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2
Focus for ARMD--Case Studies
Because of the breadth of activities undertaken by the NASA Aeronautics Research Mission Directorate
(ARMD) and the size and time limits of this study, the committee selected three case studies for more detailed
analysis. These three case studies are NASA's Integrated Systems Research Program's Environmentally Respon-
sible Aviation (ERA) project and the Fundamental Aeronautics Program's Hypersonics and Supersonics projects.
The committee believes that the three case studies selected are representative of the breadth of ARMD and of the
flight research issues facing the organization. Subsonic aeronautics research programs in aviation safety, airspace
systems, and fundamental subsonic aeronautics form the backbone of ARMD and account for a vast majority of
the funding. The ERA project was chosen by the committee to represent subsonic flight research because it was
formed to integrate a number of promising technologies developed under ARMD subsonic research programs to
show how they can improve fuel efficiency and reduce the emissions and noise of subsonic aircraft in flight. While
subsonics research supports today's industrial base, the Fundamental Aeronautics Research Program's Hyperson-
ics and Supersonics projects were chosen because they represent the emerging near- and farther-term aeronautics
and space applications that are important to the nation. In addition, the Supersonics and Hypersonics projects
were chosen because of their high reliance on flight research (in comparison to subsonics) because of ground test
facility limitations and other factors. For each of these case studies the committee discusses the current state of
the program, some of the current flight activities within the projects, and the issues in the committee's statement
of task. There are common themes to each case study that the committee believes illustrate larger issues concern-
ing the challenges that ARMD faces and how ARMD conducts flight research. The committee's analyses of the
common issues are presented at the end of this chapter.
As the committee examined the case studies and reviewed information presented to it by various NASA
centers--including during a visit to the Dryden Flight Research Center--a common theme appeared in all of
them: lack of a clearly defined "path to flight" for the projects. The committee noted that this tendency was most
prevalent for the ERA project but was common to other NASA aeronautics endeavors as well, and it resulted in
the following recommendation applicable to all of NASA's projects:
Recommendation: NASA should ensure that each of its projects has a defined path to in-flight
testing in an appropriate environment. These paths must include details of the vehicle to be used
for the flight research, be it a modification to an existing testbed or a purpose-designed and built
vehicle. The overall program must ensure that funding is available to complete the in-flight research
26
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FOCUS FOR ARMD--CASE STUDIES 27
portion of the project in a timely manner, either by appropriately using a sub-scale test vehicle or
by dedicating major funding levels to a "flagship" effort.
THE ENVIRONMENTALLY RESPONSIBLE AVIATION PROJECT
The ERA project is a part of NASA's Integrated Systems Research Program. The ERA project is an effort to
substantially improve the fuel efficiency and environmental performance--and therefore competitiveness--of the
U.S. aviation industry. U.S. aircraft must operate not only at a time when fuel prices are increasing but also in areas
such as Europe that have been tightening environmental restrictions on noise and emissions. According to NASA,
the ERA project was created to "explore and document the feasibility, benefits and technical risk of vehicle con-
cepts and enabling technologies that will reduce the impact of aviation on the environment." This impact reduction
will be accomplished by reducing noise, nitrous oxide (NOx) emissions, and fuel burn. The ERA project's primary
focus is to enable the design of aircraft that can accomplish all three of those goals simultaneously. With air traffic
expected to double by 2025, the work of the ERA project will be crucial for reducing the air transportation system's
emission of greenhouse gases and decreasing its susceptibility to volatile aviation fuel prices. 1
The ERA project's 2020 goals, as outlined in the National Aeronautics Research and Development Plan,
are to reduce noise by 42 dB, reduce NOx emissions by 75 percent, and reduce aircraft fuel burn by 40 percent. 2
To meet these goals the ERA project plans to explore and mature unconventional aircraft designs in the areas of
airframe and propulsion technology as well as vehicle systems integration. The project plans to invest in certain
technologies for meeting its goals.
One challenge facing almost every aircraft is how to reduce noise. The ERA project will specifically concen-
trate on mitigating propulsion noise and airframe noise and the interaction between the two, referred to as propul-
sion airframe aerodynamics. Propulsion noise mostly consists of fan and jet noise, and airframe noise is primarily
caused by flaps and landing gear. Engine noise can be reduced by employing ultra-high bypass engines such as a
geared turbofan engine, soft vane, over-the-rotor foam metal lines, distortion-tolerant fans with active noise control,
variable area fan nozzles, and combination metallic and polyimide foams or aerogel materials. Airframe noise
can be reduced with the use of continuous mold-line wing structures, drooped leading edge, active flow control,
adaptive and flexible wing structures, smart chevrons, and a toboggan fairing for landing gear noise reduction.
For example, to demonstrate noise reduction, NASA is conducting flight tests with a Gulfstream G550 at
NASA's Wallops Flight Facility. This will be used to demonstrate noise reduction capabilities with a focus on
aircraft design as a whole and specifically on landing gear.
Another challenge is to reduce landing and takeoff NOx emissions. There are three current plans to address
these types of emissions. One of them, the ERA CMC (ceramic matrix composite) combustor liner, will be able
to tolerate high engine temperatures. Another one is active combustion instability control that will focus on trying
to reduce combustor instabilities. Finally, the low-NOx, fuel-flexible combustor offers a high bypass ratio and
advanced combustion with fuel/air mixtures. An example of this propulsion technology research is the develop-
ment of fuel injector designs that will meet the emission standards.
