It's a crowded market and they are targeting planes that can replace jets for medium and longer distance. Which at least short term won't be electric. That would require breakthroughs in fuel cells that I think they are starting to conclude are a combination of expensive and impractical. And there's the whole notion that green hydrogen is more of a promise than a reality right now.
Battery electric makes a lot of sense for smaller planes and distances. But that's a very dynamic market with a lot of players and not a lot of clear added value for Rolls-Royce. Also, it's very different from their current market which is basically focused on jet engines for big planes. That stuff is just way out of their comfort zone.
IMHO, the commuter plane market will change quite dramatically in the next decade. Basically battery electric is not a drop in replacement for those planes. But instead that market will start shifting to much simpler and smaller planes that are dirt cheap to manufacture and operate. Basically the main cost is the battery and the maintenance. Add autonomous flight or at least vastly simpler operations to the mix and pilot cost goes down as well.
That enables flying with much more but smaller planes. Which in turn enables flying to and from much smaller airfields closer to where people want to go. With vtol, potentially even inside cities. Long term commuter jets (with fuel cells or sustainable fuel) won't be able to compete on cost for short hops.
I think you are too optimistic. While we can do everything you state, I don't think there is enough demand. Most people don't want to be a pilot these days, the exceptions are not enough to support all the R&D needed to get there. Likewise, the other niches where people use airplanes for short flights are not large enough to support the R&D needed to get there. So small flights will be stuck with 1960s airplanes they keep rebuilding, with a few small manufactures doing small refinements on designs that are decades old, as a major redesign is just too expensive. Once in a while some rich person will finance a new airplane, but it will always be a money losing investment and so only flying enthusiasts will spend that money.
> I think you are too optimistic. While we can do everything you state, I don't think there is enough demand. Most people don't want to be a pilot these days, the exceptions are not enough to support all the R&D needed to get there.
IIRC, there isn't even enough demand there to switch away from leaded fuel.
Agreed, GP is way too optimistic. Airplane manufacturing peaked in the late 1970s with over 18,000 planes manufactured a year. These days the numbers are under 3,000 planes a year!
Switching to a new power source isn't going to change the fundamental economics of airplane manufacturing. There just isn't enough demand to reach any kind of scale and it's not the gas prices - manufacturing collapsed to its lowest point in the early 1990s before gas prices went out of control.
Autonomous flight would be the game changer. The problem with small planes is that you're splitting the pilot & FO salaries across fewer people. If you're not doing that then 20 person flights become a lot more economical.
> people don't want to be a pilot these days, the exceptions are not enough to support all the R&D needed to get there
There is a massive market for short-hop flights. They're just difficult to do at a good price, at scale, with human pilots.
Autonomous short-hop air travel, especially when demand is periodic or occasional, ably complements or even beats rail and autonomous cars in many real-world scenarios.
Fuel weight for liquid fuel at start of flight: 10x
Fuel weight for liquid fuel at end of flight: 3x
Fuel weight for battery at start of flight: 100x
Fuel weight for battery at end of flight: 100x
Batteries are not a great idea for a planes primary energy source. Liquid fueled planes get lighter and more efficient as they fly, a battery plane starts with a much larger and heavier fuel load and carries it the whole trip. Not only that, battery costs a lot more than fuel tanks.
>Liquid fueled planes get lighter and more efficient as they fly, a battery plane starts with a much larger and heavier fuel load and carries it the whole trip
I saw a concept once that had the plane drop the big battery after takeoff (maybe after reaching cruising altitude too) and let the battery fly back to the airport autonomously. Then it doesn't have to carry that dead weight for the entire trip.
But, just like the promise of extended range batteries you could tow behind your EV for long trips, it's probably not real-world feasible.
At least in theory the battery could be used to recover some of the energy on descent (similar to regenerative braking, but with the spinning propeller instead of wheels). No idea if that’s at all efficient or if anyone experimented with this though.
I agree, we should limit flight to exclusively across large oceans. And replace flights over land with more practical low carbon options like high speed trains.
Lower pilot costs are unlikely any time soon. The FAA might eventually allow single pilot operation for some cargo flights, but it's just not going to happen for passenger airliners larger than an air taxi. The routine flying operations can be automated to an extent, but nothing on the horizon will allow for automated failure management. Two experienced pilots are the bare minimum to handle the workload of major in-flight emergencies.
Where do you think the term autopilot came from? ;)
Smaller planes means more crowded airspace. I bet the permits will be the biggest obstacle. How would you price these? It would be hilarious if small planes took over instead of high speed rail. I could see cheaper helicopters being popular.
Airspace is used very inefficiently right now. With today's tech it's ridiculous we're still using primarily human vision for collision avoidance in most conditions, and in instrument conditions, spacing is typically 3nm.
If you mostly have maneuverable VTOLs or even with more automated systems on traditional planes, you could safely bring down that spacing considerably. Imagine if we required cars on the highway to keep even a 1 mile spacing/following distance and then complained about highway congestion.
I mean learning to fly a plane is about the price of a car and the rental price is ~200/hr. You can use it really for recreational purposes only because it can only transit between certain places & it seats 2 people. That really puts it into the expensive hobby category.
If you had autopilot remove the need to learn to fly the thing and provide for increased density of air space + figure out how to let aviation vehicles takeoff and land more flexibly, it would become the commute option of choice for more people (it would still be quite pricy due to fuel costs but you’d see way more of them)
Oh, wouldn't it be hi· lar· i· ous to see 250 gCO2eq/km/person domestic flights overtake 4 gCO2eq/km/person rail... and the numbers for helicopters are even worse!
