>Fossil fuel driven flight is not viable in a sustainable future. We need to understand this.

But it's the reality. Electrification of individual ground transportation, and the phasing out of gasoline cars, is absolutely inevitable over the next 20 years. But jet fuel isn't going anywhere for a long, long time. It's just a matter of physics. It's foreseeable to have small scale electrified commuter aircraft shuttling people within 400 miles. But any type of long haul flight will be done with turbine engines burning kerosene. Even with a 10x increase in energy density for LiPo batteries, we still wouldn't be there.

I don't disagree with anything you've said, but not having a viable alternative to fossil fuel driven flight right now doesn't justify accelerating the damage it's doing by leaning further into it.

Aviation is small fish though. REALLY small fish. This type of aviation even more so. It accounts for only 1-2% of anthropomorphic CO2eq production. Benefits outweigh the bad. I'm not aware of climate scientists actually caring about supersonic travel.

I'm kinda surprised to see this kind of hostility. Same thing happens when nuclear is suggested even though the IPCC HIGHLY advocates its use. It is all about relative impact. Part of the problem with resolving climate change is that even the people who acknowledge it fight among themselves and don't push for both current technologies (which includes nuclear) and research for new technologies (fusion, batteries, and better solar/hydro/wind). We need to just listen to what the experts say, not what you read in some blog post or HN comment.

Aviation is currently a small fish because it's currently available to such small part of the population on a regular basis. For those that take part of it it's a major part of their footprint. Scaling it up to more people is very unsustainable. Therefore fossil fuel aviation is unsustainable in a world where more and more people get richer.

> Same thing happens when nuclear is suggested

It's not the "same thing". Nuclear has some sustainability benefits. Bringing back commercial hypersonic air travel seems to have no such benefits.

If we cut carbon out of everything else, the price of oil will drop, and aviation will be able to greatly expand.

Air travel is low now only because it's expensive. People world gladly take many, many more flights if they were cheaper.

Of course if we taxed carbon this problem would go away, and taxing international flights would probably be easier than a general carbon tax, if flights were all that was left.

Internet experts, politicians, bureaucrats and intellectuals can argue until the end of time about which CO2-emitting products and services deserve to, or should, exist.

Just the same way the expertise of the most-brilliant central planners in the USSR and elsewhere allocated resources.

It doesn't work. There's a better way which is also consistent with democracy and individual choice. But people don't like the sound of it.

> There's a better way

You mean putting a price tag on emissions I assume?

Yes of course. Just tax carbon (and use the proceeds to give a flat rebate to everyone).

I’m not sure why you’re downvoted... this is 100% the best way to incentivize reduction in carbon emissions. And just keep upping the tax gradually as needed.

Is it? Flat carbon trading without any credit schemes is as good and has some pretty good precedent going for it (nox and sox markets)

It's the next-best solution. The only reasonable argument in favor that I've seen is that it is easier and more authoritarian (maybe be careful believing this is a good thing?) to set a hard cap. But a carbon tax can always be adjusted.

It's inferior in econonic efficiency and comprehensive coverage to a carbon tax.

And if implemented incorrectly, it becomes corporate welfare, and this has already happened. It has potential to be just another corporatist-cronyist scheme at taxpayer's expense.

And to date government and bureaucracy have been pretty horrible about solving climate change.

Carbon tax is a simple, elegant, efficient, effective solution. Most people just dont like the sound of it though.

If you edited your original post to add carbon tax, it would probably read a lot clearer. (I upvoted it, I agree)

How would you solve the trade component though? Because carbon production would just shift elsewhere unless:

* there was an international treaty where states each agreed to raise carbon taxes and cut other taxes or do a dividend, or

* import tariffs were levied in proportion to the carbon used in imports from countries that didn't have a similar tax

The latter would demand a large bureaucracy and have a lot of distortions.

