Dr. Andrew Ketsdever
Assistant Professor
Department of Mechanical and Aerospace Engineering
University of Colorado at Colorado Springs
aketsdever@eas.uccs.edu
http://eas.uccs.edu/aketsdever
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Efficiency
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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Specific impulse
Thrust
Inert mass fraction
All three must be optimized in order to
achieve desired outcome
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Temperature
Small
Space
Booster
Boost
Glide
Vehicles
•Solid
Staged
Combustion
Thrust
Chambers
Cruise
Missiles
Liquid
Rocket
Engine
Nozzles
NASP
Satellite
Propulsion
Booster
Time, sec
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Most launch vehicles are rockets, which suffer
from low specific impulse compared with airbreathing 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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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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35,000-lb thrust class, 9-stage compressor, SFC 2.17 1/hr
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200
SUBSONIC TURBINE ENGINE
HIGH ALTITUDE SUPERSONIC TURBINE ENGINE
RAMJET, AIR-AUGMENTED ROCKET
ALTITUDE, KFT
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LOW ALTITUDE SUPERSONIC TURBINE ENGINE
HYPERSONIC RAMJET
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50
0
0
1
2
3
4
5
FLIGHT MACH NUMBER
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7
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Combined cycle Propulsion
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“Low speed” cycle + scramjet
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Rocket Based Combined Cycle (RBCC): Mach 0--25
air-breathing +rocket + scramjet + rocket
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Turbine Based Combined Cycle (TBCC): Mach 0--4, 5
turbine + scramjet
• Scramjet
– Supersonic combustion ramjet
– Hydrocarbon (Mach 3-8)
– Hydrogen (Mach 3-15)
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Vehicle and Propulsion system are totally integrated
No Moving Parts Necessary
Mach 4 and higher
Body
Fuel
Cowl
Combustor
Forebody
(Compression)
Nozzle
Inlet
Isolator
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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."
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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
Over-Under configuration
Accelerator Turbines
Turbine-engine inlets
•Cocooning hot turbine
engines will be a
technical challenge
•Tail rockets would likely
be added if vehicle is the
first stage of launch
system
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Rocket-Based Combined Cycle promises
a propulsion system that can achieve
good performance from M = 0--25
Body
Strut &
Rockets
Cowl
Combust
or
Forebody
(Compression)
Inlet
&
Door
Nozzle
Isolator
Vehicle and Propulsion system are totally integrated
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Air-Augmented
Ejector Mode
Mach = 0—3
AIR
AIR
M <1
Ramjet Mode
M = 3—6
GREEN ARROWS: FUEL INJECTION
AIR
M >1
Inlet Closed
Scramjet Mode
M = 6—10
Rocket Mode
M > 10
Each mode is sub-optimized in its operating range
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Pulse Detonation Engine
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Operating Concept
Detonation is initiated
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Detonation wave moves
through fuel-air mixture
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Fuel is mixed with air
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Detonation wave exits engine
Air drawn in by reduced pressure
Resulting high pressure gas
fills detonation chamber
Typical:
40 cycles/sec
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Element
Color
Sodium
Iron
Magnesium
Calcium
Silicon
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