oceans to different continents. People tend to fly much much longer distances than they drive. Distance isn't everything, many many flights are avoidable/suitable for alternative modes of transport. This [0] estimates that 18% of flights of adults in the UK are "long haul". 40% were either domestic or short haul in Europe, both of which are replacable by trains. The longest domestic flight in the UK is from Gatwick to Inverness, and takes just under 2 hours, or an 8 hour train journey. [0] https://fullfact.org/economy/do-15-people-take-70-flights/ https://fullfact.org/economy/do-15-people-take-70-flights/ - (Note this was just the first source I found)
gersh 7y ago
It might be better to just capture CO2 from the Ocean or the air, and then use renewable energy to make jet fuel. While the efficiency of the process may not be super high, it will be carbon neutral. See https://www.weforum.org/agenda/2018/02/bill-gates-to-strip-c02-from-air-for-clean-fuel/ https://www.weforum.org/agenda/2018/02/bill-gates-to-strip-c... and https://www.greencarcongress.com/2014/04/20140408-navy.html https://www.greencarcongress.com/2014/04/20140408-navy.html.
tonyedgecombe 7y ago
Aviation looks like the industry least likely to go green to me. I doubt electric planes are ever going to be viable for anything other than a short hop which would be better done by train. Synthetic fuels sounds interesting until you look at how much fuel they consume. The trend is quite obviously in the wrong direction: https://www.statista.com/statistics/655057/fuel-consumption-of-airlines-worldwide/ https://www.statista.com/statistics/655057/fuel-consumption-... It's often quoted as 2% of global emissions, my (admittedly back of the envelope) calculations come out 50% higher without the cost of burning it at high altitude nor refining the fuel nor the infrastructure on the ground to support air travel. My guess is emissions from air travel will continue to rise as the world develops and they will take an increasing share of the total as other sectors decarbonise. This all leads on to political problems, how are you going to convince the poor to reduce their emissions when they see their rich neighbours jetting across the world on holiday.
- stingraycharles 7y ago
  I think it’s important to look at this from a different angle: sure their requirements are high, and they may not be able to go completely green in a short timeframe, but should we therefor not even attempt it? It’s not difficult to imagine a hybrid system at some point in the near future, and/or other ways of reducing the carbon footprint. Focus on those positive things, rather than “this will never be completely green, so why bother?”
  - tonyedgecombe 7y ago
    “this will never be completely green, so why bother?” You are putting words in my mouth, I never said that. The industry has been reducing emissions per mile pretty much since it was founded. Looking at that graph I posted it is having the opposite effect to what we want. Jevon's paradox and all that. My personal solution was to stop flying, I haven't got on a plane for 19 years. I'm not sure that is palatable to most people here though, it certainly isn't to the airline industry.
  - jerome-jh 7y ago
    They may reduce the carbon footprint per mile, but the physics of thermal engines imposes hard bound to what can be achieved. The article mentions the delta wing design may save 20% on fuel consumption. However those gains are completely swallowed by the traffic increase which is about +30% every 10 years if I remember correctly. The target for 2050 is completely unrealistic, considering the traffic increase and the long cycles of the aviation industry. It may be achieved with hydrogen, assuming it can be produced in large enough quantities with renewables. "should we therefor not even attempt it?" Oh they certainly want to look as if they were trying to reach there objectives ... for the moment it is business as usual. The production of conventional, kerosene powered planes has never been so high and still increasing.
