TO WHAT EXTENT IS POSSIBLE TO DESIGN THE MOST EFFICIENT AND EFFECTIVE HIGH-SPEED PLANE?

TO WHAT EXTENT IS POSSIBLE TO DESIGN THE MOST EFFICIENT AND EFFECTIVE HIGH-SPEED PLANE?

 To make the required improvements in practically every area of the air transportation system's overall performance, aircraft performance improvements are important. Notably, the operational expenses, specifically the cost per seat-mile, serve as a vital metric for evaluating the performance of aircraft in the airline industry. While the payload multiplied by block speed (the average gate-to-gate speed for a specific mission leg) yields a fundamental measure of aircraft productivity (National Academies of Sciences, Engineering, and Medicine, 2003). As such, plane’s speed plays a crucial role in aircraft productivity.  Airplanes work better in an environment with less friction making them swift and effective. There are no wheels that need to be continuously rolled over the ground (at least while in flight), and the air is thinner at higher altitudes, which significantly lessens air drag. The idea behind building a quick and efficient airplane is straightforward: reduce air drag by making the aircraft as aerodynamically efficient as feasible. This goes beyond simply developing more efficient engines. Thus, the aircraft can travel quicker and use less fuel to go from point X to point Y if it produces less air drag. 

Usually, the goal of the design process is to give the aircraft a droplet-like overall shape. By decreasing the amount of turbulence produced as the vehicle goes forward through the air, its so-called streamlined shape lowers form drag (OpenStax, 2016). The designer has the final say in how well this is executed, but other factors can also play a role. For example, consider large passenger airplanes, which deviate from a droplet shape and adopt a tubular form. This design choice is driven by the exorbitant expenses associated with crafting a body of such magnitude, which outweigh the benefits. Aircraft designers recognized early in aviation history that any form of strut, wire, landing gear, or protrusion from the main body substantially raises air drag, leading to reductions in speed, endurance, and range. Retractable landing gear and a single, outwardly unsupported wing soon became commonplace. 

In order to reduce skin friction, planes with little wetted surface area have been designed, essentially consisting of one single body with wings. The skin friction rises as the surface area increases, which occurs when a larger object is subdivided into multiple smaller objects with an equivalent total volume. This, in turn, affects the available cargo and passenger space. (Krossblade Aerospace Systems, n.d). This is because, in the case of a sphere, for instance, the surface area only rises with a square, whereas the volume expands with the cube of the diameter. This implies that a bigger sphere exhibits a lower proportional surface area compared to a smaller one. Ongoing research and development efforts aim to design skin surfaces inspired by nature, which would minimize friction with incoming air. 

Additionally, flight tends to be faster and more efficient with long, slender wings of equal area compared to shorter, stubbier wings (Remmerie, 2018). The enhanced performance is attributed to the longer wings' reduced wing tip area, which decreases the formation of undesirable tip vortices. These vortices can develop on any wing tip when high-pressure air is pushed upward towards the lower pressure at the wing's top surface from below. Birds in flocks utilize V-shaped formations, leveraging the upward flowing air created on the leading bird's wing to facilitate easier lift generation for those flying behind and to the side (Remmerie, 2018).  Also, the winglet, sometimes known as the sharklet or wingfence, is a relatively new invention in aviation industry. These are tiny wingtip extensions that act as a barrier to keep the high-pressure air beneath the wing from forming parasitic tip vortices. In doing so, the majority of the high-pressured air is kept from escaping to the upper side of the wing, which would result in an energy loss, increasing the energy efficiency of the wing. 

Designing high-speed supersonic aircraft such as SR-71 A relies on propulsion system. An aircraft's propulsion system provides its power. It directly affects an aircraft's performance parameters and manner of flight. The SR-71A is outfitted with a unique propulsion system termed as a "turbo ram jet" engine because of its distinct mission profile (Xue et al., 2014). A turbo ram engine is a multistage engine with a turbojet engine at its core and air passageways leading to the ramjet section. The turbojet portion of the engine draws in all air at low speeds in order to produce thrust. However, due to the ram effect, the mass flow increases significantly at high speeds, preventing anything from passing through the turbojet. Instead, the flow is directed through the ram jet section, where combustion takes place, resulting in the generation of effective thrust. Aerodynamic thrust, which can be enhanced by thoughtful inlet design, is the portion of the thrust that the intake contributes to at high speeds. A propulsion system known as a turbo-ram jet combines the functionalities of a ram jet engine and a turbojet engine, working together to provide propulsion throughout the entire range of flight. The SR-71's propulsion system, as described by Xue et al. (2014), is driven by two J75 turbojet engines produced by Pratt & Whitney. The SR-71's remarkable engine inlet design is primarily responsible for its quickness and agility. The SR-71 can cruise at speeds higher than Mach 3.2 thanks to its air intakes, which cause the air to slow down to subsonic speed as it reaches the engine. 

In conclusion, the pursuit for heightened performance in the aviation industry axes on the pivotal role of aircraft speed and efficient design. The industry's priority on reducing operational expenses, especially the cost per seat-mile, demonstrates its dedication to economic viability. Optimizing productivity and fuel economy requires a precise aircraft speed, which is determined by aerodynamic efficiency. An aircraft's ability to fly quickly and efficiently is shaped by design factors such as wing configurations, skin friction reduction, and streamlining to minimize form drag. The SR-71A's turbo-ram jet engine serves as an example of how propulsion systems have evolved and how cutting-edge technology have been integrated to produce remarkable speeds and agility. Accordingly, a future where air travel is not only quicker but also more economically and environmentally sustainable is being paved by the industry's continued advancement of aerodynamics, design advancements, and propulsion systems. 

References 

Efficiency and speed of airplanes. Krossblade Aerospace Systems. (n.d.-a). https://www.krossblade.com/efficiency-and-speed-of-airplanes.

 Remmerie, W. (2018, September 12). How do winglets improve aerodynamics? AirShaper. https://airshaper.com/videos/how-do-winglets-improve-aerodynamics/ubvr1w1hH80. 

National Academies of Sciences, Engineering, and Medicine. (2003). Securing the Future of U.S. Air Transportation: A System in Peril. Washington, DC: The National Academies Press. https://doi.org/10.17226/10815. OpenStax. (2016, August 3). University physics volume 1. 6.4 Drag Force and Terminal Speed | University Physics Volume 1. https://courses.lumenlearning.com/suny-osuniversityphysics/chapter/6-4-drag-force-and-terminal-speed/.

Xue, H., Khawaja, H., & Moatamedi, M. (2014, December). Conceptual design of high-speed supersonic aircraft: A brief review on SR-71 (Blackbird) aircraft. In AIP Conference Proceedings (Vol. 1637, No. 1, pp. 1202-1210). American Institute of Physics.