The Future of Flight

The aerospace industry was once on a huge technological drive moving forwards but then regulations seem to have got the better of innovation. What do I mean? In the 1970’s concordes regularly flew at supersonic speeds, the Boeing 747 carried a similar amount of people to what it does today. Yes, we have made large leaps forward in manufacturing and engine efficiency but its not the same leaps that we being made in the 1960’s and 1970’s.

Source: Cathay Pacific Airlines

However, in recent times we have seen startup companies like Boom Supersonic, demonstrating a business case and viable proposals of a supersonic passenger aircraft. We have also heard many great minds, in particular Elon Musk, who we believe knows quite a bit about the aerospace and battery technology industries, quote that all forms of transport other than rockets can become electric. We have also seen a number of startups working on proposals for electric propulsion aircraft. Is this the future then? We will see more supersonic passenger aircraft flying and cleaner forms of propulsion for flight? This blog is going to look behind the physics and first principles engineering to better understand the viability of these technologies and where the future of flight really lies.

Source: Reuters

One of the main reasons that modern planes fly at the altitude they do is because they are at a point where the atmosphere is thin enough to reduce aerodynamic friction but still able to get enough oxygen to ignite the engines. This entire principle can be blown out the door if electric planes become commercially viable. There would be no need for oxygen and they would be able to fly at much higher altitudes where there is limited aerodynamic friction. Modern aircraft are propelled using carbon based fuels such as gasoline and kerosene. With stricter regulations and a requirement to clean up the atmosphere, we are now looking at more efficient propulsion methods, one of which is electric. Other methods of improving efficiency and decreasing aircraft emissions is utilising electrification for the systems on-board an aircraft, improving aerodynamics and reducing the weight. All of these are currently being researched and implemented with the 2 prime examples being the Boeing 787 Dreamliner and the Airbus A350 XWB. So, in terms of the future of the aerospace industry, the next advancement in propulsion is full electrification. But how would an electric aircraft be propelled?

Electric aircraft are likely to utilise propeller and turboprop to generate the thrust. A propeller design is simpler and would require far less energy consumption but this is not realistically feasible to create the lift required for conventional passenger jets. NASA is currently researching electric and hybrid-electric turboprop engines and hope to have demonstrator aircraft in the near future. Another propulsion method is a conventional contained fan. This is similar to the propeller proposition however a significant difference is the surrounding ducting reduces noise. This can be seen on the Airbus E-Fan aircraft but as we have discussed previously with a traditional propeller approach, the trust would not be significant enough to create a passenger jet. The electricity can be provided by a variety of sources. These include; batteries, ground power cables, solar cells, ultracapacitors, fuel cells and power beaming. Of these sources, the only viable solutions for passenger aircraft is batteries, ultracapacitors and solar cells; assuming that the technology of all these increase significantly. The solar impulse aircraft has shown that solar is a viable method, however, again it would be difficult to create enough energy storage for commercial purposes unless the wingspan and fuselage provide enough surface area to continually provide enough energy to the battery. A significant issue with a solar option is that they could only fly during the day unless the battery could also be charged from ground but nonetheless, this limits its uses. The one major design factor that may help electric aircraft become viable is that composite materials and battery technology are exponentially progressing with respect to their overall historical development. As well as this, aerodynamics is being optimised through the use of CAE and electric aircraft will be able to fly at much higher altitudes, due to no requirement for oxygen to fuel the engine ignition and subsequently allowing the aircraft to fly through limited atmospheric forces and utilise its thrust to extend range. I believe commercialised electric aircraft are certainly going to make an appearance in the future but there are certain developments that need to occur to make them viable; similar to what Tesla has done for the electric car.

Source: Zunum Aero

Another area of the aerospace industry that I can foresee large developments is in supersonic aircraft. This is a much simpler option than creating an electric aircraft as it is no secret that the technology has been around for decades but why are there currently no supersonic passenger aircraft flying currently? The main reason that we don’t have supersonic flight these days is purely down to the concordes economic viability. It has been argued that the concordes sound was the driving factor for its demise but this just simply isn’t true. The Concorde had a sonic boom which was loud but once at speed it was actually much quieter than other passenger aircraft due to being so aerodynamic and reducing aerodynamic noise. This ultimately lead to regulations that stated no aircraft (other than military) could not fly supersonic over any land mass. Additionally, there was some other economic issues with the Concorde. This included a crash which increased maintenance costs and the disaster that was 9/11, causing a significant drop in people using flight as a method of travel.