NASA's plan to tackle fuel burn is composed of three parts: reducing drag via laminar flow, reducing weight
via advanced structures, and reducing specific fuel consumption via ultra-high bypass ratio engines. Drag reduction
can be achieved by using many tools and techniques, such as aircraft design and propulsion (see Figure 2.1). For
example, the hybrid laminar flow control will use a suction technique, and the natural laminar flow will consist
of a thin wing design that reduces friction drag. The Gulfstream G-III "Gloved Wing" aircraft is being developed
by a partnership with Texas A&M University, Gulfstream Aerospace, and the Air Force Research Laboratory.
This project will demonstrate drag reduction by using discrete roughness elements. It will also be working on a
compliant flap in which changes are made to the curvature of the flap to create more lift. Weight reduction will
1 NASA Aeronautics Research Mission Directorate, "Environmentally Responsible Aviation Project: Integrated Systems Research Program,"
available at http://www.aeronautics.nasa.gov/isrp/era/index.htm, last updated February 3, 2011.
2 NASA Aeronautics Research Mission Directorate, "Fundamental Aeronautics Program: Subsonic Fixed Wing," available at http://www.
aeronautics.nasa.gov/fap/sfw_research_overview_feature.html, last updated September 9, 2009.
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28 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
FIGURE 2.1Artist's rendering of a possible future subsonic aircraft using boxed-wing configuration to reduce drag and
increase fuel efficiency. This is one of many possible configurations for future airliners. SOURCE: NASA/Lockheed Martin;
available at http://www.nasa.gov/topics/aeronautics/features/future_airplanes_index.html.
consist of the Protruded Rod Stitched Efficient Unitized Structure (PRSEUS), which will be composed of stitched
carbon-epoxy material. Finally, reducing specific fuel consumption will not only help improve fuel efficiency but
also suppress noise.
Substantial improvements in fuel efficiency will probably require entirely new aircraft designs that are dif-
ferent from the traditional "tube and wing" design. The ERA project is investigating novel hybrid wing body
configurations that integrate airframe and propulsion systems to improve fuel efficiency as well as help meet 2020
noise reduction goals.3 The Boeing/NASA X-48B BWB sub-scale research aircraft is the first step in that process
(see Figures 2.2 and 2.3). The X-48B flew its first flight test on July 20, 2007, and recently completed Phase 2
testing.4 The aircraft will resume flight testing in the X-48C configuration, with two turbofan engines instead of
three turbojet engines used on the X-48B.
The ERA project's goals are the N+2 goals, or 2020 technology benefits relative to a large twin-aisle reference
configuration, including a 42-dB noise reduction below the stage 4 noise requirements, a 75 percent reduction in
landing and takeoff NOx emissions below Committee on Aviation Environmental Protection 6 (CAEP 6) require-
ments, and a 50 percent reduction in aircraft fuel burn. These final technologies will include airframe technology,
propulsion technology, and vehicle systems integration.
In an effort to achieve these goals, the ERA project is investigating 36 different projects, with the goal of
reducing them to only 6 in phase 2, which is planned to take place in spring 2012. In the committee's view, it
is important to reduce the projects based on technical merit and not on their expenses to date. NASA had plans
to develop a "sub-scale test vehicle" by 2016 to demonstrate a number of the key technologies identified in this
3 NASA Aeronautics Research Mission Directorate, "Fundamental Aeronautics Program: Subsonic Fixed Wing," available at http://www.
aeronautics.nasa.gov/fap/sfw_research_overview_feature.html, last updated September 9, 2009.
4 NASA Dryden Flight Research Center, "Back in the Air: X-48B Resumes Flight Tests at NASA Dryden," available at http://www.nasa.
gov/centers/dryden/status_reports/X-48B_status_09_21_10.html, last updated September 21, 2010.
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FOCUS FOR ARMD--CASE STUDIES 29
FIGURE 2.2 The X-48B being tested in the Full-Scale Tunnel at NASA's Langley Research Center in Hampton, Virgina.
SOURCE: Courtesy of Boeing/Bob Ferguson. Image ID k63682-03. Copyright © Boeing.
FIGURE 2.3 The X-48B in flight. SOURCE: Courtesy of NASA/Carla Thomas; Photo ED07-0192-03.
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30 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
phase. However, in January 2012 NASA indicated that because of lack of funding, the agency had backed away
from plans for development of this test vehicle.5
All of these goals will be accomplished with the support of academia and industry. To this end, the ERA proj-
ect created working groups and technical interchange meetings, developed Space Act Agreements for cooperative
partnerships, and used the NASA Research Announcement Project to solicit promising research ideas. 6 Once the
technology is successfully developed, the ERA project will be able to share its knowledge with others, such as
the Fundamental Aeronautics Program.
Hurdles and Limitations for the ERA Project
The ERA project faces both technical and procedural obstacles in achieving its goals. The technical obstacles
may be resolved by creative engineering, but the procedural obstacles require innovative budgetary and managerial
solutions in design and use of facilities.
Certain issues that arise in low-NOx engines, particularly combustion instabilities, are intrinsically system
dependent and cannot be evaluated on flame tube or sector facilities. Some full-scale engine testing and flight
testing is needed to evaluate how these issues manifest themselves and are influenced by the inherent operational
issues that arise in flight.
