Blast from the Past: The Supersonic Comeback Tour
Issue 13 (09/01/2024): A look into why supersonic flight went bust and why it's about to start making a comeback.
As a Manchester United fan, it’s far more exciting to reminisce about the good old days than the complete catastrophe nowadays. Among which, there’s a famous tale of Manchester United flying to Spain on the Concorde ahead of their European Cup Final against Bayern Munich (which we narrowly and famously won). After listening to all the interviews, press was more excited to hear about the team’s experience on the Concorde and not what formation and substitutions they had planned for the match.
Anyways, leaving the glory days behind, it seems like supersonic flight left the world just the day good football left Manchester United - a long time ago. But recently, the thought and dream of supersonic flight has risen again, and has gained significant backing in terms of VCs, public interest, and even government support (to some extent…).
But the thought of waking up in LA just to be in time for Lunch in Tokyo and grabbing dinner in Paris just sounds too exciting not to look into it more. Of course, this dream isn’t cheap nor sustainable but neither is the vision for any supersonic company. The vision is efficiency, speed, luxury, and speed. Did I mention speed?
There’s a number of exciting projects in the works both by the government as well as private ventures - some more probable than others - but exciting nonetheless. This article covers the projects I’m excited about, and a bit of an outlook of perhaps why the dream was dropped after it had already been seen early in the millennia and what may be the future of the industry.
Trip down Memory Lane
There were a total of 14 Concorde aircrafts that cumulatively made almost 50,000 flights carrying over 2.5million passengers faster than the speed of sound which hasn’t occurred commercially since 2003 on a regular basis.
The Concorde hung its boots up for many reasons - some of which may not be entirely obvious. Let’s understand the inspiration behind the Concorde and the reasons for its imminent downfall.
Need for Speed: The Concorde
Do you ever check the speed of the flight you are on when it’s 36,000 feet up in the air? The little LCD display in front of your cramped seats that shows you where your flight is, the ETA until touchdown, and the current altitude and speed? Arguably that number fails to exceed 600 mph, which already feels incredibly fast. Now let’s rewind two decades ago when the Concorde could fly more than twice the speed of sound, hence the name supersonic. In numbers, that’s more than 1350 mph. Imagine, a flight from New York to San Francisco in about three hours.
But, there’s more to life than just speed and that’s what really caught up to the Concorde (pun intended).
Expensive to Operate
We all know that even nowadays the most expensive part about flights has always been the fuel cost and the same story runs here. The Concorde would make a profit of about 30-50 million Pounds for British Airways in the excellent years, with this figure falling negative a few years after the millennia. British Airways stated that there would be an operating cost of about 1 Billion pounds. Furthermore, the Concorde required maintenance far more than other aircrafts.
Noisy
We always hear about the “supersonic boom” that happens once a flight hits the speed of sound. That shockwave has previously shattered windows, scared passersby, among other things which caused numerous cities to issue noise complaints and petition to the FAA. Essentially, a law went into effect by the FAA in 1973 stating that the operation of a civil aircraft at anything above Mach 1 is prohibited over land in the United States, which was adopted by numerous countries in Europe as well. This is why we only witnessed Concorde flights across the Atlantic, and then a few flights throughout Europe.
Air France Concorde Crash
Concorde interest and passenger count diminished significantly after the Air France Flight 4590 accident in July 2000 as well as the global reduction in flight usage after 9/11. This significantly reduced the top line margins for the Concorde which coupled with regulatory pressure caused its fall in demand.
The Rebirth
In 2020, however, the FAA established a special corridor that meanders over Kansas for testing civilian aircrafts at supersonic speeds. This comes after privatized pressure to potentially enable supersonic flight once again - with the stipulation to address the initial issues regarding fuel consumption and noise consumption. The projects covered here aim to solve the latter issue of noise pollution; however, fuel consumption isn’t exactly the highest priority for these companies just yet.
NASA’s Supersonic Flight: X-59
The main inspiration behind this article has been the impending reveal of the NASA X-59 aircraft on Jan 12 (article written Jan 8). NASA hopes the current ban on supersonic flight over the land will be lifted after their research has aimed to achieve what NASA calls a “sonic thump” instead of the “sonic boom”. NASA calls their new achievement the X-59 Quiet SuperSonic Technology (QueSST) airplane. NASA operated tests in the Glenn Research Center in their Supersonic Wind Tunnel using a X-59 model using Schlieren images (photograph of fluid flow, refer to Figure 1 as an example).
Figure 1: Wind Tunnel Tests Validating quieter sonic boom of X-59
“With the X-59, we want to demonstrate that we can reduce the annoying sonic booms to something much quieter, referred to as ‘sonic thumps,’” said John Wolter, lead researcher on the X-59 sonic boom wind tunnel test. “The goal is to provide noise and community response data to regulators, which could result in new rules for overland supersonic flight. The test proved that we don’t just have quieter aircraft design, but that we also have the accurate tools needed to predict the noise of future aircraft.” - nasa.gov
This is a collaboration between NASA and Lockheed Martin and its aim is to overturn the ban of supersonic flight and achieve first flight in 2024 with the mission duration through to 2027. The current mission is to collect ample data for how quiet the boom really is such that they can feed the updates to regulators.
It’s an interesting initiative with the core problems in mind to reform from why we previously saw supersonic flight stop. It’s one of the most promising projects and I’m excited to see what comes of it after the demonstration on January 12.
Exosonic Supersonic Jet
With the same aims as NASA, Exosonic is working with regulatory bodies to support the overturning of the ban on mainland supersonic flight.
