Aviation industry tries to go green
phys.org
phys.org
The trend is quite obviously in the wrong direction: 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.
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?”
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.
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.
The heavier a plane is, the more fuel it needs. But fuel has weight, too, which means you need even more fuel! Reducing fuel consumption translates to exponential operational savings.This is also why planes with batteries are problematic: batteries store much less energy per kg than fossil fuel. I doubt that the increased efficiency in going electric is going to offset the extra consumption due to the increased weight.
Even if they reduce emissions by 50% by 2050, flying will still produce ~5 more times CO2 than taking the train. And guess, what? The railway industry is also working to reduce emissions and with trains there's just so much more you can improve with much less investment.
By 2050, aviation might very well produce ~20 times the emissions of railways, even though it has halved its emissions.So, with our current knowledge, the best way to reduce aviation emissions is...taking the train.
I live in the UK and caught a train to London then a Eurotunnel train to Paris and it was probably quicker and easier when you account for time spent in departures and going through airport security.
It seems that the cost of an additional passenger on a train is almost zero, so why do trains not attempt to reduce per-ticket prices to increase capacity and become more competitive against low cost airlines?
In your example, the train from London to Paris in my experience has almost always been nearly triple the cost of a flight.
It is. But the cost of the first passenger is massive.
Think of all these rails (and the terrain under it you have to pay a hefty price for), all the bridges etc.
You mention the Paris-London train, just the tunnel did cost $21 billions, add the high speed rails before and after it and you are probably at close to $40 billions in infrastructure before the first train can do the trip.
Trains are orders of magnitude greener than planes, but unless you massively tax planes, or massively subsidize trains, they'll always be more expensive than planes.
The east coast is already covered by an excellent train line. That line could be made faster to be more competitive but it already handles far more passengers than air.
Now let’s look at some other popular routes.
Chicago to LA? 2,000 miles. That would take around 10 hours nonstop on the fastest high speed train. Make that even worse for New York to LA, and you can bundle in destinations like Denver, Las Vegas, Seattle, San Francisco, etc into those long distance routes that simply don’t make sense from an eastern city.
How about popular vacation routes, like Boston to Orlando? 1300 miles, so that’s at least 7 hours assuming the train never stops.
The new-ish Amtrak CEO is correct to focus on intercity routes that are between closely packed cities. The US does need more train routes similar to the Hiawatha Service or Northwest Corridor and they need to go faster.
But even this type of buildout will be limited when you consider the size of cities in the US. If you fly from Indianapolis to Pittsburgh you’ll be on a 50 seat jet or you’ll transfer to somewhere like Detroit. What sort of train carrying 50 people will be anywhere close to economically viable?
Sure, we could use some rail connection between something like Houston and Dallas but then those passengers will also have to rent a car or use a taxi frequently at their destination. At that point you are competing with individual driving.
Back to the Hiawatha Service, if I’ve got two people in my party it’d be cheaper to drive and possibly even Uber the entire way if I had four people in my party.
The leader in high speed rail, China, has nearly ideal conditions to work with. They have huge populations concentrated in dense urban areas with low car ownership. They have almost all major cities concentrated on on one coast. They have low labor costs and a centralized government structure that doesn’t have to consider property rights or environmental impact when building out infrastructure.
I'm not even considering the delays because of weather, technical, etc.
Trains don't have as much potential for being delayed (train schedules have a lot less variance because the track is pretty much fixed and the timetables too), and they take you right from the city center to the destination's city center.
Comfort doesn't compare either, you don't have to pay extra so you can actually sit down like a human being and retain your dignity.
And if the trains were electric instead of diesel like they are in the US, I wouldn't be surprised if it was also cheaper than flying.
As a counterexample to China, Switzerland has an amazing rail network. Trains going from anywhere to anywhere, comfortably, reliably, quickly, and multiple times a day. And yet, the country is very mountainous, and has lots and lots of smaller cities.
That means they’d probably cost more than commercial jets, because the crew is being paid for a longer period of time.
It also seems like jets can fly in far more inclement weather than blimps, but I’m no expert in that.
Also, the Hindenburg went at 100+ km/h in the 30's, we're already using many kinds of vehicles that go at similar speeds and don't cost more than commercial jets. Hopefully we could beat the 30's technology in speed, that's just the lower bound.
edit: also, correcting my terminology, I should have talked about "rigid airships" instead of "blimps" apparently - blimps are like balloons with little engines, and the Hindenburg & modern credible air travel blimpy looking designs are "rigid airships".
In a world in which heavier-than-air flight becomes less affordable, there might be some niche uses. In general, my sense is that lighter-than-air craft are simply too close to the limits of potential engineering and materials.
The question is not "how can we keep our air travel habits?" after all.
