Figure 1: DALL·E generated image of a futuristic electric passenger airplane flying above white clouds and mountains, digital art

Dreams of soaring through the air and out of the atmosphere entirely have inspired humans for thousands of years. And unsurprisingly, those dreams have attracted innumerable people who want to cash in on starry-eyed investors. But the space also attracts clear-eyed engineers and business people working to move people and goods around the world and into orbit.

And so an acrobatic flight through another sexy vs meh quadrant chart to complement the ground transportation and marine shipping segments in the series.

What defines sexy? Lots of press. Frequent headlines. Gushing talking heads who should know better. Promises of hyperbolic deployment and profits. SPACs or ICOs. VCs. Glistening PhotoShop renders. Curves. Lots of fanbois and fangrrrls who take every opportunity to rant about its wonders.

Meh? Few media headlines. Business as usual. Stuck in narrow and industry-specific journals. Lots and lots of numbers, and often not a lot of hype. Sometimes lots of institutional investment.

Practical? Lots of deployment. Lots of deals. Lots of straightforward growth. Economically viable. Don’t assume the laws of physics are mutable. Don’t assume human nature will magically change.

Foolish? Ignore laws of thermodynamics. Ignore better alternatives. Ignore tiny market potential. Ignore the history of failures of exactly the same thing. Ignore human nature. Ignore denominators. Delivery always fading into the future. PowerPoint and PhotoShop, not production.

Figure 2: Quadrant chart of sexy vs meh for aviation and aerospace

And so, into the quadrants, starting with sexy and practical, which has some good stuff in it. 

Sexy and practical

Let’s start with SpaceX. I’d have called it ‘reusable orbital rockets’ but that would have been too long and it would have implied that there was actually more than one player in this space. 

Not only is SpaceX eating the launch delivery market with much cheaper and more frequent launches, a full third of all orbital launches in 2022 globally, but its StarLink near-Earth orbit constellation is helping coordinate Ukrainian military efforts and is showing up on airplanes to provide amazing in-flight delivery of kitten videos. Part of my odd past included putting satellite internet connections in far northern bank branches built on permafrost and trying to assist in a small way with getting Australia’s high-speed internet-for-everyone national broadband network delivered, so I know the value and difficulty of getting connectivity urban dwellers take for granted into less developed areas. This is a game changer for global education, part of the solution for bringing the last billion people out of deep poverty and remote resource extraction automation.

Next in the quadrant is pilotless aircraft winging their way through our skies. It doesn’t get as much hype as cars that drive themselves, but that’s in part because autopilot has been a feature of aviation for over a hundred years, starting in 1912 with Sperry Corporation’s gyroscope and hydraulics mechanism. But it’s been ramping up quickly in recent years as smaller flying vehicles are increasingly autonomous, and there’s information sharing going on between big and small aircraft innovators. But while XWing is making it clear that it’s comparatively trivial to have an aircraft fly itself from hanger to hanger and that autonomous ground movement and flight is easier with planes than urban streets are for cars, it has to exist in an air traffic controlled world where safety certification is key. That’s going to take time, and more on that later.

Finally in this quadrant, although dipping into the meh range are unmanned aerial vehicles aka drones. From tiny remote controlled toys to extreme sports autonomous athlete chasing camera platforms to 4 meter diameter agricultural spray drones to military drones loitering over battlefields well over ten thousand kilometers from their minders, aviation is increasingly without pilots. Why does it dip into meh? Well, some of the most impactful forms of UAV innovation are hiding out in pedestrian rural automation areas, not in cities and definitely not in Instagrammed extreme sports.

Admittedly, there’s some sexy nonsense here, but ideas of Amazon drones dropping into suburban backyards or hovering off of condo balconies is a tiny fraction compared to the massive revenue and value growth in this space. We’re now at a point where over 90% of American farmers own drones or are using drone services for field and crop data gathering and many are extending that to heavy-lift drones dropping herbicides, fungicides, pesticides and fertilizer on crops, displacing much more expensive, heavier and soil-compacting tractors. Wind turbines are being inspected by drones. Linear assets like transmission lines are being imaged by drones and machine-learning is stitching the data together into actionable insights. Helicopters and smaller fixed wing aircraft are gathering dust as drones eat their revenue streams.