I really wonder if a mixed approach isn't best. Make the planes like trains, where the propellors would be electric motors, while there's a generator in the fuselage running on AVFUEL it was already going to burn in a jet engine. Reduced complexity, centralized weight, possibly modular system where bigger loads can be possible with a generator swap for more output and propellor swap for more bite.
I'm sure some level of batteries would be required for safety if the generator dies mid flight, but a load of emergency batteries is much smaller than a load of main fuel cell batteries.
That type of series hybrid architecture works well in locomotives where weight isn't much of an issue but it's totally unsuitable for aircraft. The necessary generator hardware is too heavy, and it loses a lot of efficiency compared to a direct mechanical connection.
Some sort of parallel hybrid architecture is more likely for short to medium haul airliners. They will use somewhat smaller turbine engines for cruise, augmented by battery powered electric motors for takeoff (or emergencies).
Turboprops that is turbine driven propellers(also turbines produce some trust) are very efficient. Better than generators you could use. And they are also simple for power produced.
Only down side really is that the optimal speed is quite a bit lower than jets.
When I worked in London a lot of weekly commuters flew rather than to the train from Scotland, or even Manchester given the absurd peak time train fares even though flying was usually slower on that route.
These commuter trips definitely won’t be replaced with small planes since capacity at London airports is too constrained.
You assume that you would need big airports. The UK is full of smaller airports. And more could be built if there is demand. Noise and pollution are much less of a factor with electrical planes. And with vtols, any open space or roof potentially qualifies as a spot where you can land. Most of the constraints with current aviation don't really apply here.
Batteries are heavy. Teslas are very heavy cars. Aircraft are extraordinary light, compared to ground-based vehicles. Even in flight, large aircraft will burn a lot of their fuel during ascent. Electric powered aircraft get to drag around the heavy used batteries until recharge. And then you have to figure out how to refuel. Until a significant change in battery density, electric planes aren't going to be a thing.
A luxury car usually weighs more due to higher quality materials, larger displacement, more overall modules and wiring. Tesla is an ecobox made with cheap materials so majority of its weight is the battery.
Sure, when you're comparing them to German tanks, they look pretty normal weight. How about a Kia? The K5 is comparable to a model 3, if not as nice, and it maxes out at 3,534 lbs
>Even in flight, large aircraft will burn a lot of their fuel during ascent.
I've been wondering if this offers any escape. Suppose that you have a power supply from the ground during the initial acceleration, and the final cruising velocity is not much higher. Or just build a huge ramp.
It sounds like a joke at first, but it might not be impossible. You just need some kind of reverse linear induction motor that doesn't require much weight on the plane side. Perhaps the fuselage is the magnet? If the takeoff acceleration is 2g, you need a 1 km ramp. The varying lift of the wings will be an obstacle, though this might be manageable with flaps. Of course, a 2g takeoff would be a dramatic experience for the passengers.
This principle is already in use in "Ski-jump" aircraft carriers[0] like the British and Chinese use, compared to the catapult operated American carriers. The problem is it isn't remotely high enough. It does have an effect on take off distance, so for that short amount would help for fuel efficiency, but then you still have +30,000ft to climb. 737's often cruise at 30-40k feet, as the air is thinner up there so there's less drag and you have better fuel efficiency. Even if you launched airplanes off the tallest structure ever built (Burj Khalifa, 2,700ft), you'd still have the majority of the climb ahead of you. Planes go high.
My non-credible idea would be to just use an Apple-style magsafe charger on the back of the airplane that disconnects midair at 30,000ft and falls on the helpless people below.
It's not takeoff that consumes a lot of fuel, it's climbing to cruising altitude. You're not going to get much savings with a launch catapult. A catapult really only helps with shortening the runway distances required to take off (e.g. off an aircraft carrier).
If you're going to try and get an aircraft to cruising altitude without using its own energy, surely the easiest concept is with a tug aircraft towing to altitude. Hell, there's even fairly speculative concepts like Magpie envisaging a series of tows.
>Until a significant change in battery density, electric planes aren't going to be a thing.
There's a big caveat there though. Current aircraft engines are extremely expensive to operate and maintain, regardless of fuel costs. Even a simple GA piston engine would cost more to operate than a small commercial EV aircraft's motors. Replacing turbines with electric motors will provide cost savings that actually make small commuter flights economical again. Kerosene and jet engines aren't going anywhere for the long haul flights. But the future for electric aviation is in the sub 300 mile regional commuter market, where it's faster than a train and has the simplicity of catching a bus.
Sub 300 miles the train should be faster door to door. Trains a better able to get into the middle of a city - airports both take a lot of space and are noisy so they get pushed to the edge of the city. Trains are also better able to integrate with a public transport system so they are easy to get to. Trains don't have the silly security lines (normally - though planes don't need them either). Trains also don't have large economic benefits from every seat full, so they can better handle someone making a last minute decision to go.
Note that I said should above. The reality is North America has terrible train service, and management (congress!) doesn't care: so airplanes end up better despite all reasons they are worse for short trips.
I struggle to conceive of a green future for aviation. I'm not saying we can't have planes, we absolutely should and for many applications they are the only answer: but high speed rail could offer a lot of what airlines currently do at significantly lower cost to both passengers and to the environment, and with less need for such extensive and radical safety features as are required for aircraft.
But just like, reading this comments about everything from batteries to from-ground power sources for ascent to dragging dead batteries after use... like, what if we just flew less? Yes for international travel that needs to happen at speed, a plane is basically the best option. But for... basically everything else, what if we just sacrificed some convenience to not be dumping industrial amounts of waste into the atmosphere?
