DESIGN-CENTERED INTRODUCTION TO AEROSPACE ENGINEERING

Welcome to Aerospace Engineering

DESIGN CENTERED INTRODUCTION TO AEROSPACE ENGINEERING

Topics1. Course Organizationg2. Today's Dreams in Various Speed Ranges3. Designing a Flight Vehicle: Route Map of Disciplines4. Mission Specification & Take Off WeightNotes 25. Force Balance during flight6. Earth's Atmosphere7. Aerodynamics8. Propulsion9.Performance, Stability & Control10. Structures and Materials11 Hi h S d Fli ht11. High Speed Flight12. Space Flight

Requirements Definition / Mission Specification

First, we have to decide what we want the contraption to do.

Then we will think of a "typical mission profile".

To do these, we must find out- what our customers really want, - what others have been able to achieve in the past, and - what opportunities are opened by new developments

Note: In industry, this is a crucial stage requiring massive effort and intense thi ki b thi i i t b th b i t it th ’ f t thinking, because this is going to be the basis to commit the company’s future. It involves discussions, analyses and trade studies with the airlines, financiers,regulating agencies, airports, law-makers and advertising / marketing agencies. Engineers have to learn to excel in this environment Engineers have to learn to excel in this environment.

Exercise: Do You Agree With This Market Survey?High Speed Civil Transport: Comparative Perspective Conclusion: No Market for 500 Aircraft!

Source: HIGH SPEED RESEARCH LESSONSNASA Office of Aero-Space

High-Speed Civil Transport: Comparative Perspective. Conclusion: No Market for 500 Aircraft!

Concorde HSCT G l

pTechnology Report to the NASA Advisory CouncilAugust 3-4, 1999

North Atlantic1976

MarketEntry In Service Year

Atlantic & Pacific2005

Concorde HSCT Goals

2.03000100

yCruise Speed (Mach)Range (nautical miles)P l d ( )

2.45000 - 6500250 300100

400,00087

Payload (passengers)Takeoff Gross Weight (lb.)Required Revenue (¢/RPM)

250 - 300700,00010

PremiumExempt

q (¢ )Fare LevelsCommunity Noise Standard

StandardFAR 36 - Stage 3

7520a

Noise Footprint (sq. mile)Emissions Index (gm/Kg fuel)

55

Challenge: Show that the addition of Eastern Hemisphere markets make Show that the addition of Eastern Hemisphere markets make

the Supersonic Transport viableNote: Note: •US Studies focused on transatlantic and transpacific. Ignored Eastern Hemisphere routes.•UK / European aerospace studies generally in sync with U.S. program funding profiles.•Example: British/European Hypersonic aircraft Moon-Mars interestExample: British/European Hypersonic aircraft, Moon Mars interest…•Many NEW viable over-water routes: Europe- South India; India-South Africa – South America. •Chennai /Kochi –Australia/Singapore/ Hong Kong/ Indonesia/ Korea/Japan•Rapid expansion of air travel in and around India and China. Rapid expansion of air travel in and around India and China.

Design Step 1

1 Write a Requirements Definition1. Write a Requirements Definition2. Market survey: list the possible number of aircraft to be made, considering the market. 3. Write a Mission Profile

Short-haul passenger aircraft using hydrogen fuel.

Request for Proposals

General requirements: An aircraft suitable for business traffic between cities, starting in 2013.

Exercise: Mission Specification

Regional Jet Aircraft using hydrogen Typical Mission Requirements

Atlanta – Rayleigh-Durham NCfuel.Range: 1600 kmCruise Speed: 500 kmph minimum80

Albuquerque-San Antonio Denver-Atlanta in summerShort turn-around time

ff80 passengers Fuel-efficientIndependent operation: No “jetway” needed. Reliable: all weather

Per passenger:Average mass:

Special Requirement: Operate from Denver and Albuquerque Year-Round

Baggage average: Water, food etc.Total passenger loadC Cargo: Total Payload:

Weight Estimation & Benchmarking

The mass to be carried is the "payload": the load which we get paid to carry.

g g

Once payload is determined we ask: "Haven't others tried to do something similar or close to this? How much did their aircraft weigh?

“Benchmarking“ – get rough idea of the weight fractions of the various systems involved.

