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high-speed Civil Transport Study
#
Nummary
poeing Commercial Airplanes
f»Jew Airplane Development
fONTRACT NASl-18377
IepTEMBER 1989
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NASA Contractor Report 4234
High-Speed Civil Transport Study
Summary
Boeing Commercial Airplanes
New Airplane Development
Seattle, Washington
Prepared for
Langley Research Center
under Contract NASl-18377
rUASA
National Aeronautics and
Space Administration
Office of Management
Scientific and Technical
Information Division
1989
CONTENTS
Page
FIGURES AND TABLES v
FOREWORD vii
SUMMARY ix
INTRODUCTION 1
MARKET/MISSION REQUIREMENTS 3
Market Needs Projections 3
Required Vehicle Characteristics 5
Air Transportation System 6
Design Requirements 9
ENVIRONMENTAL CONCERNS 10
VEHICLE DEVELOPMENT 10
Initial Assessment 10
Final Assessment 14
REQUIRED TECHNOLOGIES 17
Advanced Jet Noise Reduction Concepts 17
Emission Reduction Concepts 17
Fuel Technology 19
Aerodynamics 19
Stability and Control 20
Structures and Materials 20
Weight and Balance -22
Impact of Improved Technology 22
ENVIRONMENTAL EVALUATION 23
Upper-Atmosphere Emissions/Ozone Impact 23
Community Noise 24
Sonic Boom 26
ECONOMIC EVALUATION 28
Economic Viability 28
CONCLUSIONS 30
Market and Competition 30
Environmental Concerns 30
Technical Feasibility 31
Economic Viability 31
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ui
Page
RECOMMENDATIONS 31
Technology Development Program 31
Technology Needs 32
REFERENCES 33
IV
FIGURES AND TABLES
Figures Page
1 High-Speed Civil Transport Activities 1
2 High-Speed Civil Transport Study Plan and Schedule 2
3 Year 2000 International Traffic Distribution Forecast Based on
Total of 1,100,000 Passengers/Day 4
4 Revenue Passenger Mile Forecast 4
5 HSCT Traffic Distribution-Year 2000 5
6 Overwater Distance 6
7 Fleet Size Versus Seats 7
8 Effect of Design Range on Fleet Size 7
9 Fleet Size Versus Turn/Through Time 8
10 Superhub Airport Network 9
11 Units Required-Year 2015 9
12 Average Trip Time— Superhub System 10
13 Conventional-Fueled Engine Concepts 12
14 Cryogenically Fueled Engine Concepts 13
15 Mach 2.4 Configuration 14
16 Mach 3.2 Configuration 14
17 Mach 3.8 Configuration 15
18 Mach 4.5 Configuration 15
19 Mach 6.0 Configuration 16
20 Mach 10.0 Configuration 16
21 Mach 2.4 Baseline Configuration 17
22 Jet Noise Reduction Concepts 18
23 Drag Breakdown— Mach 2.4 Baseline 19
24 Lift/Drag Versus Mach— Mach 2.4 Baseline 20
25 Structural Material Candidates and Projected Temperature
Range for HSCT Application 21
26 Impact of Technology— Mach 2.4 Baseline 22
27 Impact of Technology— Mach 2.4, 247-Seat Airplane With
Year 2000 Certification, 5,000-nmi Design Range 23
28 HSCT Growth Strategy 24
29 Noise Contour at 85 dBA-Comparison of HSCT to 747-200 25
30 Low-Sonic-Boom Configuration 26
31 Mach 1.5 Pressure Signature and Loudness Predictions 27
32 Economic Viability— Technology Impact on Fleet Size Based on
Mach 2.4, 247-Seat Design With 5,000-nmi Range 29
33 Economic Viability— Impact of Speed Based on 247-Seat Design
With 5,000-nmi Range 29
Tables
1 High-Speed Civil Transport Mission Perspective 3
2 Design Mach Number Selections 11
FOREWORD
This report documents work completed for phases I, II, and III on high-speed civil transports under
NASA contract NASl-18377. The New Airplane Development group of Boeing Commercial Air-
planes, Seattle, Washington, was responsible for the study. Charles E. K. Morris, Jr., NASA Langley
Research Center, was NASA program manager. Michael L. Henderson and Frank H. Brame were pro-
gram managers for Boeing Commercial Airplanes. Boeing task managers were: Robert M. Kulfan for
phase I and II Engineering; John D. Vachal for phase III Engineering; William H. Lee and Roger W.
Roll for Marketing; and Donald W. Hayward and Edward N. Coates for Special Factors.
The Boeing team consisted of—
Manager HSCT Design Development
Aerodynamics
Configurations
Finance
Marketing
Noise
Payloads
Propulsion
Special Factors
Structures and Materials
Systems
Weights
M. I. K. MacKinnon
D. N. Ball, T H. Hallstaff, G. T Haglund,
J. C. Klein, S. S. Ogg, J. A. Paulson,
S. E. Stark, P E Sweetland, T E. Trimbath,
G. H. Wyatt
T Derbyshire, V. K. Stuhr
G. J. Gracey
R. E. Bateman, T. Higman, S. C. Henderson
J. G. Brown, G. L. Nihart
D. P Lefebvre
J. J. Brown, G. B. Evelyn, R. B. McCormick,
J. Merrick, P. Ormiston
N. M. Barr, J. H. Foster, O. J. Hadaller,
A. M. Momenthy
J. W. Fogelman, D. L. Grande, T. E. Munns,
D. G. Stensrud, R. T Wagner
A. W. Waterman, T. Timar
J. D. Brown, M. W. Peak, J. P Rams
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SUMMARY
A systems study of the potential for a high-speed commercial transport has addressed technology,
economics, and environmental constraints. Market projections indicated a need for fleets of transports
with supersonic or greater cruise speeds by the years 2000 to 2005. The associated design requirements
called for a vehicle to carry 250 to 300 passengers over a range of 5,000 to 6,500 nautical miles. The
study was initially unconstrained in terms of vehicle characteristics, such as cruise speed, propulsion
systems, fuels, or structural materials. Analyses led to a focus on the most promising vehicle concepts.
These were concepts that used a kerosene-type fuel and cruised at Mach numbers between 2.0 to 3.2.
Further systems study identified the impact of environmental constraints (for community noise, sonic
boom, and engine emissions) on economic attractiveness and technological needs.
Results showed that current technology cannot produce a viable high-speed civil transport; signifi-
cant advances are required to reduce takeoff gross weight and allow for both economic attractiveness
and environmental acceptability. Specific technological requirements have been identified to meet
these needs.
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INTRODUCTION
Present projections predict that the worldwide demand for long-range air travel will double by the
year 2000 and nearly double again by year 2015. This growth in the market will occur at the same time
that increasing numbers of aircraft in the existing fleet will be retired due to age and noise rules.
Manufacturers must make difficult and long-lasting decisions in the next 5 to 10 years concerning
future products so that sufficient time is allowed for development. One option to consider is a new
generation of commercial transports that cruise at speeds of Mach 2.0 or greater and can serve both
the Atlantic and Pacific markets.
Boeing Commercial Airplanes conducted a three-phase study of the potential for future high-speed
civil transports (HSCT) under NASA contract NASI- 18377 between October 1986 and August 1988.
The primary objectives were to identify the most promising concepts in high-speed transports and to
guide the development of requisite technology that may not flow directly from the National Aero-Space
Plane or other existing programs. To achieve this it was necessary to examine the environmental, opera-
tional, and nonvehicle factors that will influence the vehicle configuration, supporting facilities and
systems requirements, and overall program viability. Also, it was essential to identify and account for
those market and economic factors that must be considered to provide a commercially acceptable
high-speed transport system.
The study examined the requirements of a future HSCT as affected by the environment, oper-
ational concerns related to other HSCTs and subsonic aircraft, and the market demand for aircraft
after the year 2000. Market assumptions were developed for an HSCT operating in this timeframe.