jamil7 7y ago
Is a large part of this also a political issue? with subsidies and tax breaks on fuel the aviation industry is not really incentivised to innovate and cosumers are not incentivised to seek other modes of transport since flying is often the cheapest and fastest.
- belorn 7y ago
  Every single mode of transport is subsidized so its hard to say if air transportation is getting more or less incentives. Using Swedish numbers and some estimates. Tax on car owners only pay around 1/3 of the road network. The ticket price on train, according to a person working in that space, said that the ticket paid about 2/3 of the costs that the train company paid for any given trip. The train network also get infusions from time to time by the government, and stations are supported/built using local taxes and fees. Boats get tax breaks on fuel, and ports are usually subsidized when built. There might also be subsidizes involved in ice breaking, cleaning and management of the waters and channels around ports. Planes get tax breaks on fuel, and airports are subsidized when built. Out of those, I would guess that the train system is the least subsidized model but I have nothing to actually support that claim beyond a gut feeling. I would like to see a good summarize of what each sector get and where the money comes from.
  - jamil7 7y ago
    Thanks for the detailed info. I honestly don't know the details well enough and hence framed my comment as a bit of an open question. This makes me wonder, in Germany it is possible to get a decently priced domestic train ticket or at least a comparable price to a domestic flight but one needs to book far in advance whereas this isn't the case when booking a flight. If it's not subsidies and taxes what is making train travel so uncompetitive with flying?
    - Leherenn 7y ago
      Infrastructure costs, they are absolutely massive compared to what you need for planes.
  - 7y ago
dredmorbius 7y ago
Aviation more than any earlier transport mode is fundamentally based on high power-to-output engines and fuels with both high volumetric and weight energy density. It's little surprise that within years of practicable petrol-fueled automobile engines, powered flight became a reality. Within a quarter century, propeller-driven craft had all but achieved their design zenith (the DC-3), and jet propulsion was being deployed within four decades. Aerodynamics, controls, navigation, traffic control, and business systems around passenger, freight, and parcel delivery have accounted for most advances since. Notable among failures have been both supersonic and lighter-than-air craft. Both see limited (mostly military) use. Commercial viability has been lacking. The alternatives to the present subsonic, large-scale, heavier-than-air, fuel-based transports are ... limited. Electric propulsion solves the power-to-weight problem (electric motors are remarkably poweful and efficient), but not the energy-storage problem. Batteries have at best about 1/10th the energy storage by weight of hydrocarbon fuels. Supersonic flight simply requires too much fuel, on top of other environmental concerns: noise, high-altitude pollution. Unscheduled subsonic jets achieve better flexibility than supersonic scheduled flights for those needing (and able to affort) it. Lighter-than-air craft seem to fragile, finicky, dangerous, and expensive to operate. Changed air travel economics might address that last, but the fact that ultra-lightweight, tremendously voluminous structures capable of lifting only modest cargos and subject to extreme peril from high winds and inclement weather ... does not seem promising. (Though Germany did operate international Zeppelin service for much of the 1930s. I may be overly pessimistic.) There are alternatives to fossil hydrocarbon fuels. Most have extreme shortcomings. Hydrogen as an energy carrier is possible but has remarkably low volumetric energy density, as well as poor