I'm reminded of how much air quality improved almost worldwide when covid first hit and offices were shut down, offices that, I remind you, continued to function largely just fine after a period of adjustment to remote work. I'm obviously extremely for making all transportation tech more efficient, but an under-discussed element I feel in this is just... doing less shit? Moving fewer people when moving said people isn't really needed? Maybe not growing all the pineapple in one country and shipping it over to a different country to be packaged in plastic and then shipping those all over the world so everyone on the planet has ready access to pineapple, a ton of which is just going to go straight in the garbage because we don't actually need all that damn pineapple?
I would've thought that the main challenge is the density of energy storage. It's hard for a battery to beat kerosene.
The article mentions the industry took a hit during Covid. It's interesting to note that a company like Air Lease Corporation (which buys aircraft and leases it to airlines) basically soldiered on unaffected by the pandemic [https://valustox.com/AL - there's a big dip in profit a year ago, but that's due to the Russian war sanctions].
Plus burnt jet fuel weighs nothing, whereas a spent battery weighs the same as a fully charged one.
It seems there needs to be a radical price difference between electrical and chemical energy before the virtues of the rocket equation are overcome for airline travel.
Considering just how cheap renewable energy can be, even poor efficiency might not matter. If you have process that can be scaled by supply of cheap electric power, it could work even if there is inefficiencies in process and in use.
A spent battery doesn't weight anything if you drop it once it's done; similarly the spent fuel has weight if you have to store the hot gasses after burning.
Turning a fossil fuel based plane carbon free has the same weight problem
> It's interesting to note that a company like Air Lease Corporation basically soldiered on unaffected by the pandemic
Because governments bailed out airlines so that leasing companies wouldn't go default which would then have caused the banks to get into trouble. It's ~180 billion dollars each year just for new airplanes - with ten or fifteen years worth of active contracts, a collapse of the industry would have let the 2008ff crisis look harmless.
The article doesn't mention that, but I'm sure that is the root. Electric planes might make sense for short trips - a handful a enthusiasts fly to work every day (they live at/near an airport and work at/near an airport) instead of driving. A handful of rich people will hire an airplane (or helicopter) to get around cities faster. Some cross water transit is served by short haul flights (ferries are cheap, but boats are slow because of physics). However these are tiny niches and don't cover much air travel. In general air travel doesn't make sense unless your trip is 1500km or more, and the weight of batteries needed for those trips just doesn't make them possible.
We know how to make zero carbon jet fuel today using WWII technology (which has been improved on since, and can be improved). The hard part is cost: synthetic fuel generally costs 4 times as much as pumping oil. (synthetic fuels normally use coal or natural gas for the energy but the process would work with renewables). Still this is very promising: we know from experience it scales up to produce very large volumes of great fuel, and there is reason to think we can make it better/cheaper.
Carbon-neutral generation of hydrocarbon fuels from air with solar energy surplus is the future for applications that need energy density.
There will never be a battery that's anywhere close to 13kwh/kg of gasoline or similar fuels. So the 2nd best thing is to generate emission free gasoline and burn it as cleanly as possible.
I think this may be wise given the rapid pace of development that batteries are still undergoing. Pretty hard to create a design around a battery when you dont even know what chemistry you are working with. And there is a bit of a revolution happening with lower carbon fuels, even though it sucks compared to pure electric, and it still has a lot of work to make sense(https://www.youtube.com/watch?v=OpEB6hCpIGM). I was under the impression though that this was a potentially good area for hydrogen fuel? can anyone confirm?
Summary: Jet-A/A1 kerosene is the current mass fuel for passenger planes in the United States, and its dirty, but the most economical.
Simple biofuels have all sorts of chemical drawbacks that make them a nonstarter. super processed biofuels however, can match the properties of JetA/A1 very closely, but they are very recently developed. Unfortunately, right now, they cost so much energy to develop that they arent environmentally friendly at all, even disregarding the rainforest destruction it provokes (palm oils).
hydrogen may work some day but production is still too costly and it requires a complete redesign of planes and engines, unlike super processed biofuels. it also requires expensive and sensitive cryogenic storage to make energy density work.
e-fuels, or hydrogen composite fuel (liquid methanol, etc) may solve all of the above problems and grow as a more economical option rapidly, but they will still not match the cost performance of JetA/A1 which means increased costs for travel/shipping are unavoidable.
electric is an option with the most uncertainty, but there are already niche use cases that already make more sense than other options. mostly small craft and short flight distances. but that does take a decent chunk out of our current consumption. if battery chemistry keeps moving forward at a rapid pace, this could legitimately replace a lot of the air travel we do, but until those batteries are already coming out of factories, its difficult to design around.
If the development of batteries is so rapid, Rolls Royce not investing in electric engines and doubling down on fuel-burning engines instead could open them up for a book story worthy "disruption".
By the time batteries/electric plane engines suddenly become good enough, Rolls Royce might face themselves in a "why does nobody want our fuel-burning engines anymore" situation that will require multiple years to catch up to electric engine manufacturers. Multiple years of catching up that Rolls Royce might not have at the time they find themselves in the "nobody wants our engines anymore" situation.
We know the laws of physics behind batteries. The theoretical best possible battery (which assumes things like spherical cows) is still very heavy compared to burning liquid fuels.
Yes battery advancement is happening rapidly, but it can only asymptotically approach the limits which are not very good for the purposes of flight.
I believe there as chemists and physicist better qualified than me to tell you what the limits are.
Moving to battery would increase demand for power, so unless we are charging all these new batteries with low or zero carbon would we not just end up with the same issue?