Source: PC Flight

I strongly believe that we are on the brink of a new era in flight. A startup aerospace company founded by a software engineer seems the most likely to succeed in successfully bringing supersonic flight to the market. This company is Boom Technology and has been backed by at least 5 airlines (with Virgin Atlantic and Japan Air Lines being named as 2). They are due to have a demonstrator aircraft, nicknamed Baby Boom, in late 2018 as a proof of concept before official orders are taken. But what makes Boom Technology different? There have been previous startups who have attempted to bring supersonic commercial passenger aircraft to market since the Concorde’s retirement but have failed. We cannot just simply look at the physics of supersonic flight as this technology has been around for so long. It is just about looking at the business case and economic viability of an aerospace company managing a fleet of supersonic aircraft. Boom’s business plan is to look at the premium customer market for routes that are limited to the amount of landmass that they travel over. Example flights include London to New York, Miami to Santiago, LA to Sydney and LA to Tokyo. From an engineering perspective, Boom Technology is looking to optimise the use of composite materials, engine efficiency and working with government regulators on whether they should be allowed to fly supersonic over land. The major issue standing in their way with this is the sonic boom,. The use of delta wings, which is part of Boom’s design, will also lead to additional noise energy due to a requirement of having a larger engine to make the cross section of the aircraft similar throughout the length of it, but at full altitude is noise really a problem to people on the ground? The only issue is when it is climbing and reaching supersonic speeds at lower altitudes, however, we shouldn’t be too negative on the prospect of this. Minded, for those who live near airports it will cause a number of issues but the likes of NASA are currently working on optimisation and reducing the sound a sonic boom makes. How are they doing this? Ultimately, a sonic boom is not created when an aircraft goes supersonic, it is simply the sound waves travelling behind an object rather than in front. It is a continuous wave of energy and will only be observed if the person is with the “cone” of these waves that run behind the aircraft travelling at supersonic speeds. Additionally, the sonic boom on take off can be overcome by having a higher inclination angle on take off maintaining the same level of thrust. We also need to consider the engine when discussing noise energy. A conventional Boeing 747 engine mounted to an aeroplane with delta wings will lead to a decreased mass flow through the engine and produce additional noise energy. Again, the cross section of the whole aircraft needs to be considered, so a conventional turboprop engine is not viable in terms of meeting FAA regulations. All in all, I believe the technology and economic viability for supersonic flight is there and we will definitely see commercial aircraft flying supersonic on certain routes in the near future as long is the physics is harnessed in the correct way to produce an efficient and lower sound energy producing aircraft.

Source: Science Uncovered

So, where does the future lie. Well we really don’t know until the proposed aircraft such those created by Boom Technology and Zunum Aero are in production and flying with airliner branding. The most likely to developments will come from the large aerospace companies such as Airbus and Boeing, with Airbus planning to put their e-fan aircraft into production in the near future for demonstration and training purposes whilst they have a long term vision of a 70 - 90 person aircraft to be in production within 20 years. The smaller start-up companies may have all the backing in the world but until passengers are buying tickets, they are still conceptualised ideas and have no influence on the customer. It has only in recent times that startup companies have begun to look at physical products as opposed to software with the likes of Tesla and Bastion Bikes. To complicate matters further, Elon Musk’s SpaceX recently announced that alongside its developments of the Big Falcon Rocket (BFR), they will also be developing it for around the world travel using the Big Falcon Ship (BFS) as can be seen in the following video.

SpaceX’s primary goal is to build a city on Mars and make humanity a multi-planetary species. Through the research and development of the BFR, SpaceX also believed that there would be a potential market for utilising the ship part of rocket to get anywhere around the world from one point to a destination in less than 1 hour. This was simply a conceptual idea with their primary goal of creating the BFR for space exploration purposes. For that reason, I can’t see this being a viable form of around the world transportation anytime in the near future. To start with, SpaceX would have a large amount of additional regulations to make a spacecraft into a passenger transportation system which is in a completely different world to astronauts being able to go into outer space. SpaceX has shown remarkable developments in its field, but this is in the space industry, not the commercial aviation industry. Additionally, rockets are extremely loud, so as can be seen in the video there would be no chance of landing on land. This is a similar issue to what supersonic aircraft will have to overcome but rocket launches are even louder the most sonic booms with multiple parts of the spacecraft reaching or decreasing from supersonic speeds at various instances. In terms of logistics, there would then have to be effectively “floating airports” with transport via water to a nearby city. This concept would also require massive integration with the current airspace system that commercial aviation requires. For a rocket launch, there are major exclusion zones around the launch pad that is usually controlled with the facilitation of the air force. We also need to understand the this would not be a comfortable flight for the passenger either, with extreme gravitational forces acting upon them in take-off and landing. I think feasibly, this certainly won’t be happening anytime in the near future. SpaceX may well achieve its goals of producing the BFR and exploring the opportunities of making life multi-planetary but at its current scale with its current capabilities, I struggle to see a business case for such development. A far more realistic option is a sub-company of Elon Musk’s Tesla Motors and SpaceX collaborating to create an electric propelled aircraft. However, how much can this man take on?

Source: SpaceX

To conclude this blog, I wish to add a personal note. I have spent a great deal of time working in the automotive industry and also had experience working for a major aerospace company. From my perspective the aerospace industry, rightfully or wrongfully, is so tightly regulated that it limits the innovation and new technologies that improve the future of flight. This is in contrast to the automotive industry where innovation is a major driving factor in everyday design and the industry is struggling to keep up with the technology for each programme, which is why I foresee changes to vehicle programme time spans. The engineering technology and fundamental physics will allow for the likes of SpaceX’s and Boom Technologies concepts to become viable if regulations are continuously reviewed. In the near future I believe supersonic will be the first advancement, followed by the electrification of aircraft, which will become more viable exponentially due to leading innovators in the battery technology industry, such as Tesla. In the future, I hope to see point to point journeys in less than 1 hour become a possibility but there are so many developments that need to be made and I simply cannot see SpaceX doing this alone when their sole driving factor is to deliver a self sustaining city on Mars. However, in saying that, Elon Musk’s companies always seem to deliver and I wouldn’t be confident in ruling out their proposed ideas. Only time will tell!

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Luke T Seal Engineering