The study evaluated both supersonic and hypersonic aircraft. Initially, aircraft were evaluated through
Mach 10.0; the latter phases looked at supersonic only (under Mach 6.0) (fig. 1). Propulsion concepts
were investigated in conjunction with the fuel technology required. A screening process was employed
to determine the best Mach number range for further investigation of the environmental issues such
as community noise, effect on the ozone layer, and sonic boom. The economic impact of the configura-
tions investigated were compared throughout the study. Figure 2 illustrates the flow of the study proc-
ess through the three phases.
Mach
Supersonic
Hypersonic
Mission
Transport
Transport
Fuel
Conventional
Cryogenic
Certification date
2000 to 2005
2015 to 2025
NASA contract
Phase I ^
Phase II <4i
Phase III •4-
Mach 2.4 to 10
2.4 to 5
2.4 to 3.2
Figure 1. High-Speed Civil Transport Activities
5-U90027R1-124
Table 1. High-Speed Civil Transport Mission Perspective
Transport type
Concorde
U.S. SST
HSCT
Year In service
1971
1975
2000-2015
Market
North Atlantic
North Atlantic
Atlantic and Pacific
Range (nml)
3,500
3,500
5,000-6,500
Payload (passengers)
100
200
250-300
TOGW (lb)
400,000
750,000
750,000
Community noise requirements
None
Stage II
Stage III
Revenue required
(cents/revenue passenger miles)
87
60
9-10
5-U90027H1-125
Table 1 indicates the level of challenge posed by this goal of an economically attractive, environmen-
tally acceptable HSCT Passenger count must increase significantly from the Concorde to be economi-
cal, and noise and emission levels must be greatly reduced.
A capable HSCT like the one postulated in table 1 would compete well even with advanced subson-
ics because of reduced flight times. It is important that U.S. manufacturers understand the potential
of such an airplane as a product or a competitor. Ignoring the HSCT's potential, or delaying the timely
development of technology that could make it a viable product could bring about the loss of a signifi-
cant national opportunity to the competition from abroad. If successful, this competition would reduce
the United States' traditionally high market share in the international marketplace for large,
long-range commercial transports. Even worse, commitment to a program without an adequate tech-
nological and environmental database could lead to an expensive failure. Both arguments lead to the
conclusion that it is justified and highly desirable to continue research and development of key technol-
ogies for an environmentally and economically sound HSCT.
MARKET/MISSION REQUIREMENTS
Market Needs Projection
The market forecast is based on major market area passenger flows as defined in the "Boeing 1987
Current Market Outlook" (ref. 1). The Market Outlook covers the time period from 1987 through the
year 2000 and projects that world air travel will grow at an average rate of 5.3% per year. The market
application for an HSCT is derived from the "international scheduled" portion of this forecast that
represents 22.8% of the total world demand for the year 2000.
Not all of this market is applicable for a long-range airplane, however. Figure 3 graphically depicts
that portion of the international traffic allocated to the HSCT. All passenger demands less than 300
passengers per day, less than 2,500 nmi in distance, and all intraregional demands were excluded. As
a result only 28% of the international demands (or about 6.4% of the world passenger forecast) are
considered HSCT study markets.
The traffic forecast for 2015 was developed by assuming the individual markets are maturing, and
therefore grow at 85% of their average rates from the years 1995 through 2000. This resulted in almost
doubling the year 2000 demand, with the Pacific Rim area forecast increasing at a greater rate (53%
of the revenue passenger miles in year 2000 and 60% in 2015) (fig. 4). The total HSCT passenger de-
mand potential (without allowances for stimulation) is forecast to be 315,000 passengers per day by
year 2000 and 600,000 per day by 2015. This is certainly adequate potential traffic to justify a commer-
cially viable HSCT However, if significant ticket price increases are required for HSCT configura-
tions, market elasticity could reduce the demand for an HSCT below acceptable levels.
Legend:
g HSCT
study
markets
North America to
Europe it 'b
North America
to Asia 5.4%
Europe to
Asia, 3.9%
Pacific
Rim, 4.1%
Other, 4.1%
Under 2,500 nml,
26.5%
Intrareglonal,
45.9%
Figure 3. Year 2000 International Traffic Distribution Forecast Based on Totalof 1, 100,000 Passengers! Day
5-U90027R3-ia8
1,250
1,000 —
750 —
Revenue
passenger
miles, billions
per year
500 —
250
Year 2015
1,107 billion RPM
Year 2000
572 billion RPM
Other
Pacific Rim
Europe to Asia
and Pacific
North America to
Asia and Paplfic
North America to
Europe
Figure 4. Revenue Passenger l\Aile Forecast
4-U«»27R2-127
Required Vehicle Characteristics
The development of HSCT market requirements demanded an assessment of not only the size and
distribution of the market, but also of certain airplane characteristics. These characteristics include
speed, design range, airplane through time and airport turnaround time, and passenger seat count
within the market. Each characteristic was examined parametrically and then in more detail as re-
quired. The parametrics considered two basic environments: (1) an "unconstrained" environment
(that is. Great Circle routing and sonic boom allowed over land), and (2) a "constrained" environment
that assumed no sonic boom over land and some rerouting to maximize time spent in supersonic
cruise. In both cases, existing airport curfews were observed and all the passengers were served within
a postulated universal airline system.
Additionally, the market potential is subject to certain unknowns in terms of stimulated passenger
demand due to shorter trip times and decreased demand due to ticket price increases over subsonic
prices. Stimulation, as such, was not included in the basic study; however, the effect of ticket price
was examined.
Figure 5 shows the distribution of nonstop passenger trips and revenue passenger miles. About
half the passengers and 40% of the revenue passenger miles would be satisfied by a 4,000-nmi design
range. Ninety percent of the passengers, representing 84% of the revenue passenger miles, could be
satisfied by a 6,000-nmi design range.
A detailed analysis was conducted of 10 specific market areas in which airplane productivity and
HSCT passenger trip time savings were used to evaluate design-range capabilities. Design range is
important because it affects the number of intermediate stops required to serve the airline's network.
Stopovers will reduce airplane productivity and increase travel time.
As seen in figure 6, four of these ten markets have more than 85% of their routes over water and
the others range from 50% to 80% over water. These same four markets represent approximately half
of the passengers and 41% of the revenue passenger miles. The remaining "mostly overland" markets
100
75
Cumulative
F>ercentage
50
25
1
Nonstop
passenger
trips
1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000
Great Circle distance, nml
Figure 5. HSCT Traffic Distribution - Year 2000
4-U90027-128
100
Percentage gQ
over water
Eastern Western Europe
North North to South
America America America
to Europe to Asia
Pacific
Rim
Eastem
North
America
to Asia
Westem
North
America
to Europe
Mid-North Mid-North
America America
to Europe to Asia
Europe
to Asia
and the
Pacific
Othef
Figure 6. Overwater Distance
4-U90027-128
cannot use an HSCT as effectively as the overwater markets if there is a constraint forbidding any
overland supersonic flight. These markets, then, will require flying long distances subsonic over land
and reflect the need, in many cases, to deviate from Great Circle routing to reduce overland flight dis-
tances. This natural differentiation of markets (predominantly over water versus over land) provides
a useful division to evaluate the HSCT design-range requirements relative to productivity (number
of airplanes required) and passenger trip time.
Figures 7 through 9 are indicative of the overall results for the best-case potential: unconstrained,
supersonic, overland flight with Great Circle routing. These results indicate maximum gains in produc-
tivity between Mach 2.0 and Mach 8.0. There are, also, trades between Mach number and the other
parameters. A 7,000-nmi design range, Mach 3.0 vehicle, for example, has the same productivity poten-
tial as a 4,500-nmi design range, Mach 10.0 vehicle (fig. 8).
Air TVansportation System
Twenty-seven conventional airports were selected as primary candidates for use by the HSCT. A
vehicle designed for a sea-level takeoff field length of 12,000 ft will impose little additional require-
ments to existing runways at these international airports. Airport modifications required for the fleet
of subsonic vehicles anticipated for the years 2000 to 2015 would cover most of the needs of a super-
sonic transport in the Mach range considered most viable. Some additional modifications to taxiways
and loading areas may be required because of the vehicle's length (60 ft longer than a 747).
