Historically, vertical take-off and landing (VTOL) vehicles have been relegated to helicopters and expensive military aircraft. Yet the design, as applied to commercial aircraft, has not been successful without significant sacrifices in flight capabilities.
Today, London based 4X4 Aviation is working to shift this paradigm with a revolution in the aviation industry by making VTOL flight commercially viable with its Versatile Vehicle (VV) Plane design.
According to the company’s founder and director, Thorsten Reinhardt, VTOL hasn’t been commercially successful in the past because of the complexity involved in the tilting mechanics. But a redesign of these mechanics is only one part of the company’s vision.
“Local and national economies, as well as developing countries, are today struggling to meet the ever-increasing demands for transport infrastructure,” explains Reinhardt. “A viable solution will generate huge economic and social benefits for these countries.”
The solution, as proposed by 4X4 Aviation, involves development over four areas, including a power generator, electric turbine, software, and energy storage unit. “It is an infrastructure solution,” adds Reinhardt.
The key to the company’s commercial success will be in its patented gimbal-mounted power units, which allow for VTOL without the traditional, and costly, motorized titling mechanisms.
“The way that we generate the tilting mechanics is simply by using the power of the individual power units,” explains Reinhardt. A process that is analogous to that of a scale. “You put five pounds on one side and five pounds on the other, the scale will be level,” he adds, “but if you put seven pounds on one of the two sides, the scale will move.”
The weight in this scale analogy is the vehicle’s power units which are made up of four electric turbines. “The power unit rotates over its central axis over a specially designed gimbal that is currently being patented,” says Reinhardt. A design that allows each unit to move freely in all directions, eliminating the need for complex tilting mechanisms. “Hence, in the VV-Plane, the altitude of the unit is determined by the velocity of each single electric turbine within its cluster,” he adds.
The electric turbines, or e-turbines, are based on multiple stage electrically driven blades that function as outer runners and stators. Controlling the turbines is the company’s software that uses multiple sensor inputs, from both gyroscopic and acceleration sensors, and microcontrollers to continuously adjust the position of the craft.
Providing power to the e-turbines is an onboard generator and energy storage system fueled by a multi-staged thermodynamic engine built from off-the-shelf components. According to the company, the engine could eventually achieve a 75% fuel efficiency with close to zero emissions.
“A lot of engines lose the majority of their efficiently through heat,” explains Reinhardt. “We are reusing our heat by turning it into a steam and running it on the same engine, but on a different cycle that is optimized to the actual steam cycle characteristics; this dramatically increases the efficiency of the entire system.”
An electric-gas hybrid design, the engine powers the onboard generator which is based on a combined cycle combustion machine called the RT. The machine uses sinus discs instead of a heavy crankshaft, in addition to patent pending piston technologies.
“Patent-pending piston-within-piston technologies are able to use the heat created from the combustion, channel it to the outer piston, and create additional energy using a separate cycle,” explains Reinhardt.
While this greatly increases the efficiency of the vehicle, it was also one of the principal challenges the team had to overcome.
“The biggest challenge was handling the transfer of heat from the combustion chamber at the optimal efficiency levels in the RT,” explains Reinhardt. “It is well known that the majority of inefficiencies in combustion engines are heat based, so it was kind of the holy grail of getting around solving this issue which we will continue to improve throughout the RT’s development path.”
The RT is also lightweight and power dense, and like computer clusters, it is designed to be connected in a series to output the required power. This power is then stored in a pressure vessel called the e-storage.
“The e-storage is used as a buffer system that can quickly be charged and discharged with a compressor using the RT principle. The system can use extra heat during the expansion process, or cold during the compression process,” explains Reinhardt, making the RT multifunctional in its application.
The e-storage is made from two composite sleeves that are inflated to a desired diameter and then resin infused. For applications on the ground, the e-storage is made with two differently sized composite cylinders that are inserted within each other.
“A special structure process will allow structures be built with segments assembled in any desired shape,” adds Reinhardt. “This allows an inexpensive and fast assembly for a wind turbine towers or any other structures.”
While the approach in the VV-Plane is slightly different, Reinhardt is currently unable to disclose any details regarding the process as certain aspects are still in the process of being patented.
Mirroring the e-storage simplicity, the fuselage has no complex mechanical moving parts, further reducing the cost to manufacture. Reinhardt describes it as “low-tech,” a choice made so that licensees in developing countries will able to produce their own aircrafts in order to generate economic growth.
The design also lends itself to mass production, and the company has proposed an innovative assembly method that would allow around 30 aircrafts to be assembled every month.
For Reinhardt, finding the right partner to facilitate the manufacturing and design process was one of the biggest challenges. “What we are trying to achieve may be mind blowing to some people,” he says. “Finding a partner that can understand where we want to be in the future is quite difficult.”
However, the company is currently backed by a number of investors who will help facilitate full scale production over the next three years. The next steps in this process will unfold after the company demonstrates its current prototype, a date that is set for the end of September 2014.
The model that the company will be demonstrating measures roughly a meter by a meter, and according to Reinhardt, the prototyping process was, relatively speaking, straight forward.
“I’m very lucky that I have very good people working with me that enable us to overcome those challenges that lay in the way between the conceptual work and the actual flying prototype we have now,” he adds. “That makes life a lot easier.”
With the first flying VV-Plane prototype, VTOL flight is one step closer to commercialization, and Reinhardt nearer his dream of providing developing countries with an economically viable infrastructure solution.
“As you can hopefully see, all our technologies packed together enable the VV-Plane, but they are also able to operate independently,” says Reinhardt. “Therefore, our technologies offer infrastructure solutions, especially for those places in the world where infrastructure, no matter if it is energy or road based, is not available.”
Filed Under: Aerospace + defense