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Challenges, Enabling Technologies and
Technology Maturity for Responsive Space
Dr. Kevin G. Bowcutt
S. Jason Hatakeyama
Boeing Phantom Works, Huntington Beach, CA
AIAA 2nd Responsive Space Conference
21 April, 2004
Introduction
• Over the past 20 years there have been numerous attempts
to develop a new RLV
– All failed or prematurely canceled
– All share a common issue: lack of technology maturity of
fundamental components to meet needs of RLV safety,
reliability, affordability and responsiveness
• Focusing only on the truly enabling RLV technologies in a
national effort should help break this cycle
– Identify enabling technologies, assess their readiness, create
detailed tech development roadmaps, and create a national
program with sufficient will and resources for success
• Limited maturity and analysis uncertainty of highly reusable,
rapid turnaround, low cost rocket and air-breathing engines
make optimal RLV propulsion choice unclear
– Employ a JSF-like fly-off of both engine types to gather data
needed to decide which approach best meets RLV user needs
Propulsion System Fly-Off Model
• Joint Advanced Strike Technology (JAST) program
established in 1994 to create “building blocks for affordable
development of the next-generation strike weapon system”
• Joint Strike Fighter (JSF) program then pitted X-32 direct lift
propulsion against X-35 shaft-driven lift fan
• Analysis-based performance, turnaround time and cost
projections contain insufficient data and fidelity to support
conclusions about rocket vs. air-breathing RLV choice
– Develop both engines sufficient for flight test and to enable
evaluation of performance, turnaround time and cost metrics
– Conduct JSF-like fly-off between RLV boosters to gather data
necessary to make concrete concept selection decision
– Minimize flight development cost, but retain sufficient booster
performance to gather needed decision data and to yield an
initial RLV spiral for global strike and/or responsive spacelift
Rocket vs. Air-Breathing Turbine RLV Booster
• Reusable hydrocarbon or LH2
rocket booster stage
• Expendable upper stages
• Reusable Mach ~ 4 turbine or Mach 4
turbine + Mach 6 ramjet booster stage
• Expendable upper stages
• Next RLV spiral could replace expendable 2nd stage with a reusable
rocket stage, or perhaps a reusable scramjet or RBCC powered 2nd
stage if air-breathing option wins fly-off
• Other vehicle classes could be developed from mature tech base
– Key to rapid system development is integrated vehicle design and MDO
Mach 4+ Turbine Accelerator Engine Can Be
Developed to Meet RLV Requirements
• Given SR-71 & XB-70 experience, Mach 4 turbine a largely
evolutionary advancement
• Principal challenges for RLV applications: high thrust-to-weight
ratio, thermal management, airframe integration, increased
reliability and service life
Turbine Based System :
Key to Enabling Tomorrow’s Propulsion Systems
Access to Space
 $10,000/lb payload (Goal : $100/lb)
 Long Turn Around Time
 High Maintenance
Re- usability <20 missions
 Limited Launch & Landing sites
8- 10 missions per year
Military
SR71
 Max. Mach = 3+
 Thrust/Weight = 4 ( low)
 Maintenance High
 Elaborate Lubricants
Durability Low
Space Shuttle
RTA Features :
Quick Turn Around Time (Airline like Operations)
Re- useable > 1000 missions
Versatile Usage & Launch and Landing sites
Low Maintenance
Air Travel
High Durability
1000’s of Flights per Year
Mach >4
Thrust/Weight > 10
Cost: $ /lb Payload Low
Conventional
Fuels & Lubricants
 Max Mach = 2.
