[HN Gopher] Rolls-Royce calls off bets on electric planes, says ...
___________________________________________________________________
Rolls-Royce calls off bets on electric planes, says low-carbon fuel
is future
Author : burkaman
Score : 119 points
Date : 2023-11-29 15:36 UTC (7 hours ago)
(HTM) web link (electrek.co)
(TXT) w3m dump (electrek.co)
| Lord-Jobo wrote:
| 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?
|
| 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.
| samuelstros wrote:
| Your statement sounds like a contradiction.
|
| 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.
| nabla9 wrote:
| Rolls Royce is owned by BMW. BMW does strategic investments
| and R&D for them.
|
| They just look what they need for next few models.
| hgomersall wrote:
| Different Rolls Royce: https://en.wikipedia.org/wiki/Rolls-
| Royce_Holdings
| samuelstros wrote:
| The Rolls Royce company of discussion is not owned by BMW.
| The car brand Rolls Royce is owned by BMW.
| bluGill wrote:
| 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.
| vorticalbox wrote:
| 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
| Vvector wrote:
| Last time I checked, solar and wind power were low-carbon.
| triceratops wrote:
| > so unless we are charging all these new batteries with low
| or zero carbon
|
| It's not exactly science fiction.
| burkaman wrote:
| 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.
| manishsharan wrote:
| 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.
| ssharp wrote:
| 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.
| mjamesaustin wrote:
| 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.
| thinkcontext wrote:
| 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.
| unethical_ban wrote:
| 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.
| denimnerd42 wrote:
| 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.
| handy2000 wrote:
| Do you mean synthetic fuel? Haven't heard of Formula1 being
| interested in biofuel.
| denimnerd42 wrote:
| There's no mention of biofuel in the article. But yes any
| technology designed to reduce the impact of the fuel
| production/use cycle. In F1 it's branded as synthetic fuel
| right? It's like a natural gas derived fuel but could be
| derived from anything the scientists engineers can make
| work. Jet fuel is heavier so starting with an oil derived
| from bio matter might make more sense. Either way something
| designed with less impact than drilling for fuel.
| handy2000 wrote:
| The fuel mentioned in the article -- "sustainable
| aviation fuels, or SAF" -- is biofuel I believe, not
| synthetic fuel.
| denimnerd42 wrote:
| oh gotcha. To me it's all in the same. Some engineered
| alternative that produces less carbon. it's terribly
| semantic though because every fuel today is engineered to
| produce less emissions.
| handy2000 wrote:
| Right, agreed - it's an improvement over what we
| currently use! From what I read E-fuel is very expensive
| to produce, so I was surprised by the possibility of
| airplanes switching to it.
| denimnerd42 wrote:
| Sounds more feasible than electric planes though. That
| never made viable sense to me. At least they could build
| a 737 sized alternative fuel plane today.
| rswskg wrote:
| It's a huge part of the 2026 rule changes.
| handy2000 wrote:
| E-fuel is different from SAF that is described in this
| article. E-fuel is carbon-neutral and SAF is low-carbon
| (made from tallow, algae, etc).
| handy2000 wrote:
| > Is it snake oil?
|
| It's biofuel made from palm oil, algae, tallow, etc.
| alkonaut wrote:
| 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:
|
| 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.
| rswskg wrote:
| 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.
| camgunz wrote:
| 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.
| fcantournet wrote:
| 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.
| robertlagrant wrote:
| Snake oil is at least renewable. Just grow more snakes.
| micromacrofoot wrote:
| not really "sustainable" but "more sustainable"
| Ekaros wrote:
| It probably will not be sustainable...
|
| But it might be carbon-neutral... Which might not or might be
| part of sustainability...
| graphe wrote:
| Hydrogen could be the fuel of the future. Go for the moonshot,
| a space elevator.
| tialaramex wrote:
| 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.
| AshleyGrant wrote:
| A jet turbine is an internal combustion engine. It isn't a
| "reciprocating" engine, though.
| cherryteastain wrote:
| Well, unless it has an afterburner like Concorde's engines
| dredmorbius wrote:
| That's still considered "internal" combustion, as the
| combustion is occurring within the context of the engine
| itself.
|
| The traditional contrast to the I.C.E. is the external
| combustion of a _steam engine_ , where the combustion
| occurs in a boiler, which then directs steam to the
| actual reciprocating engine (in a traditional steam
| engine).
|
| _Steam turbines_ actually _could_ be a case of an
| external-combustion turbine, as these are powered by
| steam which is heated externally to the turbine itself
| (e.g., there is no internal combustion chamber).
