Aviation Is on a Low-Carbon Flight Path
scientificamerican.com
scientificamerican.com
I'm much more optimistic about low-carbon jet fuels. Biofuel options here have already been trialed successfully. And some new synthetic fuel companies [2] that use direct air capture CO2 are looking promising.
[1] https://arpa-e.energy.gov/sites/default/files/Grigorii-Solov... [2] https://en.wikipedia.org/wiki/Carbon_Engineering
[1] https://www.pipistrel-aircraft.com/aircraft/electric-flight/...
https://www.pipistrel-aircraft.com/locations/#tab-id-2
https://www.dw.com/en/electric-flight-finds-its-wings-at-slo...
They have electric planes, and they have flight schools, but whether the two actually intersect or not isn't immediately clear.
This is more on an engineering challenge, unlike much better batteries which will require a fundamental scientific breaktrough.
It's an absolutely huge engineering challenge, but at least it doesn't require a discovery worth of the Nobel prize in chemistry (which I guess much improved batteries would warrant).
Battery energy density is steadily improving every year. The 2019 Nobel Prize in Chemistry went to the inventors of the lithium ion battery.
https://www.nobelprize.org/prizes/chemistry/2019/press-relea...
It's a hard problem, and most proposed solutions are extremely novel and risky, like having an all-battery tugboat that tows the plane up to cruising speed/altitude before returning to the airport to charge or get a battery swap— obviously bad because risky, also adds 50% to runway capacity to land all the tow planes.
Is it too crazy?
That seems quite dangerous - to both the aircraft and everyone onboard, as well as to anyone on the ground in the path of this cable.
Simply put, that's just not how aviation works.
Mechanical failures aren't uncommon in aviation, but for an aircraft to not be able to divert and return to the ground, a lot has to go wrong all at once. It's infinitesimally rare for all systems to fail at once on an airliner. There simply isn't a problem of airliners dropping out of the sky, ever. They're incredibly robust machines.
However, with your idea, we'd be relying on a single system to prevent catastrophic failure. That's a massive step backwards for aviation.
That doesn't even begin covering the problems with delivering enough electricity over this cable to power an airliner at takeoff... That cable would need to be a very thick gauge of wire and very heavy - causing all sorts of it's own problems.
It's actually an interesting supposition, because whether it's gasoline or electric, it should be cheaper and more reliable to run a ground operation than to pack fuel that is expelled before anything meaningful has happened.
But having also launched from a carrier myself, I wouldnt want that g force everytime I fly commercially.
If I was a carrier pilot, I doubt I'd ever get used to that!
Yes, but the reason they're used is because it's infeasible or too expensive to build an aircraft carrier long enough to have jets reliably take off from them without this extra boost. Even so, those catapults are fairly short: notice they're only a fraction of the length of the carrier.
They're not used in regular airports because they're not absolutely necessary, the way they are on aircraft carriers. It's more expense, and planes can do without them. However, there's a cost to this: the planes need bigger engines and more fuel to take off reliably. And bigger engines are less efficient overall (as in cruising). So there would be a significant fuel savings if you could count on having catapults on the ground to help get the plane to takeoff speed: you could downsize the engines, and carry less fuel, saving a lot of money overall per flight (not to mention all the carbon pollution).
Finally, the extra g-forces shouldn't be a big deal. There's high g-forces in a carrier launch because the catapults are very short. And until recently, they were steam powered. This needn't be the case with commercial aviation: they can use modern electromagnetic launchers, and they can make the catapults very long (as long as much of the runway), to have lower peak acceleration. Basically, the planes and passengers would not need to experience higher g-forces than they already do; they'd just be getting them from the catapult instead of solely from the engines.
https://en.m.wikipedia.org/wiki/Space_fountain
https://en.m.wikipedia.org/wiki/Cloud_Nine_(tensegrity_spher...
Regardless of the specifics, it's obvious that any of these schemes is a logistical and technical nightmare compared to "taxi up to the terminal, plug in the refueling hose while people and cargo are loaded onto the plane." It's unlikely that the private sector will be too enthusiastic about investing in anything like this without heavy incentives.