storage and handling capabilities. It's unlikely to be utilised. Biofuels can be effectively precise analogues of present avgas (petrol) and jet (kerosene) fuels. The problem is that even the small fraction of energy demand represented by aviation fuel use is beyond the capabilities of agriculture to produce. In 2014, Boeing touted "the biggest breakthrough that there is out there" in biofuels. At 75 gal/acre-yr (mean of reported production) and 16 billion gallons of aviation fuel consumption in the US (2013 BTS RITA estimate), 21.3 million acres would have to be under cultivation. That's about 330,000 mile2, or a region 577 miles on a side. On the map, you could start in Shreveport, LA, head west to Hobbs, NM, north to Denver, CO, east to St. Joseph, MO, and south to Shreveport again, traversing seven states and completely bounding two (Kansas and Oklahoma). https://old.reddit.com/r/dredmorbius/comments/1wo2hl/boeings_biofuel_breakthrough_less_than/ https://old.reddit.com/r/dredmorbius/comments/1wo2hl/boeings... The one possible alternative I've seen, and one which isn't obviously* impractical, is fuel synthesis: creating the liquid hydrocarbon fuels powered flight is dependent on from non-fossil sources. The notion's not new -- it strongly resembles the coal-to-liquid-fuels process employed in Germany during WWII, and in South Africa since the 1950s. The notion was suggested by M. King Hubbert in 1964 (http://www.hubbertpeak.com/hubbert/EnergyResources.pdf http://www.hubbertpeak.com/hubbert/EnergyResources.pdf (PDF) p. 139), and has been explored at the Brookhaven National Laboratory, M.I.T., US Naval Research Laboratory, and a Google X Projects startup (since folded), over the past five decades. The chemistry is sound. Scaling to military or commercial capacities, and economics, have been found wanting. There's not much in the energy situation which gives me much hope. This remains among the very few bright spots, despite 50+ years of less-than-overwhelming progress. (I'd looked at a fair bit of the history and research a few years ago on Reddit, most represented in this search: https://old.reddit.com/r/dredmorbius/search?q=fischer+tropsch&restrict_sr=on https://old.reddit.com/r/dredmorbius/search?q=fischer+tropsc... )
ncmncm 7y ago
The best prospect for the future of clean aviation depends on moving to hydrogen fuel. The appeal of hydrogen arises from its extreme energy-mass density: a kg of hydrogen offers several times the oxidized enthalpy of a kg of kerosene, with zero carbon pollution, so much less fuel would need to be hoisted up to 40,000 feet. Hydrogen-burning aircraft could devote the difference to more payload, or to the same payload with a much lighter airframe and smaller engines. Older aircraft simply could not compete. The hydrogen could power fuel cells for electric drive, or be burned in turbines, or some of both, e.g. turbines for takeoff, fuel cells for cruise. The only problem with hydrogen is that, even liquified, it takes up a lot of space. This demands a change to an architecture with more interior space, such as a lifting body (or just a wider body), to provide room for more tankage. More tankage for carbon fuel would be pointless because the extra weight would displace cargo lifting capacity; anyway, present aircraft have enough range. Liquid hydrogen tankage has become much more practical since the discovery of aerogels. Mass production of aerogel enables practical commercial liquid-hydrogen tankage. Hydrogen for aviation is much more practical than for other modes of transportation, because there is no distribution problem. Hydrogen can be produced anywhere using solar and wind generating systems, operating whenever the sun is out or the wind is blowing. The oxygen also produced, that would otherwise be vented, could also be liquified and and carried on board for cruise at very high altitudes, further improving efficiency. A few airports used by long-haul aircraft, locally supplied, would suffice to bootstrap the industry.