For example, fuel weight may be 50% of the take-off weight of a long-range airlinerp , g y g g g

How Take-off Gross Weight (TOW) of an Aircraft is Broken Out

Component Fraction of TOWof TOW

Payload Fraction: passengers+ crew, baggage, food&water, cargo TOWWpayload

Propulsion Fraction: Engines, engine control systems, nacelles, fuel lines, fuel pumps, fuel tanks TOW

Wengines

Structure and Controls: Everything else fixed to the aircraft: wings, fuselage, control surfaces, instruments, landing gear, TOW

Wstructure

WFuel Fractionhydraulic systems, airconditioning, lights, interior furnishings.

TOWWfuel

Total: 1.0

N t H b k it t t k th t thi i i l d d hNote: However you break it out, you must make sure that everything is included somewhere,and only once.

Example: Computing TOW

Takeoff Gross Weight is simply the Payload divided by the Payload fraction.

For example, if the Payload is 30,000lbs, and we find that a reasonable payload fraction that we can achieve is 0.15, then the TOW is 30,000 / 0.15 = 200,000 lbs.

This is an estimate. You just learned how to get across the most difficult “canyons” of technical uncertainty in engineering: You JUMP across it. You make a “reasonable guess”, see where it leads, and then refine the guess as you learn more.

The rest of the design is to make sure we come in under this estimate, when we calculate everything else.

When we have a rough calculation of all the other things, we will go back and "iterate", many times to refine our estimates, so that the whole vehicle gets better. For this we will spare no technical effort but it will take years technical effort, but it will take years.

BenchmarkingThere is a wide range of answers to our question on the payload fraction. Some craft weigh only 4 times their payload; others weigh 10 times the payload. There is some similarity between these "payload fractions" for aircraft which have similar "missions"

d l d I f l if i “ i i ” b “ il ” f th and payloads. In our case, one way of classifying “missions” may be “passenger-miles” of the mission, the product of the number of passengers and the number of miles of range. Surely there are many other ways of doing the classification.

Payload Fraction

Passenger-miles

EMBRAER 190 COMMERCIAL REGIONAL JET, BRAZIL

Dimensions: Wingspan 28.56m, Overall length 36.15m, Height 10.48m

Source: http://www.aerospace-technology.com Last viewed 11/27/05

Fuselage depth 3.35m, Cabin length 25.39mMaximum width 2.74m, Maximum height 2.00mWeightsOOperating weight 26,200kgMaximum payload 12,400kgMaximum fuel 13,000kgM i t k ff i ht t d d E b 190 45 990kMaximum take-off weight, standard Embraer 190 45,990kgMaximum take-off weight, Embraer190 Long Range 48,500kgMaximum landing weight 42,500kgPerformancePerformanceCruise speed 0.80 Mach, 870km/hRange, standard Embraer 190 3,334kmRange Embraer190 Long Range 4 260kmRange, Embraer190 Long Range 4,260kmTake-off field length 1,829mLanding field length 1,280m

Sukhoi Su-30MKI

Crew: Two. Engine: Two AL-31F turbofans, each rated at 12,500 kgf (27,550 lbs) of full afterburning thrust. Engine Thrust-To-Weight

Length 21.94 mWingspan 14.70 mHeight 6.36 m)

Ratio: 8.7:1

Max Speed: At Sea Level - 1350 km/h; Mach 2 above 11 000 meters

Wing Area 62.0 m2Empty Mass: 17,700 kgTypical Load (Su-30M) 24,000 kgabove 11,000 meters.

Service Ceiling: 17,500 meters.

Climb Rate: 230 m/s; 45,300 ft/min. Max

(Su-30MKI) 25,670 kgMax Takeoff Su-30M 33,500 kg(Su-30MKI) 34,000 kgF l C it 9 400 kClimb Rate: 230 m/s; 45,300 ft/min. Max

Range: 3000 km with normal fuel load of 5270 kg; 5200 km with in-flight re-fuelling

Fuel Capacity 9,400 kgMax Payload 8,000 k)

G Limit: +9.

