AC 2010-2270
UNDERGRADUATE STUDIES OF SUPERSONIC
TRANSPORT DEVELOPMENT
Narayanan Komerath
Daniel Guggenheim School of Aerospace Engineering
Georgia Institute of Technology
Atlanta
PROJECT EXTROVERT: Learning To
Innovate Across Disciplines
Project Structure for EXTROVERT:
Learning To Innovate Across Disciplines.
Skills
Library
DesignCentered
Introduction
McMahon Solutions
Library
Propulsion
Physics
Chemistry
UR
Here
Advanced
Concepts
Thermal
Sciences
Controls
System
Design
Case
Studies
Library
Composites
Elasticity
Strength
Materials
Space
Science
HighSpeed
Gasdynamics
LowSpeed
Fluids
Core Subject Knowledge
Engg.
Disciplines
Social
Sciences
Public Policy
Concept Development Exercise
Exercise in challenging “conventional wisdom” and taking a fresh look at a global
challenge problem.
Aim:
Make supersonic airline travel viable for the mass market.
Approach:
•Conceptual design at several levels, combining technical
knowledge with global demographics, economics,
sustainability and public policy issues.
•Validate calculations by confirming present day conclusions,
then challenge assumptions and show alternative path to
viability.
•Go from requirements definition to “ticket price per seat mile”
•Refine technical design and economics
High-Speed Civil Transport (HSCT)
Why did the NASA-Boeing-GE-UTC effort fail?
Lets see some slides from NASA’s final report on the HSR program. Source: NASA
An HSCT would reduce the flight times
from California to Japan to approximately
4 hours
Aeronautics R&T
“Three-Legged Stool”
Technology Availability
Market Acceptability
Policy Supportability
Source: NASA
Organization of this presentation
•Introduction to the project
•5 different levels at which concept development has been pursued.
-AE1350 Freshman Introduction to Aerospace Engineering
-AE3021 High Speed Aerodynamics
-AE2xxx Special Problems
-AE4xxx Special Problems
- Undergraduate thesis
•Technical issues & results
•Observations regarding evolution of student experience
•Conclusions
•Acknowledgements
AE1350 Freshman Introduction to Aerospace Engineering
2 hour freshman course, taught in Spring 2010. Several prior teachings since
1997, using Conceptual Design as the gateway to aerospace engineering.
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Designing a Flight Vehicle: Road Map
Force Balance During Flight
Earth's Atmosphere
Aerodynamics
Propulsion
Performance
Stability and control
Structures and Materials
High Speed Flight
Space Flight
Major assignment, done in teams
of two:
Conceptual design of a short-haul
(~1000 mile range) subsonic airliner
to carry 150 passengers.
Spreadsheet calculation procedure,
with range and structure
fraction used as metrics of viability.
Revise to incorporate liquid hydrogen
fuel. Compare performance of the two
versions. Calculate lifecycle carbon
savings at today’s Carbon Market
prices.
Conceptual Design at Freshman Level
• For given specifications, estimate payload using common sense (e.g., “What is the average weight
of a passenger on an airliner? How much food and water should be carried per passenger?”)
• From benchmarking guess Payload Fraction. Find Take-Off Gross Weight.
• Wing Loading from benchmarking, find planform area. Fix span, find Aspect Ratio.
• For selected cruise altitude and speed, find CL and CDi.
• Guess low speed CD0. Find cruise L/D and Speed for Minimum Drag.
• Use thumb-rules to select a suitable engine and number of engines.
• For the selected engine, find thrust-specific fuel consumption from published data, and
estimate thrust at altitude.
• For specified range, find the fuel weight fraction needed at takeoff.
• Given engine thrust-to-weight ratio, see if structure weight fraction is enough to build the aircraft.
• Once the cruise point design is shown to close, find the steady flight envelope, against
aerodynamic stall, thrust available, and maximum climb rate.
•Find takeoff and landing distances.
Implemented on spreadsheet for iteration, integration and plotting.
GLOBAL DEMOGRAPHICS AND AIRLINE ROUTES
AE3021 High Speed Aerodynamics
Final 3-hour core course in aerodynamics/fluid dynamics/gas dynamics,
following 3 hours of AE2020, Low Speed Aerodynamics, and 4 hours of
AE3450, Thermodynamics and Gas Dynamics.
Compressible potential flow for subsonic and supersonic aerodynamics.
Shock/expansion analyses, compressible boundary layer calculations.
Major Assignment (teams of 2): Select an airplane configuration and
analyze one subsonic and one supersonic design point, calculating lift to
drag ratio without resort to CFD.
Used Sears-Haack body and compressible boundary layers to estimate
minimum drag for supersonic aircraft.
AE 2xxx and 4xxx Special Problems
2 sophomores (alumni of AE1350, Spring 2010) and 3 seniors (all following
completion of Aircraft Design capstone design course, 2 after AE3021 as well)
signed up for 3-hour Special Problems, across 2 semesters.
1 other student signed up for an Undergraduate Thesis project.
Summary of Issues
Questions for consideration by undergraduates:
• Drag implication of using hydrogen, given lower fuel weight fraction
• Effect of post-1990 demographics and economics on market projections
• Viable destinations, flight times, curfew and business implications
• Impact of Global Warming/ Carbon emission reduction initiatives
• Noise implications of hydrogen-powered SST?
• Radical concepts to take advantage of the different features of hydrogen
fuel, supersonic flight, and airport logistics
Technical issues & results
Issue #1: Lack of market. No incentive to build SST, because the passengers would
be the same ones who now pay for first/business class tickets that make transonic
airline routes profitable.