Sexy and foolish

For every practical but still click-baity aspect of aviation and aerospace there are two or more purported innovations or solutions that are simply foolish. 

Leading the flock in this quadrant is urban air mobility (UAM), the idea that we’ll be living in a Jetsons’ future with electric origami rotorcraft, eVTOLs, that take off and land vertically on car park rooftops and soccer fields, then contort themselves into an efficient horizontal flight profile, whisking people and goods over densely populated areas while children play obliviously below in school yards and parks. 

We do have working vertical take off and landing aircraft that turn into airplanes, but they are all military, and they have a distressing tendency to fail, killing passengers and crew. The US military’s Osprey is a poster child for this class of aircraft, having killed 51 people who were ill-fated enough to be in the overly complex beasts when they failed. None of those failures were as a result of being shot at. They weren’t even in active battle zones. It’s just really hard to turn a helicopter into an airplane and back again. If you want Transformers, stick to movies. At peak valuation there was about $29 billion in SPAC-fueled pump and dump stocks, but that has collapsed by $24 billion, with no entrants being remotely capable of being certified for anything except recreational jaunts over unpopulated land or water after passengers sign away all rights to sue for their survivors.

Supersonic and hypersonic passenger aircraft are prominent in this segment too. The first is faster than the speed of sound and the second is five times as fast, which means both can theoretically outrun the howls of outrage of their investors when they fail. Boom and Destinus have pride of place here. Boom’s $150 million USD of funding falls likely 100 times short of what is required, and it can’t seem to find anyone to manufacture an engine for its plane, leaving it unable to even make noise, never mind make a sonic boom. Destinus is a Swiss entrant which convinced seven credulous investors and the Spanish government to give it $56 million USD, an even tinier fraction of the requirement, but they added hydrogen for extra sexy at the expense of even more reality.

Ground effect planes aka ekranoplans have cupped wings and ride a cushion of speed-created air between wings and mostly water. They’ve been around for decades, with the Soviet Union investing heavily, yet never achieved anything remotely like the promises that they claimed. But repeated past failures with nothing remotely like a reason why anything is different now is a feature in the world of overhyped investor magnets. New entrants are taking money from the credulous, with Boston-based Regent making a claim that it is going to build a fleet of electrified ones and South American Aquila Global claiming that it is going to be building new internal combustion versions.

And then there’s short take off and landing airplanes, with the twist these days being that they’ll be electric and hence magically have anything more than the tiny niche of short landing competitions and some remote bush plane uses. These tend to sink into military requirement swamps, as the only real market is for weird front line logistical machines. They certainly have no more merit for urban air mobility than eVTOLs, although many of the founders hunting funding pretend that they are excellent for landing on children’s playing fields, as if that’s something anyone wants to have happen.

Before I get to the other very big and wasteful segment, I’ll touch briefly on space tourism. William Shatner’s reaction was probably the most apt. Having been comped a Blue Origin visit to 102 kilometers above the surface, Shatner was devastated, shot through with overwhelming sadness at the vast coldness of space and the destruction we were wreaking on Earth. Not a great PR moment for Bezos, and a fitting response to rich men paying hundreds of thousands or millions for bragging rights. Branson’s Virgin Galactic is equally senseless. At least SpaceX’s $55 million each guestronauts did something while they were up there, although nothing that much more highly qualified and trained actual astronauts couldn’t have done vastly more of no doubt. But still, sexy and deeply impractical, something for the uber rich to do when they are bored of buying super yachts.

But first among foolishness in this quadrant is for hydrogen and its synthetic fuel derivatives. As I’ve noted many times with mind-numbing details on the basics of physics, economics and industrial manufacturing, hydrogen will never be as cheap as the wishful thinking of its boosters suggests. Price points touted by earnest young MBAs working for McKinsey and the like are usually plucked out of the air to coincide with the price per unit of energy of current fossil fuels, an exercise in fabulation, not analysis.