|
| Not all steam turbines are _combustion_ engines, however.
| A nuclear power plant 's steam turbines are fed by steam
| created from nuclear fission rather than chemical
| combustion. Some solar thermal power systems runs steam
| turbines based on _solar_ power, and I believe that most
| geothermal power involves steam and turbines.
| Functionally, the steam turbine bits of these systems are
| identical to a coal-fired steam turbine, but the heat
| cycle differs.
| dboreham wrote:
| > 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.
| FredPret wrote:
| 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].
| anon84873628 wrote:
| 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.
| Ekaros wrote:
| 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.
| wayfinder wrote:
| It's not generating the energy -- it's storing it. Fossil
| fuels are massively more energy dense than our current
| electric batteries.
|
| Fossil fuels are literally dead animals pressurized by
| Earth... all that energy went into the fuel. Planets work
| on massively larger scales of energy than human society
| right now and we're using stored energy created by planets
| to fly.
| sokoloff wrote:
| > Fossil fuels are literally dead animals
|
| By mass, fossil fuels are mostly from plants, algae, and
| bacteria rather than animals.
| lovecg wrote:
| The energy is not exactly stored in the fossil fuels
| directly. Indeed you have to put in extra energy to break
| those bonds - pulling atoms apart is work. The "stored"
| energy comes from the fact that long time ago various
| processes split various compounds into two components, A
| and B. And putting them back together makes them snap
| like magnets with enough force to release some extra
| heat. We call A "fuel" since that's the part that's
| somewhat difficult to come by. We often forget about B
| altogether as it's literally all around us. Fossil fuels
| are fundamentally efficient for flight since the oxygen
| is something you don't have to carry around with you
| (unless of course you're going to space).
| Manuel_D wrote:
| It's not a matter of electricity cost, it's a question of
| watt hours per Kg. A battery powered plane cannot fly far,
| no matter how cheap electricity is, because the energy
| density just isn't there: https://en.m.wikipedia.org/wiki/E
| nergy_density#/media/File%3...
| Ekaros wrote:
| I'm really talking about synthetic fuels made using
| electric energy.
| itsyaboi wrote:
| Traditional fuels would also benefit from the cost
| savings of cheap renewable energy.
| thinkcontext wrote:
| Don't forget watt per volume. H2 has great w/kg but poor
| w/liter.
| 8note wrote:
| 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
| otterley wrote:
| Are you seriously suggesting that airplanes could just drop
| batteries weighing tons while flying across the sky?
| barelyauser wrote:
| Since this is HN, he probably is. And not only that, he
| is probably going to select this as his hill to die on.
| Good luck.
| panopticon wrote:
| > _a spent battery weighs the same as a fully charged one_
|
| 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
| bluGill wrote:
| 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.
| mschuster91 wrote:
| > 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.
|
| [1] https://www.statista.com/topics/3877/aircraft-leasing/
| FredPret wrote:
| Absolutely wild how much machinery we have flying around
| mschuster91 wrote:
| Yeah, and these things cost a ton of money - around 200
| million $ for your average Airbus A320. If you now ask
| yourself, hey how are airlines making money, the answer is:
| they aren't, the money all comes from frequent flyer
| programs [1] - it's gotten so ridiculous that the value of
| many airlines has shrunk to less than their FFP programs
| are worth and they are loss leaders [2]!
|
| Barely any airline actually has physical or real estate
| assets any more in their own name. It's all leased, rented
| or otherwise not on their books anymore, which was
| contributing to how badly airlines were losing money during
| COVID.
|
| [1] https://www.theatlantic.com/ideas/archive/2023/09/airli
| nes-b...
|
| [2] https://happyrichadvisor.com/loss-leaders/
| okay0 wrote:
| No one is paying 200m for an a320
| datadrivenangel wrote:
| The future of electric planes is going to be based on drone motor
| technology at this rate!
| bprater wrote:
| 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.
| ramesh31 wrote:
| >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.
|
| 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.
| bluGill wrote:
| 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.
| majormajor wrote:
| It's hard for me to imagine (in the US) the government
| allowing an explosion in small commercial flights w/o TSA
| and all that rigamarole. If you get 10x, 100x the volume
| today, with a less upper-crust passenger base, the
| perceived security/terrorism risk probably starts getting
| talked about.
| JakeTheAndroid wrote:
| and there is already a massive shortage of ATC employees
| right now. At minimum this would need to be addressed and
| more than double the workforce of ATC. That's without
| accounting for any additional infra that might be needed
| to support a 10x or 100x in traffic.