35 points by dnetesn 7y ago

WalterBright 7y ago

The motivation for the 737MAX was it burns 15% less fuel.

gpapilion 7y ago
Fuel saving solutions are always attractive in the industry. Originally it was thought jet engines would fail due to their fuel consumption, but the reduced maintenance requirements made them more attractive.
- WalterBright 7y ago
  Yup. Piston aircraft engines indeed need tons of maintenance. A huge number of moving parts coupled with trying to minimize the weight and maximize the power is the cause. In WW2 the Germans fitted aircraft engines to their tanks, which worked great when the engines ran, but too often they didn't due to battlefield conditions. (Germany was also terribly short of avgas, which crippled those tanks.)
  - newnewpdro 7y ago
    > In WW2 the Germans fitted aircraft engines to their tanks, which worked great when the engines ran, but too often they didn't due to battlefield conditions. (Germany was also terribly short of avgas, which crippled those tanks.) This sounded interesting so I skimmed the tanks mentioned in [0] and only found mention of prototypes exploring use of a turboshaft engine [1] from [2]. [1] explicitly states "none of these was fitted operationally", so I don't get the impression that these ever even encountered battlefield conditions before Panther II was canceled. [0] https://en.wikipedia.org/wiki/German_tanks_in_World_War_II https://en.wikipedia.org/wiki/German_tanks_in_World_War_II [1] https://en.wikipedia.org/wiki/GT_101 https://en.wikipedia.org/wiki/GT_101 [2] https://en.wikipedia.org/wiki/Panther_II_tank#Engine https://en.wikipedia.org/wiki/Panther_II_tank#Engine
    - zabzonk 7y ago
      Don't know about the Germans, but the British used modified aero engines quite extensively in tanks - https://www.wikiwand.com/en/Rolls-Royce_Meteor https://www.wikiwand.com/en/Rolls-Royce_Meteor
      - newnewpdro 7y ago
        That's pretty smart, using de-tuned aviation engines. But unlike what WalterBright is describing, these were appropriately reconfigured to not require high-octane fuel.
      - snovv_crash 7y ago
        Indeed, my grandfather was in one in Italy late in the war. From the stories he told, the crew one time got it up to 40MPH, then the crankshaft snapped.
    - WalterBright 7y ago
      I didn't mean a gas turbine engine, but a piston engine designed for aircraft. (Gas turbines don't run on avgas.) With a quick look I can't find a cite for my claim, just that the British did use Merlin aviation engines in some of their tanks.
      - newnewpdro 7y ago
        I couldn't find mention of anything else aviation-related in the per-tank pages, and the Maybach WWII engines page [0] doesn't speak to it either. Do you have any good references we can check out? [0] https://en.wikipedia.org/wiki/List_of_WWII_Maybach_engines https://en.wikipedia.org/wiki/List_of_WWII_Maybach_engines
        WalterBright 7y ago
        I have a few hundred books on WW2, it's possible I'm mis-remembering it. I am ashamed :-(
  - redis_mlc 7y ago
    > Piston aircraft engines indeed need tons of maintenance. Modern small piston aircraft engines under 250 HP have average TBO of 2,000 hours and can be operated beyond that with oil analysis. That's fine for commercial use, and piston engines only use 1/3 to 1/2 the fuel of jet engines, though that may be because of the use of a propeller. So you trade fuel efficiency for engine maintenance, and I think they'd average out. DC-3 operators can maintain their piston engines just fine with one mechanic. (Large turbofan engines like the 737 MAX uses are basically resurrecting the propeller in terms of moving a large volume of air, rather that relying on only a jet of air.) I don't think there is a lot of data for larger piston engines. 1,000 HP engines and larger in WW2 had issues at the time, but that was 75 years ago. Metallurgy and production methods have improved since then. Also WW2 engines were boosted (supercharged and water/alcohol-injected) and the military didn't care about longevity as airliners do today. For example, the American supercharged P-38 was the fastest fighter of WW2, while the version sold to Britain wasn't, and was a dog. Source: commercially-rated pilot, WW2 student.
    - sgent 7y ago
      I don't know what the data is, but the DHC-8/Q-400 is a fairly popular regional airplane outside the US, and depending on the model goes from 1300 - 5000hp. https://www.pwc.ca/en/products-and-services/products/regional-aviation-engines/pw100-150 https://www.pwc.ca/en/products-and-services/products/regiona...
      - redis_mlc 7y ago
        Both the DHC-8 and Q-400 are turbo-prop (ie. jet-engined) airplanes, not piston.
    - WalterBright 7y ago
      A Lockheed Constellation had 4 × Wright R-3350-DA3 Turbo Compound 18-cylinder supercharged radial engines, 3,250 hp (2,424 kW) each https://en.wikipedia.org/wiki/Lockheed_Constellation https://en.wikipedia.org/wiki/Lockheed_Constellation That's 72(!) cylinders. Then you've got the superchargers, variable pitch propellers, and on and on. It's a bit of a miracle one could get them all running at the same time :-/ BTW, Lindbergh flew the Atlantic on a single engine. He rejected multi-engine designs because the reliability would be halved. He selected the most reliable engine available at the time.
himinlomax 7y ago
Correction, the motivation for the 737MAX was that the Airbus A320neo burns 15% less fuel.
yason 7y ago
They don't seem to burn any fuel at all , as far as I can tell!
- dredmorbius 7y ago
  In-flight fuel consumption was optimised by engineering a short flight profile and substituting bulk fuel consumption on ground following landing.