Air travel has been transformational, fast, reasonably convenient, and cheap. It's also been an accident of geohistory, in many regards. The coming / current fuels transition will raise the costs of many things, transport included, and air transport most especially. One of the lessons of history is that the consequences of costs falling, as many have through the industrial revolutions, have subtle and profound influences, mostly unanticipated by those who first started down specific technical pathways.
My sense is that rising costs will operate similarly. We'll have much of the knowledge and technical understanding achieved over the past 200 years, but we'll see costs rising or capabilities falling in many domains. And that will have profound and subtle ripple effects.
Small aircraft may be possible, and perhaps slow airships, but the era of mass bulk human transcontinental transport, quite probably not so much. Or possible, but at prices at some multiple of today: 2x, 10x, 100x, 1,000x. Or transoceanic travel of 1-3 days, rather than 6-18 hours.
Getting back to airships: there are only so many materials available. An airship requires some sort of frame, some sort of lifting gas containment, motors, an energy source, and passenger or cargo facilities. Even excluding hydrogen as a lifting gas, they've proved expensive and dangerous. Vehicles such as LEMV / Airlander 10 are not strictly rigid, but is in part supported by pneumatic pressure. The craft itself was written off after coming loose from moorings in high winds.
Top speeds will be on the order of 160 - 240 kph, rather than 1,000 kph for jet aircraft. Flight levels will likely be < 1,000 meter -- Hindenberg cruised at 300m, though often much lower. That's well into weather, which airships handle poorly. LEMV had a requirement to operate to 20,000 ft (6,000 meters), though it only reached 3,500 ft (1,000m) in testing.
I've watched and read breathless accounts of an airship revival for decades. To date they've failed to meet promised capabilities.
Train is better for short hops between highly populated areas, but not so much between islands with 10k peoples. Many short flights are between places where only other option is car + many hours on ferry, and for them an electric plane would be perfect
Why we've to damage our planet so much just to see some locations?
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.theguardian.com/world/2019/dec/11/worlds-first-f...
Of course far from intercontinental jet, but it’s a start :)
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.
tbh, I'm not sure exactly how hydrogen combustion compares to hydrocarbon combustion in terms of environmental harm. I suspect it's still a lot cleaner overall. a lot of people think hydrogen combustion is totally clean and just creates water as exhaust, so I like to point this out.
There are were more rockets like this (kerolox for first stage & hydrolox for upper stage), like for example Atlas 5. Other rockets used kerolox boosters, such as for example Energia & IIRc some of the new Chinese rockets.
”Liquid hydrogen was only one half as dense as kerosene. This density ratio indicated that, for the necessary propellant, an LH2 tank design would require a far larger tank volume than required for RP-1. The size would create unacceptable penalties in tank weight and aerodynamic design. So, RP-1 became the fuel.”
(RP-1 And Jet A are almost identical.)
In applications where cross-sectional area is an exponential factor (read: atmospheric flight), volume is significant!
Why batteries over synthetic jet fuel? Hydrocarbons are great for this purpose. The problem is where the carbon is coming from.
Burn jet fuel made from atmospheric carbon and you solve the problem overnight.
If it can solve the problem, I'm keen to learn more.
The announcements (and references) made this sound like entirely novel technology. In truth it dates in part to WWII and German production of fuel from coal (also practiced by South Africa), and was suggested as an alternative to fossil fuel consumption in the 1960s by M. King Hubbert (of Peak Oil fame) and the Brookhaven National Laboratory.
There's been substantial additional work at Brookhaven, M.I.T., USNRL, and a (failed) Google X-Project attempt.
The fundamental chemistry is sound, scaling and costs are the principle concerns. Costs are strongly influenced by the grotesque underpricing of fossil fuels, by a factor of millions, based on the geological processes of formation. Account properly for those, and the economics straighten out.
(Though much of the present world turns out to be much more expensive than we'd accounted for.)
Numerous posts and references at my subreddit:
https://old.reddit.com/r/dredmorbius/search?q=fischer-tropsc...
Specifically, history of research to the 1960s:
https://old.reddit.com/r/dredmorbius/comments/28nqoz/electri...
Compilation of papers from Heather Willauer et al:
https://old.reddit.com/r/dredmorbius/comments/22k71x/us_navy...
Problem is it used a lot more energy than pumping oil out of the ground. In theory we can get the energy from solar or something, but still it needs a lot of energy.
Good news it the process as been successfully used on the scale of providing fuel for entry countries. Thus we know it scales to something larger. There are other options that look promising in a test tube but don't seem to work at larger scales yet.
Electric offers dramatic reductions in engine noise and maintenance, along with far more reliability/safety. I can see that being a selling point to some aviation execs, Norway has been trying it out, hope it works for them.