Ideally when we have kerosene based fuel cells we could have small electic aeroplanes that will be much easier to control, and would allow more frequent direct flights, instead of having to collect 100s of people together make them wait several hours, and drop them at an inconvenient location.
But I do wonder how much power is actually expended at takeoff versus climbing or cruising flight. According to [1], only ~19% is used for both takeoff and climb, so electrifying the runway to save the fraction of the 19% used while in contact with the ground is probably not worth it.
[1] https://aviation.stackexchange.com/questions/47262/how-much-...
Nah. If someone can't handle a few g's in takeoff, maybe they shouldn't be flying, and should should stay home, or maybe in a nursing home. I know it sounds mean, but seriously, think about it: aircraft transport isn't always comfortable. Turbulence happens, and it can be extremely rough at times, even injuring people severely if they're not belted in. If someone is too frail to handle being launched by an aircraft carrier catapult (which, remember, also launch those big AWACS planes, not just small fighter jets), then they're not suited for handling turbulence either.
Also, don't forget, the latest generation of catapult technology is actually pretty gentle. The USS Ford's "EMALS" catapults are electromagnetic, rather than steam, and one of the big stated benefits of this is that it's gentler on the airframes than the old steam catapults. It's still going to subject the pilots/passengers to several g's, but probably lower peak acceleration than the older technology did.
Maximum power requirements come from take-off and climb-out, so the engine size is designed around the max take-off power. This means that the engine is over-designed and less-efficient for the majority of the flight.
By implementing a hybrid engine, the gas-powered component and the electric powered component work together to provide take-off power requirements. By the time the aircraft reaches cruising altitude, the batteries are dead, and the gas-powered component works alone. This allows the engine to be designed for the cruise power requirements, which results in a much more efficient engine. UTC is currently experimenting with this concept.
https://www.flightglobal.com/news/articles/utc-to-test-hybri...
Yes it's not carbon neutral, but it's a step in the right direction.
However I also wonder why, if electric motors are a solution here, there hasn't been a comparable fuel-powered extra-takeoff-engine. Why would this not have the same benefits? Or are extra engines simply too complicated mechanically unless they are motors?
(The liked article is about modifying a Dash 8, which is a turboprop, and perhaps it's easy to have oversize propellers for takeoff, and just connect a motor to the same gearbox.)
Military aviation has dealt with this in various ways:
1. Carried aloft by a larger plane
2. Towed aloft be multiple other planes
3. Jet assisted takeoff
4. catapults
5. drop tanks
6. mid-air refueling
https://www.youtube.com/watch?v=7QYlueabGDg
Jettisoning 200,000 lbs of batteries would be even worse.
To be honest, the worst parts of flying are usually all those other passengers anyways. If you could scale up a fleet on-demand small electric planes. Flying would improve. If you account for all the waiting time, it might be just as fast too.
Flying anywhere near as far as from Birmingham, Alabama to Fort Collins, Colorado is also an exceptionally hard problem for electric aircraft.
The appropriate figure of merit is range and specific energy (i.e. useful energy stored per unit mass), and that IS a limitation, but range of up to 500 miles is feasible for pure electric using existing batteries and structure and aerodynamic efficiency tech. Double or quadruple that is possible with cleverness and more exotic approaches. Even long-haul is possible with certain approaches to pure electric flight (either lithium-air, which has just as high theoretical useful energy as something like gasoline, or staging).
The only way "large aircraft" or "high power" is a limitation is just the speed at which things can be certified. Large passenger aircraft cost billions to bring to market, so companies are super conservative about it. But this isn't a fundamental technical limit of electric flight.
[0]Technically, there are structural scaling laws which detract from efficiency as you get bigger, but they don't become strong until you're very large... And they're countered by perhaps even more important positive Reynolds Number scaling effects, i.e. your lift to drag improves as your scale increases.
We'll have to get rid of the fiction that we're going to be able to just plop in electric motors and batteries in existing civil transport vehicles without any change in architecture or operations.
Sailplanes are probably not the right model to go flying IFR to minimums, something that airlines do regularly.
I'd like to see a prototype of an electric airliner which can fly forever, but every half hour or so a car-sized battery with little stubby wings flies up and docks into the back of the plane.
... today.
