1 supersonic flight diana mann feb 19, 2008. 2 agenda review of speed regimes problems at high...

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Supersonic Flight

Diana Mann

Feb 19, 2008

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Agenda

• Review Of Speed Regimes

• Problems At High Speeds

• Supersonic Engines

• Special Materials

• Aerodynamics

• Special Shapes

• Bonus Section – Hypersonic X-Plane

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Velocity, Force, and Temperature Increase

Review of Speed Regimes (1 of 4)

Graphic courtesy of NASA Glenn Research Center

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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

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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



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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



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Operational Envelopes

http://www.aircraftenginedesign.com/custom.html4.html

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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

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Supersonic Engines

• Propeller Propulsion

• Turbofan Engines

• Ramjet Engines

• Scramjet Engines

• Rocket Engines

As engines become more powerful,

Thrust Increases

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General Thrust Equation


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Excess Thrust(Thrust – Drag)


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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

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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

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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

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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)– Ti: 3263 °F (1795 °C)– TPS (Silicon): 2588 °F

(1420 °C)

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Space Shuttle Thermal Protection System – Ceramic Tiles

http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system

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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

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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

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Speed of Sound


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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 CenterText courtesy of http://en.wikipedia.org/wiki/Laminar_flow

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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 winghttp://en.wikipedia.org/wiki/Shock_wave

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Normal Shock Waves

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Oblique Shock Waves

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Crossed Shock Waves

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Shock Wave Imaged at Mach 7

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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

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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

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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

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Special Shapes (1 of 2)

http://airwarrior.afkamm.co.uk/Aerodynamics/aero5.shtml

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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

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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

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• 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

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• 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

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• 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 7

http://www.edwards.af.mil/news/story.asp?id=123084673

412th TW tests X-51 antennasAn 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)

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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.html4.html• http://en.wikipedia.org/wiki/

Aerodynamics#Supersonic_aerodynamics• http://www.wilk4.com/misc/soundbreak.htm

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EngineSim Exercises

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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 ____________

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• 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? _______________________________

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• 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 _________

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• 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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This workforce solution was funded by a grant awarded under the Workforce Innovation in Regional Development (WIRED) as implemented by the U.S. Department of Labor’s Employment and Training Administration working in partnership with the Colorado Department of Labor and Employment, the Metro Denver Economic Development Corporation, and the City and County of Denver's Office of Economic Development. The solution was created by the grantee and does not necessarily reflect the official position of the U.S. Department of Labor. The Department of Labor makes no guarantees, warranties, or assurances of any kind, express or implied, with respect to such information, including any information on linked sites and including, but not limited to, accuracy of the information or its completeness, timeliness, usefulness, adequacy, continued availability, or ownership. This solution is copyrighted by the institution that created it. Internal use by an organization and/or personal use by an individual for non-commercial purposes is permissible. All other uses require the prior authorization of the copyright owner.

1 supersonic flight diana mann feb 19, 2008. 2 agenda review of speed regimes problems at high...

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