Flight research is required to evaluate and prove many of the technologies that can dramatically improve fuel
efficiency. Few if any wind tunnels are capable of accurately predicting the drag reduction of natural and forced
laminar flow, and therefore the reduction in fuel burn, that can be achieved by natural or forced laminar flow. Wind
tunnels also do not allow the researcher to discover operational issues that may arise with laminar flow, such as
the effect of dirt, icing, or other residue on the wing surface. Wind tunnels are extremely limited in their ability to
perform noise level testing. Test facilities do exist that can reproduce the environment accurately enough for the
analysis of propulsion system emissions. However, some of these facilities are outside NASA's control. The use
of these ground-based facilities do not allow for the investigation of these technologies as an integrated system
with other technologies.
Currently the only non-conventional aircraft configuration being tested is that of the Blended Wing Body
Boeing X-48, a sub-scale radio-controlled aircraft that has been tested at the Dryden Flight Research Center. NASA
Langley is also performing research using a 5.5 percent scale generic transport aircraft called AirSTAR. 7 Other
unconventional aircraft configurations are being tested in ground-based facilities, but integration and flight test are
a very important part of the process of understanding the new technologies. If the new technologies of ERA are
to be realized by 2025, any non-conventional configuration will have to be tested and matured by flight research.
Economical Solutions and Budget Scenarios for the ERA Project
The ERA project tries to address the development and testing of these new technologies in an economical
way. The use of sub-scale test vehicles to perform flight research on specific projects, testbed aircraft to evaluate
individual concepts, partnerships to cut costs, and decision points to narrow in on the most promising develop-
ments are all mechanisms of focusing resources on the ERA project's most promising new technologies. Even
though NASA's current fleet of aircraft is fairly large and diverse, it will most likely not be able to meet all of the
needs of the ERA project. For instance, flight test of open rotor propulsion systems will require an aircraft in the
Boeing 717 or 727 class as a testbed.
NASA Langley has used sub-scale flight research in the past. To meet all of the program goals these technolo-
gies will have to be simultaneously integrated and flight tested on representative airframes. These aircraft must be
5 S. Trimble, Flight Global, "Funding Cuts Put NASA Commercial X-Plane on Hold," available at http://www.flightglobal.com/news/articles/
funding-cuts-put-nasa-commercial-x-plane-on-hold-366840/, January 12, 2012.
6 NASA Aeronautics Research Mission Directorate, "Environmentally Responsible Aviation Project: Integrated Systems Research Program,"
available at http://www.aeronautics.nasa.gov/isrp/era/index.htm, last updated February 3, 2011.
7 T. Jordan, W. Langford, C. Belcastro, J. Foster, G. Shah, G. Howland, and R. Kidd, "Development of a Dynamically Scaled Generic
Transport Model Testbed for Flight Research Experiments," NASA Langley Research Center, Hampton, Va., August 2004.
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FOCUS FOR ARMD--CASE STUDIES 31
of the correct configuration and of adequate scale to demonstrate the true effectiveness of the technologies. This
is not to say that sub-scale flight test vehicles such as the X-48 and AirSTAR are not extremely valuable. These
sub-scale models are very important risk mitigation tools.
Testbed aircraft can also be used to perform research in an economical way. The validation of new propulsion
technologies will require full-scale testbeds. The testing of these technologies as an integrated vehicle system will
require full-scale flight test vehicles of specific configurations. Either these testbed vehicles can be modified, such
as the Gulfstream G-III being used for laminar flow research, or the aircraft can be purpose-built to be recon-
figurable like the Air Force Research Laboratory's Multi-Utility Technology Testbed (MUTT) aircraft, which is
designed to determine the boundaries of wing flutter for aircraft. The development of these testbeds can provide
experience with the integration of multiple technologies. Testing of airframe technologies, specifically new light-
weight structures and the flight dynamics of non-conventional configurations, will require new flight test airframes.
Additional partnerships in programs with other government agencies and industry provide a method to eco-
nomically perform research. But to make sure that these technologies are readily available to be used by others,
NASA will have to partner in a way that does not limit the use of the research and data by others. For instance,
collaboration between NASA, the Department of Defense (DOD), or some other agencies on a national subsonic
experimental aircraft that would allow for advanced aerodynamic, structural, and engine technologies may provide
an avenue to economically achieve the ERA project's N+2 goals.
If the budget for the ERA project remains unchanged, NASA will have to rely on partnerships if it is to make
significant progress toward its N+2 goals. NASA can try to decrease the number of funded research projects in
phase 2 of the ERA project to ensure that the most promising of the technologies moves into flight research. The
use of sub-scale flight research aircraft would provide some ability to test some airframe technologies, such as
structures/materials as well as adaptive/complex interactive systems. However, most of the advances in propulsion
technologies will require larger flight vehicles because of the scaling of thrust, mass flow, rotations per minute,
and thermodynamics and combustor technologies. Also, the scaling of acoustic energy with mass flow testing of
noise reduction technologies using surrogate and sub-scale vehicles can be conducted; however, the applicability
of this data may be limited. Some testing of noise reduction technologies using surrogate and sub-scale vehicles
can be conducted; however, the applicability of this data may be limited. In the committee's view, NASA's plans to
develop a sub-scale test vehicle by 2016 represented the next logical step in advancement of this program. The com-
mittee believes that the recently announced plans to delay development of such an aircraft are unfortunate and also
believes that the ERA project cannot make significant progress unless it actually conducts further flight research.