Electricity and electrolyzers would both have to be a tiny fraction of their current price, and even then industrial scale facilities have close to 30 other components which are already commoditized and so aren’t going to get cheaper. Then the hydrogen would need to be compressed massively or liquified for distribution, both with additional massive energy losses. Using hydrogen as a store of energy requires a willingness to make things vastly more expensive and complex than they need to be in pretty much every use case. Hydrogen will always be multiples of the cost of Jet A and very obvious alternatives.

But for aviation? It’s much worse. While Rob Miller, Cambridge professor and director of the Whittle Laboratory recently asserted on Michael Liebreich’s Cleaning Up podcast that you could in fact put hydrogen in narrow-bodied aircraft, not requiring a massive lifting wing that wouldn’t fit in current airports, there are a couple of outstanding issues. 

The first is that in order for liquid hydrogen at 20° above absolute zero to be in the fuselage with warm-blooded human beings, it has to be completely separate from them in its own airtight compartment at one end of the plane. It does have to be in liquid form, otherwise the flights would be very, very short because you can only compress wisps of hydrogen so much. 

And it does have to be in the fuselage in tanks as close to perfect balls as possible in order for it not to evaporate into uselessness while, for example, the airplane sits on a runway waiting for approval to take off for a couple of hours. The only way that a hydrogen aircraft for human beings could conceivably be certified is if the souls were completely firewalled from the cryogenic flammables. 

Certification wasn’t touched on at all in the discussion, and in fact only appears once in the Whittle Lab’s report on aviation energy alternatives and is not referenced as a variably weighted concern against any of the options they list, as if it is a foregone conclusion that that is the easy part when in fact it’s the hardest and most expensive part for commercial aviation. Certifying a bog standard commercial airliner variant is a hundred million dollars or more, and certifying a novel airframe with a novel propulsion system is well into the billions.

And then, assuming the fuel is at the back of a longer plane, what happens when it is consumed? The plane gets lighter unevenly, and it becomes increasingly nose heavy. It becomes impossible to fly and impossible to land. This is a fundamental problem of this model that once again constrains hydrogen-fueled flights to very short distances. You can’t solve it by spreading hydrogen through the fuselage with the passengers, or by separating the flight crew from everyone else including the people who keep them fed and in coffee. 

Finally, an airplane is a pressurized aluminum tube that flies at 30,000 feet. Hydrogen is a gas that delights in leaking as it’s the second smallest molecule in the universe, is very hard to detect, and ignites at both much lower temperatures and a very wide range of ratios of hydrogen to air. Proving that basic internal systems like coffee makers and microwaves, or vape pens smuggled into washrooms for that matter, won’t turn the airplane into a rapidly dispersing fireball will be very expensive.

Every solution for hydrogen aviation runs into insurmountable obstacles, and it’s remarkable that it keeps being put forward.

And that’s before we get to the inane ideas that thousands of truck loads of hydrogen will be delivered to airports daily, or that airports will be doing multi-step, highly energetic liquifying of hydrogen. Even NASA can’t keep the stuff safe, and SpaceX is moving off of hydrogen entirely because it’s so hard to work with safely. There is no model of distribution and fueling at commercial airports that withstands the slightest scrutiny, but it’s waved away as if, like certification, it’s immaterial.

But what about plug-compatible synthetic fuels made from hydrogen? We can make kerosene synthetically, but the processes all have to have not only that very expensive hydrogen, but also additional molecules and more processes that consume more energy, which means that they’ll be even more expensive. Making fuels from sunlight, wind, water and air is entirely possible, but it’s never going to be cheap. If you start with green hydrogen for energy, every pathway is expensive.

Hydrogen and synthetic fuels made from them are a dead end for aviation, but thankfully there are sensible alternatives.