There's a lot of money in batteries these days.
But from what I gather, it's not just about the batteries, but also about coming up with a design that takes advantage of the possibilities offered by simple electric motors.
There is at least one airline transitioning to only electric aircraft already [1]. It's one that focuses on short range flights. And as energy density continues to increase, the range and applications of all-electric aircraft will too.
[1] https://electrek.co/2019/03/26/harbour-seaplanes-electric-ai...
All the pieces exist for fuel cell powered jets. They've already got the performance levels needed. All they need is to put them together into a cohesive package, and put a shit ton of effort into reliability engineering.
Granted a little heat for the cabin is handy, but the rest is largely useless.
Even without heat capture, SOFCs run at 60-65% efficiency, which is probably good enough.
[0] https://www.ge.com/reports/call-ecomagination-ge-building-co...
Wikipedia lists the GE90-115B at 10kW/kg, four times better than your SOFC. Did you just combine motor and fuel cell to get 17.5kW/kg? That would be hilarious.
> With cogeneration, SOFCs are reaching 80-85% efficiencies
That's creative accounting. You're counting waste heat as if it was useful.
It turns out it was one of the best things I've done. Experience taught me what I never could have imagined -- how much my life improved. Like dropping Facebook on steroids. What I expected to miss I got more without flying, plus improved relationships, community, and connection.
A few months in I decided to go for a second year. I'm 4.5 years in now. I may fly again, I don't know, but I want to less and less.
EDIT: Amazingly, my TEDx talk on this experience went live minutes ago: https://youtu.be/sTYiHr1lu10.
Everybody tells me what I would have said before, that it's impossible to avoid, which is why I pointed out how the experience changed everything. It turns out many things were possible I didn't think were.
I've been thinking about this a lot trying to root out the unintended consequences of such a plan, but I can't think of any.
Record keeping, administration, etc.
You could replace it all with simple calculations:
Landing Tax: (tax rate) * (landing weight) * (distance traveled within US airspace)
Takeoff Tax: (tax rate) * (takeoff weight)
The two taxes you listed do nothing to make people who travel more pay more per mile than somebody doing their one flight a year to Disney.
Is there a reason the Nth mile should be taxed more than the 1st when the environmental impact of the Nth mile and the 1st are the same?
There'll be time after us.
For example, a round trip flight between NY and London is said to melt 3 cubic meters of arctic ice per passenger. So it wouldn't be unreasonable for airlines to be required to offset that in some way?
If so, then we just disagree on how to structure the tax but mostly agree on the need to reduce damaging flights.
1554 miles / (80 miles/gallon) * 6.8 lbs/gallon = 132 lbs
I was actually a bit surprised how little it is. It gets better in newer aircraft assuming all seats are taken.
[1] https://en.m.wikipedia.org/wiki/Jet_fuel
[2] https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#Mediu...
I am reminded of an acquaintance of mine who once told me he had no choice but to drive, because he lived in a little village with one bus a day, but commuted into London. What he had overlooked is that he'd chosen to live in this village.
You'd still be paying more for longer and more frequent flying, but you'd also be hitting personal jets harder than full flights, less fuel efficient planes and flight paths against better ones - and it would be reduced even further if an airline managed to electrify.
Although that still ignores the additional warming effect of radiative forcing caused by flight.
https://curiosity.com/topics/airplane-contrails-are-contribu...
The trick is to pitch it so that you don't have much impact on the 85% of the population who do 30% of the flying, but you strongly discourage the 15% of the population who do 70% of the flying [1]. Partly as a practical measure to ensure it's not so unpopular it gets repealed, but partly because those 15% are probably capable of making changes to their lifestyle or way of working that will drastically cut flights, whereas the other 85% are flying where they have to, to see their family at christmas or whatever, or for their one summer holiday.
You couldn't do that by taxing fuel, or aeroplanes, or anything other than individual people flying.
[1] https://fullfact.org/economy/do-15-people-take-70-flights/
The wrinkle I see with escalation of taxes per person per year is while my company would happily pick up the tab for work travel, I’d be upset if my Christmas trip home cost me thousands more because I’d done a handful of business trips.