| ramesh31 wrote:
| >That's without accounting for any additional infra that
| might be needed to support a 10x or 100x in traffic.
|
| The TSA requirement is nil for 10 person flights and
| these would be VFR only anyways. You would avoid a vast
| majority of the need for added ATC by operating between
| uncontrolled fields and relying on enhanced automation.
| The traditional airport model doesn't really apply when
| flights can be made so casually. Imagine a world where
| tiny runways that only service EVs are integrated into
| the city and you can hop between them as easily as
| catching a bus. Crosscountry travel would be also be
| possible via smaller hops, and cost less than a direct
| long haul jet liner ticket.
|
| All of that is enabled by the orders of magnitude
| reduction in operating costs. EV Alice is claiming
| $200/hr to operate an aircraft that has the equivalent
| performance to a $1k+/hr turbine within the range
| limitation.
| ToucanLoucan wrote:
| 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?
| scythe wrote:
| >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.
| Manuel_D wrote:
| 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).
| Sohcahtoa82 wrote:
| You just need a fast enough catapult mounted on a slope.
| ;-)
|
| An object dropped at 30,000 feet would be traveling at
| about 3,000 mph when it impacted the earth, ignoring the
| atmosphere.
|
| Maybe launch at 4,000 mph to overcome drag to throw
| something into cruising altitude? We'll just wear some
| noise canceling headphones to block out the OVERSPEED
| alarms.
| Arelius wrote:
| I mean, isn't ignoring the atmosphere ignoring like 90%
| of the domain?
| bhandziuk wrote:
| Just for perspective this is about mach 5. But I guess
| there is no speed of sound if you're ignoring the
| atmosphere :)
| Night_Thastus wrote:
| A catapult that launches a commercial aircraft with
| enough force (over a typical runway length) to get it to
| cruising altitude with no other power source would also
| turn all the passengers into raspberry jam.
| Ekaros wrote:
| I wonder how much energy would be stored in that catapult
| and what would happen if something went slightly wrong.
| Like it got stuck midway... Will we have a plane left? Or
| how many pieces?
| njarboe wrote:
| So the ramp needs to be about 35,000 feet high?
| matt_heimer wrote:
| So if I understand correctly you'd like to shoot planes into
| the sky with a giant railgun?
| baz00 wrote:
| I think getting the passengers to flap has a similar
| physics outcome.
| standardUser wrote:
| This is how they launch some jets on aircraft carriers. It
| sounds ridiculous to apply that to a passenger jet, but not
| really any more ridiculous than the fact that we routinely
| fly through the air for thousands of miles in the first
| place.
| Kye wrote:
| I'm no expert, but catapulting a sturdy ~30 ton fighter
| plane seems like a fundamentally different engineering
| challenge to catapulting a ~400 ton aluminum can.
| standardUser wrote:
| The E-2 Hawkeye is one of the largest plane that
| regularly uses catapult takeoff and it has a wingspan of
| 92' and weighs about 43,000 lbs.
|
| A220 and 737 both carry roughly 100-150 passengers and
| have wingspans of 115-120' and the lightest versions
| weigh around 130,000 lbs.
|
| Seems doable if the jet and catapult system were
| specifically designed for this purpose. Maybe less
| plausible for jumbo jets.
| greedo wrote:
| Catapults just shorten the runway needed. The plane still
| needs a ton of fuel to climb to altitude. Plus, I doubt
| you'd ever get a lot of civilians to fly off a
| catapult...
| standardUser wrote:
| The goal is to reduce the onboard fuel needed to achieve
| flight. I thought that was obvious from the parent
| comment.
|
| > Plus, I doubt you'd ever get a lot of civilians to fly
| off a catapult...
|
| I'm sure many short-sighted people said that about
| passenger air travel in general. Plus, if you actually
| watch a video of a modern catapult launch, you will see
| that it would be mostly invisible to passengers.
| acoard wrote:
| 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.
|
| [0] https://en.wikipedia.org/wiki/Ski-jump_(aviation)
| kirrent wrote:
| 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.
| thebruce87m wrote:
| Would you class them as very heavy? Trying to find some figures
| to compare: https://www.quora.com/Is-a-Tesla-heavier-than-an-
| ICE-car-of-...
|
| 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
| GauntletWizard wrote:
| 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
| matthewfelgate wrote:
| He's right to gut pointless divisions on fake futures:
| - Carbon capture is nonsense. - So are flying taxis.
| - So are electric planes. - Hydrogen planes is even more of
| a joke.
| hawk_ wrote:
| Why is hydrogen plane a joke?
| netrap wrote:
| The fuel is too dangerous to store..