http://www.bharat-rakshak.com/IAF/Images/Current/Su-30/Su-30d1.jpg

BOEING 787: http://www.aircraft-info.net/aircraft/jet_aircraft/boeing/7e7/Boeing 787 - 7E7 200 250 200-250 passengersMax. Take off weight: 201,200 Kg.Max. Landing weight: ?? Kg.Cruise Speed: Mach 0 85Cruise Speed: Mach 0,85.Max. Range: 15,700 km.Wing Span: 59 m.Wing Area: ?? m²Wing Area: ?? m .Length: 56 m.Height: ??mBoeing 787 - 7E7 PowerplantsBoeing 787 7E7 PowerplantsBypass 10:1 ratio, quiet engines. Fuel efficiency of the engines will contribute up to 8% of the increased aircraft up to 8% of the increased aircraft efficiency. General Electric GENX and the Rolls-Royce Trent 1000, each with 55,000lb to 70,000lb thrust. , ,Main technical risk: Carbon Composite Primary StructureMain risk: Point-to-point operations vs. Hub&Spoke operations

http://www.fas.org/man/dod-101/sys/ac/f-35.htmJoint Strike Fighter(L kh d M ti / N th G )

U S Ai F U S M i C U K R l N U S N

(Lockheed Martin / Northrop-Grumman)

U.S. Air Force, U.S. Marine Corps, U.K. Royal Navy, U.S. NavyVariants Conventional Takeoff and Landing (CTOL) Short Takeoff and Vertical Landing (STOVL) Carrier-based (CV)Propulsion Baseline: Pratt & Whitney F119-PW-100 derivative from F-22 RaptorAlternate Engine: General Electric F120 coreE t W i ht 22 500 lb 24 000 lbEmpty Weight ~22,500 lbs ~24,000 lbsInternal Fuel 15,000 lbs 16,000 lbsPayload 13,000 lbs 17,000 lbsy , ,Maximum Takeoff Weight ~50,000 lbsLength 45 feet, Wingspan 36 feet 30 feetSpeed supersonicCombat Radius over 600 nautical milesCrew oneCrew one

http://www.jsf.mil/gallery/gal_photo_cdp_loc_stovl.htm

http://www hitechweb szm sk/x50 files/CRW jpg

X-50 Boeing Canard Rotor Winghttp://www.hitechweb.szm.sk/x50.files/CRW.jpg

http://www.defenseindustrydaily.com/images/AIR_GyroLifter_lg.jpg

http://spaceflightnow.com/news/n0302/18osp/ospconcepts.jpg

Design Step 2

6. Determine payload

Mass per passenger = ( ) kgSupplies per passenger = ( )kg

Baggage per passenger =C fli ht ( )kCargo per flight = ( )kgTotal payload = ( )kg

7 Determine payload mass fraction7. Determine payload mass fraction

8. Determine TakeOff Gross Weight (TOW)

FORCE BALANCE IN FLIGHT

The wings (and the horizontal tails to some extent) support the weight of the whole aircraft. The rest of the aircraft just hangs from these "lifting surfaces". j g gOf course the wings and tails themselves have weight. On most aircraft, the wings contain most of the fuel.

We can use Newton's Laws of Motion to calculate the acceleration of an aircraft, and thus to decide how the forces on the aircraft must be balanced to make it go in a desired direction.

Newton's First Law of Motion

Defines the concept of equilibrium. It says:

An object continues to be in a state of rest or uniform motion unless there An object continues to be in a state of rest or uniform motion unless there is a net force acting on it.

N t ' Thi d L f M tiNewton's Third Law of Motion:Every action has an equal and opposite reaction.

F l if th i f i l d th t hi h ll f d th i ft For example, if the engine of an airplane produces thrust which pulls forward on the aircraft, then the aircraft pulls on the engine in the opposite direction.

Newton's Second Law of Motion:Force = Rate of Change of MomentumForce = Rate of Change of Momentum.or, Force = mass*(rate of change of velocity) + velocity*(rate of change of mass)If the mass remains unchanged, Force = (mass)*(acceleration)

Force and acceleration are vectors: they have magnitude and direction. If two vectors are equal, i.e., vectors are equal, i.e.,

or,BA

kBjBiBkAjAiA zyxzyx

Two vectors can be equal only if their corresponding components are equal. Thus Newton’s 2nd law can be expressed as 3 scalar equations:

Then

yy

xxBABA

expressed as 3 scalar equations:

zz

yy

BABA

)( UmdF

)(mudtdFx

dmeans:)(dt )(mv

dtdFy

)(mwdF

means:

)(mwdt

Fz

ExampleExample

A rocket expels 10kg/s at an exit velocity of 4000 m/s. At the instant under consideration, A rocket expels 10kg/s at an exit velocity of 4000 m/s. At the instant under consideration, it’s mass is 10,000 kg.

