1. 1 Supersonic Flight Diana Mann Feb 19, 2008

2. 2 Agenda Review Of Speed Regimes Problems At High Speeds Supersonic Engines Special Materials Aerodynamics Special Shapes Bonus Section – Hypersonic X-Plane

3. 3 Velocity, Force, and Temperature Increase Review of Speed Regimes (1 of 4) Graphic courtesy of NASA Glenn Research Center

4. 4 Review of Speed Regimes (2 of 4) Low Subsonic V < 250 mph General Aviation – Commuter Propeller Propulsion Aluminum Skin Straight Wings High Subsonic V < 600 mph Airliners Turbofan Engines Aluminum Skin Swept Wings Graphics courtesy of NASA Glenn Research Center

5. 5 Low Supersonic V < 1500 mph Fighter Planes Afterburner Engines Aluminum Skin Swept Wings High Supersonic V < 2500 mph Spy Planes Ramjet Engines Titanium Skin Small Wings Review of Speed Regimes (3 of 4) Graphics courtesy of NASA Glenn Research Center

6. 6 Low Hypersonic V < 6000 mph X - Planes Scramjet or Rocket Engine Cooled Titanium – Nickel Skin Short Wings High Hypersonic V < 17,500 mph Space Shuttle Rocket Engines Thermal Protection System Short Blunt Wings Review of Speed Regimes (4 of 4) Graphics courtesy of NASA Glenn Research Center

7. 7 Operational Envelopes http://www.aircraftenginedesign.com/custom.html4.html

8. 8 Problems at High Speeds Large Forces –Forces increase as the square of velocity Need Bigger Engines Need Stronger Airframe Need Special Shapes High Temperatures –Friction heating increases with velocity Need Special Materials Need Active Cooling Slide courtesy of NASA Glenn Research Center

9. 9 Supersonic Engines Propeller Propulsion Turbofan Engines Ramjet Engines Scramjet Engines Rocket Engines As engines become more powerful, Thrust Increases

10. 10 General Thrust Equation Graphic courtesy of NASA Glenn Research Center

11. 11 Excess Thrust (Thrust – Drag) Graphic courtesy of NASA Glenn Research Center

12. 12 Ramjet Engines No moving parts Speed of the jet "rams" or forces air into the engine The ramjet develops no static thrust and very little thrust in general below the speed of sound Ramjet vehicles require some form of assisted takeoff, such as another aircraft or booster http://www.ueet.nasa.gov/Engines101.html#types

13. 13 Scramjet Engines Ramjets with supersonic combustion are known as SCRAMJET (supersonic combustion ramjet) engines –Air-breathing engine in which the airflow through the engine remains supersonic Another engine system is required to accelerate the aircraft to ramjet velocities http://en.wikipedia.org/wiki/Scramjet

14. 14 Rocket Engines Rocket engines are reaction engines –The basic principle driving a rocket engine is Newton’s 3rd Law: “To every action there is an equal and opposite reaction" –A rocket engine ejects mass in one direction and benefits from the reaction that occurs in the other direction as a result http://science.howstuffworks.com/rocket.htm

15. 15 Special Materials Address larger forces and increased temperature at high velocity –Aluminum Skin –Titanium Skin –Cooled Titanium / Nickel Skin –Thermal Protection System (TPS) Melting Points –Al: 220 °F (660 °C)FC –Ti: 3263 °F (1795 °C)FC –TPS (Silicon): 2588 °F (1420 °C)FC

16. 16 Space Shuttle Thermal Protection System – Ceramic Tiles http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system

17. 17 Aerodynamics A branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object http://en.wikipedia.org/wiki/Aerodynamics Designers match airframe and propulsion system capabilities

18. 18 Aerodynamics Is Really Fluid Dynamics When an object passes through the air, it creates a series of pressure waves –These waves travel at the speed of sound As aircraft speed increases, the waves compress and merge into a single shock wave moving at the speed of sound –Speed of Sound 761 mph (~1,225 kph) at sea level –A.k.a. Mach 1 http://en.wikipedia.org/wiki/Sonic_boom

19. 19 Speed of Sound Graphic courtesy of NASA Glenn Research Center

20. 20 Laminar Flow Laminar flow occurs when a fluid flows in parallel layers, with no disruption between the layers It is the opposite of turbulent In nonscientific terms laminar flow is "smooth," while turbulent flow is "rough" Graphic courtesy of NASA Glenn Research Center Text courtesy of http://en.wikipedia.org/wiki/Laminar_flow