Foolish and meh

There’s only really one entrant in this quadrant, lighter than air, powered aircraft. Blimps and dirigibles have been around forever, with the first powered flight over 170 years ago. And they’ve been tossed around the sky by the wind, updrafts and downdrafts with each incarnation, impossible to dock in all but the gentlest of conditions.

As floating billboards on calm and sunny days at the ballpark, they had a niche. But every decade, some innovator thinks that it’s time for blimps to finally take over aviation. The most recent ones like the H2 Clipper even claim to be excellent delivery mechanisms for hydrogen, as they are just big powered bags of hydrogen, after all. That ignores the reality that if they deliver the hydrogen they are merely deflated bags lying on the ground, but this doesn’t seem to dampen their enthusiasm. 

Very few people get excited about this class of perpetual failure, so it’s merely meh.

Practical and meh

Finally we get to serious aviation solutions that don’t get enough attention. Let’s start with repowering existing airframes with electric motors, batteries and often generators. You’ll note that this crosses over into the foolish category.

There’s a good reason for that. As much as I am personally looking forward to flying the electric Beaver floatplane from Vancouver to Victoria when it’s finally in service, on today’s batteries and tomorrow’s range is much more limited than current gas turbines allow. A tremendous amount of airplanes today are no longer being manufactured, and fixing one often involves cannibalizing the rusting hulk of another, a major line item in Harbour Air’s expenses. And older airframes didn’t have the advantages of lightweight composites or computational fluid dynamic modeling optimization of their curves. They fly, but inefficiently compared to modern planes. Getting the ballast right when you replace slowly diminishing avgas or Jet A in wing tanks with batteries in various places, a generator tucked somewhere else and a smaller but still existing tank for divert and reserve fuel is challenging.

But that said, firms like Ampaire are wedging hybrid systems into still-in-production airframes with significant success. Their process includes improving aerodynamics as well, increasing efficiency. And as Cory Combs, Ampaire’s co-founder told me when we spoke the other day, there’s a lot of room for hybrid systems to improve efficiency on most classes of aircraft, including replacing jet auxiliary power units (APU) that don’t work above 10,000’ with batteries that work on the tarmac and at 30,000 feet. Many airframes can have extended, lower carbon lifespans with hybridization albeit with some operational changes and several recertification hoops to be flown through.

To continue on the theme of electrification of aviation, new airframes with pure electric and hybrid electric drive trains are coming along rapidly. With ballasting for batteries instead of Jet A or avgas engineered from the ground up, wing aspect ratios a bit closer to gliders and even slipperier and lighter airframes, with current battery energy densities we can easily see 200-400 km ranges for 4-100 passengers with hybrid generators and fuel saved for divert and reserve purposes. Like Jay Leno’s old Chevy Volt, many hybrid aircraft wouldn’t burn any fuel in a year of service. Aircraft from a variety of firms including Flimax, ELECTRON, Heart and EOS are likely to be fulfilling useful commercial missions within years, and will have decades of productive service. 

Figure 3: Projection of aviation fuel demand through 2100 by author

Of course, energy for aviation isn’t going to be satisfied with batteries, and hybrids still require fuel that should be low carbon. But as noted, hydrogen and synthetic fuels made from it aren’t going to be the solution. So what will be?

Sustainable aviation biofuels, usually referred to as SAF biofuels, are the likely answer. In my projection of aviation energy demands through 2100, batteries eat more and more of the bottom of the market until they are capable of fulfilling all of it late in the century, but biofuels provide most near term decarbonization. 