Response: Post-1990 changes in air routes, global demographics and economics.
Issue #2: SST not viable in 1960s, certainly not viable today with high fuel prices.
Response: True for hydrocarbon-fueled SST. Not viable at all.
Issue #3: LH2 requires large volume causing unacceptable supersonic body drag.
Response: Not true. Large improvement in payload fraction due to high heating value
of H2 means that the airplane is much lighter, and hence drag is not higher.
Issue #4: Mach 2.5+ flight requires advanced materials. M<1.7 is inefficient.
Response: M>1.4 not needed for mass market. Overall architecture is efficient at 1.4
Sears-Haack transonic drag estimate provides upper bound for ideal drag.
OBSERVATIONS REGARDING EVOLUTION OF STUDENT EXPERIENCE
1.
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Conceptual Design Procedure: Freshmen comfortable and pick up quickly.
Project Document for the conceptual design project to counter “last-minutitis”.
Cross-disciplinary exploration comes easily for freshmen, harder for seniors!
Basic knowledge issues persist with seniors and graduate students.
Implementation Experience:
Undergraduate thesis student decided that taking courses was easier.
Taking advanced courses confuses students! Only a few build the trait of
thinking about the methods that they learn.
• Students from AE3021 and Capstone Design reluctant to use simple conceptual
design process given in AE1350. Eventually realized that their complex formulae
gave the same results when used correctly.
• When faced with unacceptable numbers, hesitant to do anything about it!
(L/D <3 – but “only in cruise”!) AIAA Student Conference paper withdrawn.
• Poster prepared and discussed with better results.
• Paper to peer-reviewed conference done successfully.
6. Vertical Integration aspects: After enough iterations, and given examples,
students do pick up and do an excellent job.
SUMMARY OF OBSERVATIONS
Overall design calculations
Market / demographics issues
Applying “theory” learned in classes
Capturing essence of design approach
Using math to develop bounds
CONCLUSIONS
1. Multilevel process to explore a high-risk concept using undergraduate participants.
2. Vertical and horizontal knowledge integration aspects explored, with differing levels
of success and difficulty.
3. Simple conceptual design procedure permits students to explore advanced aircraft
concepts and see what is needed to make the design close.
4. Process then used as starting point for detailed configuration analysis.
5. Conclusions on the LH2 SST:
• Huge change in Eastern Hemisphere demographics, politics and economics
• Large rise in engine T/W and drop in TSFC since Concorde days
• Fossil-fuelled SST is still not viable at today’s fuel prices
• LH2 drag penalty is absent, due to large gain in payload fraction.
• LH2 becomes more attractive as fossil costs rise and H2 costs decrease.
• LH2 SST development costs can be partially met by carbon market savings.
6. Opportunities to improve depth and breadth of learning, and project performance.
7. Iteration helped students reach a good level of project completion.
ACKNOWLEDGEMENTS
The work reported in this paper was made possible by resources being
developed for the “EXTROVERT” cross-disciplinary learning project under
NASA Grant NNX09AF67G S01. Mr. Anthony Springer is the Technical
Monitor.
Valuable technical resources on high speed aircraft aerodynamics came from
the Boeing Company, courtesy of Dr. B. Kulfan.
Potential HSCT Economic Impact - 1990 View
2005-2020 Long Range Over-Water Market
Subsonic Only — No HSCT
United States
( 747 / 767 / 777
MD-11 / MD-12 )
65%
Large
Subsonic
Medium
& Large
Subsonic
Europe
( A300 / A330 /
A340 )
35%
Medium
Subsonic
U.S. HSCT Program
United
States
79%
Large
Subsonic Medium
& Large
Subsonic
Medium
Subsonic
HSCT
U.S.
Team
Europe
21%
Offshore HSCT Program
United
States
49%
Large
Subsonic
Medium
Subsonic
Medium
& Large
Subsonic
HSCT
Europea
n Team
Long range airplane market share could be driven by HSCT
Potential for a $200B swing in U.S. sales and 140,000 new jobs
Europe
51%
High-Speed Civil Transport
Comparative Perspective
Concorde
Source: NASA
HSCT Goals
North Atlantic
Market
Atlantic & Pacific
1976
Entry In Service Year
2005
2.0
Cruise Speed (Mach)
2.4
3000
Range (nautical miles)
5000 - 6500
100
Payload (passengers)
250 - 300
400,000
Takeoff Gross Weight (lb.)
700,000
87
Required Revenue (¢/RPM)
10
Premium
Fare Levels
Standard
Exempt
Community Noise Standard
FAR 36 - Stage 3
75
Noise Footprint (sq. mile)
5
20a
Emissions Index (gm/Kg fuel)
5
High-Speed Civil Transport Development
Business Implications
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Source: NASA
Studies by Industry have Indicated that HSCT Development Costs Could be
more than Twice the Level of Current Subsonic Airplanes
If the Product is Successful:
– Industry will Face 15-18 Billion Dollar Negative Cash Flow with a Break
Even in the 7 -10 Year Range assuming Continuous Production
If the Product is Unsuccessful:
– High Development Costs and Investments would be Unrecoverable
– The Ability to Compete for Advanced Subsonic Airplane Sales would be
Significantly Degraded
– Significant Impact to Market Share and Balance of Trade
These Technical and Economic Risks Make it Unwise to Commit to a Product Development
Program without a Clear Demonstration of Technical and Cost Viability