21. 21 Shock Waves (1 of 3) The speed at which some portion of the airflow over the wing first equals Mach 1.0 is termed the Critical Mach Number –This is also the speed at which a shock wave first appears on the airplane A shock wave is formed where the airflow suddenly returns to subsonic flow Shock wave becomes more severe and moves aft on the wing as speed of the wing is increased Eventually flow separation occurs behind the well- developed shock wave Cross Section of a wing http://en.wikipedia.org/wiki/Shock_wave

22. 22 Shock Waves (2 of 3)

23. 23 Shock Waves (3 of 3)

24. 24 Graphic courtesy of NASA Glenn Research Center Normal Shock Waves

25. 25 Graphic courtesy of NASA Glenn Research Center Oblique Shock Waves

26. 26 Graphic courtesy of NASA Glenn Research Center Crossed Shock Waves

27. 27 Shock Wave Imaged at Mach 7

28. 28 Schlieren Photography Schlieren photography is a visual process used to photograph the flow of fluids of varying densities –Used to visualize airflow over an aircraft traveling at supersonic speeds –Maps the variations of density in fluids Since shock waves are regions of higher pressure than normal air pressure, their density is greater than that of normal air pressure Pressure differential created by the shock waves allows the shape of the shock waves to be imaged –Invented by the German physicist August Toepler in 1864 to study supersonic motion Its role is changing due to the increasing use of computational fluid dynamics, where the same principle is used to display the computed results as flow images

29. 29 Computational Fluid Dynamics Computational fluid dynamics (CFD) is one of the branches of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems involving fluid flow During preprocessing –The geometry (physical bounds) of the problem is defined –The volume occupied by the fluid is divided into discrete cells (the mesh) The mesh may be uniform or non uniform –The physical model is defined equations of motions + enthalpy + radiation + species conservation –Boundary conditions are defined Specifies fluid behavior and properties at the boundaries of the problem For transient problems, the initial conditions are also defined The simulation is started and the equations are solved iteratively as a steady-state or transient Finally a postprocessor is used for the analysis and visualization of the resulting solution A computer simulation of high velocity air flow around the Space Shuttle during re-entry. http://en.wikipedia.org/wiki/Computational_fluid_dynamics

30. 30 Vapor Cones The condensation “cloud” marks the approximate location of the shock wave It’s called the Prandtl-Glauert singularity –The point at which a sudden drop in air pressure occur –Generally accepted as the cause of the visible condensation cloud that often surrounds an aircraft traveling at transonic speeds http://en.wikipedia.org/wiki/Prandtl-Glauert_singularity http://en.wikipedia.org/wiki/Image:FA-18_Hornet_breaking_sound_barrier_%287_July_1999%29.jpg

31. 31 Special Shapes (1 of 2) http://airwarrior.afkamm.co.uk/Aerodynamics/aero5.shtml

32. 32 Special Shapes (2 of 2) NASA believes that aircraft of the future can mimic the flight of birds, flying more efficiently and safely This video shows what NASA has observed in the flight of an eagle that can be translated into a concept for a future aircraft For example, just as a bird uses different feathers on its wings to control flight, aircraft wing shapes can be designed to change and adapt to constantly changing conditions of flight Or, an aircraft can mimic the way a bird lands, greatly decreasing the amount of fuel and runway space required http://www.hq.nasa.gov/office/aero/videos/eagle_morph.htm

33. 33 Bonus Section – Hypersonic X-Plane (1 of 4) The X-43A was a small experimental research aircraft designed to flight- demonstrate the technology of airframe-integrated scramjet propulsion at hypersonic speeds above Mach 5 http://www.nasa.gov/centers/dryden/history/pastprojects/HyperX/index.html

34. 34 Bonus Section – Hypersonic X-Plane (2 of 4) On June 2, 2001, the X-43A "stack" -- a modified Orbital Sciences Corporation’s Pegasus XL booster topped with the Hyper-X research vehicle -- was released from a B-52 carrier aircraft Booster ignition went as planned, with the aircraft accelerating on its predetermined high-altitude ascent Seconds later, however, booster fins broke off and the aircraft spun out of control The vehicle was then destroyed by range control http://www.space.com/businesstechnology/technology/x43a_report_030718.html