I realized recently that a carbon tax isn't like an income tax. An income tax only occurs on profits, whereas a carbon tax is an input tax. This makes the jurisdiction shifting problem more acute.

A carbon tax is still my preferred solution, but was wondering if you had any ideas on how to get around this.

I dont really have a strong opinion or definitive answer.

What I know is that many other industries deal with somethint like this. Not just taxes, but costly regulation hurts domestic production. For example, countries which do not respect responsible fishing practices have a competitive advantage.

Part of the answer can be: just dont let those countries sell fish within the US. Others can be international treatise or laws.

If I were king, I'd need to spend more time to consider my options, but I guess a treatise is in order. I dont see how any climate change action within the US's 350M population will do anything meaningful to solve the problem if the other 6.5Billion are not cooperating.

> The only reasonable argument

Except for the fact that markets are a great way to manage rivalrous goods, dynamically balance economic need against cost without the need for a centralized authority to have high-touch meddling (which presents a corruption danger), oh and most importantly, ad I said, they work, empirically, as with the United States SOX and NOX markets

Initial post wasn’t meant to be hostile at all and I’m still unsure of whether or not supersonic travel is a net positive or negative.

My issue was with the parent comment essentially suggesting that you can justify boosting emissions from flight travel because we still rely on fossil fuels, so might as well double down. Nobody was suggesting that we immediately cease all flight travel. I’m open to the possibility that supersonic travel is a net positive, but the argument needs to be around what we’re getting in return for the emissions and why that’s worth it.

>We need to just listen to what the experts say

People saying supersonic travel is a step in the wrong direction are listening to experts who agree that our use of fossil fuels is a threat to humanity and the environment. And what about when experts disagree? There has to be some level of independent thought to parse and apply what experts are putting forward.

> I'm not aware of climate scientists actually caring about supersonic travel.

Because there isn't any. None. Zero. Why would you be aware of people worrying about something that currently doesn't exist?

> Why would you be aware of people worrying about something that currently doesn't exist?

I'm not sure how to break this to you, but scientists are generally aware about up and coming technologies. And we do think about potential future impact.

So let me rephrase

>>I'm not aware of climate scientists actually caring about potential future implementations of supersonic travel.

I'm not sure how to break this to you, but supersonic flight isn't an up and coming technology.

It's decades old, and it's failed for economic reasons.

Climate scientists worrying about the impacts of supersonic flight would be like Ornithologists looking to spot dinosaurs in the wild.

That’s because they’re more aware of the history of commercial supersonic transport than the investors at Boom, and therefore have no reason to worry.

Haters can't make up their minds...

You don’t expect to see an unvarnished historical perspective derided that way here, but I suppose you have a point. Can you tell me where I’ve changed my mind on this issue?

By that standard you shouldnt be using the internet. The “damage” is questionable to say the least. There is a whole group of poor people who need access to fossil fuels to survive, but are you going to stop them from getting it in the mame of climate change? Are you goin to stop buying computers and other products build and distributed using the internatioal supply change? If not why expect others to do what you dont?

I don't understand this logic. How does one action with unfortunate side effects excuse another?

Sure perhaps we shouldn't be using the internet. Or perhaps we should do a lot more to make sure that the energy used for powering the internet is sustainable.

But our deficiency in that area doesn't make this activity any better.

Who are you to decide what is ok and what is not? How do you know that building a supersonic jet doesent open up for other technologies or methods that wil improve effectiveness of fuel consumtion? I dont understand with what logic you get to decide that your consumption is ok but other peoples use isnt.

Nonsense. It's less than 1% of our carbon emissions iirc. In theory we could convert that over to biofuels and/or hydrocarbons produced using CO2 from the atmosphere, at which point it would be carbon neutral. It may be the only reasonable way to get the energy density we need for practical air travel in the near term.

“The global aviation industry produces around 2% of all human-induced carbon dioxide (CO2) emissions. Aviation is responsible for 12% of CO2 emissions from all transports sources, compared to 74% from road transport.”