If the ARMD budget is increased a modest amount and the ERA project receives a share of this budget, the
number of flight research opportunities will increase. If this additional budget was directed into scale or sub-scale
test vehicles, the integrated research could be performed on at least the airframe technologies and, to a lesser
amount, noise reduction. It would remain difficult to perform any propulsion technology research unless full-scale
aircraft were to be modified to serve as flying testbeds. Either of these two options would allow for research to
be conducted on truly integrated systems and without the limits of many of the ground test facilities. This flight
research would still allow for the process of discovery that is so important to the development of new technologies.
If more money becomes available, the NASA ERA project could examine the feasibility of developing a full-
scale or nearly full-scale aircraft incorporating numerous projects from the ERA phase 1 portfolio. This flying pro-
totype could be designed to act as a flying testbed for future concepts. This type of project allows the development
team to truly develop the technologies through their integration on a new vehicle. This type of project allows for
full discovery throughout the program's life cycle. The concept of competition between designs and collaborative
work with other government agencies such as DARPA (Defense Advanced Research Projects Agency) may provide
greater opportunity to achieve the goals of the ERA project.
Summary
The ERA project has established N+2 goals relating to the 2020 time frame. To achieve these goals the ERA
project has approximately 32 projects being executed within its phase 1. Of these projects only a limited number will
be carried forward into phase 2. Current planning is for six projects to move forward. Of these six it is unclear what
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32 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
planning has been performed to take the technologies into flight research. In some cases there are testbed aircraft;
however, in others, such as open rotor propulsion systems, no vehicle has been identified. Without transitioning
these technologies into flight they cannot be developed to a technology readiness level (TRL) of 6 or higher. The
process of integrating these systems onto an aircraft and performing in-flight research offers the opportunity of
discovery, which cannot be realized in the ground testing environment alone.
Finding: If NASA determines that progress in Environmentally Responsible Aviation is a priority, the
agency could collaborate with the Department of Defense, the Federal Aviation Administration, other
government agencies, and industry on a subsonic experimental aircraft that would integrate multiple
advanced aerodynamic, structural, and engine technologies. The most effective approach would be to
ensure that the flight test program, while integrating multiple technologies, is also planned so as to test
single objectives for each test. With a view to maximizing effectiveness, as these collaborations are carried
out the distribution of research results and data cannot be limited to industry and academia and should
be understandable, presentable, and accessible to a broad audience.
THE SUPERSONICS RESEARCH PROJECT
NASA's supersonics research project has evolved from decades of research and technology development into
high-speed flight regimes. But the United States has yet to bring civil supersonic flight into commercial service
as was done with the now-retired Anglo-French Concorde and short-lived Russian Tu-144. 8 While these aircraft
did enter service in the 1970s, they suffered high operational costs and tremendous political pressures associated
with the same environmental issues that we face today--excessive fuel burn, high-altitude emissions, high carbon
footprint, ozone depletion, and objectionable takeoff and landing noise. The United States had rightly removed
itself from the commercial supersonic transport race because the advanced technologies were not yet available to
achieve both environmental and economic success.9
Today, commercially viable supersonic flight--for smaller aircraft such as business jets--remains a highly
desired market for the aviation industry and is within reach, provided that existing research efforts are advanced
to their next stage. The Supersonics project, one of four projects managed under NASA Aeronautics' Fundamental
Aeronautics Program, exists today to develop the tools and technologies necessary to achieve this goal. Stating
as its objective to "eliminate technology barriers preventing civil supersonic airliners," 10 the supersonics research
project contains a broad and diverse portfolio that has been refined through past programs like the United States
Supersonic Transport (SST), Supersonic Cruise Aircraft Research (SCAR), High Speed Civil Transport (HSCT),
High Speed Research (HSR), and DARPA Quiet Supersonic Platform (QSP), 11 each building on the work of
previous researchers and engineers. The 1997 NRC review of HSR concluded that flight demonstration to TRL 6
was necessary to prove sustained supersonic performance of integrated aircraft technologies under development. 12
In 2001, Commercial Supersonic Technology, The Way Ahead added that public acceptance of the sonic booms
generated by commercial aircraft was also a necessary component for technology demonstration and that it would
be necessary to stimulate development of regulatory standards for sonic booms. 13 HSR successfully defined the
feasibility of addressing concerns about high-altitude emissions and airport/community flyover noise, although
commercially viable solutions were not yet available at the time.14 The Supersonics project continues to work
8 G. Thomas, G. Norris, C. Forbes Smith, S. Creedy, and R. Pepper, Plane Simple Truth--Clearing the Air on Aviation's Environmental
Impact, Aerospace Technical Publications International, Perth, Western Australia, 2008, pp. 20-21.
9 National Research Council (NRC), Commercial Supersonic Technology: The Way Ahead, National Academy Press, Washington, D.C., 2001.
10 P. Coen and L. Povinelli, NASA, "Fundamental Aeronautics Program: Supersonics Project," briefing to the National Research Council
Committee to Assess NASA's Aeronautics Flight Research Capabilities, June 13, 2011, Washington, D.C.
11 NRC, Commercial Supersonic Technology, 2001, p. 8.
12 NRC, U.S. Supersonic Commercial Aircraft, The National Academies Press, Washington, D.C., 2006, p. 4.
13 NRC, Commercial Supersonic Technology, 2001.
14 E.M. Conway, High-Speed Dreams--NASA and the Technopolitics of Supersonic Transportation, 1945-1999 , John Hopkins University
Press, Baltimore, Md., 2005.