Units
800
700 —
600 -
500 -
400 —
300 —
200 —
7,000-nml design range
2-hr turn/through time
100
12 3 4 5
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Design Mach number
Figure 7. Fleet Size Versus Seats
4-U90027-130
900
Number of units
required
800 -
700 -
600 -
500 -
400 -
300 -
2-hr turn/through time
283 seats
200
Design range
4,500 nmi
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Design Mach number
Figure 8. Effect of Design Range on Fleet Size
4-U90027R1-131
800
700
600
Number
of units
required
500
400
300
200
100
• 7,000-nml design range
• 283 seats
<y
Turn/through
time 4 hr
3 hr
1
1
I I
<>
-0
2 hr
1 hr
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Design Mach number
Figure 9. Fleet Size Versus Turn/Through Time
4-U90027-132
Consideration also must be given to the influence of high-speed travel in heretofore uncontrolled
airspace; however, no special Air Traffic Control electronic equipment will be required. The HSCT-era
avionics systems will greatly enhance HSCT integration into Air Traffic Control environments.
Special airports would probably be required to accommodate the needs and improve the produc-
tivity of a hypersonic HSCT (airplanes with cruise Mach number of 6.0 or greater), which is expected
to operate with weights greater than 1 million pounds. This higher speed vehicle will also require spe-
cial fuel systems and will probably not meet community noise standards.
To improve the productivity of a hypersonic HSCT, the average stage length must be long enough
to provide a substantial period of time at cruise.
A network of strategically located "superhubs," shown in figure 10, was developed to maximize
the average stage length of the hypersonic HSCT. These hubs would be fed by subsonic airplanes, with
service between the hubs by airplanes with cruise speeds of Mach 6.0 and greater. The productivity,
measured by units required, and the average trip time for this superhub system were compared when
serving the same market, with more direct routing and either an all-subsonic fleet (Mach 0.84 cruise)
or an all-supersonic fleet (Mach 3.2 cruise, Mach 0.9 over land).
Figure 11 compares the units required in the year 2015 for each case. The all-subsonic system (with
525-seat airplanes) requires about 560 units, while the all-supersonic, Mach 3.2 system (with 283 seats,
subsonic over land, and waypoint routing) requires 50 fewer units. The third bar in figure 11 shows
that the system using superhubs requires more units (90 more than the subsonic and 110 more than
the supersonic system), but 370 of these are subsonic (and less expensive) airplanes.
Figure 12 compares the average trip time for the three systems. Both the all-supersonic and the
hypersonic-subsonic superhub system show significant gains over the all-subsonic system. The super-
hub system at Mach 6.0, however, shows no gain over a Mach 3.2 system and only a 1 hr improvement
at Mach 15.0. This is because the feed portion of the trip and the passenger transfer at each end of
the high-speed leg consumes almost 4 hr (even assuming an optimistic 30-min transfer time).
In conclusion, the benefits, in terms of the travel time savings of a dedicated superhub network,
are minimal. Productivity gains are offset by the requirement for a large number of subsonic feed
Figure 10. Superhub Airport Network
4-U90027-133
1,000
Units
500 —
All subsonic
Mach 0.84,
525 seats,
6,660 nmi
All supersonic
Superhub, mixed
subsonic and Mach 8.0,
283 seats
iviacn j.^,
283 seats,
\V Dedicated \V
sV\ Mach 8.0 Xv
\N\\\\\\\^
t
I
5,500 nmi
K
Feed
Mach 0.84
Figure 1 1. Units Required- Year 2015
4-U90027-134
airplanes. The hypersonic airplanes are likely to be very expensive because of both the technology re-
quired and the small number of units needed (less than 300). Operating costs are also likely to be high.
In addition, six dedicated ground facilities would have to be built, the cost of which must be included
in the economic evaluation of the total transportation system.
Design Requirements
The study airplanes were designed to a set of requirements that included payload at 247 passengers;
range of 5,000 nmi with a growth objective of 6,500 nmi, a maximum takeoff field length of 12,000 feet
at sea level 86 °F, and a maximum approach speed of 160 keas at maximum landing weight.
15
10 -
Hours
High speed flight
Transfer, 30 min at each end
All-subsonic
system
(Mach 0.84)
All-supersonic
system
(Mach 3.2)
Superhub
system
10 15 20
Dedicated design Mach number
Figure 12. Average Trip Time -Superhub System
5-U90027R1-135
ENVIRONMENTAL CONCERNS
Environmental acceptability is a key element of any HSCT program. If not properly accounted
for in the HSCT design, environmental limitations could substantially reduce use of the vehicle and,
in the most extreme circumstance, prohibit vehicle operation altogether. The primary areas of environ-
mental impact identified by this study were engine emissions effects, community noise, and sonic
boom.
A viable HSCT must be designed so that its engine emissions have no significant impact on the
Earth's ozone layer. This is based on the justifiable public concern about the impact of long-term de-
pletion of the Earth's protective ozone layer.
Operation out of conventional airports was determined to be a requirement for achieving adequate
HSCT utilization. Accordingly, a viable HSCT must produce noise levels no higher than its subsonic
competition. Studies indicate that, with projected suppression technology, achievement of FAR36
Stage 3 noise levels may be possible.
The sonic-boom overpressure level of a large, long-range HSCT designed for minimum weight is
unacceptably high for overland flight in populated areas (overpressure of 2 to 3 Ib/f^). Commercial
overland supersonic flights are, therefore, not allowed by U.S. law. The airplanes under study have
been evaluated with subsonic flight profiles over land, which results in an adverse economic and mar-
ket impact. Thus, there is impetus to explore low-boom designs that allow some form of overland
supersonic operation.
VEHICLE DEVELOPMENT
Initial Assessment
The technical and industrial progress achieved in the last century has demonstrated that, given
enough time, technical achievement is almost limitless. Thus, rational judgments on technical
feasibility must be in reference to specific time scales. For HSCT development, two time periods were
defined. The first timeframe was defined as the earliest date that an economically viable and environ-
mentally safe HSCT could be produced. The certification date was judged to be the year 2000, and
is consistent with projections of market needs in terms of international traffic growth and current sub-
sonic fleet replacement. The second time period defined was the year 2015 when certain advanced
10
technologies would have matured, some of which could possibly be developed as part of the proposed
National Aerospace Plane program.
The initial assessment of vehicle technology was organized into studies for each of several bands
of Mach number (table 2). These bands were defined either by differences in technology readiness
dates or in classes of airframe and engine technology.
Three engine manufacturers, Aerojet General, General Electric, and Pratt and Whitney, provided
data for advanced, conceptual engines appropriate for a series of commercial transports with a cruise
speed between Mach 2.4 and Mach 10.0. Turbomachinery cycles were used to power the lower Mach
number vehicles. A combined turbomachinery-ramjet cycle was used at Mach 4.5, an air turboramjet
at Mach 6.0, and a supersonic-combustion scramjet at Mach 10.0. Engine cycle thermodynamics and
properties of the available engine materials influence the engine cycle choice for each flight Mach num-
ber. The engine concepts are illustrated in figures 13 and 14.
Mach 3.2 is near the projected upper limit of using wing-integral fuel tanks for cruise fuel. Mach
3.2 operation will require extensive development of fuels with higher thermal stability and fuel tank
designs with low thermal conductivity. Mach 4.0 is near the projected upper limit for conventional
turbojet-fan engine cycles and for thermally stable jet fuel (TSJF) use. Mach 4.0 is also considered to
be the upper limit for a year 2000 HSCT because of very high technology risks and formidable design
complexities that would need to be addressed in this relatively short development time period. For
the year 2015, the continued technology development programs would provide more efficient configu-
rations for Mach numbers up to Mach 4.0. In addition, the more advanced technology would open
up design options for even higher Mach numbers.