Concorde
 $/Passenger: high
(London to NY: $10,000)
 Sonic Boom
Future
• NASA Revolutionary
Turbine Accelerator
(RTA) program
developing mid-scale
Mach 4+ turbine that
could be used for RLV
fly-off
• Program at risk given
President’s new space
exploration initiative
Rocket Engine Design Goal Interactions Hamper Ability
to Meet Performance, Operability and Cost Objectives
T/W
Life
MTBOH
Failure Rate (Cat)
Failure Rate (Benign)
Failure Rate (Benign)
MTBOH
Life
Isp
T/W
Design Goals
Failure Rate (Cat)
Design Goals
Isp & T/W Conflict
With Operability
• Engines have been
designed separately for
goals of performance, cost
and operability, but the
challenge of achieving all
three objectives
concurrently remains
formidable
Routine Turn Time
Legend
Red = Conflicting goals
Green = Consistent goals
Rocket high energy-density, low operational time and few design generations make
design to meet all RLV objectives challenging
Space Shuttle Main Engine
Designed for High Performance
Cycle
FRSC
Propellants
LOX/LH2
Thrust in Vacuum
512, 950 lb
Thrust at Sea Level
418,660 lb
Isp in vacuum(s)
452 sec
Mixture Ratio
6.0:1
Dry Weight
7,480 lb
Chamber Pressure
3,008 psia
Nozzle Area Ratio
69:1
http://www.boeing.com/defense-space/space/propul/SSME.html
Delta IV RS-68
Designed for Low Cost
Propellants
LOX/LH2
Thrust in Vacuum
745,000 lb
Thrust at Sea Level
650,000 lb
Isp in vacuum(s)
410 sec
Isp at sea level
365 sec
Mixture Ratio
6.0:1
Dry Weight
14,560 lb
Chamber Pressure
1,410 psia
Nozzle Area Ratio
21.5:1
http://www.boeing.com/defense-space/space/propul/RS68.html
NGLT RS-84 Prototype
Designed for Operability
•
•
•
•
•
•
•
ORSC cycle
Lox/RP-1
Single ox-rich pre-burner
Parallel turbine drive
1,050 klbf prototype
Design at PDR (June ’03)
Optimized for safety &
reliability
No Existing Engine Meets Cost & Operability Goals
NGLT Program Had Embarked on Operable Engine Demos
Major rapid turnaround
technologies:
• Rapid drying & purge
• Leak-proof systems
• Automated health
management systems
with limited visual
inspections
• Non-pyrotechnic ignition
systems
Key challenge is
technology integration
and system design
Hypersonic Air-Breathing RLV Example of
Proposed Technology Maturation Process
• Four technologies deemed critical and enabling for a
hypersonic air-breathing RLV (Boeing Technical Fellowship
Advisory Board Study, 2003)
–
–
–
–
Air-breathing propulsion
High-temperature materials & thermal protection systems (TPS)
Reusable cryogenic tanks and integrated airframe structures
Integrated vehicle design and multidisciplinary design
optimization
• 3 of 4 enabling technologies common to rocket and airbreathing RLVs
• All should be matured to a TRL = 6-7 before embarking on
RLV development (same holds true for reusable rocket
propulsion)
Scramjet Propulsion and TPS Technology
Readiness Level Assessment
Propulsion
TRL
Engine Materials ...................................
Cooled Engine Panels ..........................
Scramjet Combustors (Mach>7) .........
Fuel Injectors/Flame Holders ..............
Integrated Flowpath-Hydrocarbon ......
Integrated Flowpath-Hydrogen ...........
Engine Seals .........................................
Engine Sensors ....................................
Engine Active Control System ............
TBCC Flowpath Integration .................
11
22
33
Cooled CMC
44
55
66
77
High Temp Cooled Metals
Uncooled
Structure
Mach>7
Mach>7
Mach>7
Thermal Management
Hypersonic Aerothermodynamics ......
Boundary Layer Transition ..................
Engine Flowpath Thermal Design .......
Thermal Management/Control System
High/Ultra-High Temp M & S ................
Actively Cooled Thermal Protection ...
Durable Thermal Protection ................
Mach>7
Mach>7
Mach>7
Low
Maintenance
88
High Maintenance
99
Cryogenic Tanks, Structures and Vehicle Design
Technology Readiness Level Assessment
Structures and Materials
TRL
Integral Metallic Cryotank ......................
Integral Composite Cryotank .................
High Temperature Metallic Structure ....
High Speed (Mach 3-7) Structures .........
Hypersonic (Mach 7-14) Structures .......
Hypersonic (Mach 0-14) Structures .......
Aero-servo-elastic Structures Analysis
Vehicle Design and Optimization
Parametric Geometry Generation ..........
Discipline Analysis Integration ..............
High Fidelity Analysis Automation ........
Probabilistic Analysis .............................
Multi-disciplinary Design Optimization
Cost Modeling ..........................................
Manufacturing Modeling .........................