The rocket is moving at 5000 m/s relative to earth. Find it’s acceleration. g

Thrust = rate of change of momentum of the fluid being expelled = (mass per second) x (change in velocity) of the fluid= 10x 4000= 40,000 N

Thrust Mdu/dt + U dM/dt = 10,000*a + 5,000*(-10)

40,000 = 10,000*a -50,000

Acceleration a = (40,000 + 50,000)/10,000 = 9 m/sec2

Newton's Second Law of Motion:

Force = Rate of Change of Momentum.Force Rate of Change of Momentum.

Since Momentum = mass*velocity, the above becomes

Force = mass*(rate of change of velocity) + velocity*(rate of change of mass)

If the mass remains unchanged,

Force = (mass)*(acceleration)

Note: Example of mass changing: A rocket-powered vehicle, whose mass decreases as propellant is dumped out the back end. Strictly, the mass of an aircraft keeps decreasing too, as it consumes fuel. However, this occurs pretty slowly compared to the rate at which a rocket consumes fuel.

Force and acceleration are vectors: they have magnitude and direction. If two vectors are equal, i.e.,

then,

Two vectors can be equal only if their corresponding components are equal.

Coordinate system

We usually use the "right-hand rule".

The "Freestream Vector ". Equal and opposite to the flight velocity.

Lift L is perpendicular to the freestream vector

Drag D is parallel to (along)

(but it may be up, down or sideways).

Thrust T is along the thrust direction.

U ll i l i ft h th th t t i ti f d l t l th Usually, commercial aircraft have the thrust vector pointing forward, almost along the aircraft fuselage, but they also have "thrust reversers" which can point the thrust backwards.

.

Weight acts towards the center of the earth (or whatever the closest massive h l b d i ) Th t t ti heavenly body is). The two component equations are:

Al X Along X,

Along Z: g

Total acceleration vector of the aircraft is given by the components along the x,y and z directions.

In the case above there is no acceleration along the y direction because In the case above, there is no acceleration along the y-direction because there is no net force along that direction.

Straight And Level Steady Flight

In Straight and Level Steady Flight, where all the accelerations are zero, Lift = Weight, and Thrust = Drag.

L = W L W

T = D

Case 2: When the aircraft is flying almost level

So if L>W the vehicle accelerates upwards (note that upwards is z) Also if T>D the

Case 2: When the aircraft is flying almost level

So, if L>W, the vehicle accelerates upwards (note that upwards is -z) . Also, if T>D, the vehicle accelerates forward. If L = W, the aircraft flies level, or rises and falls at constant speed. If T = D, the aircraft flies at constant speed.

Case 3:

Acceleration is zero, but

From the X-momentum equation,

From the Z-momentum equation,

.

Rate of ClimbRate of Climb

Dividing the X-momentum equation by the Z-momentum equation,

If is small (as is usual under a routine climb condition where one is not in any ( ydesperate hurry), the value u is fairly close to the magnitude of the veliocity vector, U. Then, approximately,

If w>0 then the aircraft is climbing From these we note:If w>0, then the aircraft is climbing. From these we note:

1) If the lift is greater than the weight, then the aircraft will accelerate upwards.

2) If the thrust is greater than the drag the aircraft can climb if the thrust acts at 2) If the thrust is greater than the drag, the aircraft can climb if the thrust acts at an angle to the flight direction. So there are different ways of achieving the same result.

Sideward Forces: Turn To help protect your privacy, PowerPoint prevented this external picture from being automatically downloaded. To download and display this picture, click Options in the Message Bar, and then click Enable external content.

the centrifugal force. Note thatthe centrifugal force. Note that

is the centripetal force: the force directed towards the center.

is the radial acceleration.