Above Mach 4.0 it is projected that cryogenic or endothermic fuels would be required to satisfy
heat sink demands. Mach 6.0 is near the upper projected limit for liquid methane, endothermic fuels,
and the ramjet as the cruise propulsion system. Mach 8.0 is near the projected upper limit for uncooled
structural materials. At Mach numbers below this limit, however, areas such as the wing leading edges
or nacelle inlets may require localized active cooling. At Mach numbers above 8.0, active cooling of
structural materials is projected. Vehicle concepts for Mach numbers of 6.0 or greater were designed
for dedicated superhub operations because the design compromise for achieving both high-speed and
low-speed performance would have been prohibitive.
Initial vehicle development evaluated 21 configuration concepts designed for Mach numbers be-
tween 2.4 and 10.0. A screening process was used to evaluate the concepts on the basis of risk versus
benefit. Of the 21 configurations, 6 were chosen for further development (figs. 15 through 20). Based
on the following trends and study results, further work was concentrated on the lower range of Mach
numbers:
a. Aircraft size and design complexity increase significantly with increasing design Mach number.
b. The airplane maximum takeoff weight is very sensitive to projected technology improvements for
the higher Mach numbers.
Table 2. Design Mach Number Selections
Region
Mach range
Year of certification
Limitation
1
2
3
4
5
2.0 to 3.2
3.2 to 4.0
4.0 to 6.0
6.0 to 8.0
8.0 to 25.0
2000
2000
2015
2015
2015
Thermally stable Jet fuel In wing tank
Thermally stable Jet fuel
Turbofan/turbojet
Endothermic fuel
Liquid CH4
Ramjet
Uncooled structural materials
4-U90027-138
11
Forward
variable area
bypass injector
Takeoff mode
Aft variable area bypass Inlector
Split fan
Coannular acoustic plug nozzle-
Supersonic Cruise Mode
(a) GE Mach 3.2 Variable Cycie Engine
Supersonic Cruise Mode
Variable flap
Crossover duct-
Takceoff Mode
(b) P&W Turbine-Bypass Engine Witfi NACA Nozzie
SXXi
Afterburner
Nozzie
(c) P&W Afterburning Turbojet
Figure 13. Conventional-Fueled Engine Concepts
5-U90027R2-136
12
Intake guide vanes (open) Variable nozzle
Low Mach number
■ Intake guide vanes (shut) Variable nozzle
^m'.
s^^^
High Mach number
(a) GE Mach 4.5 Tandem Turbo Ramjet
Compressor
-Turbine
Variable area nozzle
— ( jmmi^
Turbine manifold -
Fuel-rich
mixture
to turbine
Combuster
Pump
(b) Aerojet Mach 6.0 General Air Turbo-Ramjet
Turbojet mode
Take off, climb, and accelerate to transonic speeds
•'~*.^^_--' 1
Turtx)jet-ramjet mode
Transonic to supersonic speeds: climb and accelerate
Ramjet/scramjet mode
Supersonic climb, acceleration, and cruise
(c) P&W Mach 10.0 Turbo-Ramjet-Scramjet
Figure 14. Cryogenically Fueled Engine Concepts
5-U90027R2-137
13
ECONOMIC EVALUATION
The concept of life cycle operating costs has been developed to satisfy the need for an economic
companson method that accounts for the actual cash direct and indirect costs incurred^" operatTn^
an airplane as well as mcluding all "ownership costs." Cost elements identified include the Mow ng
a. Cash direct cost elements, which include- luiiuwing.
1. Flight crew costs.
2. Fuel burned.
3. Airframe maintenance.
4. Engine maintenance.
5. Hull insurance.
b. Indirect costs, which include—
^' tXmlnf^ ^''''"'"^' ^"'""^' ^•^'^'■^f^-ha^dling. maintenance, and ground handling
c. LL'rlTp ^o'tt'"'^ ^^'^^' P^^^^"g^^-h^"d""8' ^g^"<=y commissions, passenger insurance).
econ^mi^vTaS orHsTr'^n'H"''' ? ^'""I"' '^''^'"^^ "'^ ^^^^'^ °P^^^^'"g '^'' ^o evaluate the
economic viability of HSCT study configurations. This economic horizon is a trendline relationshio
of life cycle operatmg costs and airplane size. It was based on projected advanced derivat^I of 1^^
Boeing 767 and 747 aircraft and allows comparisons of a wide variety of passenger sLt counts TO^
economic model was used in all phases of the contract to define market value omfcT desifins^nd
IsSeT"'" '''''"" ^'^'"^"'"^"^"^"^"^^^^^^^
Ek;onomic Viability
uJl ^' ,7"°'"*'^^ "y ^'^•'•^'/he HSCT must provide a reasonable financial return for both the air-
m^Kt h. 1 "J^^^^f^^^"^^^,^- ^y •"^'■^^^^d operating and ownership costs associated with an HSCT
must be largely overcome by increased productivity due to speed. The sale price must a low an ade
quate return on investment and still elicit enough demand for Ihe HSCT to justify thetrgeir^estoem
in development and production costs. To the extent that increased costs cannm be SZe bv in
creased productivity, higher ticket prices must be charged, thereby reducing the markefSdim^na^
estimates have been made of the response of the projected HSCT market fo iLTeases in pri^ '^
th.t '""K^",' of technology based on this evaluation, is illustrated in figure 32. TOs evaluatfoiThows
that presem day technology is not adequate to allow the necessary profit margin rMachT4 HS^^
designed with today's technology would require a 50% to 60% increase in average ticket price oS
contemporary subsonic transports. This would reduce demand to the point that fhe tota worid^de
fleet requirement is estimated to be 300 units or less, an inadequate number to support a vTable pro-
gram. However, with technology available for year 2000-certified airplanes, the requ^ed revenues a^e
ower, primarily because of the smaller vehicle required to perform the design mSn ^e resuU s
that a ticket price increase of 18% would be required and the fleet reauirement won IHh!
rnrarbrsi'^^rwouM""^^^^^^
increase by 8%. This would result in a fleet requirement of 950 to 1 050 units
The impact of design Mach number on the market captured by the HSCT is shown in figure 33
Assuming year 2m certification, increasing design speed from Mach 2.4 to Mach 2 sToists fhe fare
ZT XTZ^^" ^f '"'"'^"f '^' '^^'^'' '^^'""''^ ^° 30%, requiring a fleet size oMO^o 5M unks
1^-^rtll ri!" '^S!ir.?.f; ^^y}^' -'^--'^ to -n the Required return on nvStm'm
Variable
Intake
Intake guide vanes (open) Variable nozzle
Low Mach number
Variable
Intake
Intake guide vanes (shut) Variable nozzle
High Mach number
(a) GE Mach 4.5 Tandem Turbo Ramjet
Compressor
-Turbine
Variable area nozzle
/ juuiuiliiS
Turbine manifold -
Fuel-rich
mixture
to turbine
Combuster
Pump
(b) Aerojet Mach 6.0 General Air Turbo-Ramjet
TurtDojet mode
Take off, climb, and accelerate to transonic speeds
Turbojet-ramjet mode
Transonic to supersonic speeds: climb and accelerate
^^^sfcCJ^ yy "v, i'v!!! » — "r^^ ^
■ »^.:?*;;J<
Ramjet/scramjet mode
Supersonic climb, acceleration, and cruise
(c) P&W Mach 10.0 Turbo-Ramjet-Scramjet
Figure 14. Cryogenically Fueled Engine Concepts
5-U9CK)27R2-137
13
Figure 15. Mach 2.4 Configuration
4-U80027-139
Scale, ft
25 50
Figure 16. Mach 3.2 Configuration
4-U90027-140
c.
Average block time decreases slowly as design cruise speed increases above a Mach number of 3.0,
suggesting economic gains will not increase proportionally with design cruise Mach number,
d. Significant technology and design advances are required for an efficient long-range HSCT, even at
lower supersonic cruise Mach numbers.
