Aerodynamics of Supersonic Aircraft - Essay Example

Aerodynamics of Supersonic Aircraft Student’s Name Institutional Affiliation Aerodynamics of Supersonic Aircraft The following paper aims at discussion the aerodynamics of a supersonic aircraft. It will include the theory of supersonic flight, the effect of shock wave, the sonic boom, and supersonic wing designs. The Theory of Supersonic Flight When an aircraft is in flight or flying, there are four forces involved including life, thrust, weight, and drag. Supersonic flight is one of the four forces. Basically, there exist four systems of flight including the subsonic, transonic, supersonic, and hypersonic (May, 2015). An object or aircraft that is in supersonic flight is flying at speeds higher than that of sound. This means that supersonic aircrafts fly faster than the speed of sound. According to May, (2015) the speed of sound is approximately 1,236 kilometers per hour (768 miles per hour) at sea level. Supersonic speeds are measured or described by Mach numbers. A Mach number is defined as the ratio of speed of the airplane to the speed of sound (May, 2015). This means that any flight that is higher than Mach 1 is considered supersonic. One of the common objects that undergo supersonic flight is a bullet. As illustrated in Figure 1, a bullet fired from a firearm travels 1.5 times faster than the speed of sound. Moreover, common military aircrafts can also fly at supersonic speeds. According to May, (2015) the Concorde is also the most popular passenger aircraft to fly about twice the speed of sound. Figure 1: Bullet in Supersonic Flight (May, 2015). For an aircraft to reach supersonic speeds it requires greater thrust to help push it through the additional drag that is within the transonic region. For instance, U.S military jets are powered by rockets that add increased thrust greater than common airplanes (see Figure 2). This allows the aircraft to break the sound speed barrier enabling the aircraft to fly at speeds greater than that of sound. Therefore, only powerful aircrafts in terms of thrust can be able to fly at supersonic speeds. Figure 2: U.S Military Hornet aircraft flying at supersonic speeds (May, 2015). Shock Wave A shock wave is simply air that is pushed aside with great force as objects fly in the air. According to Anderson, (n.d) a shock wave is an irreversible process triggered by thermal and viscosity conduction effects inside the shock wave. When aircrafts are flying at supersonic speeds, air is molecules around the aircraft are pushed aside in a cone-shaped design (see Figure 3). The shock wave is also the displacement of air molecules as the aircraft flies in air (Gibbs, 2014). As the air is dispersed, it forms a cone of pressed air that move outward and backward in all directions. The air moves in a manner that it extends all the way to the ground. The force used to displace air molecules causes the shock wave. Moreover, as seen in Figure 3, all aircrafts produce shock waves in the form of a cone at the nose and tail or at the front and back. The shock waves cannot be seen with the naked eye (Anderson, n.d). Nonetheless, scientists invested the shadowgraph that enabled one to see the shock waves generated from objects moving at supersonic speeds (See Figure 4). As speed increases, the shock wave discontinuously increases in temperature and pressure (Anderson, n.d). This means that at high supersonic speeds, more shock waves are generated while increasing the temperature around the aircraft. Shock waves in the transonic region cause a decreased airflow thus creating increased drag. This means that the force behind an aircraft or the force pulling the aircraft backwards is increased. Additionally, this causes the life force to decrease. In the transonic region, an aircraft may not be able to reach supersonic speeds because of shock waves. Nonetheless, supersonic aircrafts use numerous instances of shock waves that hinder airflow reaching the engines. The overall effect of shock waves is allowing higher speeds at the transonic region, but as it increases drag, it still cannot move at supersonic speed (Anderson, n.d). However, the number of shock waves generated can easily enable an aircraft to fly in the supersonic region travelling at speeds higher than that of sound. Figure 3: Transonic flow over an airfoil (Anderson, n.d). Figure 4: Shadowgraph of shock waves from a bullet in supersonic flight (Anderson, n.d).. Sonic Boom According to Gibbs, (2014) a sonic boom is defined as the thunder-like sound or blast an individual on the ground receives when an aircraft flies above them in a speed faster than sound. The cause of the sonic boom is the release of pressure that builds up as air is displaced by the moving aircraft at supersonic speeds. In this case, the shock wave is behind the sonic boom. As described