Operations/Campaign Modeling & Sim
Design/Simulation Integration ................
11
22
33
44
Al/Li
55
66
77
88
Aluminum
Metal Matrix
Gr-EP & Gr-Bmi Composites
Advanced
Metallics/Ceramics
Titanium Matrix Composite
Mach 7
C/C Wing
Box
Hybrid
Cryotanks
Multidisciplinary
Analyses
Mach 3
Integral TankPassive TPS
Active & Passive
Cooling
Hot Structures
Analysis
99
Notional Enabling Technology Roadmap
04
05
06
07
08
09
10
11
12
13
Materials, TPS &
Structures
Integrated
Vehicle Design
& Optimization
Integrated
Ground Test &
Numerical Sim
Space Access
Flight
Demonstrations
Other
Mission
Applications
15
16
17
18
19
Mixing, combustion, kinetics, fuels,
materials, MDO methods, instrumentation,
fluid mechanics, numerical simulation, etc.
Fundamental
Research
Air-breathing
Propulsion
14
Large-Scale Engine
Ground Test
Mid-Scale Engine
Ground Test
Small-Scale Engine
Ground Test
High-speed Turbine
Ground Test
TPS/Structures
Integration
Automated Data Flow
Cost Model
Actively Cooled TPS & Boundary
Layer Transition Flight Test
Ultra High Temp
Passive TPS
Component Ground Tests
TMS/TPS Components
Validate Horizontal Launch Capability
With Conformal H2 Tanks
TPS/Hot Structures
Conformal H2 Tanks
Parametric
OML/Layout
Complete MDO System
Full Mission Simulation
Ground/
Flight Ops
Simulation
Manufacturing
Simulation-Derived MDO
Objective Functions
Simulation Tool
Upgrades
Facility Upgrades
Small-Scale
Small-Scale H2
H2 && HC
HC Demos
Demos
Mid-Scale
Mid-Scale H2
H2 Demo
Demo
Potential Residual CAV
Launch Capability
Large-Scale
Large-Scale H2
H2 Demo
Demo
H2 Space
Access
Vehicle
HC Hypersonic Missile
Mid-Scale HC Flight Demo
HC Hypersonic ISR, Intercept, Global Strike, Transport
Notional Hypersonic Air-Breathing Propulsion
Technology Roadmap
04
05
06
07
08
09
10
11
12
Fundamental
Propulsion Physics
Research
Component
Technology
Development
15
16
17
Component
Tests
Mid -Scale Engine
Design, Fab & Test
Design
Fab
• Extend NASA Hyper-X Hydrogen Engine Testing From Mach 8-14
• Complete AFRL HyTech Hydrocarbon Engine Testing From Mach 4-8
Freejet Tests
Large -Scale Engine
Design, Fab & Test
Design
PDR
Design
DDR
Fab Ground Test
Fabrication
RTA Mid-Scale Ground Demonstrator
Critical Component
Ground Testing
Rig Tests
Large-Scale Ground Demonstrator
TJ-SJ Mode Transition: Ground or Flight Demo
Flight Demonstration
Flight Tests
Mach 3-14 Mid-Scale
SRR PDR
& CoDR
Mach 0-14 Large-Scale
18
Inlets, Isolators, Injectors,
Combustors, Nozzles, Materials,
Cooled Panels, Fuels
Small-Scale Engine
Ground Testing
Mach 3-7 Small-Scale
- Hydrocarbon & H2
14
19
Friction, heating, combustor/inlet
interaction, injection, mixing, flame
holding, cooling, chemistry, etc.
Reactivate/Modify Test
Facilities
High-Speed Turbine
Engine
13
CDR
Fab
Flight Test
Flight Test
Summary
• Over the past 20 years there have been numerous attempts
to develop a new RLV, but none have succeeded due in part
to lack of maturity of enabling technologies
• Focusing only on the truly enabling RLV technologies in a
national effort should help break this cycle
• Rocket and air-breathing turbine engines both require similar
time, money and risk reduction to concurrently achieve RLV
performance, cost and operability objectives
– Existing uncertainties make best choice for RLV unclear
• A JSF-like fly-off of both rocket and air-breathing RLV
boosters could be used to determine approach that provides
best capabilities for Operationally Responsive Space