Final Assessment
During the final study phase, new configurations were developed at Mach 2.4, 2.8, and 3.2. Evalua-
tion of these configurations indicated that the lowest maximum takeoff weight, operating-empty
weight, and block fuel occurred at Mach 2.4. Even though the minimum block time occurred with the
14
Figure 17. Mach 3.8 Configuration
4-U90027-141
Figure 18. Mach 4.5 Configuration
4-U90027-142
Mach 3.2 configuration, maximum economic potential occurs at Mach 2.4. This occurred because im-
proved utilization due to reduced flight times was not enough to offset the increased cost of a heavier
Mach 3.2 configuration. Technical risk evaluation in conjunction with this configuration assessment
was reason to focus the environmental impact studies at the lower Mach numbers. The Mach 2.4
baseline airplane is shown in figure 21. This airplane has a maximum takeoff weight of 745,000 lb, a
wing area of 7,466 ft^, and an engine airflow of 582 Ib/s.
15
Scale, ft
25 50 100
I."
i:
U;=;
p — ■■tin
ciz:
10
iHZL
c:!!r
1=IUJ
"•: ^r^il
Figure 19. Mach 6.0 Configuration
4-U90027-143
Scale, ft
25 50
100
,, tu-^
wm JL iM
F/gare 20. Mach 10.0 Configuration
4-U90027-144
16
Scale ft
Figure 21. Mach 2.4 Baseline Configuration
4-U90027-145
REQUIRED TECHNOLOGIES
Advanced Jet Noise Reduction Concepts
Jet noise can be diminished either by reducing the jet velocity or through nozzle noise-suppressor
technology. The jet noise reduction concepts considered in this study are illustrated in figure 22. Partic-
ular attention was given to a naturally aspirated, coannular (NACA) nozzle concept. The NACA nozzle
is a high-radius-ratio plug nozzle system incorporating a crossover duct, which allows ambient (sec-
ondary) air to cross inside the primary stream and be aspirated through the inner annulus of the coan-
nular nozzle. The aspirated ambient flow is intended to provide rapid mixing on the inner boundary
of the outer annulus primary stream to reduce the jet noise. The NACA nozzle has been shown to
provide significant aspiration of free stream air with small performance penalties at takeoff
conditions. Consequently, it is believed that the NACA nozzle offers good potential for jet noise reduc-
tion with small thrust penalties. However, this concept would require considerable development to
confirm its performance and qualify it for use on a commercial airplane.
Emission Reduction Concepts
Achieving the goal of having no significant effect on the ozone layer may require the reduction of
oxides of nitrogen (NOx) engine emissions. The engine manufacturers conducted studies of derated
engine cycles and high-risk, low-emission combustor concepts. The concepts considered most promis-
ing were the staged-lean combustor; rich-burn, quick-quench combustor; and lean, premixed and pre-
vaporized combustor. These concepts could potentially reduce emissions in a range from three-fourths
to one-sixth of the untreated level, but would require an aggressive research and development effort.
17
Pneumatic
oscillators
Acoustic Lining
Suppressor
y
V2
Inverted Velocity Profile
Ejector
Observer
Shield stream (high
temperature, low velocity)
Supersonic cruise mode
Crossover duct
■ Variable flap
Takeoff mode
Thermal Acoustic Shield Turbine-Bypass Engine With NACA Nozzle
Figure 22. Jet Noise Reduction Concepts
5-U90027R2-148
18
Fuel Technology
The fuel technology study identified and evaluated production, cost, property, and other nonair-
craft system-related factors that would affect the use of both conventional and unconventional fuels
in HSCTs. The fuels study included modified conventional, endothermic, cryogenic, and other fuels
such as slushes and gels. The study emphasized—
a. The availability and cost associated with modified conventional fuels (thermally stable jet fuels).
b. Liquid methane costs (liquid methane is assumed to be the same as purified liquefied natural gas).
c. On-airport costs for both conventional fuels and liquid methane.
Aerodynamics
The aerodynamic design of each of the study configurations included optimized camber/twist dis-
tributions and area-ruled fuselages. The wing spanwise thickness distributions and airfoil shapes were
constrained by structural depth requirements. The nacelles were shaped and located aft under the
wing to develop favorable aerodynamic interference subject to ground clearance, engine geometry con-
straints, and structural design considerations.
High-speed aerodynamic characteristics for all of the concepts were developed using the methods
from earlier NASA studies. Projections for year 2000 technology improvements have been included
in the drag build-ups. These projections include skin friction drag reduction resulting from the use
of an outer surface treatment such as riblets over 90% of the vehicle wetted area; reduction in volume
wave drag and drag-due-to-lift resulting from design methodology improvements; and incorporating
an improvement in the wind tunnel to flight test drag correlation.
The drag breakdown for the baseline airplane is shown in figure 23 and lift/drag versus Mach num-
ber is illustrated in figure 24.
The high lift system is designed to increase wing lift for liftoff and touchdown. It must be designed
to minimize drag during climbout and approach to reduce airport noise levels. In general, the lead-
ing-edge and trailing-edge flaps are simple hinged surfaces. Low-speed performance is improved by
repositioning the flaps relative to the conventional low-drag position for higher lift. For liftoff and
touchdown, leading edge flaps were raised to increase vortex lift. After liftoff, the flaps were positioned
for minimum drag.
100
Total
cruise
drag,~%
50
Drag due to lift
Friction
Volume wave
Figure 23. Drag Breakdown— Mach 2.4 Basel ne
4-U90027-147
19
Lift/drag 12 —
1.2 1.6
Mach number
Figure 24. Lift /Drag Versus Mach—Macli 2.4 Baseline
2.0
2.4
4-U90027-148
Stability and Control
The primary task for stability and control has been the estimation of horizontal and vertical tail
size and center-of-gravity limits that satisfy critical stability and control criteria. HSCT configurations
are designed using a control-configured vehicle design approach that employs the flight control system
to stabilize as well as control the airplane, which results in a more efficient aerodynamic and structural
configuration. The required stability augmentation system must be of sufficient capability and reliabil-
ity to provide acceptable handling qualities over the operational flight envelope up to the maximum
useful angle-of-attack. The flight control system will be used to limit or prevent excursions outside this
envelope.
Structures and Materials
Candidate structural materials were selected by (1) surveying published research, material suppli-
ers, and aerospace contractors to identify commercial or developmental materials with potential appli-
cability; (2) estimating mechanical properties based on available published data and developmental
goals; and (3) forecasting availability by assessing progress in development versus goals, determining
technical complexity in achieving these goals, and estimating process scaling necessary to support a
large production program. A significant development effort to ensure availability of technology was
assumed. Potential materials, maximum use temperatures, and predicted availability are summarized
in figure 25.
20
Polymer matrix composites
• Epoxy
• Polyetheretherketone
• Toughened BMI
• Thermoplastic polylmlde
• Polylmlde
• Fluorlnated polylmlde
Legend:
I I Year 2000 availability
IMWI Year 2015 availability
Metals
• Aluminum
• Aluminum lithium
• RS aluminum
• Titanium
• RS titanium
• Intermetalllce
Metal matrix composites
• Aluminum matrix
• Titanium matrix
• Intermetalllo matrix
300
1,800
600 900 1,200 1,500
Temperature range, °F
Figure 25. Structural Material Candidates and Projected Temperature Range for HSCT Application
6-U90027R3-149
The structural materials for Mach 2.8 and below judged to have the most potential and to be avail-
able for year 2000 certification were identified. These materials were high-temperature thermoplastics
or toughened thermosetting polyimide composites. Ingot titanium alloys were selected for the higher
Mach numbers. Even though they have the most potential for a lightweight, cost-effective HSCT, poly-
meric composite systems for high-temperature service have inadequate processibility and unproven
long-term, thermal and environmental resistance for application in a commercial program.
Significant development is required to optimize these materials, develop automated processing
methods, and evaluate their long-term performance in the severe HSCT environment.
By the year 2015, it is projected that the maturation of metal matrix composite and rapid solidifica-
tion technology will make them available for application on the HSCT. Current material forms, pro-
cesses, and production equipment available in the industry are not adequate to produce the large
structure required for an HSCT program. Development is necessary to scale processes and evaluate
long-term, high-temperature performance of these materials.