nradov 7y ago

There are a number of other initiatives underway to reduce greenhouse gas emissions from commercial aviation. Synthetic kerosene can be manufactured using power and heat from renewable energy sources. Electric motors can be used for taxiing so that the turbines only have to be started immediately before takeoff. The electromagnetic catapults used on the latest Navy aircraft carriers can be scaled up to launch redesigned airliners from runways on land with lower accelerations. But it will probably take many years until any of these innovations are widely deployed.

chrisseaton 7y ago
> Electric motors can be used for taxiing so that the turbines only have to be started immediately before takeoff. I thought that this was pointless because the engines needed that time during taxiing to warm up properly anyway? If you moved them to the runway electrically they'd then just need to sit there burning fuel for five minutes to warm up. Naval jet fighters, which launch through steam or electronically and don't need to taxi further than a few metres, still sit there for ages warming up. They don't just turn on and go.
- WalterBright 7y ago
  I know that for piston engine aircraft, it is critical that the engine be properly warmed up before takeoff. Otherwise, the engine would likely stall shortly after liftoff, leading inevitably to a crash. This is a common cause of accidents. I don't know specifically about jet engines, but as the engine is designed to run while hot, and metal expands when hot, I'd be quite surprised if it wasn't necessary to warm them up before full power, too. Drag racing engines will often be warmed up using some sort of electric blanket. Even for your car, it's a bad idea to floor it while the engine is cold.
  - imsofuture 7y ago
    I know that for piston engine aircraft, it is critical that the engine be properly warmed up before takeoff. Otherwise, the engine would likely stall shortly after liftoff, leading inevitably to a crash. This is a common cause of accidents. This is not true. Engine start to takeoff is usually at least a few minutes, but there is no critical temperature factor for the engine (barring extreme heat or cold). It's a lot like a car, you don't want to overly stress by flooring it when cold, before oil is circulating comfortable -- but running for 10s of seconds is plenty to get going.

cgrealy 7y ago

The big win would obviously be electric aircraft, but I doubt we'll see that in my lifetime (barring a massive breakthrough in battery technology). The problem is even the best batteries have a much lower energy density compared with traditional fuels. Also, a battery that weighs 100kg when full weighs pretty much 100kg when empty. Real Engineering did a pretty good video on the topic https://www.youtube.com/watch?v=VNvzZfsC13o https://www.youtube.com/watch?v=VNvzZfsC13o

moltar 7y ago
World's first fully electric commercial aircraft takes flight in Canada https://www.theguardian.com/world/2019/dec/11/worlds-first-fully-electric-commercial-aircraft-takes-flight-in-canada https://www.theguardian.com/world/2019/dec/11/worlds-first-f... Of course far from intercontinental jet, but it’s a start :)
- cgrealy 7y ago
  Did you watch the video I posted? It specifically talks about converting a small aircraft and says you could get "about 20 minutes". Building an actually useful commercial plane (i.e. something along the lines of 737 or A320) is an order of magnitude more difficult, in fact, basically impossible with current battery technology.
  - benhurmarcel 7y ago
    For electric airliners, most promising research centers on hydrogen fuel cells, not batteries. It brings a lot of issues (mainly volume and cooling), but still it's being seriously considered.
    - anovikov 7y ago
      Why not just liquid hydrogen, burned in a jet engine? Yes it has density about 12x lower then kerosene, but specific energy is about 3x higher so for the same fuel volume, we get 4x less range. In fact better than that, because of much lower weight and about 2/3 power ratio of fuel burn to aircraft weight and about 40% of weight of a typical plane being fuel, it being gradually burned during flight... it adds about 11% of range, so like 28% of the kerosene-powered range for the same fuel tank volume. So about 4500-5000km, with added benefit of fantastic takeoff performance (low weight). Enough for cross-USA travel, and non-Arctic cross-Atlantic flights (anywhere in CONUS->Bangor, Maine->Shannon, Ireland->Anywhere in EU)... solves the problem as i see it?