You're just moving the problem from the vehicles to the power generation
No, even if you're charging your batteries with carbon-emitting power plants, those plants are much more efficient than the engine in a car or plane. Internal combustion engines are very impressive technology, but they are constrained by their form factor, and can't possibly extract as much energy from fuel as a large power plant.
In reality, almost every power grid in the world is already cleaner than an internal combustion engine, and rapidly becoming cleaner as more renewable energy is deployed.
Isn't this a better outcome ? Instead of having millions of mobile sources of emissions , you will have few thousand sources of emissions which could be regulated, monitored and modernized.
79% of new energy capacity added in 2022 was clean energy (solar, wind, storage), so yes we can expect that the increased demand for power will mostly be met with low carbon solutions.
Renewable energy is already cheaper to build than coal or gas plants in many places, and it will just continue to scale as the technology improves.
I don't see the issue unless the fuel-powered cars are able to reduce carbon emissions at a faster pace than the energy grid can, which seems doubtful.
In the US on average an EV gets the equivalent of 91mpg. On the dirtiest local grid (MROE) it gets 42mpg, the cleanest (NYUP) is 247mpg. 42 isn't that great but for most driving habits it will eventually come out ahead in carbon emissions.
That's for cars, a plane's lifetime emissions are way more weighted towards fuel.
What are the chances that planes are just not a viable mode of travel in 100 years time? It would be interesting if it only existed for less than 200 years throughout all of human history.
We have to have planes - they are the most effective way of waging war.
The US DoD is rolling out big initiatives to address the "post-fuel" era like technologies that convert captured carbon into jet fuel and micro reactors on bases to power these systems. In 10 years or so the same technology will filter down to commercial aviation and everything will be just fine.
Governments doing whatever it takes and spending any amount to make sure they still have flying vehicles is one thing, but being an economically viable civilian mode of transportation is another.
With existing technology, a truly global rail system is highly tractable, if you're willing to forgo a transatlantic crossing (either EU <-> NA or Africa <-> SA). Other than that, bridges and tunnels already connect three continents: Europe, Asia, and Africa.
The biggest challenges are the Bering Strait, the Darién Gap, and the South-Asia to Australia crossings.
The Bering Strait is shallow (30--50 m) and narrow (85 km) enough that a conventional tunnel similar to the Chunnel should be viable. It's interesting to note that extant sea routes are already quite close to an Alaska-Siberia land crossing, as the Great Circle from the US West Coast runs along the track of the Aleutian Islands. With trains' greater speed, freight transit times might actually benefit.
The Darién Gap is a swamp, jungle, and mountain barrier to a continuous land crossing between North and South America, between Panama and Columbia. Roughly 100km of this is not traversed by any established roadway. Environmental, political, cultural, and economic concerns have barred creation of a vehicle roadway, but at least technologically the region should be amenable to rail.
The ocean between Indonesia and Australia is, as with the Bering Strait, reasonably shallow, though parts of it are exceedingly seismically active. A mix of bridge and tunnel connections is conceivable and there are actually proposals that have been ... floated ... such as here:
"Beijing to Sydney by Train: The Potential Development of a Singapore, Indonesia & Australia Rail Network" (2015)
That leaves the Atlantic as the largest present transport route without a ready option.
Conditions are too rough for a floating bridge, and the ocean is too deep for a conventional tunnel. The option of a submerged floating tunnel, proposed as part of Norway's E39 highway, might offer an opportunity for a continuous rail link between both North America and Europe, and possibly South America and Africa (say, Recife to Freetown or Monrovia). Both would be extraordinarily ambitious and would strain extant technology, but are at least theoretically possible.
Transit times would depend on rail speed.
At 320 kph, a 3,200 km (200 mph, 2,000 mile) transatlantic crossing would be a 10 hour journey, ideal for a night train. A 480 kph (300 mph) speed, fastest present tracked rail, would drop that to 6h 40m. At 970 kph (600 mph), roughly jet airliner cruise speed, 3h 20m.
Advantages over air travel should be greater energy efficiency, elimination of turbulence and weather considerations, possibly greater per-passenger space and luggage allowances, and far more continuous departures and arrivals. Disadvantages would be lack of view, technical risks (including catastrophic system failure), and likely longer transit time. I suspect that maximum tunnel speeds will tend to reflect present train systems, which range from 160 -- 300 kph (100 -- 185 mph).
Transoceanic rail crossings have some history at least in the proposal stage:
I wonder if satellite-based system to use space-based solar power generation and convert to microwaves to beam power to aircraft would work? Store just enough on the plane for take off and emergency landing nearby plus a buffer for in-flight space power. For long flights the plane receives a beam of energy. Everyone would probably die from being cooked but it may work.
Just to put that into perspective: a 747 uses 90 MW peak power during takeoff. And that's the useful power it needs as thrust, so the engines produce quite a bit more than that.
Yeah, microwaves are right out. Lasers, maybe, but lasers that can focus so closely qualify as offensive weapons.
Generally, less-focused lasers, picked up by nighttime solar farms that absorb sunlight directly in the daytime, are a much more likely medium for orbital power than microwaves. Monochromatic light can be converted to electrical power with much higher efficiency than can blackbody solar radiation. Lasers producing no greater intensity than sunlight worry people less than microwave radiation.
“Mid-flight a Boeing 747 uses around 4 litres of jet fuel per second. Therefore given the energy density of jet fuel, approximately 35 MJ/litre, a Boeing 747 consumes energy at a rate of around 140 MW (million watts).