Not to mention creating confusion and hassle for travelers, whose ticket price can’t be calculated and paid in advance (because you don’t know how many trips I’ll have taken before that flight), or who share a common name.
I think it's a little like how utilities price water. Water is very inexpensive at first. But if you are filling a pool and watering your lawn a lot, the gallons get more and more expensive.
I know of one case where a coworker ended a business trip by taking vacation days and a several day cross Atlantic cruise ship home which was likely worse than even a plane trip to an island as it didn't involve hauling essentially an entire luxury hotel thousands of miles.
I suspect a better idea for encouragement if anything would be subsidizing efficient clear neccessity/better than current baseline transit. Like say if living closer to work was subsidized along with public transit - both replacing or shortening automobile commutes.
Where the tax revenue goes isn't the biggest deal since getting a price on carbon alone will result in shifting incentives towards lower carbon behaviors and investments. In my experience watching debates about Carbon Taxes where I live, generally speaking, when people complain about where the money is going they are not arguing in good faith and trying to just spread FUD about the policy to prevent a carbon tax.
The second part of your response is somewhat frustrating though. It absolutely does matter what the tax is used for. This can’t just be an excuse for the total tax that I pay to be increased with the additional funds being put towards things like war fighting in far off lands. That’s maybe not as much of a problem in Canada as it is in the U.S. It’s unreasonable to dismiss any concerns about how the tax revenue is used as FUD.
You would also displace a lot of travel to private autos, with a decrease in safety/increase in fatalities and typically an increase in fuel consumption when comparing a single occupancy car to a fairly full flight. Plus, if I’m going to be driving a car 500 miles pretty regularly, I’m going to splurge for a nice, big, comfy car and it’s not going to be an electric. Since I currently fly rather than drive on road trips, today I can drive a small electric as my daily driver.
When you factor in the time constraint, specifically the timeframes outlined in the IPCC SR 1.5 report, then you simply cannot claim that direct air capture fuels are a meaningful part of the conversation of what to do with air travels footprint.
I am 100% in favor of continued and increased investment in R&D for DAC. I am 0% delusional that it will be a viable solution in the timeframe we need it to be (same goes for thorium and fusion).
If you're not solving for the time constraint and the curve shape in this graph, you're not talking about "solutions" you're just chit chatting about (cool) tech: https://www.ipcc.ch/site/assets/uploads/sites/2/2019/02/SPM3...
Minor point, people seem to marry DAC with synthesizing fuel, probably because Carbon Engineering has gotten a lot of press. Fuel can be synthesized from CO2 from any source. It is my understanding that DAC is currently more expensive than capturing from a point source, like a natural gas power plant. This is due to CO2 being such a small percentage of the atmosphere vs 10%+ from plant flue gases. So, while DAC is more expensive and there are still substantial point sources of CO2, fuel made from DAC will be more expensive from point source capture.
this kind of high-anxiety circular reasoning is hopefully the 'bargaining' phase before you move onto acceptance.
you are living in a world of spherical cows, not in the reality of the climate emergency.
please understand that as the body counts rise this level of "technically correct" pedantry will be seen for the rather gross complicity it is.
As for cost, I'm not ignoring it, it was my point. Fuel from one pathway costs more from another pathway. High cost is a barrier to taking a solution out of the lab and actually putting it into action to causing less CO2 to be emitted. If 2 fuel pathways have the same carbon footprint but one costs less than the other why would you choose the one that costs more?
I'm willing to listen if you would like to explain why you think DAC is better but so far you haven't done that, you've just been insulting which I don't get.
The actual topic at hand here is the GHG footprint of air travel (see topic, OP). My comment was about the time constraint provided by the IPCC that people fail to include in their analysis. Here you are 5 replies deep twisting my arguments into their opposite while failing to even address, let alone refute or propose your own alternative for the central point.
On a micro level your behavior is just garden variety piss poor social skills (can't say i'm the best either!). On a macro (and specific to this topic, climate change) level your behavior is the sand in the gears that keeps any of the rest of us from discussing this challenge in good faith and reaching rational conclusions. You are poisoning the well. You are pissing in the pool. Please stop.