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FOCUS FOR ARMD--CASE STUDIES 33
multiple areas of research in high-temperature materials, lightweight structures, lean-burn combustion, aeroservo-
elasticity/controls, instrumentation and automation, efficient airframe/propulsion configuration development, and
integration of synthetic cockpit vision systems.15 All aspects of the supersonic system sharing the airspace can
benefit from system-level flight research and testing. However, at an annual allocation of $40 million, making up
less than one-quarter of the Fundamental Aeronautics Program's budget, 16 the Supersonics project lacks sufficient
resources to continue this broad path and solve the critical technology barriers holding back this highly sought
after capability.
Narrowing focus during DARPA QSP, researchers agreed that with respect to sonic boom, low-boom flight
is more readily achieved using smaller aircraft. For decades, economic and technical viability had been studied
for large 300-passenger, >500,000 pound commercial transports.17 As cost-effective utilization of small regional
jets and corporate aircraft has grown, scientists and industry engineers have turned their collective interest toward
smaller 100,000-pound-class business jets and airliner concepts, significantly improving the chance of success
for both economic and technical feasibility.18 The solution to the sonic boom problem now appears within reach
and will enable a market for corporate aircraft to advance collective knowledge, opening the door for future small
supersonic airliners (see Figure 2.4).19
In the past decade, the Supersonics project has carried its broad portfolio into many areas of flight research.
Using existing aircraft and NASA fleet assets at Dryden Flight Research Center, sonic boom shaping has shown
much progress in flight projects like the DARPA F-5 Shaped Sonic Boom Demonstrator, NASA/Gulfstream F-15
Quiet Spike, and NASA F-18 low-boom dives (see Figure 2.5).20 Other important flight work includes supersonic
laminar flow/boundary layer transition in partnership with Aerion Corporation, airframe/propulsion integration
inlet and jet plume studies like LANCETS, and external/synthetic vision systems at Langley and Ames research
centers.21 NRA (NASA Research Announcement) studies awarded to Boeing and Lockheed Martin are aimed at
N+2 time-frame (i.e., 2020) low-boom airliner configurations for wind tunnel validation, 22 seeding a future research
opportunity for a low-boom technology flight experimental vehicle. 23 Further, human and structural response to
low-boom ground acoustic signatures remains ongoing using both flight research at Dryden (e.g., HouseVibes
and SonicBOBs24) and laboratory studies at Langley's new interior effects room, which is a sonic boom playback
simulator set up to resemble a typical residential living room.25 Researchers can vary signature intensity, frequency
of occurrence, and many additional acoustic characteristics like structural transmission, rattle, and source direc-
tionality.26 NRAs regarding development and validation of sonic boom focus prediction codes and community
response test protocols for future low-boom flight research are under way at the writing of this report. 27 Nearly 45
percent of the Supersonics project resources are currently allocated to determining a solution to sonic boom, and
15 NRC, NASA Aeronautics Research: An Assessment, The National Academies Press, Washington, D.C., 2008.
16 B. Esker, "NASA Fundamental Aeronautics Program," briefing to National Research Council Committee to Assess NASA Aeronautics
Flight Research Capabilities, April 20, 2011, Edwards, Calif.
17 NRC, Commercial Supersonic Technology, 2001.
18 P.A. Henne, "Case for Small Supersonic Civil Aircraft," Journal of Aircraft 42(3), 2005.
19 NRC, Decadal Survey of Civil Aeronautics: Foundation for the Future, The National Academies Press, Washington, D.C., 2006, p. 18.
20 D. McBride, "Dryden Flight Research Center Flight Projects and Perspectives," briefing to National Research Council Committee to
Assess NASA Aeronautics Flight Research Capabilities, April 20, 2011, Edwards, Calif.
21 P. Coen and L. Povinelli, NASA, "Fundamental Aeronautics Program: Supersonics Project," briefing to the National Research Council
Committee to Assess NASA's Aeronautics Flight Research Capabilities, June 13, 2011, Washington, D.C.
22 P. Coen and L. Povinelli, NASA, "Fundamental Aeronautics Program: Supersonics Project," briefing to the National Research Council
Committee to Assess NASA's Aeronautics Flight Research Capabilities, June 13, 2011, Washington, D.C.
23 NRC, NASA Aeronautics Research, 2008, p. 25.
24 J. Klos, "Measurement of Low-Amplitude Sonic Booms In and Around Large Buildings," presentation at the Fundamental Aeronautics
Program Technical Conference, March 15-17, 2011.
25 J. Rathsam, A. Loubeau, and J. Klos, "Laboratory Study of Indoor Human Response to Sonic Booms," presentation at the Fundamental
Aeronautics Program Technical Conference, March 15-17, 2011.
26 A. Loubeau, "Sonic Boom Modeling Overview," presentation at the Fundamental Aeronautics Program Technical Conference, March
15-17, 2011.
27 P. Coen and L. Povinelli, NASA, "Fundamental Aeronautics Program: Supersonics Project," briefing to the National Research Council
Committee to Assess NASA's Aeronautics Flight Research Capabilities, June 13, 2011, Washington, D.C.
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34 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
FIGURE 2.4 Artist's depiction of a possible future civil supersonic transport that is shaped to reduce the sonic shockwave
signature and to reduce drag. SOURCE: Courtesy of NASA/Lockheed Martin; available at http://www.nasa.gov/topics/aero
nautics/features/future_airplanes_index.html.
FIGURE 2.5 "Quiet Spike" test on a NASA F-15 research aircraft. This device was used to alter the sonic boom produced by
the aircraft. SOURCE: Courtesy of NASA Dryden Flight Research Center/Lori Losey; NASA Photo ED06-0149-23.