above, the shock wave is the force or pressure that builds up as an aircraft pushes or displaces air molecules at high speeds. This cause the object or aircraft, which is the source of the sound to break the sound speed barrier (Gibbs, 2014). With the sound speed barrier broken, it means that the aircraft will fly at speeds that exceed the speed of the sound it produces. This means that an individual may see the aircraft fly above them and later get to hear the loud blast or sound it leaves behind. As the shock wave develops into a cone-shape design, it sharply releases the buildup pressure along the cone’s width. This results in the creation of sonic booms continuously as the cone spreads across the atmosphere along its flight path (Gibbs, 2014). This sharp release of force or pressure is heard as a noise or the sonic boom. There are numerous factors that impact the sonic boom such as form of aircraft, weight, size, attitude, altitude, and flight path as well as weather or air conditions (Gibbs, 2014). A heavier or large aircraft displaces more are to make decrease its life so as to maintain flight. As discussed above in the shock wave section, a shock wave basically decreases the life force and increases drag. In this case, the larger and weightier aircraft will displace more air than a smaller aircraft. In this case, the heavier and bigger aircraft will make louder sonic booms than smaller and lighter aircrafts (Gibbs, 2014). The same applies to shock waves with large and heavy aircrafts producing bigger shock waves. Altitude defines the distance or extent shock waves move before getting to the ground, which has the most substantial effect on strength (Gibbs, 2014). When shock wave cones increase in width, they reduce their intensity or strength. In general, when an aircraft is flying higher, its shock waves will travel greater distances, thus reducing the strength of the sonic boom. This means that for aircrafts to reduce sonic booms effectively, changing altitude is the most effective method (Gibbs, 2014). Other issues that may affect the strength of the sonic boom is changing flight paths such as by maneuvering as well as speed, wind, and direct of flight. Supersonic Wing Designs Increased research in supersonic airflow has resulted in advancements in how aircraft wings are deigned. The common supersonic wind designs are the Delta-wing, Sweepback-wing, and Swing-Wing (NASA, n.d). The sweepback wing is used in most high-speed aircrafts and is effective in reducing the formation of shock waves in flight. This wing design is designed to reduce drag by reducing the amount of shock waves formed while the aircraft is in fligh (NASA, n.d)t. The ability to reduce drag allows the plane to maintain high speeds while in high altitude. The delta wing is the most effective wing design for supersonic aircrafts. It is widely used in military jets and aircrafts that move at supersonic speeds. The delta wing appears as a large triangle from above and is used in the some of the modern supersonic aircrafts (see Figure 5). Some of the delta wings are designed as double where they are able to reduce the drag and lift. When landing the delta wings are also important to enable lower speeds. Figure 5: Delta Winged aircraft The swing-wing is also used in supersonic flight. Nonetheless, the swing-wing is not that effective. According to NASA, (n.d), one of the main challenges associated with supersonic flight is the tendency of the aircraft’s nose to pitch down when it moves from the subsonic region to the supersonic region. The delta wing can effectively reduce the pitch down while the swing wing requires installation of canards to stabilize the pitch down (see figure 6). Figure 6: A: Swing wing design B: Double Delta wing design (NASA, n.d). In conclusion, research on supersonic flight or the aerodynamics of supersonic aircrafts is still ongoing. Nonetheless, a lot has been achieved in terms of proving theoretical research into actual and workable research. This has led to the development of supersonic aircrafts that can move at higher speeds than that of sound. Moreover, supersonic flight research is still ongoing with different aircraft manufacturers and research institutions such as Boeing and NASA. References Anderson, J. (n.d). Research in Supersonic Flight and the Breaking of the Sound Barrier. Retrieved from http://history.nasa.gov/SP-4219/Chapter3.html Gibbs, Y., (2014). NASA Armstrong Fact Sheet: Sonic Booms. Retrieved from http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-016-DFRC.html#.VbaBm8nkjcs May, S. (2015). What Is Supersonic Flight? Retrieved from http://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-supersonic-flight-58.html NASA, (n.d). SP-367 Introduction to the Aerodynamics of Flight: SUPERSONIC FLOW. Retrieved from http://history.nasa.gov/SP-367/chapt6.htm#f105 Read More