But that’s with current aircraft supper sonic is less efficient and enables longer flights having a very outsized impact for minimal gain. You can both sleep and use high speed internet from modern jets, going 2-3x as fast adds little productivity.

On top of that emerging markets are just as happy to start flying as start driving which is pushing up flying’s impact every year.

> You can both sleep and use high speed internet from modern jets

Speak for yourself — I can't sleep on planes. Nor is airplane internet anything close to high speed by any standard. It's expensive as hell and doesn't exist over oceans. At the same ticket price, for long-haul international, I'd greatly prefer an economy-sized seat in a 2.5x shorter flight to a biz-class seat in a traditional flight.

The cost of these things are well into first class territory* which I find much easier to sleep in vs business class. Turbulence can still occasionally be a thing, but it’s less frequent on long haul flights because they have more options.

As to internet over the ocean, Gogo has quality high speed internet via satellite. If you have not flown on one of these flights or a competent competitor you will notice a real difference.

*At least until a large number of aircraft are in service. Airlines make the most money per square foot with business class, but first class is still a critical revenue stream. Free up first class space via these and run fewer large aircraft with a higher percentage of business class is going to be most efficient. This also means you end up with either fewer economy seats or more expensive ones as currently first class and business class subsidizes economy.

Much as you wish it were the case electric battery power does not have enough power density for mass aircraft transit yet. They're much too heavy. We're getting there but we're still a good decade away. You're certainly not going to get supersonic airliners with electric aircraft. (Elon Musk keeps talking about it but even he states that the energy density isn't there yet.) People need to realize the difference between fiction and reality.

How much do nuclear submarine power plants weigh? :-) Looks like on the order of 600 tons; also looks like 787s carry over 100 ton just in fuel fully loaded. So it is plausible that a scaled down nuclear sub reactor should supply plenty of energy at reasonable weight budget. Obviously you'd want it to be somewhat robust and maybe eject + parachute it for catastrophic scenarios, rather than irradiating whatever the plane runs into.

It's been tried, back in the 50s and 60s: https://en.wikipedia.org/wiki/Aircraft_Nuclear_Propulsion

Never went anywhere then but I'd be interested to see whether modern tech could make it feasible.

The problem is shielding all of the people. When you land the plane all of that ionizing radiation bounces back at the people inside giving bathing them in fatal or near fatal levels. The shielding is just too heavy and the physics of shielding make it very unlikely we can develop anything lighter.

Also should the plane have an accident you now have radioactive material spread over miles. Which is also not an easily solved problem.

> When you land the plane all of that ionizing radiation bounces back at the people inside giving bathing them in fatal or near fatal levels

Can you elaborate on what specifically about landing causes that?

The energy requirements of moving in the water and the air are completely different so its not a good comparison point. And subs use nuclear power I am pretty sure nobody wants to have planes flying with nuclear reactors over their heads.

It wasn't intended to be a comparison of subs and planes; subs just have the smallest production nuclear power plants that I know of.

I don't agree. While electric plains maybe in the future, carbon based fuels will continue to be a requirement for a long time.

Eventually we can move to produced carbon based fuel but that will take a while.

Until then, the old green idea of 'lets just not do it' is simply not viable to reduce carbon usage.

> lets just not do it

I don't see why this is any less viable than the other alternatives. It's the only option that we've already tried. Before invention of air travel.

I mean of course I see that people don't change. But that's the very thing we absolutely need to fix. We have to stay within our means. Not doing the thing that brings cost seems like a simple enough solution.

If not having commercial supersonic flight isn't viable, quodlibet.

Its not viable to stop the world from using technology and use it just because it goes against your personal preference.

Until we have better technology we have to scale down or reliance on unsustainable tech. The alternative is adverse degradation of our most sophisticated technology available - the biosphere.