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FOCUS FOR ARMD--CASE STUDIES 35
approximately 14 percent are devoted to flight research for sonic boom and other technologies. 28 The Supersonics
project is well positioned in low-boom airframe and engine integration development, sonic boom perception, and
human/structural response to make the transition to an integrated flagship program, yet flight assets do not exist
and remain to be prioritized within the agency to achieve this goal. In considering the role of experimental aircraft
and/or X-planes as they relate to advancing NASA's mission, the Supersonics project aligns with the need for a
cost-effective technology demonstration or flagship X-plane program.
While sonic boom remains the principal challenge preventing commercially sustainable supersonic operations,
much work remains in other key research areas to enable future production supersonic aircraft. The NRC 2006
Decadal Survey of Civil Aeronautics identified several areas grouped into well-integrated and efficient propul-
sion systems.29 These gaps remain today, and while a sonic boom solution may be near, the engines necessary
to enable routine efficient and cost-effective supersonic operations do not yet exist. VAATE, or Versatile Afford-
able Advanced Turbine Engines, is a collaborative research and development program between DOD, NASA,
Department of Energy (DOE), Federal Aviation Administration (FAA), academia, and industry. 30 Its objective is
to advance the state of the art in turbine engine technologies and substantively increase propulsive efficiency and
affordability while also reducing overall fuel burn. VAATE's goals are primarily aimed at meeting the needs of the
U.S. military; however, NASA can nurture the breadth of this partnership and leverage its commercial applications
as well. A robust and systematic research program is needed to bring flight validated engine technologies, 31 along
with the necessary airframe integration features needed to maintain progress in green technologies and low-boom
development. NASA can nurture partnerships with other agencies such as DOD, FAA, and others, and engine
original equipment manufacturers in an endeavor to reach this goal. (Such collaborations are further discussed
in Chapter 3.) A variable cycle engine would have advantages for subsonic as well as supersonic vehicles. For
example, transport aircraft often involve compromises on cruise performance for reduced takeoff distance; a vari-
able cycle engine can thus have significant advantages for such aircraft. A variable cycle engine testbed could
therefore be coupled with a vehicle that explores other technologies.
The committee was asked to consider three budgetary scenarios: (1) funding constrained, (2) moderate
increase, and (3) unconstrained. With a flat or reduced budget, large-scale supersonics flight research will be very
challenging. To proceed, a vigorous task reprioritization and reduction of project-supported personnel would be
necessary to reallocate funding. Labor expenses would have to be significantly reduced to free funding for discre-
tionary spending on flight hardware. In addition, NASA would require partners for significant cost-sharing with
other government agencies or industry. Such an approach would not be likely to achieve critical mass to support a
flight program inside a decade without significant narrowing of work scope and substantial partner cost-sharing.
For a moderate increase, say 120 to 150 percent of the current $40 million annual levels for supersonics work alone,
existing personnel and resources would likely be maintained near levels of the broader research portfolio and a
large-scale flight program could be developed again if rather significant cost-sharing could be found within agency
stakeholders and/or industrial partners. A resulting flight program focused on sonic boom alone could occur over
a probable time frame of 5 to 8 years. Finally, if NASA were to consider a nearly unconstrained budget scenario,
NASA could pursue a large-scale flight program on the order of $100 million to $300 million (total expenditure)
over 4 to 6 years,32 or $25 million to $50 million annually added to FY2010/2012 supersonics budget levels. Using
the higher value of a 200 percent increase in funding, it is likely that some advanced propulsion goals might also
be moved toward a transition to flight research at 6 to 8 years if these levels could be sustained. The initiation
28 P. Coen and L. Povinelli, NASA, "Fundamental Aeronautics Program: Supersonics Project," briefing to the National Research Council
Committee to Assess NASA's Aeronautics Flight Research Capabilities, June 13, 2011, Washington, D.C.
29 NRC, Decadal Survey of Civil Aeronautics, 2006.
30 NRC, Improving the Efficiency of Engines for Large Nonfighter Aircraft, The National Academies Press, Washington, D.C., 2007.
31 NRC, NASA Aeronautics Research, 2008.
32 P. Coen and L. Povinelli, NASA, "Fundamental Aeronautics Program: Supersonics Project," briefing to the National Research Council
Committee to Assess NASA's Aeronautics Flight Research Capabilities, June 13, 2011, Washington, D.C.
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36 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
of a large-scale flight research program for sonic boom could likely stimulate further industry and government
investment to enter a new era of air transportation33 for time-critical cargo and personnel.34
Finding: NASA's Supersonics project is aligned with technical challenges and research from legacy
programs and previous National Research Council studies. Care has been taken to define a balanced port-
folio over many technical disciplines while maintaining near-term payoff and long-term research needs.
Finding: NASA's Supersonics project finds itself, not unlike in generations past, unable to reach critical
and sustainable funding levels to simultaneously achieve its fundamental mission objectives and enable
the transition to systems-level flight research. The portfolio is broad and diverse but lacks the resources
to be fully effective.
Finding: Supersonics research has been prioritized to solve the largest hurdle not achieved in the high-
speed research program--sonic boom. Its pathfinder approach to small aircraft configurations (i.e., the
size of business-class jets) makes success more probable. There is now demonstrated technology for
alteration and reduction of the sonic boom signature. However, the absence of a stated quantitative limit
for allowable boom initial overpressure has been an impediment to further development of supersonic
aircraft that can fly over land.