We can then convert this rate of energy consumption into power density, that is the rate of energy consumption per square metre. Typically this is measured in watts per square metre (W/m2 ). A Boeing 747 is 70 by 65 metres. So the power density over this 70 by 65 metre square is approximately 30,000 W/², and of course the power density over the surface area of the plane will be a few times higher, over 100,000 W/m²”
There may be gains there if electric motors are more efficient than jet engines (are they?), but overall, you’d need a lot more power than solar.
I think that density is attainable, but wouldn’t bet on it being practical except, maybe, for military use, and probably not for planes but for ground use (beaming energy to a base in Iraq may be easier than transporting oil there via trucks driving through a war zone)
For powering planes, I guess you’ll have to give up speed. That drastically decreases power need at level flight (the planes that flew around the world on solar energy were slow for a reason)
You also will have to track the plane withyour energy beam as it moves.
I've not heard of sustainable aviation fuel. Is it snake oil? Why wouldn't it just be "sustainable fuel" suitable for trains and automobiles?
And if we simply slowed the world down a little bit I wonder if blimps could take over for a majority of ocean-crossing journeys. Not that it will ever happen.
Trains are, by their nature, very suitable for electrification. As with renewable energy the expense is almost all capital, it's cheaper to run electric trains it's just expensive to build electric railway lines they run on.
Planes are not well suited to electrification. Trainers can reasonably be made electric, as might certain commercial purpose aircraft, but if there will be electric New York to LA passenger flights it won't happen any time soon.
Although the fuel in a Cessna would be AvGas which is basically leaded gasoline, essentially anything you'd pay to fly on has turbine engines running on JetA which is basically kerosene instead. Small local planes, especially in Europe might look like just the Cessna only bigger, but the propellers are spun by a jet turbine, they don't have internal combustion engines.
It's just the same as the non-fossil versions of diesel like HVO100 and similar. Whether this fuel is "sustainable" or "emission free" of course depends on how you see it. It will depend on what the source of the fats used is, and how those were produced, how much and what energy was used in the processing and so on. But at least it's significantly better than regular fossil fuel.
An interesting thing about this is that there has been quite a lot of infrastructure built to create these fuels for road transport in the last decades. So if road transport is electrified but flight isn't, then all those resources could quite easily be redirected to make aircraft fuel instead. If I recall the interview correctly that I heard regarding the flight mentioned below, I think there are some countries that have enough biofuel production (currently for road transport) already, to replace all the aircraft fuel used domestically.
The first commercial transatlantic flight with this type of fuel was just two days ago:
> I've not heard of sustainable aviation fuel. Is it snake oil? Why wouldn't it just be "sustainable fuel" suitable for trains and automobiles?
Planes don't run on the same fuel as trains and automobiles.
The basic idea is pretty simple: it's all hydrocarbons. We traditionally use hydrocarbons grown as plants millions of years ago and stashed in the ground until we dig them up/pump out the ground. We don't put the carbon back in the ground -- it goes into the atmosphere mostly.
"Sustainable" fuels are the same thing except you grow the plants today.
Since plants growing today use carbon from the atmosphere, even when the fuel is burned like traditional fuel, you're not adding much net carbon to the atmosphere.
Everything else is mere details, such as: growing plants today is much more costly than digging up plant material from the Cambrian; the fuel has to have the same energy density as traditional fuels; it has to not gunge up the engine; etc.
They are developing these fuels for Formula1 and the like. Probably won't see them in road vehicles due to cost. But never know. It's likely normal fuels in hybrids or pure electric vehicles will be better (cheaper and lower carbon). For trains overhead electrification would be better.
I'm not sure the fuel itself is that low carbon but the cycle of producing it may be. I'm sure a quick search would reveal they produce slightly less CO2 or something in a suitable engine.
It's a hydrocarbon chain produced from corn and waste fats. Fairly similar to bio fuel for cars. Sustainable trains are nuclear powered.
Blimps are either too slow or can't carry enough cargo. Solving the use of heavy tanker fuel is quietly a massive priority, the naive answer is nuclear, the real world answer isn't clear.
The way it's "sustainable" is that it's not a fossil fuel (well, currently it's 50% fossil fuel, they hope it can be 100% fossil fuel free by 2030), so it's just part of the normal carbon cycle like forest fires and breathing.
IMO it's probably just a stand-in until hydrogen really works.
It's snake oil.
It's renewable is the same sense that cow farts are renewable : if you dedicated the entire arable surface of the planet you could make fuel with it for 5% of our consumption.
Don't get me started on the oil USED to produce this wonderful green fuel.
Readit News
Battery electric makes a lot of sense for smaller planes and distances. But that's a very dynamic market with a lot of players and not a lot of clear added value for Rolls-Royce. Also, it's very different from their current market which is basically focused on jet engines for big planes. That stuff is just way out of their comfort zone.
IMHO, the commuter plane market will change quite dramatically in the next decade. Basically battery electric is not a drop in replacement for those planes. But instead that market will start shifting to much simpler and smaller planes that are dirt cheap to manufacture and operate. Basically the main cost is the battery and the maintenance. Add autonomous flight or at least vastly simpler operations to the mix and pilot cost goes down as well.
That enables flying with much more but smaller planes. Which in turn enables flying to and from much smaller airfields closer to where people want to go. With vtol, potentially even inside cities. Long term commuter jets (with fuel cells or sustainable fuel) won't be able to compete on cost for short hops.
IIRC, there isn't even enough demand there to switch away from leaded fuel.
Switching to a new power source isn't going to change the fundamental economics of airplane manufacturing. There just isn't enough demand to reach any kind of scale and it's not the gas prices - manufacturing collapsed to its lowest point in the early 1990s before gas prices went out of control.