| buildsjets wrote:
| I am BuildsJets now, but 20 years ago I was
| BuildsCryoFuelsystems.
|
| Go look at the cross section of an actual hydrogen-powered
| aircraft that has flown actual missions under it's own power,
| such as the Boeing Phantom Eye. The USSR's TU-155 flying
| testbed aircraft does not count, it did not fly under
| hydrogen power or fly an actual mission, it just ran an
| engine in the air.
|
| Observe how much of the airframe's space is used by fuel
| storage, compared to payload. Now do the same thing for a
| commercial airliner, and realize that commercial aircraft are
| just barely profitable with their current payload:fuel weight
| ratio.
|
| Also, did you know that when you refuel a liquid hydrogen
| tank, a significant portion of the fuel is vented off to the
| atmosphere? In the case of the Space Shuttle, LH2 filling
| losses are around 20% of total fuel load. Then there are
| boil-off significant losses while the vehicle sits around
| warming up. So to be most efficient, you would need to either
| fuel up IMMEDIATELY before loading passengers, or hot-loading
| propellant with passengers on-board, like SpaceX does, and
| the FAA prohibits for commercial passenger operation. There
| are also boil-off losses in the transportation and storage
| equipment to consider, and boil-off losses everytime you
| transfer to a different storage or transportation medium.
| akamaka wrote:
| Just a few months ago, Universal Hydrogen did a 200-mile
| flight of their Dash-8 which has been converted with one
| hydrogen engine. I'm not going to make any predictions
| about the future price of hydrogen vs. other fuels, but it
| doesn't seem like there are any insurmountable technical
| barriers to mid-range hydrogen airliners.
| PeterisP wrote:
| Storage of large quantities of hydrogen is a pain and also
| heavy (which matters a lot on a plane), so if you really want
| clean fuel, then synthetic hydrocarbons make more sense on a
| plane than hydrogen.
| Manuel_D wrote:
| Hydrogen has great energy density by mass. But creating a
| very lightweight container to store either liquid hydrogen or
| highly pressurized hydrogen is challenging. More feasible
| than powering planes with lithium batteries, though.
| standardUser wrote:
| All of those things are possible and being actively developed
| by countless companies and governments. They may not end up
| being economically feasible on any meaningful scale. That
| doesn't make them fake or nonsense.
| jillesvangurp wrote:
| 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.
| graphe wrote:
| 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.
| unglaublich wrote:
| 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!
|
| https://ourworldindata.org/travel-carbon-footprint
| graphe wrote:
| I'm wondering if helicopter pads make a big difference or
| if they're taking off from the ground. Sky bridges,
| underground walkways, or trams could be used in highly
| congested areas, but the US lacks long term planning, and
| can't into 3D space.
| aeternum wrote:
| 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.
| Nzen wrote:
| Perhaps the distance requirements reflect airplane wakes,
| rather than collision avoidance [0]. Analagously, I don't
| like to follow cars closely on wet roads, given the plume
| of side spray [1].
|
| [0] https://www.faa.gov/air_traffic/publications/atpubs/aim
| _html... subsection 7-4-9, titled Air Traffic Wake
| Turbulence Separations
|
| [1] https://www.youtube.com/watch?v=C-1-btUcMiA 20 seconds
| long
| aeternum wrote:
| Wake turbulence is mostly a concern for small planes
| following large planes. In the right conditions (pilots
| visually maintaining separation), planes do get quite
| close and at many airports like SFO, it's the only way to
| accommodate all the scheduled flights:
| https://www.youtube.com/watch?v=NLCcxCdrL5w
| mminer237 wrote:
| > spacing is typically 3nm
|
| For anyone else not that familiar with aviation and very
| confused, this means three nautical miles--about 31/2
| regular miles, not that it's smaller than a transistor fin.
| vlovich123 wrote:
| 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)
| bluGill wrote:
| 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.
| civilitty wrote:
| 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.
| tivert wrote:
| > 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_.
| S201 wrote:
| It's not that there's not a demand for unleaded avgas, I'd
| say most GA pilots are ambivalent to leaded vs. unleaded
| fuel; they just want whatever makes the prop spin.
|
| The issues with the unleaded avgas rollout are purely
| bureaucratic. The FAA has been dragging its feet for
| literally decades to get it done. Even when we have fuels
| like G100UL approved which is a drop-in replacement for
| ~80% of the GA fleet, it still takes forever to get across
| the finish line.
| histriosum wrote:
| Indeed. G100UL is drop in for the entire piston GA fleet,
| though, not 80percent.