Finding: A critical need now exists to integrate low-boom configuration design and human/structural
response work into large-scale flight validation. NASA has yet to identify an existing flight vehicle for
low-boom validation and is therefore unable to accomplish its objectives related to sonic boom. Having
already dedicated significant resources to flight projects, supersonics is positioned for a large-scale inte-
grated flight program, similar to its legacy X-plane programs.
Finding: Much work remains in other challenging areas like variable cycle propulsion, sustainable super-
sonic cruise efficiency, lightweight and high-temperature materials, and aero-propulso-servo-elasticity.
Yet without solving the low-boom overland issue, economic viability for a product vehicle may, as with
the Concorde and the High Speed Civil Transport program, again be unattainable.
Finding: The requirement to perform supersonics flight research will dictate a vehicle of a specific size,
requiring a program nearing $25 million to $50 million annually (depending on duration). On its current
course, NASA cannot enable a program of this size. Program schedule and results are highly dependent
on the level of achievable and sustained investment.
These findings led the committee to its final two findings concerning NASA's supersonics research project:
Finding: If NASA determines that progress in supersonics is a priority, then given the progress in low-
boom technology that has been demonstrated over the past decade and in light of this research challenge
being the principal remaining barrier to routine supersonic operations, NASA together with the FAA could
proceed immediately with an integrated technology experimental aircraft program to validate low-boom
acoustic ground signatures and establish a set of quantitative criteria for the sonic boom footprint over land.
Finding: If NASA determines that progress in supersonics is a priority, and recognizing that engine
technology and propulsion integration remain the next critical investment barrier to progress in this field,
NASA together with DOD could develop a robust technology maturation and flight validation program
33 NRC, Decadal Survey of Civil Aeronautics, 2006.
34 P.Coen, NASA, "Fixing the Sound Barrier, Three Generations of U.S. Research into Sonic Boom Reduction . . . And What It Means to
the Future," briefing for Federal Aviation Administration Public Meeting on Sonic Boom, July 2011.
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FOCUS FOR ARMD--CASE STUDIES 37
with key partners for fielding a product variable cycle engine and the integrated propulsion systems for
supersonic flight.
THE HYPERSONICS RESEARCH PROJECT
NASA more than any other U.S. government agency or private concern has a critical need to maintain strong
leadership capabilities in hypersonic flight research and technology because all NASA spacecraft must success-
fully fly through the hypersonic regime in order to perform their missions. In addition NASA is charged with
expanding the frontiers of aeronautics, and sustained hypersonic flight is a major aeronautical challenge. 35 The
ARMD hypersonics research project has done a good job up to this point in maintaining and advancing its model-
ing and simulation, ground test, and flight research capabilities even though its budget has dropped by a factor of
approximately five over the past 5 years. It has achieved this by leveraging partnerships with other NASA mission
directorates and other U.S. government agencies such as the Air Force. However, under the current and projected
budgets hypersonic project flight research activities are projected to cease within 2 years, and maintenance of the
NASA hypersonic modeling and simulation and ground test competencies is under threat of collapse.
The Hypersonics Project and Flight Research
Today, rocket-powered expendable launch vehicles reach hypersonic speeds in the upper atmosphere while
transporting payloads to orbit, and low-lift/drag, unpowered hypersonic entry vehicles return to Earth from orbit
and other heavenly bodies and transit the atmospheres of other planets to land robotic exploration systems.
Although these are extraordinary accomplishments, hypersonic flight is far from routine, and its potential is not
fully exploited. Since the early 1950s, hypersonics research has experienced numerous boom and bust cycles. The
successful systems developed over this time period (X-15, Apollo, space shuttle, etc.) are products of the boom
cycles, but once these systems were developed, most hypersonics foundational research was terminated, requiring
regeneration of capabilities when the next vehicle development cycle started. There is a unique opportunity at
this point in time to capitalize on a core of hypersonics researchers within NASA, DOD, and industry who were
trained in hypersonics during the boom associated with the National Aerospace Plane (NASP), X-33, X-34, and
the Next Generation Launch Technology (NGLT) reusable launch vehicle programs, hypersonic flight research
programs such as the X-43, X-51, and Hypersonic Technology Vehicle 2 (HTV-2) as well as recent planetary and
Earth-entry programs such as Pathfinder, Stardust, Mars Exploration Rover, and Mars Science Laboratory. Today,
hypersonics research is at the same crossroads that supersonics was 50 years ago--it is possible but not nearly
optimal. A stable, long-term commitment to investment in hypersonics research, including physics-based modeling
and simulation, ground test, and flight research, would allow sufficient understanding of the underlying physics
to improve design methods to the level of certainty required to fully utilize the possibilities of hypersonic flight
and allow it to become routine.
Many advances in design and analysis tools, test techniques, and understanding of the basic physics of hyper-
sonic flow, as well as high-temperature materials and structures, have recently been made because of the work
done under the recent hypersonics programs mentioned above, but much is still left to be learned. Some of these
advancements have been fully or partially verified through application to the design of successfully flown hyper-
sonic systems (planetary probes, for example) and flight experiments (X-43 and X-51). While the ability to design
and build certain hypersonic systems clearly exists, designers often resort to large margins to mitigate uncertainties,
which reduce system capabilities and increase costs. Large uncertainties in aerodynamics, aerothermodynamics,
material properties, structural response, durability, and integrated system performance often kill the use of new
technology, significantly alter mission plans, or result in poor input to risk assessment. In addition to deficiencies
in the understanding of some basic physical phenomena and the resulting predictive uncertainties, substantial
deficiency also exists in the ability to predict the operational cost, safety, and reliability of these systems, much
35 The National Aeronautics and Space Act, Pubic Law No. 111-314, 124 Stat. 3328, December 18, 2010.
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38 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
less optimize a system on such metrics. Developing methods and tools that adequately model fundamental physics
and allow credible optimization for operational factors will allow highly beneficial hypersonic systems to emerge.