There is a massive market for short-hop flights. They're just difficult to do at a good price, at scale, with human pilots.
Autonomous short-hop air travel, especially when demand is periodic or occasional, ably complements or even beats rail and autonomous cars in many real-world scenarios.
Fuel weight for battery at start of flight: 100x Fuel weight for battery at end of flight: 100x
Batteries are not a great idea for a planes primary energy source. Liquid fueled planes get lighter and more efficient as they fly, a battery plane starts with a much larger and heavier fuel load and carries it the whole trip. Not only that, battery costs a lot more than fuel tanks.
I saw a concept once that had the plane drop the big battery after takeoff (maybe after reaching cruising altitude too) and let the battery fly back to the airport autonomously. Then it doesn't have to carry that dead weight for the entire trip.
But, just like the promise of extended range batteries you could tow behind your EV for long trips, it's probably not real-world feasible.
Smaller planes means more crowded airspace. I bet the permits will be the biggest obstacle. How would you price these? It would be hilarious if small planes took over instead of high speed rail. I could see cheaper helicopters being popular.
If you mostly have maneuverable VTOLs or even with more automated systems on traditional planes, you could safely bring down that spacing considerably. Imagine if we required cars on the highway to keep even a 1 mile spacing/following distance and then complained about highway congestion.
If you had autopilot remove the need to learn to fly the thing and provide for increased density of air space + figure out how to let aviation vehicles takeoff and land more flexibly, it would become the commute option of choice for more people (it would still be quite pricy due to fuel costs but you’d see way more of them)
https://ourworldindata.org/travel-carbon-footprint
I'm sure some level of batteries would be required for safety if the generator dies mid flight, but a load of emergency batteries is much smaller than a load of main fuel cell batteries.
Some sort of parallel hybrid architecture is more likely for short to medium haul airliners. They will use somewhat smaller turbine engines for cruise, augmented by battery powered electric motors for takeoff (or emergencies).
Only down side really is that the optimal speed is quite a bit lower than jets.
These commuter trips definitely won’t be replaced with small planes since capacity at London airports is too constrained.
Maybe SAF provides an answer for these flights, but it would likely be prohibitively expensive.
The solution likely is mandating carbon offset payments for these passengers.
We've already seen a shift to smaller planes. Fleets are replacing 747s with 787s, and the A380 is already out of production.
Sorry, but the 2010s called, and want their naïve techbro optimism back.
Tesla Model S - Curb weight 4,647 lbs Audi A8 - Curb weight 4,751 lbs BMW 7 series - Curb weight 4,244 - 4,848 lbs
Tesla Model 3 - Curb weight 3,627 to 4,072 lbs Audi A4 - Curb weight 3,450 to 3,627 lbs BMW 3 series - 3,582 to 4,010 lbs
I've been wondering if this offers any escape. Suppose that you have a power supply from the ground during the initial acceleration, and the final cruising velocity is not much higher. Or just build a huge ramp.
It sounds like a joke at first, but it might not be impossible. You just need some kind of reverse linear induction motor that doesn't require much weight on the plane side. Perhaps the fuselage is the magnet? If the takeoff acceleration is 2g, you need a 1 km ramp. The varying lift of the wings will be an obstacle, though this might be manageable with flaps. Of course, a 2g takeoff would be a dramatic experience for the passengers.
My non-credible idea would be to just use an Apple-style magsafe charger on the back of the airplane that disconnects midair at 30,000ft and falls on the helpless people below.
[0] https://en.wikipedia.org/wiki/Ski-jump_(aviation)
There's a big caveat there though. Current aircraft engines are extremely expensive to operate and maintain, regardless of fuel costs. Even a simple GA piston engine would cost more to operate than a small commercial EV aircraft's motors. Replacing turbines with electric motors will provide cost savings that actually make small commuter flights economical again. Kerosene and jet engines aren't going anywhere for the long haul flights. But the future for electric aviation is in the sub 300 mile regional commuter market, where it's faster than a train and has the simplicity of catching a bus.
See Eviation Alice for an example: https://www.popularmechanics.com/flight/a41453056/eviation-e...
Today's battery tech is just barely good enough at this point to start becoming useful for these kinds of flight profiles.
Note that I said should above. The reality is North America has terrible train service, and management (congress!) doesn't care: so airplanes end up better despite all reasons they are worse for short trips.
But just like, reading this comments about everything from batteries to from-ground power sources for ascent to dragging dead batteries after use... like, what if we just flew less? Yes for international travel that needs to happen at speed, a plane is basically the best option. But for... basically everything else, what if we just sacrificed some convenience to not be dumping industrial amounts of waste into the atmosphere?
I'm reminded of how much air quality improved almost worldwide when covid first hit and offices were shut down, offices that, I remind you, continued to function largely just fine after a period of adjustment to remote work. I'm obviously extremely for making all transportation tech more efficient, but an under-discussed element I feel in this is just... doing less shit? Moving fewer people when moving said people isn't really needed? Maybe not growing all the pineapple in one country and shipping it over to a different country to be packaged in plastic and then shipping those all over the world so everyone on the planet has ready access to pineapple, a ton of which is just going to go straight in the garbage because we don't actually need all that damn pineapple?
The article mentions the industry took a hit during Covid. It's interesting to note that a company like Air Lease Corporation (which buys aircraft and leases it to airlines) basically soldiered on unaffected by the pandemic [https://valustox.com/AL - there's a big dip in profit a year ago, but that's due to the Russian war sanctions].
It seems there needs to be a radical price difference between electrical and chemical energy before the virtues of the rocket equation are overcome for airline travel.