I did not say you advocated for DAC. I said I was willing to listen to you explain why you thought DAC was better than point source capture. You said point source capture was "madness" while on the other hand saying DAC research was something you'd be willing to fund. I didn't (and still don't) understand why you think that. Don't think I twisted anything.
You were at angry gibberish in your first reply to me, I tried to give you the benefit of the doubt and merely asked you to explain your position. Obviously, that was a mistake.
which side are you on?
https://www.theguardian.com/environment/2019/nov/05/climate-...
the bodies are piling up. are you a polite german or a rude one?
i'm a rude one.
Only if you equally value energy at the time of burning and the time of conversion.
Imagine a natural gas peaker plant that captures CO2 during its typical operation, but it converts that CO2 back into a synthetic fuel during periods of energy surplus (when renewables provide more than 100% of the demand). The synthetic fuel is then essentially a battery, which just happens to be energy-dense.
There also reasonable ways of acquiring a "green" CO2 stream that does not involve fossil fuels; non-liquid biofuels (ex, cellulose or charcoal) would work here.
Everyone in this thread is pointing out how difficult the engineering is to convert aviation to something emission-free.
To me it seems obvious that we should focus on shrinking the 98% as fast as we can. While we should also work on decarbonizing air travel, I am pretty sure that if we decarbonized everything _else_ that the environmental impact of air (and space!) travel would not be enough to fuel global warming on its own.
Further, because the impact is so much smaller, it might be more feasible for air travel to eventually be required to perform offsetting direct carbon capture than to replace jet fuel with an alternative. That would make flying more expensive, which I think is fine, but it wouldn’t make flying _impossible_ which I think is at least highly undesirable.
The other 98% is made up of lots of industries that account for 1% here, 2% there, 0.1% somewhere else, and so on. We can't afford to ignore something because it's 'only' 2% of the total because that would mean ignoring everything. The reality is that we need to shrink 100% of global carbon emissions, including what's caused by aviation, and everything else.
For individuals who fly, the carbon emissions due to flying makes a non-trivial contribution to their personal carbon budget. As earth becomes more middle class and everybody starts flying, that will become a non-negligible problem.
I'm starting to think it's intentional, and it's instructive to ask why.
There is an unleaded fuel program (several candidate fuels in testing) and I believe one has a chance to be a drop-in replacement. It’s not yet certified and so we keep using 100LL (worldwide, not just in the US).
Really? The article just says its author hope for a low-carbon future for the air transport, and mentions some tiny plans by jet makers and early startups to plan to 'hybridify' airplanes.
How much low-carbon would that be? As far as I could read, the author does not even try to evaluate that and blindly hope that it should be helpful, somehow. As if he can't bear flight shame, and tries to share/sell some "hope" to cope with that.
Finding a way to store liquid hydrogen in 4x the volume (plus any required cooling/insulation and safety systems) might be a challenge for long-haul flights.
Yes there are some ways to produce hydrogen from electricity with electrolysis but at the moment 90% of hydrogen use natural gas or other hydrocarbons and release enormous amount of CO2.
Hydrogen production can be clean though.
https://www.cleanenergywire.org/news/hamburg-and-fukushima-c...
Don't misunderstand me, I want a low-carbon aviation, I'm all for it. But even if you cut the emissions by a factor 2 of each newer aircrafts, what's the point? The numbers of flights is expected to double in less than 20 years. Global emissions won't reduce at all.
https://www.iata.org/pressroom/pr/Pages/2018-10-24-02.aspx
IMHO, we need more regulations (e.g. ban domestics flights if high-speed trains are a viable alternative) rather than technological solutions.
Yes, it's silly to ignore realities like "how was the electricity powering this car produced?" OTOH, since we're talking about potential future solutions to a hard problem (hard relative to cars, for now)... you kind of need to dismiss current issues if they're solvable to in theory.
Price of electrolysis hydrogen now, when we're not using that much of it is not necessarily indicative of potential prices at scale.
To me, I think we need to focus regulation that gets high potential technologies (eg electricity production and electric transport, atm) past the point on their learning curves where ordinary price economics and/or bans on carbontech can take over.
The problem with marginal mitigation like discouraging flights or large ICE engines is that gains are one-off, and not en route to bigger solutions.