Support materials compatible with the selected structural materials are required for a viable com-
mercial program. Support materials include adhesives, seals and sealants, finishes, and lightning pro-
tection materials. Generally, support materials are available with thermal stability applicable to a
cruise speed of Mach 2.8 or below. The performance and long-term durability of current support mate-
rials are necessary for their application to the HSCT Development of improved temperature resistant
materials is required for high Mach number configurations.
Structural weights for performance calculations are based on the structural concepts, arrange-
ments, and procedures used in the study reported in "Study of Structural Design Concepts for an Ar-
row Wing Supersonic Transport Configuration" (ref. 2). A number of potential materials were selected
for years 2000 and 2015 as described previously. Based on the projected mechanical properties of these
materials, panels taken from ten locations on the fuselage and six locations on the wing were redesigned
and resized for strength, making allowance for the change in operating temperature at the higher Mach
numbers. These locations were selected to represent the range of typical design load conditions on
the airframe structure. Based on the weights of these structural elements, the weight of the airframe
for each airplane configuration was estimated for use in the performance calculations.
21
Weight and Balance
The weights databases of the Boeing 2707-300 (U.S. S.S.T.) and other studies have been used for
baseline structural sizing, loads, systems and equipment definition, design criteria, and payload sys-
tem definition. Passenger comfort level requirements according to the current Boeing and airline com-
panies' definition were substituted for the definition used in the model 2707-300. Advanced technology
materials were apphed for concepts projected to be certified in years 2000 and 2015.
Impact of Improved Technology
Advanced technology is essential to achieve the desired range capability (5,000 nmi) within a realis-
tic size limit (maximum takeoff weight of 900,000 lb). Figures 26 and 27 show the impact of technology
advances projected for year 2000 certification versus that currently available for year 1995 certification.
These data show that, collectively, advanced technology reduces the maximum takeoff weight from
1 million pounds to 745,000 lb (about 25%), with advanced structures and materials providing the larg-
est single benefit. The figures also show the same data plus the impact of further technology
Legend:
Titanium - - - •
Composite — _ —
1,800
1,600
Maximum
takeoff
weight,
lb X 1,000
1,400
1,200
1,000
800
600
400
Concorde
technology,
year 1971
certification
Present
jr technology,
\ year 1995
year
certification
r Projected
technology ,
year 2000
certification
Maximum
weight
Projected
technology,
year 2015
certification
Chicago
' Paris to * New York ^ Francisco Los Angeies New York San f^rancisco
New York to Rome •* to Tokyo to Tokyo to Tokyo to Hong Kong
M.^1,1
±
1 A
3,000
4,000
5,000
6,000
Range, nmi
Figure 26. Impact of Technology— Mach 2.4 Baseline
5-U90027H4-150
22
1,100
1 ,000 —
900
Maximum
takeoff
weight ,
lb X 1 ,000
800
700
600
500
Propulsion
Year 2000
projections
Composite
materials
Year 2015
projections
Aerodynamics systems
Composite
materials
Figure 27.
Impact of Technology— Mach 2.4, 247-Seat Airplane With Year 2000 Certification,
5,000-nml Design Range
S-U90027R2-151
improvements projected for year 2015 certification. The required maximum takeoff weight is reduced
from 745,000 lb to about 585,000 lb (about 20%), with advances in propulsion technology providing
the largest single benefit. A year 2000-certification airplane could conceivably use this technology im-
provement for the range growth strategy of the HSCT family concept (fig. 28).
ENVIRONMENTAL EVALUATION
Upper-Atmosphere Emissions/Ozone Impact
The study provided NASA with emissions data for representative fleets of airplanes for analyses
with math models of the Earth's atmosphere. The impact on the airplane size of using reduced emis-
sion engine combustion technology was studied.
Studies to assess the effect on vehicle design of incorporating reduced-emission engines indicated
that significant reduction in NOx emissions can be obtained with a resultant 2.2% to 3.7% increase
in maximum takeoff weight. Of the concepts considered, the lean, premixed and prevaporized combus-
tor has the greatest potential for NOx reduction (approximately one-sixth the base level), but carries
the highest technical risk. The staged-lean combustor provides less NOx reduction (approximately
three-fourths the base level) with what is considered a low technical challenge. The rich-burn,
quick-quench combustor may prove acceptable with a significant NOx reduction (approximately
one-fourth the base level) with a smaller maximum takeoff weight increase than either the lean,
premixed and prevaporized or the staged-lean combustor and is considered to have a lower
development risk.
23
7,000
6,000
Range,
nml
5,000
4,000
3,000
Los Angeles to Sydney
New York to Tokyo
1 200 passengers,
advanced engines
• 250 passengers,
improved engines
Los Angeles
to Tokyo
(Honolulu to Sydney
New/ York to Rome
New York to Paris
^L Initial delivery,
•^ 250 passengers
X
) Increased payload
with improved and
advanced engines
> 300 to 350
passengers,
Improved
engines
• 350 to 400
passengers,
advanced
engines
1995
2000
2005
Year
2015
Figure 28. HSCT Growth Strategy
3-U90027-152
Community Noise
Two different goals were pursued in two parallel studies of community noise and the HSCT The
first was to achieve compliance with FAR36 Stage 3 noise limits; the second was to produce the same
overall effect on the community as a Boeing 747-200 airplane configuration, which just meets the
Stage 3 criteria. The baseline configuration used very aggressive jet noise suppression technology to
reduce takeoff noise levels. In addition, vehicle configurations that had oversized engines and/or wings
were studied to evaluate the effects of these changes on the community noise levels, airplane weight,
and economics. Oversizing the wing was not beneficial. Increasing engine size in conjunction with ad-
vanced, automatic thrust modulation reduced takeoff noise to subsonic Stage 3 requirements, but also
incurred a 4.7% increase in takeoff gross weight and a significant degradation in economic potential.
In the airport study, residential noise exposure was evaluated at 18 airports; the assessments were
made with 85 dBA noise contours (footprints). TWo HSCT footprints were compared with the Boeing
747 footprint as shown in figure 29. The residential area exposure at levels greater than 85 dBA was
nearly the same for the HSCT with a 20% programmed lapse rate procedure as the Boeing-747 (actu-
ally 6.5% less because the HSCT footprint is slightly shorter). If sideline noise requirements were
somewhat reduced or trade provisions increased, maximum thrust could be used for takeoff. The use
of maximum takeoff thrust was found to expose 43.2% less residential area based on an average of
18 airports. It was found that, at most airports, larger residential communities are downrange of the
runway and the shorter footprint more than makes up for the increased width. A supersonic Stage 3
24
8
D
Q
§
CM
o>
1^
to
1^
2
o
o
o
to
o
C
1
CO
CO
tt>
o
It
c
o
0>
y>
s
p.
o
t
r-T
o
CM
t
o
O
1
<
o
c
OQ
O
O
(0
oo
n
CM
(0
o
c
o
o
o
O
o
<&
m
CO
1
O)
CM
o
<t>
o
^
o>
ii:
to Tj i:
25
noise rule that takes into account the HSCT's unique ability to climb away from the community has
the dual benefit of reducing the impact on the community and improving the economics of the airplane.
Sonic Boom
All vehicles in the viability studies were configured to fly supersonically over water and subson-
ically over land. However, because of the significant impact of supersonic overland flight on fleet eco-
nomics, a configuration was evaluated that was designed to reduce the level of sonic boom at Mach
1.5 to a potentially acceptable level. This design would potentially be capable of cruising over land
at supersonic speeds, increasing utilization and reducing flight times.
This study examined several options for reducing the sonic boom shock wave amplitude to a target
overpressure of 1.0 Ib/ft^. This level, with a typical rise time of 6 ms, corresponds to a potentially ac-
ceptable level of 72 dBA for restricted overland flight (corridors). Acceptability is based on previously
published human response testing (ref. 3).