> Also, a battery that weighs 100kg when full weighs pretty much 100kg when empty.
Offtopic: The discussion on that fact is an excellent question/answer to read on SE: https://physics.stackexchange.com/questions/34421/does-the-m...
But that was interesting to read... thanks!
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.
The infrastructure required for trains, as well as the maintenance of those tens thousands of miles of tracks have to dwarf whatever tax break planes get on fuel.
Plus airports scale much better than train stations, once it's built you're automatically linked by the most efficient route to everywhere else in the world.
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
But unlike what WalterBright is describing, these were appropriately reconfigured to not require high-octane fuel.
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.
Do you have any good references we can check out?
[0] https://en.wikipedia.org/wiki/List_of_WWII_Maybach_engines
-- "Stuka Pilot" by Hans Rudel, pg. 50Modern 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.
https://www.pwc.ca/en/products-and-services/products/regiona...
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.
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.
Supposedly a single long over ocean flight costs something the same as a whole year of driving in terms of carbon emission.
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/ - (Note this was just the first source I found)
Of course an ICE car doesn't get the same milage as that aircraft, but it's just a factor of 2-3 off. And then there's the difference in emissions and between a jet engine with its jet fuel vs the ICE car. For someone like me, even if I was driving to work, that single vacation would be a significant contribution to my travel CO2 footprint.
[1]: https://www.airmilescalculator.com/distance/osl-to-jfk/
How do you get that? A normal modern car does 5.5 L/100km (~40 mpg) nowadays.
That still isn't 4x though. You can find SUVs that get 4x worse, but they are generally heavy duty trucks doing things that cars cannot do. Per useful mass moved they do better than anything else.
I think it might be better to compare in terms of "passenger mile per unit of greenhouse effect" but then how do you even get to agreement on how to measure the greenhouse effect...
In terms of CO2 true synfuels would be clean in so far as the CO2 would have been captured earlier. The only feasible way to do this would be biomass and the synfuel would either be derived directly from a plant-based source or reuse CO2 captured from terrestrial biomass burning methanize H2 from an electrolysis plant (that would typically be run as an opportunistic sink for intermittent renewable electricity).
But it will probably take many years until any of these innovations are widely deployed.
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.
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.
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.
He said not properly warming up the piston engine meant that there was cold oil still in the reservoir, and sucking that into the engine would cause it to stall, usually right after takeoff, causing many accidents.
I've read about it in the paper myself a couple times, the report goes like the engine stalled right after takeoff and the airplane crashed. Didn't warm the engine up.
I can see this in my car. If the engine isn't warmed up, pulling into traffic often meant it would stall right in the middle of the lane I'm trying to cross, leaving me vulnerable to being rammed.
Now, if you're in an airplane overloaded with gas and bombs (and combat missions are always overloading the airplanes), you're going to make darn sure the engines are all at normal operating temperature before you start the roll. And you're going to fly right through the smoke of the previous guy whose engine hiccuped after he was committed.
I've flown in a Cessna a few times, and the pilot will always trundle out to the runway, set the brakes, and run it at full power making sure it's warmed up and both magnetos are working. I'd get out if he didn't :-)
I don't know if it was implemented generally.
https://www.treehugger.com/aviation/airports-can-cut-noise-p...
Sounds like your car is broken if that really happens.
A functioning car engine won't stall when pulling into traffic because of cold oil. Surely it will just wear out horribly and its lifespan will shorten to a fraction if you do that regularly but today's oils still work pretty good when cold and there will be some circulation to prevent pistons from grinding themselves stuck or bearings from mushing themselves into powder.
I could imagine you could get your engine stuck for real in very cold weather if you cold-start the car and floor it right away before there really is any practical oil circulation at all. Even if you really try this it's still more likely you'll wear out bearings first and get served a knocking engine rather than a stall or stuck pistons.
But your wording by "often meant" suggests that this stall would happen regularly if you did it with a cold engine so unless you live right next to a highway on-ramp your car probably had something else broken, causing it to stall.
Yeah, it happens with every carburetor car I've ever had, less so with fuel injected ones. It takes about a half mile of driving to where it won't happen.
It has higher viscosity, meaning it takes more energy to move it out of the way. As it warms up, its lubricating power decreases, but not too much, and its viscosity decreases, enabling better engine efficency. A cold engine is less efficient, but only for a short time, until it heats up.
Oil too thick to pump rarely happens in normal life. In arctic and subarctic conditions people use electric heaters to keep the oil thin enough to pump.
By this logic a solid would be the best lubrication, which it clearly isn’t.
The parts in jet engines almost all have cycle limits, so it's a big deal.
You'll notice that skydive operators reposition their Cessna Caravans using a tug - they never turn on and taxi around without a load.
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.
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...
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 (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+tropsc... )