I agree that commercial flight is a big problem. I'm just skeptical that carbon austerity can amount to more than a rounding error in the long term.
1lb of jet fuel has roughly 5kwh of energy. Of course you are going to get less than half of that out as useful work. But an airliner can carry 300000lb of fuel. So as a first order approximation you are going to need 10000+ Tesla battery packs to do the same job.
https://www.newscientist.com/article/dn11652-climate-myths-c...
1: Jet fuel makes water when burned as well: by mass it is ~18% hydrogen, and by energy content it produces 55% as much water as pure hydrogen. The fuel itself is vastly less relevant than the amount burned.
> Coal fired plane might be better since CO2 is a much weaker greenhouse gas than water.
This is a fundamental misunderstanding of how atmospheric water works.
2. Water vapor -which is a gas- is effectively set; it cannot be affected by dropping water in the air. The amount of evaporated water is only affected by atmospheric temperature.
3. Liquid water droplets in the air are just clouds. Unlike water vapor, clouds are extremely good anti-greenhouse gases. They block visible light but allow infrared through. Seeding clouds with sulfuric acid is one of the suggested ways to fight global warming.
4. Contrails are made of ice crystals, not gas or liquid water. Ice clouds cause greenhouse forcing, but the destruction of ozone and other protective gases from high-altitude radicals in jet exhaust is generally considered a larger concern.
5. This is an area of active research, not something that is neglected. All climate research needs a lot more funding.
https://en.wikipedia.org/wiki/EGTS
And longer term, electromagnetic catapults embedded in runways can be used to launch aircraft using renewable power. The engineering challenges will be huge and a new generation of airliners will be needed to make it work, but the concept is technically feasible.
https://www.theregister.co.uk/2012/09/07/airbus_smarter_skie...
but take-off and cruise use probably ROUGHLY the same amount per minute flown - because why waste time cruising at a significantly lower power setting?
> So would a hybrid model plane make sense to use jet fuel or equivalent for the most energy consuming part, then electric batteries for the least intensive parts?
Not at all, because energy is just energy, and full batteries weigh just as much as empty ones, but full fuel tanks weigh a LOT more than empty ones. And empty ones are more efficient to keep aloft.
cite: https://www.usatoday.com/story/travel/columnist/cox/2014/11/...
Breaking it down in my head, I come to a different conclusion. Engine power during cruise can maintain higher speeds at less power compared to takeoff. The wing generates lift most efficiently at the designed cruise speed when not changing altitude. Lower power at cruise doesn’t mean poor time trade off. Since the power is lower the energy (fuel burnt per minute) should be lower during cruise.
Also, you need that power for emergencies. Including separate "maximum power possible" that rips engines apart that is needed on current twin jets.
Maintain _which_ higher speeds? The ones that are lower than they could be?
Yes, a plane can generate lift more efficiently when not climbing. But it can generate more speed with more power - so why would it not generate more speed if it has power to spare?
Electric aircraft, however, sound really good in a boardroom because the logistics are "simpler" (disregarding the issue of charging gigawatt-hour batteries somehow).
The idea of a battery plane sounds too good to be true , and it 's probably decades away
Air travel is (for a certain distance) the most efficient way to travel. No infrastructure needed along the way (if you discount the air ports used as emergency targets), fast, and quite flexible. Trying to ignore that is futile.
We should simply mandate a growing percentage of carbon neutral fuels for all aircraft traveling to and from our countries. Start with 1% next year, it should be easy to implement and then increase every 2 years by another percentage point.
Owners of electrical drones know that the fun often ends after around 20 minutes with the battery being the heaviest part by far. I remember there being a drone that could fly for 2 hours with the whole body basically being the battery.
In addition some of the other pollution (NOx, particulate etc) could be more manageable when coming out of a large smokestack in a desert vs in the cramped spaces of a city (car) or upper atmosphere (plane).
I’m definitely not defending coal! Just saying the calculus is complex and multi factor.
Being forced into security theatre, not allowed your drink or food, forced to overpay in airport... Smells a lot like how housing market is regulated by councils or NY trains having higher carbon emission than Prius due to admin costs...
Most of stewardess could be replaced with a vending machine. Bunk beds made using compliant mechanisms. Tax charge passengers by weight, not by height.