Turning a fossil fuel based plane carbon free has the same weight problem
A Tesla's battery pack weighs ~3.2 nanograms less when it's fully depleted. Think of the weight savings with a bigger battery pack for a plane! /s
Because governments bailed out airlines so that leasing companies wouldn't go default which would then have caused the banks to get into trouble. It's ~180 billion dollars each year just for new airplanes - with ten or fifteen years worth of active contracts, a collapse of the industry would have let the 2008ff crisis look harmless.
[1] https://www.statista.com/topics/3877/aircraft-leasing/
We know how to make zero carbon jet fuel today using WWII technology (which has been improved on since, and can be improved). The hard part is cost: synthetic fuel generally costs 4 times as much as pumping oil. (synthetic fuels normally use coal or natural gas for the energy but the process would work with renewables). Still this is very promising: we know from experience it scales up to produce very large volumes of great fuel, and there is reason to think we can make it better/cheaper.
There will never be a battery that's anywhere close to 13kwh/kg of gasoline or similar fuels. So the 2nd best thing is to generate emission free gasoline and burn it as cleanly as possible.
Edit: Here is the video i was looking for https://www.youtube.com/watch?v=OpEB6hCpIGM
Summary: Jet-A/A1 kerosene is the current mass fuel for passenger planes in the United States, and its dirty, but the most economical.
Simple biofuels have all sorts of chemical drawbacks that make them a nonstarter. super processed biofuels however, can match the properties of JetA/A1 very closely, but they are very recently developed. Unfortunately, right now, they cost so much energy to develop that they arent environmentally friendly at all, even disregarding the rainforest destruction it provokes (palm oils).
hydrogen may work some day but production is still too costly and it requires a complete redesign of planes and engines, unlike super processed biofuels. it also requires expensive and sensitive cryogenic storage to make energy density work.
e-fuels, or hydrogen composite fuel (liquid methanol, etc) may solve all of the above problems and grow as a more economical option rapidly, but they will still not match the cost performance of JetA/A1 which means increased costs for travel/shipping are unavoidable.
electric is an option with the most uncertainty, but there are already niche use cases that already make more sense than other options. mostly small craft and short flight distances. but that does take a decent chunk out of our current consumption. if battery chemistry keeps moving forward at a rapid pace, this could legitimately replace a lot of the air travel we do, but until those batteries are already coming out of factories, its difficult to design around.
so here we are.
If the development of batteries is so rapid, Rolls Royce not investing in electric engines and doubling down on fuel-burning engines instead could open them up for a book story worthy "disruption".
By the time batteries/electric plane engines suddenly become good enough, Rolls Royce might face themselves in a "why does nobody want our fuel-burning engines anymore" situation that will require multiple years to catch up to electric engine manufacturers. Multiple years of catching up that Rolls Royce might not have at the time they find themselves in the "nobody wants our engines anymore" situation.
Yes battery advancement is happening rapidly, but it can only asymptotically approach the limits which are not very good for the purposes of flight.
I believe there as chemists and physicist better qualified than me to tell you what the limits are.
Deleted Comment
They just look what they need for next few models.
You're just moving the problem from the vehicles to the power generation
In reality, almost every power grid in the world is already cleaner than an internal combustion engine, and rapidly becoming cleaner as more renewable energy is deployed.
Renewable energy is already cheaper to build than coal or gas plants in many places, and it will just continue to scale as the technology improves.
That's for cars, a plane's lifetime emissions are way more weighted towards fuel.
It's not exactly science fiction.
In fact, just last year Airbus completed a flight with their A380 (2nd largest passenger jet in the world) using only biofuels.
The US DoD is rolling out big initiatives to address the "post-fuel" era like technologies that convert captured carbon into jet fuel and micro reactors on bases to power these systems. In 10 years or so the same technology will filter down to commercial aviation and everything will be just fine.
I am actually more optimistic this would happen than people giving up on planes tbh.
With existing technology, a truly global rail system is highly tractable, if you're willing to forgo a transatlantic crossing (either EU <-> NA or Africa <-> SA). Other than that, bridges and tunnels already connect three continents: Europe, Asia, and Africa.
The biggest challenges are the Bering Strait, the Darién Gap, and the South-Asia to Australia crossings.
The Bering Strait is shallow (30--50 m) and narrow (85 km) enough that a conventional tunnel similar to the Chunnel should be viable. It's interesting to note that extant sea routes are already quite close to an Alaska-Siberia land crossing, as the Great Circle from the US West Coast runs along the track of the Aleutian Islands. With trains' greater speed, freight transit times might actually benefit.
The Darién Gap is a swamp, jungle, and mountain barrier to a continuous land crossing between North and South America, between Panama and Columbia. Roughly 100km of this is not traversed by any established roadway. Environmental, political, cultural, and economic concerns have barred creation of a vehicle roadway, but at least technologically the region should be amenable to rail.
The ocean between Indonesia and Australia is, as with the Bering Strait, reasonably shallow, though parts of it are exceedingly seismically active. A mix of bridge and tunnel connections is conceivable and there are actually proposals that have been ... floated ... such as here:
"Beijing to Sydney by Train: The Potential Development of a Singapore, Indonesia & Australia Rail Network" (2015)
<https://www.aseanbriefing.com/news/beijing-to-sydney-by-trai...>
That leaves the Atlantic as the largest present transport route without a ready option.