justlexi93 7y ago

It is definitely a good idea. The environment changes and we need to do something about it.

animalnewbie 7y ago

Serious question, pardon my ignorance. How much is the per capita fuel consumption compared to a petrol car? Small steps are good too but I sincerely hope we can spend that effort in safety and perhaps speed. Societies progress as distances get shorter.

jcampbell1 7y ago
Airlines get about 40-60 passenger miles per gallon. Not sure if that answers your question.
- animalnewbie 7y ago
  It does exactly. Thank you. This is 4 times that of a singly occupied car. Probably more effort should go towards car pooling. And maybe electric scooters.
  - zdragnar 7y ago
    That's not outside the range of most hybrids, and even 40 isn't much far off from, say, a kia optima at all freeway miles. Even low efficiency crossover SUV types get at least half, if not better. As the sector transitions to battery over gas, the situation will only continue to improve, as it has been for years. That's not to say that proper incentives for car pooling are bad, but it's also no reason to exclude looking at improving the efficiency of planes- especially since fuel costs are so large a portion of their operating costs.
  - upofadown 7y ago
    That's only a meaningful comparison if you drive across oceans to different continents. People tend to fly much much longer distances than they drive. Supposedly a single long over ocean flight costs something the same as a whole year of driving in terms of carbon emission.
    - maccard 7y ago
      > That's only a meaningful comparison if you drive across oceans to different continents. People tend to fly much much longer distances than they drive. Distance isn't everything, many many flights are avoidable/suitable for alternative modes of transport. This [0] estimates that 18% of flights of adults in the UK are "long haul". 40% were either domestic or short haul in Europe, both of which are replacable by trains. The longest domestic flight in the UK is from Gatwick to Inverness, and takes just under 2 hours, or an 8 hour train journey. [0] https://fullfact.org/economy/do-15-people-take-70-flights/ https://fullfact.org/economy/do-15-people-take-70-flights/ - (Note this was just the first source I found)

gersh 7y ago

It might be better to just capture CO2 from the Ocean or the air, and then use renewable energy to make jet fuel. While the efficiency of the process may not be super high, it will be carbon neutral. See https://www.weforum.org/agenda/2018/02/bill-gates-to-strip-c02-from-air-for-clean-fuel/ https://www.weforum.org/agenda/2018/02/bill-gates-to-strip-c... and https://www.greencarcongress.com/2014/04/20140408-navy.html https://www.greencarcongress.com/2014/04/20140408-navy.html.

tonyedgecombe 7y ago

Aviation looks like the industry least likely to go green to me. I doubt electric planes are ever going to be viable for anything other than a short hop which would be better done by train. Synthetic fuels sounds interesting until you look at how much fuel they consume. The trend is quite obviously in the wrong direction: https://www.statista.com/statistics/655057/fuel-consumption-of-airlines-worldwide/ https://www.statista.com/statistics/655057/fuel-consumption-... It's often quoted as 2% of global emissions, my (admittedly back of the envelope) calculations come out 50% higher without the cost of burning it at high altitude nor refining the fuel nor the infrastructure on the ground to support air travel. My guess is emissions from air travel will continue to rise as the world develops and they will take an increasing share of the total as other sectors decarbonise. This all leads on to political problems, how are you going to convince the poor to reduce their emissions when they see their rich neighbours jetting across the world on holiday.