Yeah, see, saying “let’s all stop doing this thing” where the thing has diffuse long term bad effects for everyone but short term benefits for the person that does it generally doesn’t work. People have been trying that for a long time. It has to be written into law, or the benefits (economic or otherwise) need to be tilted toward doing the right thing.

I think a large carbon tax is the only shot of getting everyone on track with reducing impact.

Yes. No disagreement here. We absolutely need to put it into law. Although, making such legislation happen doesn't seem to work either. But we need to make it so.

I think slower flight might be best for long distance travel. Something like an airship. I don't know much about the technology, but my naive view is that the technology is undervalued. An airship has VTOL, is quieter, is more spacious, produces less carbon emissions, etc.

Weather issues are one problem for airships. Actual ships are an option for transatlantic routes but there is basically one limited alternative for that. People basically want cheap and fast. Once you get beyond driving that mostly means subsonic planes.

Thanks, I was not aware of the weather problems.

I'd be willing to take a slower option and I think at least some others would too as long as it's less cramped.

International airline travel can already be pretty much as roomy as a mass of people are willing to pay for on a route. And shifting to a slower mode of transportation that's equally or even more roomy tends to carry a big premium as well. Taking the train or a ship on a multi-thousand mile trip costs more than certainly economy flying does. You can generally travel in comfort. You just need to pay for it.

My wife and I took our then-infant daughter on a 2800km train ride about five years ago (Toronto to Saskatoon by VIA Rail). We paid extra to have sleeping berths with meals included vs regular seats, but overall it was pretty expensive and slow:

- You spend a lot (would estimate 30%+) of time waiting on sidings for freight trains to pass in the other direction because there's only a single track owned by the freight company, so their trains get priority.

- There's no back up plan, and only a few trips a week. Our train happened to run on time, but I had a family member try to take it a few years later and ended up having to cancel for refund and fly instead because the train was running 24h late and she needed to be home for something.

- It's priced and advertised as an "experience" comparable to going on a cruise. They serve you nice food, but obviously the cost of all that service is baked into the ticket— no one is pretending that you'd choose this option just to get to your destination.

- We got our fares for around 60% off, but it was still $450 per adult, I think, which was a lot more than our return flights were (we could afford neither the time nor money required to take the train in both directions). Getting these fares required weeks of monitoring for VIA's "discount Tuesday" promotions and then building our travel plans around the specific dates offered.

- No wifi or even cell reception for most of the route. The northern Ontario section of the route is extremely remote and not at all scenic— just mile after mile of unremarkable forest.

Maybe there's room for an option that's slightly more comfortable and slightly slower, if that's what an airship would offer? But as far as the train goes, it's lots more comfortable and many times slower, but there's just no way to make the cost comparable to flying when you need to pay for all those hours of staff and equipment.

Air ships were already obsolete before the Hindenberg disaster. Being by over twice as much the most expensive mode to travel in, having to take a trickle shower, share a dry toilet with 20 other people, and sleep in a bunkbed (all to save weight) is an extremely lousy deal.

Edit: Why are people downvoting this? I just googled it and confirmed what I posted here.

An airship has far lower payload capacity and is SLOW. VERY SLOW. A car on the interstate would outpace one.

Could we at least use them for bulk transport of non-perishable goods? Container ships are slow too, and we're fine with that.

No. The payload fraction is just too poor. For instance, the Hindenburg, which was the largest, most advanced Zeppelin ever built, had a payload capacity of only 21,000lbs. That's using hydrogen, which, is, obviously not real safe. If it had used helium instead, it would have had a payload capacity of -34,000lbs.

For comparison, a single 40' standard container has a maximum load of 57,000lbs, and a large cargo ship can carry thousands of those.

What was the mass of the Hindenburg without the lift gas? Doubtless modern composites could significantly reduce that mass, which could go directly into increased payload.

Alternatively, an airship of the same mass of the Hindenburg could be made significantly larger, and since payload scales with the lifting gas volume, payload would also increase.