By Newton's 3rd Law of Motion the By Newton's 3rd Law of Motion, the centrifugal force is the reaction, which is equal and opposite to the centripetal forceforce.

Note: To pull tighter turns (i e smaller Note: To pull tighter turns, (i.e., smaller R), at a given value of U, must be made larger.

If t t l h i ht d i thi If we are not to lose height during this turn, must be as large as W.

Example of “G-forces”: Artificial Gravity” by RotationArtificial Gravity by Rotation

••Humans need near 1g for longHumans need near 1g for long term livingterm living••Humans need near 1g for longHumans need near 1g for long--term living.term living.

••Artificial gravity at rim of rotating wheel: Rotation rate Artificial gravity at rim of rotating wheel: Rotation rate

••must be lower than 1 RPM to avoid disorientationmust be lower than 1 RPM to avoid disorientationmust be lower than 1 RPM to avoid disorientation.must be lower than 1 RPM to avoid disorientation.

Radius ~ 1km. Radius ~ 1km.

AERODYNAMIC CONTROL SURFACES:

PITCH CONTROL

If th lift i i h d If the lift on one wing is changed relative to the other, the aircraft tends to roll, and this causes a turn, as seen aboveas seen above.

If the lift (side force) on the vertical tail is changed, the aircraft tends to yaw. Then the aircaft must roll to avoid sideslippingthe aircaft must roll to avoid sideslipping.

Much Remains To be Learned About Flight•Today's designs can fly over 100 times as fast as the Wright Flyer, and go right out into Space, circle the earth every 90 minutes or so, and return to precise touchdowns on earth.

•1920s: people believed that airplanes had reached the limits of speed and altitude. Experts “proved” that there was no “scope” in this field.

•Humans: 102 years of powered flight experience•Birds and insects: 1 million + years of evolution. •Cannot match control precision, landing versatility, payload fraction, engine weight fraction, fuel costs, maneuverability, reconfigurable geometry, or structure weight fraction.

By comparison with birds and insects:

•Today’s aircraft: fragile and clumsy. •Stiff, rigid wings that can't flap, twist, fold or thrust to any significant degree. N d l d l t ffi t l t •Need long runways and complex traffic control systems.

•You have to drive through 2 hours of downtown traffic and spend an hour and a half at the airport and another 30 minutes on the taxiway to make a flight of 200 miles. When e la nch spacecraft onl abo t 30% of the str ct re and 10% of the total la nch mass •When we launch spacecraft, only about 30% of the structure and 10% of the total launch mass

ever reaches orbit: the rest is wasted.

Aspect of Aerospace Engineering Basic disciplines / courses needed from the 1st 2 Aspect of Aerospace Engineering Basic disciplines / courses needed from the 1st 2 years of engineering school

Mission Specification Technology forecasting market surveys vehicle Mission Specification Technology forecasting, market surveys, vehicle performance, economics, social sciences, political science

Weight Estimation Statistics, technology forecasting

Aerodynamics Physics, calculus, computer science, optics, lasers, y y , , p , p , ,signal processing, image processing, acoustics, thermodynamics

Propulsion Physics, thermodynamics, chemistry, lasers, optics, environmental sciences, acoustics

Performance Physics, Statics and Dynamics, calculus; flight mechanics

Structures Materials Statics Dynamics Strength of MaterialsStructures Materials, Statics, Dynamics, Strength of Materials.

Layout and detail design Engg. graphics, psychology, economics, ergonomics

Stability Statics, calculusControls Laplace transforms, differential equations, electrical

engg computer scienceengg., computer science

Instrumentation & communications Optics, electronics, signal processing, computing

S l i El t i it ti l h i t Space propulsion Electricity, magnetism, nuclear engg., chemistry, physics, dynamics, thermodynamics

Trajectories & space mission design dynamics, astronomy, modern physicsj p g y , y, p y

Spacecraft design heat transfer, materials, photoelectricity, thermodynamics, chemistry, physics, physiology.

Flight Simulation Flight mechanics, image processing, engg. graphics, computer science, control theory.

Ground and flight testing and experimentation

All aerospace engg. disciplines, physics, chemistry, mechanical design, electronics, signal processing, image processing, computer science.

Lifecycle cost Manufacturing, Systems Engg., Optimization, Economics, Political and Legal Issues.