stingraycharles 7y ago
I think it’s important to look at this from a different angle: sure their requirements are high, and they may not be able to go completely green in a short timeframe, but should we therefor not even attempt it? It’s not difficult to imagine a hybrid system at some point in the near future, and/or other ways of reducing the carbon footprint. Focus on those positive things, rather than “this will never be completely green, so why bother?”
- tonyedgecombe 7y ago
  “this will never be completely green, so why bother?” You are putting words in my mouth, I never said that. The industry has been reducing emissions per mile pretty much since it was founded. Looking at that graph I posted it is having the opposite effect to what we want. Jevon's paradox and all that. My personal solution was to stop flying, I haven't got on a plane for 19 years. I'm not sure that is palatable to most people here though, it certainly isn't to the airline industry.
- jerome-jh 7y ago
  They may reduce the carbon footprint per mile, but the physics of thermal engines imposes hard bound to what can be achieved. The article mentions the delta wing design may save 20% on fuel consumption. However those gains are completely swallowed by the traffic increase which is about +30% every 10 years if I remember correctly. The target for 2050 is completely unrealistic, considering the traffic increase and the long cycles of the aviation industry. It may be achieved with hydrogen, assuming it can be produced in large enough quantities with renewables. "should we therefor not even attempt it?" Oh they certainly want to look as if they were trying to reach there objectives ... for the moment it is business as usual. The production of conventional, kerosene powered planes has never been so high and still increasing.

jamil7 7y ago

Is a large part of this also a political issue? with subsidies and tax breaks on fuel the aviation industry is not really incentivised to innovate and cosumers are not incentivised to seek other modes of transport since flying is often the cheapest and fastest.

belorn 7y ago
Every single mode of transport is subsidized so its hard to say if air transportation is getting more or less incentives. Using Swedish numbers and some estimates. Tax on car owners only pay around 1/3 of the road network. The ticket price on train, according to a person working in that space, said that the ticket paid about 2/3 of the costs that the train company paid for any given trip. The train network also get infusions from time to time by the government, and stations are supported/built using local taxes and fees. Boats get tax breaks on fuel, and ports are usually subsidized when built. There might also be subsidizes involved in ice breaking, cleaning and management of the waters and channels around ports. Planes get tax breaks on fuel, and airports are subsidized when built. Out of those, I would guess that the train system is the least subsidized model but I have nothing to actually support that claim beyond a gut feeling. I would like to see a good summarize of what each sector get and where the money comes from.
- jamil7 7y ago
  Thanks for the detailed info. I honestly don't know the details well enough and hence framed my comment as a bit of an open question. This makes me wonder, in Germany it is possible to get a decently priced domestic train ticket or at least a comparable price to a domestic flight but one needs to book far in advance whereas this isn't the case when booking a flight. If it's not subsidies and taxes what is making train travel so uncompetitive with flying?
  - Leherenn 7y ago
    Infrastructure costs, they are absolutely massive compared to what you need for planes.
- 7y ago