Oh, and throw the Hindenburg's aluminum piano over the side.

I note with interest that you say the Hindenburg would have had a greater payload with Helium rather than Hydrogen. Why do you say that?

> I note with interest that you say the Hindenburg would have had a greater payload with Helium rather than Hydrogen. Why do you say that?

I did not say that. Note the negative.

I saw the dash, but didn't understand it. If the payload with hydrogen is 21,000lbs and it is -34,000 pounds with helium, then it seems like it wouldn't even get off the ground. But clearly, it did get off the ground with passengers using helium, it was designed to fly with helium.

No it wasn't. The German Zeppelin's always run hydrogen. At the time the US had the only real supply of helium and they wouldn't sell to Germany.

Okay, I stand corrected about it flying on helium, thank you for correcting me, +1. However, the Hindenburg was designed to fly using helium as the lift gas.

https://en.wikipedia.org/wiki/Hindenburg-class_airship#Lift_...

The article goes on to say the difference in lift between hydrogen and helium is only 8%.

Edit: drop the apostrophe on zeppelins

8% of 500,000lbs is....

Thanks for posting. These are interesting figures that show airships are not as good as I suspected.

Why is that an absolute? Can't biofuel sources be refined into jet fuel?

I understand that subsidies currently create perverse incentives in that industry, but I struggle to see why bioengineered carbon-neutral jet fuel is fundamentally not viable. That thinking seems very closed-minded.

Biofuels have been a disaster inasmuch as we've destroyed enormous amounts of rainforest to grow them, releasing quite a bit of carbon in the process (and destroying wildlife habitat, of course)

That'd not an argument that carbon-neutral supersonic jets are impossible and should be abandoned.

Biofuels doesn't necessarily mean subsidized corn fields... for example, algae and bacteria grown under specialized LEDs powered by renewable energy are another path forward.

Perfect is the enemy of the good. We can research supersonic jets in addition to better electric storage and propulsion systems.

That's great if we have the algae and bacteria. Right now we don't seem to. Maybe we should invest the money there.

In theory, you can power a big car on responsibly sourced fuel. In reality, selling millions of big cars is a huge problem, because of course people will understandably put in the cheap, ubiquitous fuel for which they're not covering externalities.

> Perfect is the enemy of the good.

This saying is not suitable here because unsustainable technology isn't good. It's simply not worth the cost and we are borrowing from the future.

If the venture would be unprofitable up until the point when it would be sustainable would we still push money into it?

I say we should treat any venture that is unsustainable the same way we treat those that are unprofitable. But we don't. We allow unsustainable ventures to carry on without ever becoming sustainable. Which means that it is constantly borrowing (stealing) means from everyone else.

In my mind the most viable way to make air travel sustainable is to use synthetic fuels produced with commercialised fusion power and atmospheric greenhouse gases as input.

It sounds very sci fi and I'm not sure it would even work on a napkin calculation produced by a thermodynamics professor.

Sure; it's not an unreasonable approach for making such travel carbon neutral; the idea being you're sequestering parity amounts of carbon via the atmospheric gases -> fuel process, and nuclear power covers the inefficiency of such a process.

Downsides include:

1. It's only neutral. It doesn't remove gases we've already released.

2. The process is almost certainly extremely expensive. Until something like emissions taxes are levied, it will not be a competitive fuel.

It's slightly better than neutral. Captured atmospheric carbon would be stored out of the atmosphere in fuel tanks until use. And we could decide to capture and sequester more than we plan to burn again, since in this scenario we have the capturing tech sorted out.

Sure, under the assumption it's cheap to sequester more than all of the oil we extract out of the ground and consume today, then some could be stored to make it neutral or even positive. There are two big steps in there that might or might not ever happen.

Long term you could switch to biofuel or similar https://en.wikipedia.org/wiki/Aviation_biofuel