The configuration studies focused on a Mach 1.5 overland design because the concept allowed a
more reasonable fuselage length and required only minimum changes to an arrow wing. The resulting
airplane is shown in figure 30. Compared to the Mach 2.4 baseline, the forebody was lengthened by
10 ft and widened slightly, a wing strake was added, nacelles were staggered, and an arrow planform
was used for both the wing and horizontal tail. The maximum takeoff weight for this low-boom configu-
ration is approximately 3% greater than the baseline aircraft.
The initial attempt at achieving a low-boom profile was only partially successful. In particular, the
inexact design methods resulted in undesirable intermediate shocks and a strong tail shock. Because
the human auditory system is sensitive to shock waves, only a small reduction was obtained. Pressure
signature and resulting loudness predictions at Mach 1.5 are shown in figure 31. More detailed
configuration design studies are required to reach the target of 72 dBA.
Figure 30. Low-Sonic-Boom Configuration
5-U90027R 1-154
26
Baseline at Mach 2.4
Target
2—1
1 —
Overpressure,
Ib/ft2
-1 —
-2 — '
Low-sonlc-boom
configuration
500
~1
X = ft
Pressure Waves at Ground
Calculated
loudness, dBA
85—1
80 —
75 —
70
65— '
Target ■
Baseline at Mach 2.4
Low-sonlc-boom
configuration
Real atmosphere
typical variation
1 \
2 4 6 8 10 12 14
Shock wave rise time, msec
Resulting Loudness
Figure 31. Mach 1.5 Pressure Signature and Loudness Predictions
4-U90027H1-155
27
ECONOMIC EVALUATION
The concept of life cycle operating costs has been developed to satisfy the need for an economic
comparison method that accounts for the actual cash direct and indirect costs incurred in operating
an airplane as well as including all "ownership costs." Cost elements identified include the following-
a. Cash direct cost elements, which include—
1. Flight crew costs.
2. Fuel burned.
3. Airframe maintenance.
4. Engine maintenance.
5. Hull insurance.
b. Indirect costs, which include—
1. Airplane-related (cleaning, fueling, aircraft-handling, maintenance, and ground handling
equipment).
2. Passenger-related (food, passenger-handling, agency commissions, passenger insurance)
c. Ownership costs.
An "economic horizon" was used to provide a reference life cycle operating cost to evaluate the
economic viability of HSCT study configurations. This economic horizon is a trendline relationship
of life cycle operating costs and airplane size. It was based on projected advanced derivatives of the
Boeing 767 and 747 aircraft and allows comparisons of a wide variety of passenger seat counts This
economic model was used in all phases of the contract to define market value of HSCT designs and
the revenue required to obtain the desired return on investment for those designs for which prices were
estimated.
Ek;onomic Viability
To be economically viable, the HSCT must provide a reasonable financial return for both the air-
lines and the manufacturers. Any increased operating and ownership costs associated with an HSCT
must be largely overcome by increased productivity due to speed. The sale price must allow an ade-
quate return on investment and still elicit enough demand for the HSCT to justify the large investment
in development and production costs. To the extent that increased costs cannot be overcome by in-
creased productivity, higher ticket prices must be charged, thereby reducing the market. Preliminary
estimates have been made of the response of the projected HSCT market to increases in price
The impact of technology, based on this evaluation, is illustrated in figure 32. This evaluation shows
that present day technology is not adequate to allow the necessary profit margin A Mach 2 4 HSCT
designed with today's technology would require a 50% to 60% increase in average ticket price over
contemporary subsonic transports. This would reduce demand to the point that the total worldwide
fleet requirement is estimated to be 300 units or less, an inadequate number to support a viable pro-
gram. However, with technology available for year 2000-certified airplanes, the required revenues are
lower, primarily because of the smaller vehicle required to perform the design mission. The result is
that a ticket price increase of 18% would be required and the fleet requirement would be
approximately 650 to 750 units. If year 2015-certification technology was used, ticket price would only
increase by 8%. This would result in a fleet requirement of 950 to 1,050 units.
The impact of design Mach number on the market captured by the HSCT is shown in figure 33
Assuming year 2000 certification, increasing design speed from Mach 2.4 to Mach 2 8 boosts the fare
increase to over 25% and reduces the market captured to 30%, requiring a fleet size of 400 to 500 units
Ihe Mach 3.2 design does not close, as the yield required to earn the required return on investment
is rising more steeply than the yield available.
The key assumption behind the economic closure trends shown in figures 32 and 33 is the trade
of market share against ticket price for a 50% time savings. If the decline in market share with higher
ticket price is steeper, then the "yield available" cuive of figures 32 and 33 may have lower slope with
2o
Average
yield,
C/revenue
passenger
miles
20
18 —
16 —
14 —
12
10
Yield
available
Subsonic
fleet
yields
250 to 350
units
I
• 65% load factor
• Based on 50% time savings
Today's technology
Yield
required
for 12%
return on
Investment
650 to 750
units
I
950 to 1.050
units
I
100
" 25 50 75
Mari<et captured by HSCT, %
Figure 32. Economic Viability— Technology Impact on Fleet Size Based on Mach 2.4, 247-Seat
Design With 5,000-nml Range
5-U90027R2-156
20
18
16
Average
yield,
0/revenue 14
passenger
miles
12
10
• 65% load factor
• Based on 50% time savings
Yield
available
IVIach 3.2
Yield required
for 12% return
on investment
Subsonic
fleet
yields
400 to 500
units
650 to 750
units
1
100
25 50 75
Market captured by HSCT, %
Figure 33. Economic Viability— Impact of Speed Based on 247-Seat Design With 5,000-nml Range
5-U90027R2-157
29
decreasing market share. This would move the closure point to even lower values of marker share and
sales base.
While there is considerable uncertainty in the technical projections and the economic analyses of
all such studies, results indicate the Mach 2.0 to 2.5 vehicles have maximum potential for economic
viability. Compared to transports with greater cruise speeds, they maximize fleet size and meet the
market needs for year 20(X) to 2005 introduction. Additionally, they represent reduced development
investment and risk because of reduced size, complexity, and costs.
CONCLUSIONS
Market and Competition
The market results show that a viable HSCT could acquire a significant portion of the growing,
long-range, worldwide market. However, to achieve this result, the airplane must have the following
characteristics:
a. Environmentally acceptable (no special operating limits other than subsonic flight over land).
b. Adaptable to the year 2000 airport system (i.e., no superhubs for the HSCT alone).
c. From about 250 to 300 seats (in triclass seatings). Final seat definition is a function of productivity,
which depends on Mach number and design range capabilities.
d. A range of 5,000 nmi initially with growth to over 6,000 nmi. This increase will occur through weight
growth; the use of improved engines; minimizing intermediate stops, which increase airline costs
and passenger trip times; and allowing maximum flexibility of the airplane within an airline's sys-
tem. Maximum flexibility will be reached only if the HSCT is used on routes suited to its capabili-
ties, rather than as a direct substitute for 747 missions.
e. Economically competitive with a year 2000 subsonic fleet (i.e., increases in utilization must over-
come increased operating and ownership costs).
f. Cruise Mach number should be consistent with minimum operating costs and maximum produc-
tivity when considering design range tradeoffs.
An HSCT with these characteristics could justify a total fleet size of over 1,200 aircraft between
the years 2000 and 2015, serving primarily the long-range (2,500 nmi and greater), high-density market.
Environmental Concerns
The primary areas of environmental impact identified by this study were—
a. Engine emission. Projections of advanced low-emissions burner technology indicate that an NOx
emissions reduction from 30 + lb to approximately 5 lb of nitrous oxide emissions per 1,000 lb of
fuel burned is possible. A clearer understanding of the effect of engine emissions on the atmo-
sphere is being investigated using the best atmospheric models available and data from the current
HSCT studies. This knowledge is essential to understanding the design requirements for an envi-
ronmentally acceptable HSCT
b. Community noise. The study shows that with projected suppression technology, achievement of
FAR36 Stage 3 noise levels may be possible. The primary issues involved in achieving Stage 3 levels
are—
1. Development of projected jet-noise suppressor technology.
2. Possible modifications to the Stage 3 rules. The unique characteristics of an HSCT could justify
a different trade between sideline noise and takeoff noise, which could further reduce noise to
the majority of the community. Requirements could also focus on the area exposed to a given
sound level to take into account the operating characteristics of an advanced HSCT in reducing
residential area exposed to noise.