dredmorbius 7y ago

Aviation more than any earlier transport mode is fundamentally based on high power-to-output engines and fuels with both high volumetric and weight energy density. It's little surprise that within years of practicable petrol-fueled automobile engines, powered flight became a reality. Within a quarter century, propeller-driven craft had all but achieved their design zenith (the DC-3), and jet propulsion was being deployed within four decades. Aerodynamics, controls, navigation, traffic control, and business systems around passenger, freight, and parcel delivery have accounted for most advances since. Notable among failures have been both supersonic and lighter-than-air craft. Both see limited (mostly military) use. Commercial viability has been lacking. The alternatives to the present subsonic, large-scale, heavier-than-air, fuel-based transports are ... limited. Electric propulsion solves the power-to-weight problem (electric motors are remarkably poweful and efficient), but not the energy-storage problem. Batteries have at best about 1/10th the energy storage by weight of hydrocarbon fuels. Supersonic flight simply requires too much fuel, on top of other environmental concerns: noise, high-altitude pollution. Unscheduled subsonic jets achieve better flexibility than supersonic scheduled flights for those needing (and able to affort) it. Lighter-than-air craft seem to fragile, finicky, dangerous, and expensive to operate. Changed air travel economics might address that last, but the fact that ultra-lightweight, tremendously voluminous structures capable of lifting only modest cargos and subject to extreme peril from high winds and inclement weather ... does not seem promising. (Though Germany did operate international Zeppelin service for much of the 1930s. I may be overly pessimistic.) There are alternatives to fossil hydrocarbon fuels. Most have extreme shortcomings. Hydrogen as an energy carrier is possible but has remarkably low volumetric energy density, as well as poor storage and handling capabilities. It's unlikely to be utilised. Biofuels can be effectively precise analogues of present avgas (petrol) and jet (kerosene) fuels. The problem is that even the small fraction of energy demand represented by aviation fuel use is beyond the capabilities of agriculture to produce. In 2014, Boeing touted "the biggest breakthrough that there is out there" in biofuels. At 75 gal/acre-yr (mean of reported production) and 16 billion gallons of aviation fuel consumption in the US (2013 BTS RITA estimate), 21.3 million acres would have to be under cultivation. That's about 330,000 mile2, or a region 577 miles on a side. On the map, you could start in Shreveport, LA, head west to Hobbs, NM, north to Denver, CO, east to St. Joseph, MO, and south to Shreveport again, traversing seven states and completely bounding two (Kansas and Oklahoma). https://old.reddit.com/r/dredmorbius/comments/1wo2hl/boeings_biofuel_breakthrough_less_than/ https://old.reddit.com/r/dredmorbius/comments/1wo2hl/boeings... The one possible alternative I've seen, and one which isn't obviously* impractical, is fuel synthesis: creating the liquid hydrocarbon fuels powered flight is dependent on from non-fossil sources. The notion's not new -- it strongly resembles the coal-to-liquid-fuels process employed in Germany during WWII, and in South Africa since the 1950s. The notion was suggested by M. King Hubbert in 1964 (http://www.hubbertpeak.com/hubbert/EnergyResources.pdf http://www.hubbertpeak.com/hubbert/EnergyResources.pdf (PDF) p. 139), and has been explored at the Brookhaven National Laboratory, M.I.T., US Naval Research Laboratory, and a Google X Projects startup (since folded), over the past five decades. The chemistry is sound. Scaling to military or commercial capacities, and economics, have been found wanting. There's not much in the energy situation which gives me much hope. This remains among the very few bright spots, despite 50+ years of less-than-overwhelming progress. (I'd looked at a fair bit of the history and research a few years ago on Reddit, most represented in this search: https://old.reddit.com/r/dredmorbius/search?q=fischer+tropsch&restrict_sr=on https://old.reddit.com/r/dredmorbius/search?q=fischer+tropsc... )

ncmncm 7y ago

The best prospect for the future of clean aviation depends on moving to hydrogen fuel. The appeal of hydrogen arises from its extreme energy-mass density: a kg of hydrogen offers several times the oxidized enthalpy of a kg of kerosene, with zero carbon pollution, so much less fuel would need to be hoisted up to 40,000 feet. Hydrogen-burning aircraft could devote the difference to more payload, or to the same payload with a much lighter airframe and smaller engines. Older aircraft simply could not compete. The hydrogen could power fuel cells for electric drive, or be burned in turbines, or some of both, e.g. turbines for takeoff, fuel cells for cruise. The only problem with hydrogen is that, even liquified, it takes up a lot of space. This demands a change to an architecture with more interior space, such as a lifting body (or just a wider body), to provide room for more tankage. More tankage for carbon fuel would be pointless because the extra weight would displace cargo lifting capacity; anyway, present aircraft have enough range. Liquid hydrogen tankage has become much more practical since the discovery of aerogels. Mass production of aerogel enables practical commercial liquid-hydrogen tankage. Hydrogen for aviation is much more practical than for other modes of transportation, because there is no distribution problem. Hydrogen can be produced anywhere using solar and wind generating systems, operating whenever the sun is out or the wind is blowing. The oxygen also produced, that would otherwise be vented, could also be liquified and and carried on board for cruise at very high altitudes, further improving efficiency. A few airports used by long-haul aircraft, locally supplied, would suffice to bootstrap the industry.