“Exosonic aircraft are designed with sonic boom shaping technology to mute the sonic boom and avoid the disruptive booms of the past. By the time the sonic boom reaches the ground, the sonic boom will be softer, no louder than a car door closing down the street. This shaping design means that typical city traffic will drown out the sound of the sonic boom.”
Exosonic is working on two models, one for the private executives and the Gulfstream competitor and the other for commercial flight - with both looking extremely expensive even though their motto is “We want everyone to be able to fly supersonic one day - not just the ultra-wealthy”. It’s hard to believe this until we see the proof of concept, but more importantly, until we actually see the ticket prices - which is unlikely to happen until at least 2031 (that’s also when United is planning on releasing their supersonic jets). But none of this will happen until the ban is lifted by the FAA.
A Concorde boom is estimated to be just over 100 decibels: the same impact as thunder in terms of sound with the added bonus of shattering your windows. Exonic boasts their booms to be just over 60 decibels, which is as loud as your car door closing. Coupled with the speed being Mach 1.8 (just under 1400 mph) and using fuel that is said to be “sustainable fossil free”, the dream of supersonic flight seems a little more probable.
Hermeus
Hermeus, along with the name straight out of mythology, is also dreaming of a future out of DC comics. Hermeus boasts Mach 5 speeds, which is a step up from supersonic - its hypersonic. Mach 5 ends up being above 3800 mph which means you could get from New York to London in 90 minutes, instead of 3 hours on the Concorde. Hermeus has three products so let’s take a look at them. But just before that, let’s look at the engine behind these flights.
Each of the flights are built on Hermeus’s Mach 5 engine known as Chimera, which is a turbine-based combined cycle engine (TBCC). For those who are intrigued more about the engineering, here’s a good paper I read.
Essentially, Chimera is a hybrid between a turbojet and a ramjet, enabling flight from both a regular runway as well as accelerating to high Mach speeds. When flying in low speeds, the engine operates like a turbojet - similar to what we are used to nowadays. One of the results of supersonic (or hypersonic flight) is the increased temperature the flight operates in as well as the change in air pressure that causes the flight to expand it’s shape. This inflection point occurs at Mach 2, which is where Chimera has a pre-cooler which will reduce the temperature and increase performance as it transitions into a ramjet, which is fully in control by Mach 3. If you are more curious about the build, Hermes explains it here. Figure 2 is a brief visual explanation.
Figure 2: Visual representation of the transition between a turbojet and a ramjet (Source: Hermeus.com)
Quarterhorse
Hermeus’s first aircraft built predominantly for testing the high Mach speeds of the Chimera engine. The core objective is to validate the Chimera engine and it’s “on paper” ability to achieve Mach 4 and to understand how the body of the aircraft reacts.
Darkhorse
Designed for defense and national security, this is designed for government utility and may be remotely piloted. The aim of this hypersonic UAS (unscrewed aerial system) is to achieve Mach 5 speeds for defense, surveillance, and national security. We know very little about much more.
Halcyon
Hypersonic passenger flight. Mach 5. 20 passengers. Arrives in 2029. There’s not that much more information about this but this is what I’m most excited about. 2029 cannot come soon enough.
What does the future hold?
It’s hard to tell as much of the industry operates under a black box assumption and as what consultants call an “under the tent approach”. This means all movement of information only occurs on a “need to know”.
However, it seems like the years of 2028-2032 remain the inflection points regarding when supersonic travel materializes to something tangible for customers. However, for the next 4 years, below remain a few of the complications that both NASA and private companies need to overcome.
Technical Challenges
The technology for propulsion, materials and structures let alone the thermal management systems for such high speeds have been proven theoretically - however, at scale tests have not been regularly successful. Let alone the practicality, the objective at the end is to make this affordable, which is still at least a dozen years away. If you are more curious about the technical challenges, the Institution of Defense Analyses published an interesting paper.
Environmental Concerns
It’s no secret that supersonic flight traditionally drinks a lot of fuel and until the time is such where sustainable fuel is produced widely, supersonic flight will continue to demand poor mileage. Of course Hermeus and Exonic are examples of testing with sustainable fuels, but even according to them, this will not be the current state, and remains a future endeavor.
Safety
I’m excited by this technology and I’d be the first to put my hand up to jump on board any of these tests. However, the wider masses remain a tad skeptical regarding the safety of supersonic flight.
Regulatory Complications
In April of 1973, the Federal Aviation Administration, as aforementioned, banned commercial supersonic flight over land. Although flights over bodies of water are permitted, supersonic flight can’t take mainstream attention until this ban is lifted across the continental USA. It’s up to the continued efforts of NASA and these private companies to work with regulatory bodies to potentially lift this.
I’m excited for January 12th for NASA’s launch, and thereafter excited for 2029 which is where the inflection point of supersonic flight, it’s reputed tests and commercial use may start to arise more regularly.
Bibliography
https://simpleflying.com/how-much-did-it-cost-to-operate-concorde/
https://simpleflying.com/jet-aircraft-fuel-consumption/
https://www.concordesst.com/retire/faq_r.html
https://simpleflying.com/how-much-did-it-cost-to-operate-concorde/
https://www.nasa.gov/news-release/nasa-sets-coverage-for-x-59-quiet-supersonic-aircraft-rollout/
https://www.nasa.gov/centers-and-facilities/armstrong/taming-the-boom/
https://www.nasa.gov/mission/quesst/
https://www.lockheedmartin.com/en-us/products/x-59-quiet-supersonic.html
Cover Image Credit: Hermeus.com