Aerodynamics of Supersonic Aircrafts - Essay Example

Aerodynamics of Supersonic Aircrafts Name of Student Student Number Institution Course Code Name of Lecturer Date of Submission Aerodynamics of Supersonic Aircrafts Introduction Extensive advancement and innovations have been made in the aircraft industry with tremendous achievements in respect to aircraft speed and safety. This paper evaluates the theory of supersonic flight, the shock, its formation and behavior with increasing speed, its effects on the flight in the transonic region and what is a sonic boom. Further, the essay will evaluate supersonic wing designs, the effect on engines and flight controls, as well as discuss the commercial aircraft that operated this design and why it failed to succeed. Supersonic Flight Theory and Shock Waves Supersonic transport refers to aircraft designed to fly at speeds that are greater to that of sound (Mason, 2006). The design of supersonic aircraft began in the 1960s when plane companies merged ideas from existing military technologies and commercial jet programs to create prototypes. Concorde was developed by a British and French consortium; the Soviet Union also initiated its supersonic transport program with the TU-144 as the product while US had their U.S. SST produced by Boeing. However in the 1970s the US government terminated the prototype program due to its economic and environmental implications (Kulfan, 1993). With population and economic growth, coupled with the prospect of lower fuel and transport costs, as well as rapid growing income, the demand for air travel was booming in post-cold war economies. Therefore, the urge to increase profits and see to it large-scale provision of fast and efficient air travel brought about the idea of supersonic flights. Promises of high-speed travel over long distances made flights more desirable and the technology of turbojet engines swept wing aerodynamics made this possible (Kulfan, 1993). With the successes of supersonic military jets through historic times such as the cold war, various governments more so Britain, France and Germany battled in creating commercial versions of the aircraft. In the 1960s, the United Kingdom, United States, Soviet Union and France kicked off their funding of supersonic passenger transport in research and development (Hornung, 1986). To make cruising at supersonic speeds easy, various principles were developed in a bid to fight conflicting issues such as shock waves which served a major blow to supersonic plane control. An example is the supersonic wedge principle where the body of an aircraft was placed wholly under the wings to allow for the shockwave produced by the body to create pressure on the lower part of the wing, therefore, adding lift to increase efficiency in aerodynamics (Kroo, 2005). At supersonic speeds, the aircraft produces shock waves that reach the ground. Shockwaves are movements of high air that are caused by the explosion of plane surfaces on air. The pressure changes create loud sounds that are offensive to the ear. According to Kulfan, (1993) the theories of aerodynamics suggest the possibility of the reduction of the magnitude of sonic boom levels by checking on the design of the aircraft. Difficulties in aerodynamics are defined by the governing of shapes and sizes of air flow domains concerning the aircraft body and wings (Kroo, 2005). Researchers in aerodynamics while coming up with wing or body design, major on surface flow designs which are based on putting certain pressures on the surface of experimental objects then looking for the shape of objects that will provide safe surface conditions. Shockwaves cause a wave drag when the speed of the supersonic place exceeds that of sound and this drag brings about utilization of more fuel as the plane needs more thrust to push through the backward pulling forces. Supersonic aircraft are therefore designed to have more power than subsonic aircraft (Mason, 2006). The design of the wings of supersonic aircraft should accommodate a reduced lift to drag ratio. Lift to drag ratio refer to the amount of lift generated by a wing over the drag it creates as it moves through the air. The drag is caused by forces that are a result of pressure distributions on the aircraft’s body surface (Hornung, 1986). Shock waves are key concepts in the discussion of supersonic flight theories, as well as other attributes associated with the aircraft. Planes flying at less than the speed of sound results in the air in front flowing out of the way before the planes comes into contact. Pressure waves are created by the airplane passing via air which is smooth and gradual (Mason, 2006). However, when an airplane tends to the speed of sound and catches up with its own pressure waves, the air ahead gets no warning of the aircraft approach. This results to the plane plowing through the air giving rise to shock waves (Kulfan, 1993), which in turn give rise to air flowing through the shock waves having high pressure, temperature, and pressure. Achieving the speed of sound for an aircraft gives rise to the airflow above the wings reaching supersonic speed before the plane, creating a shock wave over the wing. Subsequently, the airflow behind the shock wave breaks up into a turbulent wake raising the drag (Mason, 2006). Upon reaching the speed of sound for a plane, a shock wave is formed ahead of the wings leading edge, while the shock wave formed on the wing now trails at the end. Upon tilting the wing upward, a shock occurs below its leading edge while an expansion wave occurs above its leading edge (Kroo, 2005). This creates a high pressure behind the shock wave and lower pressure behind the expansion wave giving rise to a single force that pushes the wing up and back. The effects of shockwaves on control of planes lie on the fact that shock waves cause turbulent disruptive shakes that may destroy the wing alignment, therefore, causing major accidents (Mason, 2006). Turbojet engines were utilized in the making of Concorde jets. The turbofan engines served a purpose of improving efficiency in supersonic speeds where they utilized all of the thrust to power fans whose overall function was forward speed bringing about a reduction of the jets weight and increase in lift. Various economic and environmental concerns have impeded supersonic development (Collard, 1991; Kroo, 2005). High production costs, led to high acquisition costs and therefore, governments were the sole sponsors of the endeavor. High Mach numbers produced difficulties associated with engine temperatures whereas, high fuel consumptions greatly impacted on the market