| sokoloff wrote:
| > the entire piston GA fleet
|
| All the _spark-ignited_ piston fleet, but not the diesel
| piston fleet (which cannot use G100UL [nor is it needed
| for them as diesel is already unleaded]).
| treis wrote:
| 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.
| nradov wrote:
| 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.
| guidedlight wrote:
| Nobody is going to be flying to Europe or Australia on a
| smaller plane.
|
| 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.
| advisedwang wrote:
| > Nobody is going to be flying to Europe or Australia on a
| smaller plane.
|
| We've already seen a shift to smaller planes. Fleets are
| replacing 747s with 787s, and the A380 is already out of
| production.
| freedom-fries wrote:
| 787 isn't a small plane! 787 is just 11% smaller by
| wingspan and just 3% smaller range than long-range 747. In
| large part, 747 and 380 went away because they were fuel-
| inefficient 4-engine planes, not because airlines wanted to
| fly tiny planes between LA and NY.
| anakaine wrote:
| Its definitely smaller in terms of capacity. Different
| seating configurations aside, notionally the 747 could
| seat 366 passengers whilst the 787 can seat 242.
| notahacker wrote:
| Your notional figures are low for both aircraft. You can
| get 330 passengers in the 787-10 in a reasonably spacious
| two class configuration, or cram another hundred more in
| a single class configuration.
|
| Either way the difference in cabin space is essentially
| irrelevant to arguments about "smaller planes" in the
| context of suitability for battery power.
|
| We're still talking about widebodies carrying well over
| 200 passengers which would be entirely unsuitable for
| battery powered replacements, and the 787 is larger than
| many of the other widebodies it's replacing.
| emodendroket wrote:
| Carbon offset payments kind of smell like a sham to me. I
| don't think it really solves much.
| fwungy wrote:
| 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.
| Johnny555 wrote:
| >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.
| raverbashing wrote:
| Something like a carrier launch catapult, I think, would
| make more sense to be honest
| Johnny555 wrote:
| Does the rollout from 0 - 200mph takeoff speed really use
| the bulk of the takeoff energy? I figured most of the
| energy went to climbing 6 miles in altitude.
| dredmorbius wrote:
| I believe you're correct in this.
|
| An aircraft carrier's catapult isn't about getting an
| aircraft to _altitude_ , but about getting it to _flight
| speed_ , on the attenuated runway of a carrier deck.
|
| (Landing and arrestor cables are the equivalent problem
| in reverse.)
|
| That said, a divide-and-conquer approach to reducing
| overall aircraft energy use might go some way to making
| electrically-powered flight ... at least more feasible,
| for larger payloads / passenger capacities, and
| distances, than is now conceived.
|
| This includes ground taxiing (jet engines are quite
| inefficient at low speeds) via tugs, some form of take-
| off assist, jettisonable battery packs (after take-off
| and climb phases), general lightweighting of the airframe
| itself (already a major area of both research and
| accomplishment for electric aircraft), and automation and
| removing requirements for onboard pilots and flight
| attendants (the more paying bodies the more effective the
| business proposition).
|
| There's possibly some room for optimisation of engine and
| airframe efficiencies, routing, and traffic control, and
| possibly some gains by hybrid designs (fuel + battery
| with electric drives, say).
|
| As a whole though I suspect electric aircraft have been
| oversold, and that aviation as a whole will see reduced
| availability and usage in future.
| QuercusMax wrote:
| And at a proper airfield it wouldn't need to use nearly
| as much g-force, since you can accelerate at a slower
| rate when you have a runway.
| MuffinFlavored wrote:
| > 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.
|
| This sounds unrealistic. What if the plane needs "big
| energy" in the sky for emergency failure? Isn't the
| standard in aviation failure to the level of the 3rd degree
| or something (1 signal has 2 backups for 3 total or
| something)
| Johnny555 wrote:
| I agree it's unrealistic, but not because the plane might
| need "big energy" later -- I don't see how dropping the
| battery is any different than burning the fuel?
|
| If the plane burns 25% of its fuel on takeoff and climb,
| then that fuel is gone.
|
| If the plane drops 25% of its battery capacity (which is
| now depleted) after takeoff and climb, that battery
| capacity was already depleted, it's just acting as dead
| weight.
| dredmorbius wrote:
| The difference is that when you burn fuel, you _burn
| fuel_ , and the mass exits the aircraft through the
| engine.
|
| When you discharge an electric cell, you're still
| carrying that electric cell with you.
|
| I suspect you're trying to express this and are fingering
| some _other_ element of this concept as unrealistic, but
| that 's not how your comment reads.
