Introduction to Hypersonic Propulsion

SystemsDr. Andrew Ketsdever

Assistant ProfessorDepartment of Mechanical and Aerospace Engineering

University of Colorado at Colorado Springsaketsdever@eas.uccs.edu

http://eas.uccs.edu/aketsdever

Technology Requirements

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Propulsion System FactorsEfficiency Weight Complexity Variability Longevity and cost of components Fuels (density, rheology, stowability,

handling, combustion characteristics, cost)

Materials Mission requirements (trajectory,

cost, etc.)

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Selection Process

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Performance

Specific impulse Thrust Inert mass fraction All three must be optimized in order

to achieve desired outcome

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Performance

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Materials

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SmallSpace

Booster

• SolidStaged

Combustion

Time, sec

LiquidRocketEngineNozzles

SatellitePropulsion

Booster

CruiseMissiles

BoostGlide

Vehicles

ThrustChambers

NASP

Temperature

Fuels

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Problems

Most launch vehicles are rockets, which suffer from low specific impulse compared with air-breathing systems (5000 sec. for turbojets vs. 500 sec. for rockets)

This degrades overall performance and increases weight (a good reason to investigate hybrid systems for future launch vehicles!)

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Problems

The need to carry so much fuel makes overall weight a crucial design factor

The structure of the vehicle is made as light as possible to compensate

Boosters are not strong, rigid bodies. While they are fairly strong longitudinally, they are very weak laterally

Most rockets cannot fly at significant angles of attack through the atmosphere or they would fall apart!

A rocket carrying satellites usually starts vertically, but must end in a horizontal orbit trajectory How can you control trajectories??? How do you keep from falling apart???

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Pratt & Whitney J58 Turbo-ramjet cycle

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35,000-lb thrust class, 9-stage compressor, SFC 2.17 1/hr

Flight Regimes

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200

150

100

50

0

SUBSONIC TURBINE ENGINE

HIGH ALTITUDE SUPERSONIC TURBINE ENGINERAMJET, AIR-AUGMENTED ROCKET

LOW ALTITUDE SUPERSONIC TURBINE ENGINE

HYPERSONIC RAMJET

ALT

ITU

DE

, KF

T

1 2 3 4 5 6 70

FLIGHT MACH NUMBER

Propulsion Options

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Combined cycle Propulsion “Low speed” cycle + scramjet

Rocket Based Combined Cycle (RBCC):Mach 0--25 air-breathing +rocket + scramjet + rocket

Turbine Based Combined Cycle (TBCC):Mach 0--4, 5 turbine + scramjet

• Scramjet– Supersonic combustion ramjet– Hydrocarbon (Mach 3-8)– Hydrogen (Mach 3-15)

Scramjet

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Forebody

(Compression) Shock Wave

Inlet

Body

Cowl

Combustor

Nozzle

Isolator

Mach 4 and higher

Fuel

No Moving Parts Necessary

Vehicle and Propulsion system are totally integrated

NASA X-34 Scramjet Program

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"On 16 November, 2004, NASA's unmanned Hyper-X (X-43A) aircraft reached Mach 9.6 (~7,000mph). The X-43A was boosted to an altitude of 33,223 meters (109,000 feet) by a Pegasus rocket launched from beneath a B52-B jet aircraft. The revolutionary 'scramjet' aircraft then burned its engine for around 10 seconds during its flight over the Pacific Ocean."

Turbine Based Combined Cycle (TBCC)

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• Accelerator Turbine (Mach 0—4.3) is combined with a duel-mode scramjet engine (Mach 4—8)

• Transition from turbine power to ramjet is performed at Mach 4

• Cocooning hot turbine engines will be a technical challenge

• Tail rockets would likely be added if vehicle is the first stage of launch system

Turbine-engine inlets

Accelerator Turbines

Over-Under configuration

Rocket Based Combined Cycle (RBCC)

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Forebody

(Compression)Shock WaveInlet

&Door

Body

CowlCombust

orNozzle

Isolator

Strut & Rockets

Vehicle and Propulsion system are totally integrated

Rocket-Based Combined Cycle promises a propulsion system that can achieve good performance from M = 0--25

RBCC Modes of Operation

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AIR

AIR

AIR

Inlet Closed

GREEN ARROWS: FUEL INJECTION

Air-AugmentedEjector ModeMach = 0—3

Ramjet Mode M = 3—6

Scramjet Mode M = 6—10

Rocket Mode M > 10

M >1

M <1

Each mode is sub-optimized in its operating range

RBCC-TBCC

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Pulsed Detonation Engines

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Pulse Detonation Engine Operating Concept

Detonation is initiated2 Detonation wave movesthrough fuel-air mixture

3

Detonation wave exits engineAir drawn in by reduced pressure

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1 Fuel is mixed with air 4 Resulting high pressure gasfills detonation chamber

Typical:

40 cycles/sec

Re-Entry

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Re-Entry: Meteors

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Element ColorSodiumIronMagnesiumCalciumSilicon

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