30
c. Sonic boom. Subsonic, boomless overland flight was assumed for the basic technical and economic
viability estimates. However, a preliminary low-sonic-boom-design study suggests that a combina-
tion of fuselage shaping, wing planform choice, and a cruise at reduced supersonic Mach has poten-
tial for reducing boom overpressure levels. Acceptable sonic boom levels have not been
established. Therefore, committing a design to a reduced sonic boom level is premature at this early
stage. Continued effort must be made toward developing a low-boom configuration.
Technical Feasibility
Within the Mach 2.0 to 3.2 speed range, vehicles can be operated with kerosene-based fuels, engine
cycles using conventional turbomachinery, an uncooled high-temperature composite, or a titanium
primary structure. These vehicles would be capable of operating from existing airports.
Based on the results of the contract studies and other independent studies focusing on lower cruise
speed vehicles, maximum potential for an environmentally sound, technically feasible HSCT exists for
a vehicle designed to cruise at Mach 2.0 to Mach 2.5 over water and Mach 0.9 over land.
Economic Viability
Preliminary estimates of the response of the projected HSCT market to increases in ticket cost
have been measured against the revenues needed for the airplanes studied in this and other indepen-
dent studies to provide adequate profit margins to the manufacturer and the airlines. Based on this
evaluation, the following conclusions can be drawn:
a. Present technology is not adequate.
b. A year 2000, Mach 2.0 to 2.5 HSCT shows promise (potential total market of 650 to 750 airplanes).
While this would be an adequate demand for a single manufacturer, it is not an adequate market
for two or more.
c. A Mach 2.0 to 2.5 HSCT with the advanced technology projected to be available for a year 2015
airplane (either as an all-new airplane or an advanced derivative of a year 2000 airplane) is more
encouraging. With this technology, the potential total market is estimated at 950 to 1,050 airplanes,
which clearly represents a business opportunity for two manufacturers.
d. Technology that reduces the weight and cost at Mach 2.0 to 2.5 has a much greater impact on eco-
nomic viability than technology that enables higher cruise Mach numbers.
Key areas of improvement that would directly impact economic performance are—
a. Reduced structural weight.
b. Improved engines available for year 2000 vehicles.
c. Increased aerodynamic performance through improved wing planforms and hybrid laminar flow.
Finally, while the development costs of vehicles in the preferred Mach range may be considerably
higher than the costs of a similar-sized subsonic vehicle. Government support of the production pro-
gram for an HSCT would not be required if such a vehicle were economically viable.
RECOMMENDATIONS
Technology Development Program
Potential for a successful U.S. commercial high-speed transport exists for the year 2000 market
if aggressive technology development is undertaken in the near term. It is recommended that a joint
NASA-industry technology development and validation program be undertaken to address key tech-
nology areas. This program would optimize the likelihood of achieving environmental acceptability
for, and economic viability of, an HSCT cruising between Mach 2.0 and 3.0. The cost of this program
would be a small fraction of the total development and production costs, but could be key to receiving
31
the commitment from airframe and engine manufacturers necessary to achieve the timely development
and production of a successful HSCT and, ultimately, to ensure the HSCT's success in the worldwide
marketplace.
Technology Needs
Many technology development needs are enabling, meaning that they are essential to achieve vi-
ability, and others are high-leverage items that offer significant payoff in risk reduction or economics.
The list of required and/or desirable technology developments covers virtually all technology areas
and disciplines and must be prioritized. One basis for prioritization is the development of technology
to demonstrate environmental acceptability, without which the HSCT program cannot be launched.
(Examples of these technologies are low-emission burners and noise suppression technology.) Other
factors that set priorities are the degree to which the technologies are time-critical, high-risk, or
high-cost, or are potentially high in value in economic payoff.
Based on maximum potential for environmental and economic viability, the highest near-term
priorities for technology development are—
a. Low-emissions technology.
b. Noise-suppressor technology.
c. Variable-cyle engine technology.
d. High-temperature, durable-composite structures and materials.
e. High-lift aerodynamics.
f. High-temperature metals compatible with lightweight composite structures.
These are all high-value, high-cost items that will make critical contributions to the environmental
and economic factors and they are time-critical to the aircraft certification date of year 2000. Serious
research and development of each of these items should be initiated by 1990.
Technology development needs for longer term, higher risk vehicles have been identified. These
are considered of secondary priority to the Mach 2.4, year 2000 vehicle, but could provide enhance-
ments in economics and possibly speed. They are applicable to a later timeframe for certification.
Those areas needing development include—
a. Advanced engine concepts.
b. Advanced vehicle concepts.
c. Laminar flow control.
d. Higher temperature materials for higher speed vehicles.
e. High-thermal-stability fuels.
32
REFERENCES
1. Boeing Commercial Airplanes, "Current Market Outlook," February 1988.
2. "Study of Structural Design Concepts for an Arrow Wing Supersonic Transport Configuration,"
Volume 1, NASA CR- 132576-1, August 1976.
3. Brown, J. G. and Haglund, G. T, "Sonic Boom Loudness Study and Airplane Configuration Devel-
opment," AIAA Paper 88-4467, presented at the AIAA/AHS/ASEE Aircraft Design, Systems, and
Operations Conference, September 7-9, 1988, Atlanta, Georgia.
33
(VIASA
Report Documentation Page
1. Report No.
NASA CR-4234
2. Government Accession No.
4. Title and Subtltie
High-Speed Civil Transport Study -
Summary
3. Recipient's Catalog No.
5. Report Date
September 1989
6. Performing Organization Code
7. Autlior(s)
Boeing Commercial Airplanes
New Airplane Development
8. Performing Organization Report No.
9. Performing Organization Name and Address
Boeing Commercial Airplanes
P.O. Box 3707
Seattle, Wa 98124-2207
10. Worit Unit No.
505-69-01-01
11. Contract or Grant No.
NASl-18377
12. Sponsoring Agency Name and Address
NASA Langley Research Center
Hampton, Va 23665-5225
13. Type of Report and Period Covered
Contractor Report
14. Sponsoring Agency Code
15. Supplementary Notes
NASA Program Manager:
Boeing Program Manager:
Boeing Contract Manager:
Final Report
Charles E. K. Morris, Jr.
Michael L Henderson
Danella E. Hastings
16. Abstract
A system study of the potential for a high-speed commercial transport has addressed
technology, economic, and environmental constraints. Market projections indicated a need for
fleets of transports with supersonic or greater cruise speeds by the years 2000, to 2005. The
associated design requirements called for a vehicle to carry 250 to 300 passengers over a range of
5,000 to 6,500 nautical miles. The study was initially unconstrained in terms of vehicle
characteristic, such as cruise speed, propulsion systems, fuels, or structural materials. Analyses
led to a focus on the most promising vehicle concepts. These were concepts that used a kerosene-
type fuel and cruised at Mach numbers between 2.0 to 3.2. Further systems study identified the
impact of environmental constraints (for community noise, sonic boom, and engine emissions) on
economic attractiveness and technological needs.
Results showed that current technology cannot produce a viable high-speed civil transport;
significant advances are required to reduce takeoff gross weight and allow for both economic
attractiveness and environmental acceptability. Specific technological requirements have been
identified to meet these needs.
17. Key Words (Suggested by Author(s))
High-Speed Civil Transport Market
Environment Economics
Vehicle Development
18. Distribution Statement
Unclassified - Unlimited
Subject Category 05
19. Security Classlf.
(of this report)
Unclassified
20. Security Classlf.
(of this page)
Unclassified
21. No. of pages
44
22. Price
A03
.NASA-Langley. 1989
For sale by the .National Technical Information Service, Springfield, Virginia 22161-2171
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