| Johnny555 wrote:
| I literally said that the depleted battery would be
| physically detached, I don't see how there is any other
| interpretation?
|
| _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._
|
| It's unrealistic because of all of the details in making
| a an autonomously flying battery pack that can detach
| from an aircraft in flight and do it with the kind of
| safety a civilian passenger aircraft demands.
| dredmorbius wrote:
| That's clearer.
| notahacker wrote:
| Apart from the detaching and flying a battery part,
| you've also got to seamlessly switch power source in
| midflight
|
| Otherwise you've depleted 25% of _all_ your batteries and
| jettisoned a single battery pack, which (like the others)
| is 75% full. (That might of been a source of confusion).
| Johnny555 wrote:
| That seems like the easiest part, flip the relays to
| disconnect the battery pack, evaluate remaining capacity
| and if the detachable pack is discharged by the expected
| amount and the onboard packs are full, then go ahead and
| jettison.
| calamari4065 wrote:
| This is a problem we solved _decades_ ago. At this point
| it 's such a trivial problem that it's totally irrelevant
| and not even worth discussion.
| sangnoir wrote:
| > What if the plane needs "big energy" in the sky for
| emergency failure?
|
| Electric and existing planes can already tap into another
| energy source for this - potential energy. Most planes
| have decent glide ratios and can safely travel over long
| distances for an emergency landing from cruising
| altitude, as long as the pilot can maintain control
| authority.
| etaty wrote:
| I believe dropping and catching new battery pack in the air
| is the way to go as well! Electric motors are smaller and
| can enable stationary flight. So stopping to change your
| pack is maybe a solution.
| fwungy wrote:
| They could use steam powered catapults like on carriers.
| pretendgeneer wrote:
| 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.
| freedom-fries wrote:
| Or high-speed cars. I hate trains.
| itishappy wrote:
| I'm just imagining the carnage from everyone barreling
| down the highway at 200 km/h (125 mph)...
| nrb wrote:
| Simply not realistic for major routes in the US for the
| foreseeable future. Los Angeles and New York are 2500+
| miles apart across over 10 states that would need to
| properly coordinate and invest to make this a reality.
| lovecg wrote:
| 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.
| dredmorbius wrote:
| The main drawback to that suggestion is that aircraft
| really don't need more charge as they descend.
|
| The high-energy flight segments are take-off and climb. If
| you're charging batteries on descent ... the only gain is
| that the next take-off/climb phase can use that recovered
| energy.
|
| But from a mass and capacity standpoint, which seem to be
| the real challenges for electric flight, you're gaining
| very little. The ability to get rid of the battery you've
| spent on take-off/climb would be far more useful.
| ep103 wrote:
| Or solar
| meindnoch wrote:
| _And self-driving cars should be here by 2015!_
|
| Sorry, but the 2010s called, and want their naive techbro
| optimism back.
| I_Am_Nous wrote:
| 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.
| Ekaros wrote:
| 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.
| nradov wrote:
| 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).
| emodendroket wrote:
| I feel like if we're serious about decarbonization it's likely
| that the solution involves fewer people flying, particularly on
| overland routes.
| incomingpain wrote:
| every industry inflection point always has the dinosaurs who go
| extinct.
|
| Those who don't see the inflection and want to keep their
| momentum in their set direction will find themselves in
| bankruptcy.
|
| Unfortunate that rolls royce seems to have decided not to keep
| up.
| bluGill wrote:
| There have been a lot of predicted disasters that never
| happened.
|
| There are fundamental physics in play when I confidentially say
| that battery airplanes will never be more than a small niche.
| incomingpain wrote:
| >battery airplanes will never be more than a small niche.
|
| I wish I could take that bet. I'd put whatever amount of
| money down on that.
|
| They say never say never but you are asserting fundamental
| physics prevents it from happening?
|
| Within 5 years I expect to see my local GA manufacturer start
| pumping out battery electric planes.
|
| Within 10 years it will be reasonably possible to get
| yourself on an electric plane. Regional electric planes will
| start replacing older planes. The like 20-seater type size. I
| expect the niche stuff like seaplanes probably start getting
| certified around this spot.
|
| Within 20 years the regional flight will have mostly
| converted to electric and some of the early adopters will
| have finished amortizing those planes.
|
| within 30 years the massive airliners will be replaced with
| 20MW or so battery electrics. I will even go further and say
| these won't look like traditional planes.
| xcv123 wrote:
| > you are asserting fundamental physics prevents it from
| happening?
|
| The energy density of batteries vs fuels is the current
| limitation. We don't know if this problem can ever be
| solved. A business cannot gamble on some magical hopes and
| dreams.