Conditions are too rough for a floating bridge, and the ocean is too deep for a conventional tunnel. The option of a submerged floating tunnel, proposed as part of Norway's E39 highway, might offer an opportunity for a continuous rail link between both North America and Europe, and possibly South America and Africa (say, Recife to Freetown or Monrovia). Both would be extraordinarily ambitious and would strain extant technology, but are at least theoretically possible.
Transit times would depend on rail speed.
At 320 kph, a 3,200 km (200 mph, 2,000 mile) transatlantic crossing would be a 10 hour journey, ideal for a night train. A 480 kph (300 mph) speed, fastest present tracked rail, would drop that to 6h 40m. At 970 kph (600 mph), roughly jet airliner cruise speed, 3h 20m.
Advantages over air travel should be greater energy efficiency, elimination of turbulence and weather considerations, possibly greater per-passenger space and luggage allowances, and far more continuous departures and arrivals. Disadvantages would be lack of view, technical risks (including catastrophic system failure), and likely longer transit time. I suspect that maximum tunnel speeds will tend to reflect present train systems, which range from 160 -- 300 kph (100 -- 185 mph).
Transoceanic rail crossings have some history at least in the proposal stage:
<https://en.wikipedia.org/wiki/Transatlantic_tunnel>
<https://news.ycombinator.com/item?id=33556153>
Generally, less-focused lasers, picked up by nighttime solar farms that absorb sunlight directly in the daytime, are a much more likely medium for orbital power than microwaves. Monochromatic light can be converted to electrical power with much higher efficiency than can blackbody solar radiation. Lasers producing no greater intensity than sunlight worry people less than microwave radiation.
“Mid-flight a Boeing 747 uses around 4 litres of jet fuel per second. Therefore given the energy density of jet fuel, approximately 35 MJ/litre, a Boeing 747 consumes energy at a rate of around 140 MW (million watts).
We can then convert this rate of energy consumption into power density, that is the rate of energy consumption per square metre. Typically this is measured in watts per square metre (W/m2 ). A Boeing 747 is 70 by 65 metres. So the power density over this 70 by 65 metre square is approximately 30,000 W/², and of course the power density over the surface area of the plane will be a few times higher, over 100,000 W/m²”
There may be gains there if electric motors are more efficient than jet engines (are they?), but overall, you’d need a lot more power than solar.
I think that density is attainable, but wouldn’t bet on it being practical except, maybe, for military use, and probably not for planes but for ground use (beaming energy to a base in Iraq may be easier than transporting oil there via trucks driving through a war zone)
For powering planes, I guess you’ll have to give up speed. That drastically decreases power need at level flight (the planes that flew around the world on solar energy were slow for a reason)
You also will have to track the plane withyour energy beam as it moves.
A320 900 sq m for wings and top of fuselage and elevators. https://aviation.stackexchange.com/questions/54511/what-is-t...
A320 needs 150 G Joule / hour https://www.quora.com/How-many-joules-of-energy-does-it-take... edit: make it 1.5GJ not 150
To make it easy assume 1,000 sq m and 1.5GJ spread over that area 1.5MJ per sq m/hour.
As for power transfer efficiency it may require a few thousand satellites per aircraft if this is any indication. https://www.esa.int/Applications/Technology_Transfer/More_ef...
And if we simply slowed the world down a little bit I wonder if blimps could take over for a majority of ocean-crossing journeys. Not that it will ever happen.
Planes are not well suited to electrification. Trainers can reasonably be made electric, as might certain commercial purpose aircraft, but if there will be electric New York to LA passenger flights it won't happen any time soon.
Although the fuel in a Cessna would be AvGas which is basically leaded gasoline, essentially anything you'd pay to fly on has turbine engines running on JetA which is basically kerosene instead. Small local planes, especially in Europe might look like just the Cessna only bigger, but the propellers are spun by a jet turbine, they don't have internal combustion engines.
An interesting thing about this is that there has been quite a lot of infrastructure built to create these fuels for road transport in the last decades. So if road transport is electrified but flight isn't, then all those resources could quite easily be redirected to make aircraft fuel instead. If I recall the interview correctly that I heard regarding the flight mentioned below, I think there are some countries that have enough biofuel production (currently for road transport) already, to replace all the aircraft fuel used domestically.
The first commercial transatlantic flight with this type of fuel was just two days ago:
https://apnews.com/article/transatlantic-flight-sustainable-...
> Is it snake oil?
While renewable, the worlds entire production of snake oil would only make a small dent in the fuel needs of the airline industry.
Planes don't run on the same fuel as trains and automobiles. The basic idea is pretty simple: it's all hydrocarbons. We traditionally use hydrocarbons grown as plants millions of years ago and stashed in the ground until we dig them up/pump out the ground. We don't put the carbon back in the ground -- it goes into the atmosphere mostly.
"Sustainable" fuels are the same thing except you grow the plants today. Since plants growing today use carbon from the atmosphere, even when the fuel is burned like traditional fuel, you're not adding much net carbon to the atmosphere.
Everything else is mere details, such as: growing plants today is much more costly than digging up plant material from the Cambrian; the fuel has to have the same energy density as traditional fuels; it has to not gunge up the engine; etc.
I'm not sure the fuel itself is that low carbon but the cycle of producing it may be. I'm sure a quick search would reveal they produce slightly less CO2 or something in a suitable engine.
Blimps are either too slow or can't carry enough cargo. Solving the use of heavy tanker fuel is quietly a massive priority, the naive answer is nuclear, the real world answer isn't clear.
IMO it's probably just a stand-in until hydrogen really works.
It's biofuel made from palm oil, algae, tallow, etc.
Don't get me started on the oil USED to produce this wonderful green fuel.
But it might be carbon-neutral... Which might not or might be part of sustainability...