Here's something even more ambitious - it's really bizarre that airlines buy airplanes and then decide to skimp on maintenance. They should really be leasing them from manufacturer who does all the maintenance. Same with pilots, but perhaps they could be airport staff (especially crew). Airline should only focus on ticketing and routing (similar to how energy and telco markets are "deregulated" in some countries).
All electric will require lower speeds and probably a hybrid airship airwing design
I can see it now. Max weight/batteries on take off. Controller to drain batteries serially, and as each one is exhausted, chuck it out the bottom of the plane (with some kind of landing/recovery mechanism). When you start running low on batteries, re-fuel at the nearest tanker.
Obviously I'm kidding. The tanker model is ridiculously expensive. That's why you only see it used for extremely critical things (military).
#1 - this article is a great example of how the conversation is shifting, but the mid-point we're at now is a wasteland of nonsense and cognitive dissonance. the text of the article is about the truth of what things matter to reduce your footprint (kids, flying, cars, beef), but the tone of the article and the headline is one of "things are gonna be fine because the whiz kids are working on it" soft-denialism.
#2 - the co2 footprint from jet travel is somewhere between half and 1/4th of the overall greenhouse gas emission footprint of flying. this is because nitrogen oxide and water vapor are also greenhouse gasses (particularly at altitude). It gets very complicated to factor, but at a high level you should simply 3x the carbon cost of flights for the "CO2e" total: https://en.wikipedia.org/wiki/Environmental_impact_of_aviati...
#3 - the electrification of air travel is very well under way. it will not replace trans-oceanic flights in our lifetimes, but it can replace a massive amount of regional travel, and customers can be forced to adapt to a multi-hop world (jfk <-> ord <-> den <-> sfo). If you'd like to learn a ton about the state of the art 1 year ago, check out this playlist from the Sustainable Aviation Summit last year: https://www.youtube.com/watch?v=6LDU0Wgn0Lk&list=PLWUnMAqjJ9...
You can stop kids from seeing their grandparents quite easily by raising ticket prices or taxing jet fuel. I’m not so sure that’s going to keep airlines from serving JFK-SFO direct for business travelers.
I don’t expect to see that in my lifetime (next 40 years).
I can steer or create a significant multiple of that value by visiting my teams for a week. There’s massive financial incentive for me to take that trip.
A significant part of the volume in a ballistic rocket is oxidizer which a jet does not need to carry. Liquid methane is much less dense than jet fuel, so it makes sense it would take up much more volume. Also, methane has less carbon in it than jet fuel on a per energy basis.
Still suspect you are right.
The average person does not fly in a given year. Those that do fly tend to take no more than one trip. A very small percentage of frequent flyers account for the bulk of air travel. An explicit rationing system would allow "regular" people to still fly occasionally and would have huge benefits for cutting air travel overall while impacting only the frequent flyers. People would be forced to ask if they REALLY need to fly out to NY for that meeting.
The boosts to the VR/Skype/virtual presence/hologram/conferencing field would be enormous.
Maybe I'm not as typical as I think, but all your proposal has done is cause me to drive to the one or two conferences I go to each year. Probably not a win at all since I don't drive and EV.
Unfortunately of course, that will only do so much, because the growing global demand for things like air travel, personal car ownership, meat in diets, or air-conditioning mean the numbers on this chart will start to get uglier: https://en.wikipedia.org/wiki/List_of_countries_by_carbon_di...
I just hope they don't end up more exposed to bird strike due to bigger more efficient turbines with more composite components.
If you mean "what externalities would come from turning CO2 into fuel and then burning it again to fly an aeroplane, rather than not flying that aeroplane", then that is a complicated and somewhat open question:
https://www.carbonbrief.org/explainer-challenge-tackling-avi...
For instance, if, say, converting natural gas heating to electric is a better use of energy in terms of reducing greenhouse gasses, then maybe we should do that first.
In the end, a lot of these sorts of proposals depend on cheap renewable energy, and if we can get enough solar and wind power installed then other goals become feasible. Fuel production is an interesting case because you can use surplus energy at times of low demand.
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Not a good starting point for a discussion.