situation bearing in mind the high fares. Kroo (2005) states that as the Mach number increases the optimum altitude also increases and this has implications for environmental impact and structure of the aircraft. A Mach number value 1 refers to the speed of sound in the context (Hornung, 1986). Supersonic Wings Designs The Concorde utilized the delta wing design, an advance of the swept wing concept (Collard, 1991). Subsonic aircraft had wings designed with many moveable parts for the control of the aircraft and also flaps which allowed for the production of stronger lift while flying at relatively low speeds. In the supersonic Concorde, delta wing has six trailing edges that allow the roll and pitch of the aircraft. The delta wing design allowed for the Concorde to generate enough lift at low speeds by increasing wing angles and generating little drag (Mason, 2006). The large delta shape also produces a cushion during landing. As the aircraft get closer to the ground, the air between the broad wing and the ground creates a cushion thus, the smooth landing of the Concorde even at higher speeds (Collard, 1991).The Concorde delta wing design allowed ample lift at low speeds and also provided the right amount of weight necessary for flying at supersonic speeds. Figure showing structural advantage of Oblique wings (Source: Kroo, 2005) The swept wing design is also used in supersonic aircraft and utilizes more forward speed to produce lift, creates much less drag in its wake and therefore flies faster (Mason, 2006). Supersonic flight requires different designs for wing unlike subsonic to ensure sufficient lift and production of less drag. The wings of high-speed aircraft are therefore relatively thin and more angled back allowing for reduced formation of shockwaves, as well as reducing the strength of the waves. By sweeping back the wings they become thinner to the airstream. (Kroo, 2005) Another type of wings involves the oblique wing design also known as the slewed wing in supersonic aerodynamics. The wing is designed to rotate on its pivotal center in such a way that when one side of the wing is swept forward, the opposite side is swept astern. This design aims at reducing drag at high speeds. Kroo, (2005) argue that oblique wing alignment distributes lift over twice the length of the wing thus reducing the wave drag. Although the theory of oblique wings did spark some interest in the concept, its structural characteristics have made the idea the subject of continued investigation in supersonic aerodynamics. Oblique Wings Designs (AD-1) tested by NASA in the Early 1980’s (Source: Kroo, 2005) The Concorde utilized the design and was developed jointly by the British and French governments for commercial services in January 1976. This was a significant achievement in the aviation technology with the achievement of a round trip from New York to London in three and half hours at a speed of 1,350 miles per hour. The aircraft was a symbol of speed and luxury, but it was criticized due to the noise it produced irritating those living under its flight path. At first, the operations of the Concorde were temporarily grounded for over a year after the Air France Flight 4760 on July 2000 after takeoff from Paris killing 113 people as shown below. Photo Air France Flight 4760 exploding at takeoff in Paris (Source: Mason, 2006) The downfall of Concorde as stipulated by Mason (2006) was caused by various economic and environmental factors. Its high cost of operations which saw a round trip cost as much as twelve thousand US dollars as compared to the income generated by charges on passengers served a major blow on the operation of this supersonic flight. Minimal travel routes were introduced with regard to the planes fuel carrying capacity (Kroo, 2005). The issue of noise pollution caused by sonic boom created negative political objections which saw communities more so the poor who could not afford the flight riot against the situation. Environmental objections also came up with increased depletion of the ozone layer attributed to upper atmospheric pollution. In the United States open public outcry on the environmental effect of the supersonic aircraft killed the project in its early stages and only the Britain and France consortium came up with the final supersonic aircraft. Collard (1991) stipulate that the success story of the Concorde was as a result of the international cooperation between British Aerospace and France Aerospatiale as equal partners thus pulling massive funds for the project. The Concorde design was born in times when aviation fuel was cheap, and the fuel economy was favorable. The oil crisis that marked the 1970s made the aircraft expensive to operate. The operators opted to increase of fares thus; customer reductions made it an expensive affair (Mason, 2006). The supersonic Concorde jet made its final commercial passenger flight by traveling at double the sound speed from John F. Kennedy International Airport in New York City to Heathrow Airport in London on 24th October 2003. The failing of the Concorde was cited to be high operating costs and diminishing ticket sales and the British Airways retired the fleet of Concorde bringing to a halt the commercial supersonic aircraft. Conclusion In conclusion, supersonic aircraft showed great prospects in civil aviation but, had more significant challenges such as those faced by the Concorde and it counterparts. Sonic boom issues only served as an impediment to the supersonic transport since it could only occur above large water masses such as the Pacific. This came to the realization that shock waves generated by the aircraft as they cruised through the air in supersonic speed could reach the ground thus, posing a major environmental threat. Low passenger numbers, the slump in air travel following the September 11 attacks, as well as rising maintenance costs were the reasons presented towards the halting of supersonic commercial flights. References Collard, D (1991). Concorde airframe design and development. SAE (Society of Automotive Engineers) Transactions, 100, 2620-2641. Hornung, H. (1986). Regular and Mach Reflection of Shock Waves. Annual Review of Fluid Mechanics, 18, 33-58. Kroo, I. (2005). Unconventional Configurations for Efficient Supersonic Flight. Stanford University, U.S.A. Kulfan, M. R. (1993). High speed civil transport opportunities, challenges and technology needs, Transactions of the Aeronautical and Astronomical Society of the Republic of China, 25(1), 1-20. Mason, W.H. (2006). Supersonic aerodynamics: Configuration aerodynamics. Config. Aero Supersonic Notes, 10, 1-23. Read More