|
| > within 30 years the massive airliners will be replaced
| with 20MW or so battery electrics
|
| And how much will those 20MW batteries weigh?
|
| With the current lithium battery technology, you would need
| a 7,167 metric ton battery to store the same amount of
| energy as 150 tons of jet fuel, which is typical for a long
| haul passenger jet.
| robertlagrant wrote:
| > The energy density of batteries vs fuels is the current
| limitation
|
| It's not just that. Fuels mean the aeroplane gets lighter
| with distance, especially on ascent. Batteries need _so_
| much more energy just to carry their own weight the whole
| way.
| Ekaros wrote:
| Also often forgotten thing is that aircrafts have also
| designed max landing weight. This isn't hard limit, but
| limit for normal operations. This is why they go in
| holding pattern to burn fuel for example if cabin
| pressure is lost. So not immediate emergency, but
| something where you want to land sooner than planned.
| xcv123 wrote:
| To put it in perspective, the A380 max landing weight is
| 391 tonnes, versus the 7000 tonnes of lithium batteries
| required to power a long haul flight.
| mips_r4300i wrote:
| A typical high-end 18650 li-ion cell from 1996 was 1400mAh.
|
| A typical high-end 18650 from 2023 is about 3200mAh.
|
| In other words, it took 27 years for battery tech to
| achieve a bit over a doubling in energy capacity.
|
| Even if we wait another 20+ years and batteries double
| again, it will still be an order of magnitude less dense
| than gas. In a plane, this is absolutely critical.
|
| I want to be flying electric planes, hell I'd settle for
| just an electric car that got somewhat good range. But
| battery tech has taken eons to get to where it is. We can
| only hope to get some quantum leap in storage density or
| we're going to be flying with dinosaurs for a long time.
| bluGill wrote:
| > you are asserting fundamental physics prevents it from
| happening?
|
| Yes. The chemistry of burning fuel vs batteries is very
| different. Even though engines are much less efficient,
| that doesn't make up for how much more dense fuel that you
| burn is. (you could perhaps burn the battery, but that
| would be a very different thing, and probably too toxic to
| consider in the real world)
|
| > I expect to see my local GA manufacturer start pumping
| out battery electric planes.
|
| Since GA airplanes are currently being made at a rate of
| about 3000/year you could be right and yet not make any
| dent in total airplanes.
|
| >Within 10 years it will be reasonably possible to get
| yourself on an electric plane.
|
| Maybe, but those airplanes will have a very limited range.
| For most aviation uses range is important - by the time you
| get to the airport, run all the preflight checklists: you
| could have driven the same distance as the range of an
| electric plane, and the electric plane hasn't even got off
| the ground yet! There are short range niches where this is
| acceptable, and they will switch to electric planes for
| sure.
|
| > Regional electric planes will start replacing older
| planes. The like 20-seater type size.
|
| RANGE RANGE RANGE. Most people who get in a 20 seat plane
| are going far enough that electric can't make the trip.
| Batteries are too heavy, and this is the physics of the
| chemistry that innovation cannot work around no matter how
| much you want to ignore the laws of physics and chemistry.
| xcv123 wrote:
| Try reading the article before commenting
|
| Here's a link from the article
|
| https://www.rolls-royce.com/media/press-releases/2023/13-11-...
| robertlagrant wrote:
| You need to be able to tell the difference between what will
| happen and what might happen. If you don't remember the losers,
| you will assume every idea is a winner.
| antisthenes wrote:
| 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.
| dghughes wrote:
| 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.
| Ekaros wrote:
| What is the surface area of the top of a plane? How much power
| do you need? How much power per area do you need to deliver and
| with what efficiency?
| Someone wrote:
| https://energycentral.com/c/ec/flying-without-fossil-
| fuels-n...:
|
| _"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.
| dghughes wrote:
| I wasn't planning that far ahead I'll file my patent later.
| But a quick Google shows:
|
| 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. h
| ttps://www.esa.int/Applications/Technology_Transfer/More_ef..
| .
| meindnoch wrote:
| 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.
| robocat wrote:
| It isn't just about electric planes: Rolls-Royce were trying to
| be G.E. and failing. slashing divisions such as
| R2 Factory, an in-house artificial intelligence software unit,
| and a direct air carbon capture project. Rolls-Royce said
| it would cut 2,500 management and administration jobs. The
| next head to roll is its electrical business, which develops
| propulsion systems for flying taxis and other aircraft.
|
| Did Rolls-Royce think they were a VC/incubator for inventions
| with multi-decade payoffs? Tough market.
