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Comment by lucidguppy | Hacker News Reader

Flight is a luxury of the current times that will likely not last another 100 years except for the very rich.

Why do you say that? Typical fuel consumption values for passenger aircraft are 2.5-4 liters per 100km per passenger. So if you fly 1,000km, you'll use 25-40 liters of fuel. At current prices (around 60 cents per liter), that's $15-25 worth of fuel.

A liter of jet fuel contains 35-38 megajoules of energy, which is around 10 kilowatt-hours. Assuming 5% efficiency of using CO2, water, and cheap solar electricity (3 cents per kwh) to synthesize fuel, the cost of input energy per liter would be around 60 cents, which is the same as current fuel prices. The actual cost would be higher because you need to pay for the plant, workers, consumable catalysts, transporting the fuel to airports, etc. But real world efficiency would likely be higher than 5%. Also solar panels are still getting cheaper and more efficient, so 3 cents per kWh may be considered expensive in a decade.

Even without electric aircraft, there's no reason in principle why aviation needs to be expensive or bad for the environment. If demand for petroleum causes prices to increase enough, synthesized fuels will become economically competitive.

I believe that by 2050 synthetic hydrocarbons made from carbon dioxide and clean electricity will be deliverable at a real (inflation adjusted) cost less than than 3x current oil prices, on an equivalent-energy-content basis. That could more than double the costs of a transatlantic flight, but still wouldn't price it out of reach of the upper middle class.

Synthetic methanol made with renewable energy has already been commercialized on a modest scale:

https://carbonrecycling.com/technology

Methanol can be reformed to kerosene as a drop-in replacement for oil derived jet fuel:

"Fischer-Tropsch & Methanol-based Kerosene"

https://aireg.de/wp-content/uploads/2024/07/airegWebinar_FT_...

Just build more nuclear power plants. There’s absolutely no reason why modern civilization still needs to rely so heavily on hydrocarbons. Unlimited electric energy, with a electrified rail network, public transportation and EVs for commuting, should take care of most use cases, except maybe a few where the energy density doesn’t make sense.

And don’t even get me started with the “our grid cannot handle it” nonsense. If it cannot, then make it so that it can. When this country started off, we didn’t say “our roads cannot handle the cars”, instead we built them, quite a lot of them. We can do that again.

Sure, nuclear too. I'm fine with any low-emissions energy source. Electrification can take care of most terrestrial transportation. I still think we'll eventually use synthetic hydrocarbons for long range flights and a few other niche applications like rocket launches.

At 10-15% conversion efficiency, you're burning 85-90% of your energy just making the damn fuel, requiring 6-7× more renewable infrastructure than direct electrification. Current production costs are $15-25/gallon (not the fairy tale $2-3/gallon of jet fuel), and the physics won't magically improve to hit their "3× oil prices by 2050" fantasy. To replace global aviation fuel would demand a staggering 32,000 TWh of new clean energy generation – that's roughly equivalent to building 900 nuclear plants just to make luxury jet fuel while the rest of the grid still burns coal.

You've not actually addressed the cost points he makes. You seem to bediscounting the sheer cost effectiveness of renewable power because if an ideological opposition to it.

The wonderful thing about looking at how much something actually costs is you don't need to do all the work yourself - just look at the expense of the inputs and calculate your output. Solar panel electricity is absurdly cheap.

In any case it's obvious that current direct electrification is not feasible using current battery tech, so alternatives need to be explored. Unless we find a battery tech with 10x energy density batteries aren't likely to be viable in the air.

Actual comprehensive high speed rail networks would reduce the overall carbon footprint of travel by a huge factor, while still permitting a high overall degree of affordable mobility.

A one-way ticket for an Amsterdam - Paris train, taken well in advance (2 months from now), costs $159.30. It's a 3.5 hours long trip.

https://eurorails.com/en/trains/amsterdam-centraal/paris?dat...

A similar one-way ticket for the same date for a flight costs $112 (with no bags), and it takes 1 hour 25 minutes.

https://www.kiwi.com/en/search/results/amsterdam-netherlands... (Yes, some people can say that Kiwi is a shady website, but it can find some good deals if used right.)

I think most of the public would choose the second option. And this is a 500km long trip. Anything longer, and planes win by even larger margin.

If you're talking about the US, there's more about its rail networks density than unwillingness of Americans to build new railroads. It's also because people... don't really like using trains for long-distance transit?

I'm not saying it'll cost the same, I'm saying it'll still be accessible. (Also, comfort level on a train is typically much better.)

And it'll properly price in externalities, which is not currently the case.

Also, just to quibble, I think the _total_ travel time is actually not that different considering you're supposed to get to the airport at least an hour early, and how accessible airports are to population centers relative to train stations.

If you had to catch a cab either two or from the airport, but could avoid it with a train, the costs you cite are suddenly about the same.

HSR infrastructure costs $50-80 million per kilometer in developed countries.

Chill, biofuels or gas synthesis will be fine and carbon neutral for big jets. Once solar or fusion produces the primary power cheaply the conversion loss isn't a huge deal.

I think we'll see the global rich (western middle class) continue to fly well past the onset of the famines and refugee waves.

Without a single family detached house and a regular vacation flight most "middle class" people would have no idea why to get up in the morning. Our whole culture is built around lauding and striving toward that pattern as the good life. It will have to be taken from them, they will not give it up willingly.

> It will have to be taken from them

Be careful when advocating force towards others. Violence is the last refuge of the incompetent, after all.

They may not have been alluding to violence; perhaps something like democracy itself would be enough to take that lifestyle away from the middle class. If billionaires consolidate enough power & resources and push the tax burden onto the middle class which makes yearly vacations unaffordable

Perhaps they were referring to economic force. But 'it will have to be taken' isn't a passive statement either way.

Ah yes. George Washington, Simon Bolivar, Vladmir Lenin, etc... famously incompetent.

Incompetence can take many forms. Some of them include starting a fight they can't finish.

I chose those examples specifically because they were completely successful.

Those were; many were not. Someone who takes issue with the middle class of the USA might not be.

you're committed to the username bit

yup

Density is a must have in our civilizations....

How dare you stand in the way of regular people burning hundreds of kilograms of fossil fuel in order to spend a couple days at the beach? /s

When Elon and Taylor give up their jets, I will too.

People drive to work anyway. A vacation or two every year is probably not even a double digit percent of a person’s total fossil fuel usage, and gives them a lot of happiness and reason to work and do things that are good for society.

Also: https://en.m.wikipedia.org/wiki/Fuel_economy_in_aircraft

It is pollution and it harms people. So in order to do things that are good we must harm others first (or after)?

Why is there a segment of the population that wants to live in poverty and squalor?

How much pollution is okay? Why not argue for efficiency standards rather than bans?

Everything could be said to “harm people”. Banning travel could make some people depressed and who knows what that could lead to? Or it might lead to a less connected world and less familiarity with people in other places, and maybe makes wars more likely?

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