On a lighter note

The other side of the ledger is almost as full—technologies that either failed or, more often, have not yet been fully realized such as very light jets (VLJs), light sport aircraft, diesel propulsion, electric propulsion, autonomous flight, and vertical takeoff and landing (electric and otherwise).

I remember covering the rollout of the Sikorsky S–72 X-Wing in 1986. Funded by the Defense Advanced Research Projects Agency (DARPA), the X-Wing was to demonstrate the ability to take off and land near vertically under a large X-shaped rotor and then stop the rotor in cruise to have it act as an X-wing, greatly increasing speed and efficiency over a conventional helicopter. Despite the big rollout event at the Sikorsky factory in Connecticut, the X-Wing never flew and was canceled in 1988. I can imagine the test pilots there in the briefing room pondering that transition from rotary flight to fixed-wing flight and saying, “Ahh, no thanks!”

As is often said in R&D, if you’re not failing occasionally, you’re not trying hard enough.

Today, the hype around VTOL, eVTOL, and electric propulsion in general is near epic proportions (see “eVTOLs: The Promise and the Risk,” p. 66). It even eclipses the predictions we heard in the early 2000s about very light jets darkening the sky—and if you get that little double entendre, you know what I’m talking about.

The difference today is that rather than just a handful of small GA companies or start-ups attempting to build simple, low-cost personal jets, the advanced air mobility movement (AAM), which mostly leverages VTOL and electric propulsion, is backed by some of the largest companies in the world. Rather than serving a relatively small number of wealthy individuals, as would be the case with the VLJs, AAM’s goal is to serve the masses. The AAM movement comes at an interesting intersection of technological advances and societal demands. As is often the case with major advances, progress is in fits and starts. There is no one simple achievement that will have everyone Jetson-ing around in their personal VTOL as it folds into a briefcase on the way into the meeting with Mr. Spacely.

A few years ago, most AAM companies were focused strictly on autonomous short-haul urban eVTOL aircraft powered by batteries. Today, most companies have broadened their focus to also include regional transportation, almost always including a pilot and hybrid power, mostly with a turbine generator providing at least part of the electricity to drive the rotors or propellers during certain phases of flight.

The latest trend is the embracing of hydrogen as a primary fuel source. The first hydrogen-powered airplane flew in 1957—for 20 minutes on just one engine of a Martin B–57B. More recently, ZeroAvia has been using a hydrogen fuel cell to power a variety of aircraft during its development phase. When hydrogen is the only fuel used, ZeroAvia claims those are zero-emission flights. This, of course, is where the intersection with society comes into play. Climate change warnings have been driving all manner of societal changes, from the types of cars we drive to how we generate electricity. The airlines in particular are facing immense pressure to reduce or eliminate carbon emissions. Hydrogen is an efficient fuel for generating electricity, emitting only water. The problem is that with today’s technology, creating hydrogen is highly inefficient. And even if we had an efficient way to generate it, the infrastructure changes to support a transition would be enormous. Some have dismissed it as impossible.

However, if we stop and think about what is needed to get a gallon of avgas or Jet A into our fuel tanks, perhaps the future of hydrogen isn’t so preposterous. No more drilling holes in the ground to get a barrel of dinosaur juice that must be transported to a refinery where it is brewed down into a variety of products, only a small portion of which is usable in an airplane, and then transporting that via rail, pipe, ship, or truck to a distributor where it goes on a truck to a local airport for ultimately pumping into our airplane wings. No small task. If the Industrial Age had come about powered by hydrogen, we would look askance at what might be needed to switch to petroleum fuels.

Emerging technologies: Easy to take pot shots at. Sometimes life changing.