|
| Rolls-Royce continue to develop for the nuclear power market -
| I'm guessing driven by government/military money. Compare to GE
| Hitachi: https://www.gevernova.com/nuclear
|
| Then again, looking at the General Electric website makes me want
| to short GE! Read and weep their AI initiative to develop
| buzzwords: https://www.ge.com/research/initiative/industrial-ai
| Or the bigger picture: Q: What is GE's
| mission/purpose statement? A: GE's newly defined Purpose is
| "We rise to the challenge of building a world that works."
| Q: What industries does GE operate in? A: GE has long been
| a leader in Power, Renewable Energy and Aerospace. Today, GE also
| leads in delivering solutions across Additive Manufacturing,
| materials science and data analytics.
|
| Financially, a basket of options is worth more than an option on
| a basket (RR share price).
| https://medium.com/@kentbeck_7670/decisions-decisions-or-why...
|
| Rolls-Royce blurb: Rolls-Royce develops and
| delivers complex power and propulsion solutions for safety-
| critical applications in the air, at sea and on land.
| Strategic initiatives: Detailed divisional plans that will focus
| on opportunities where key drivers give us competitive advantage:
| widebody aircraft, business aviation, transport & patrol, combat,
| submarines, governmental and marine.
| scrlk wrote:
| > Rolls-Royce continue to develop for the nuclear power market
| - I'm guessing driven by government/military money.
|
| Correct - RR are the manufacturer of the PWR reactors that
| power the Royal Navy's submarines. They are trying to
| capitalise on this by branching out in to SMRs.
| izzydata wrote:
| 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.
| cherryteastain wrote:
| What do you propose would replace them?
| izzydata wrote:
| The thing that existed before planes. Boats and trains.
| njarboe wrote:
| Before that. Walking.
| iancmceachern wrote:
| Those burn the same fuel...
| nicoburns wrote:
| Boats do, but trains are mostly electric.
| iancmceachern wrote:
| Not in the US, their mostly diesel here
| izzydata wrote:
| Boats aren't constrained by weight like planes are. You
| could put any amount of batteries on a boat and get it to
| float and move on water. They can also be moved by wind.
| I may be wrong, but I also thought there existed some
| nuclear powered boats.
| dredmorbius wrote:
| Trains, mostly.
|
| 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 Darien 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 Darien 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>
| tltimeline2 wrote:
| or just very limited. like the famous zip disk bell curve.
| dredmorbius wrote:
| What is the zip disk bell curve in this context?
| mike_d wrote:
| 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.
| izzydata wrote:
| 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.
| mike_d wrote:
| Alaska Airlines is going to start flying on a 50/50 mix of
| traditional and harvested jet fuel next year. Fully
| harvested should get certification from engine manufactures
| in the next few years.
| standardUser wrote:
| Zero, barring any kind of civilization-ending event. There is
| no conceivable way we run out of every possible fuel option.
|
| In fact, just last year Airbus completed a flight with their
| A380 (2nd largest passenger jet in the world) using only
| biofuels.
| Maxion wrote:
| This is quite a probable scenario.
| tester756 wrote:
| Close to 0
| saidinesh5 wrote:
| Or... a cleaner/more powerful fuel source comes up (nuclear,
| fuel cells, other sci fi stuff) and everyone flies their own
| "Flying Cars"(Tm).
|
| I am actually more optimistic this would happen than people
| giving up on planes tbh.
| phkahler wrote:
| I still wonder if most of the human impact on climate is not the
| CO2 but the water vapor put out by planes. See the post 911
| weather, and more recently around here a lot of people know what
| "covid sky" means. The sky was very clear and blue during the
| early shutdowns.
|
| If this hypothesis is correct then low-carbon fuels (say methane)
| are the wrong answer. Low hydrogen fuel would be better. Bring on
| the coal fired airplanes!! Sounds so silly, but hey...
| xp84 wrote:
| Is there a primer on what exactly "SAF" or "low-carbon fuel"
| actually is? It's not "just" hydrogen, or is it?
|
| It just sounds too convenient to be a real thing. "Oh, just use
| the LOW-carbon fuels. There's your problem!"
|
| Edit: Not disputing the fact that electrical airplanes present a
| staggering affront to the laws of physics due to weight. Just
| seems like the "third alternative" here (to status quo or
| battery) is being taken for granted.
| cobrabyte wrote:
| It's sort of still being defined. There's a rush to develop a
| universal SAF, but companies can develop blends of alternative
| fuel sources and get money back from the US government in the
| process.
|
| https://afdc.energy.gov/fuels/sustainable_aviation_fuel.html
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