35. 35 Bonus Section – Hypersonic X-Plane (3 of 4) NASA convened the X-43A Mishap Investigation Board (MIB) to look into the failure on June 5, 2001 at NASA’s Dryden Flight Research Center at Edwards, CA –Because of the increased thermal loads predicted for the flight trajectory, changes were made in thermal protection to the Hyper-X launch vehicle wing, fins and body Additional thermal protection was not taken into account in preflight wind tunnel test modeling Computer and wind tunnel tests to help understand what caused the failure showed the new thermal protection altered the booster’s aerodynamic characteristics http://www.space.com/businesstechnology/technology/x43a_report_030718.html

36. 36 Bonus Section – Hypersonic X-Plane (4 of 4) Enter the X-51 –The Air Force Research Laboratory’s X-51 Scramjet- Waverider is being built by Pratt & Whitney and Boeing –This scramjet demonstrator is to fly by 2009 at target speeds close to Mach 7 (around 8,050 km/h) Ground tests of the X-51A began in late 2006 –For the flight demonstrations, a B- 52 will carry the vehicle to an altitude of about 35,000 feet and then release it. –Initially propelled by an Army Tactical Missile System (ATACMS) solid rocket booster, the scramjet will take over at approximately Mach 4.5, and the vehicle will accelerate to a flight speed near Mach 7ATACMS http://www.edwards.af.mil/news/story.asp?id=123084673 412th TW tests X-51 antennas An X-51 Scramjet-Waverider mock-up hangs inside the Benefield Anechoic Facility here during the vehicle's antenna testing. The 412th Test Wing Hypersonic Flight Test Team, Electronic Warfare and Boeing began the month-long testing Jan. 28. (Air Force photo by Mike Cassidy)

37. 37 Selected Links http://www.ueet.nasa.gov/Engines101.html http://wings.avkids.com/Book/advanced.html http://travel.howstuffworks.com/turbine6.htm http://www.aircraftenginedesign.com/custom.htm l4.htmlhttp://www.aircraftenginedesign.com/custom.htm l4.html http://en.wikipedia.org/wiki/Aerodynamics#Super sonic_aerodynamicshttp://en.wikipedia.org/wiki/Aerodynamics#Super sonic_aerodynamics http://www.wilk4.com/misc/soundbreak.htm

38. 38 EngineSim Exercises

39. 39 EngineSim Exercises (1 of 4) Set the following conditions in EngineSim: –Design Mode –English Units –Turbojet –Output: Graphs –Input Speed + Altitude Set the Airspeed to 0 mph, the Altitude 0 ft, and the Throttle 100. –Record Net Thrust ___________ –Record Fuel Flow ____________ Now change the Airspeed to 350, and the Altitude to 10,000 ft. –Record Net Thrust ___________ –Record Fuel Flow ____________ What happens when you choose a different engine? –Choose a jet with afterburner Record Net Thrust ___________ Record Fuel Flow ____________ –Choose a turbofan engine Record Net Thrust ___________ Record Fuel Flow ____________ –Choose a ramjet engine Record Net Thrust ___________ Record Fuel Flow ____________

40. 40 EngineSim Exercises (2 of 4) What can you conclude about the effect of an increase in altitude and airspeed on thrust? __________________________________ On fuel flow?_______________________ Which engine is most fuel efficient? _______________________________

41. 41 EngineSim Exercises (3 of 4) What happens when you increase speed? –Select Turbojet, and set Airspeed to 1500 mph (Low Supersonic) Record Net Thrust ________ Record Fuel Flow _________ –Select Afterburner, and set Airspeed to 1500 mph (Low Supersonic) Record Net Thrust ________ Record Fuel Flow _________ –Select Turbofan, and Set Airspeed to 1500 mph (Low Supersonic) Record Net Thrust ________ Record Fuel Flow _________ –Select Ramjet, and Set Airspeed to 1500 mph (Low Supersonic) Record Net Thrust ________ Record Fuel Flow _________

42. 42 EngineSim Exercises (4 of 4) Examine the graph on the right. Where is the pressure greatest for each engine? _________________________________ Bonus Question: –How are pressure and temperature related?____________________________

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