As I noted in a recent recap of close to a decade’s effort assessing energy pathways for transportation decarbonization, as long as we don’t waste biofuels on ground transportation or shorter aviation and marine shipping routes, we have more than enough feedstock in a single pathway, stalk cellulosic ethanol to Jet A and biodiesel, to fulfill peak energy requirements. That technology set lets nature do most of the heavy lifting, uses only the stalks of plants we already grow and currently burn or throw away, uses 8,000 year old beer fermentation and 6,000 year old alcohol distillation technologies before getting to merely decades old processes to make plug-compatible fuels out of alcohol. They will work in existing aircraft and existing fueling systems in airports, burn more cleanly and with more energy than the fossil fuels they will replace, and can be blended with those fossil fuels during the transition. Agriculture is going to decarbonize over the coming decades too, making the biofuels more virtuous with each passing decade. Simple, scalable, increasingly lower carbon, less expensive than hydrogen or synthetic fuels and easy to integrate with existing aviation. There’s a reason that most major aerospace OEMs are certifying their aircraft on SAF biofuels.

But burning fossil fuels in the sky isn’t the only source of global warming challenges from aviation. There are also contrails. Not all contrails are equal climate problems, not all flights create contrails, and contrails appear far enough behind planes that it’s not possible to simply put a camera on the tail of the plane to spot them when they form. But changing flight altitudes to ones where contrails aren’t forming is a very low energy solution, so it’s a matter of getting the data on contrail formation in near real time, figuring out which ones are problematic and then communicating flight changes to aircraft. This is all very manageable for most aircraft most of the time with our current level of satellite and computer technology, and will become increasingly so in the coming decades. Not exciting, but essential.

Next is another invisible solution, digital air traffic control. This is a bit of an overloaded term as often it means putting the people in the tower in cheaper real estate a long way away, feeding them all the information through screens and often servicing multiple airports out of the same facility. Basically call centers but for air traffic control. It’s a useful approach for airport efficiency, enabling air traffic controllers to work multiple airports easily, but not the dATC I have in mind.

No, the digital air traffic control I’m thinking of is a system in which everything in the air has a unique transponder telling other aircraft and the system where they are, what altitude they are at, what direction they are going and at what velocity. The system knows where everything in the air that isn’t a bird is, and knows their flight plans. It projects potential intersections a 100 or 200 kilometers in advance and prepares flight path changes for human air traffic controllers to approve or override. Then it tells the pilot or autonomous aircraft explicitly how to adjust their aircraft’s path. 

Slowly but surely computer commands between ground and air will replace English as the language of flight control. Autonomous aircraft currently have sensible Rube Goldberg solutions where pilots on the ground monitor the airplane and flight control communications are routed from the tower to the radio in the aircraft to the pilot on the ground and back again. In the future, they’ll be computer commands that show up on a screen for a pilot in the cockpit or on the ground to agree to or question. And in the future, they’ll control most aircraft directly.

Beyond visual line of sight UAV flight corridors are a weak initial substitute for digital air traffic control, and hopefully won’t become cemented in aviation too firmly.

Maturation, certification and deployment of digital air traffic control is going to take a couple of decades to make real, and will spread from pockets of the future to the rest of the world. But it should be in place in most of the developed world by 2040 or so.

Figure 4: Regional air mobility maturity model by author

And that’s the last part of the maturation of solution areas required for regional air mobility (RAM), the final unheralded portion of aviation innovation to come into play. Autonomous flight, digital air traffic control and electric aircraft will upend the economics of flight, activating the perhaps 8,000 lightly used airports in North America and Europe with pilotless, low-cost, low-carbon, silent, electric passenger and cargo aircraft.

Regional air mobility is going to be starting with battery electrification of smaller aircraft, where the low maintenance and low cost of fuel due to efficiency of the drivetrain will enable business models that currently aren’t as economically viable. This is where disruptive aviation business models will be arising, more than not. Significant money should be behind each of the three solution areas, and regulatory and aviation industry attention that’s being wasted on hydrogen should be focused here.

And so we’ve flown through the quadrant. Some things worthy of attention are getting press and investment. Others that are worthy are languishing by comparison. Too many things, but especially hydrogen, have too much attention and resources lavished upon them. With luck, this approach to categorization will spark useful conversations and increase the speed of capitalization of actually practical solutions in aviation and aerospace.

illuminem Voices is a democratic space presenting the thoughts and opinions of leading Sustainability & Energy writers, their opinions do not necessarily represent those of illuminem.