To accomplish its goals, flight testing must work in conjunction with ground testing as well as modeling and
simulation as part of a complex process. Flight research is essential for validating the results of ground test experi-
ments and computer models. But flight research poses its own challenges--it is expensive and includes a long
lead time for projects. The NASA Hypersonics project does not have the budget to implement the required flight
research, so NASA relies on partnerships with other NASA mission directorates or non-NASA partners such as
the military services and DARPA. Most often the Hypersonics project provides the partnership with subject matter
experts, cutting-edge physics-based modeling and simulation tools, data analysis, and ground test facilities, but it
generally relies on partners to pay for or share payload and flight vehicle costs. These partnerships are absolutely
critical to the success of the Hypersonics project. NASA often provides key capabilities in modeling and simula-
tion and/or ground test to its partners. Without these partnerships, progress in hypersonics for the United States
would likely grind to a halt.
The air-breathing hypersonic flight portion of the Hypersonics project also requires flight research. This is
because ground testing alone is not able to fully replicate the hypersonic flight environment. Ground testing alone
cannot achieve the same mission duration, flow composition/chemistry, Mach number transience, or in many cases
scale, as a flight test can. While flight testing of air-breathing technology is expensive, it is required to investigate
hypersonic phenomena in realistic conditions. Well-designed/instrumented flight tests can also provide data to
verify computer models and design tools and/or mature the technology readiness levels of key technologies.
Reliance on partners has so far proven to be an effective strategy to obtain hypersonic flight data, but future
success requires the continued support of partner organizations such as other NASA mission directorates and
DOD (see Figure 2.6). Table 2.1 summarizes the current or recently completed hypersonic flight test programs
that the NASA Hypersonics project has been a part of, including an estimate of the total cost of each project and
FIGURE 2.6 X-51 test vehicle under the wing of its B-52 mothership. SOURCE: Courtesy of U.S. Air Force, photo by Chad
Bellay; Photo 090717-F-0289B-163, available at http://www.af.mil/photos/.
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FOCUS FOR ARMD--CASE STUDIES 39
TABLE 2.1 Past and Current Hypersonics Projects
Estimated
(Unofficial) Hypersonics
Cost Project Cost
Flight Purpose Partner ($ million) ($ million)
X-43A Vehicle-integrated scramjet demo None ~300 N/A
X-51A Thermally balanced, vehicle-integrated AFRL/DARPA ~260 10
scramjet demo
HyBoLT Boundary layer research (launch ATK 57 17
failure)
Inflatable Reentry Concept demo None 5 5
Vehicle (IRVE-2)
IRVE-3 Concept demo NASA Chief Technologist 17 4
HIFiRE Flight 1 Boundary layer research AFRL/Australia 9 0.2
HIFiRE Flight 2 Scramjet mode transition, Max Mach AFRL 22 10
(8+)
HIFiRE Flight 5 Boundary layer research AFRL/Australia 6 0.2
Mars Science Laboratory Martian rover NASA Science Mission 2200 N/A
(MSL) Directorate
MSL EDL Martian entry data 30 9
Instrumentation
(MEDLI)
Space shuttle Boundary layer research NASA Shuttle Office 20 1
the contribution made by the NASA Hypersonics project. In all cases, except the X-43A program that occurred
prior to the formation of the current NASA Fundamental Aeronautics Program, the Hypersonics project monetary
contributions have been quite small compared to the total project cost. However, NASA has provided partners
with valuable tools and data and experienced personnel that add value and reduce risk to the projects. NASA in
turn receives important flight data at relatively low cost, and hypersonics research and technology development
for the nation advances.
These partnership arrangements that have been so valuable to the advancement of hypersonics research and
technology advancements between NASA and other agencies are currently under threat of collapse because of
continuing budget cuts to the Hypersonics project. The Hypersonics project, funded by NASA aeronautics, has
gone from a funding level of $82 million per year in FY2006 to ~$25 million per year requested for FY2012 (not
using full cost accounting), while the NASA aeronautics budget was reduced by a much smaller factor. 36,37 It is
beyond the scope of this study to determine why such a substantial decrease in funding priority has been given to
such a vital flight regime that NASA must use to perform its missions and that could enable revolutionary new
aeronautical capabilities such as intercontinental hypersonic flight. Although the funding decrease is not due to
a lack of technical challenges in hypersonics research, some significant technical challenges still remain in air-
breathing hypersonics, which are highlighted in Goal 5 of the current National Aeronautics R&D Plan ("Demon-
strate sustained, controlled, hypersonic flight.").38 The details of Goal 5 are excerpted here in Table 2.2. In addition,
the National Aeronautics Research, Development, Test and Evaluation (RDT&E) Infrastructure Plan highlights
36 NASA, "NASA President's FY2006 Budget Request," available at http://www.nasa.gov/pdf/107486main_FY06_high.pdf, accessed July
27, 2011.
37 NASA, "FY2012 Aeronautics Research Budget Estimate," available at http://www.nasa.gov/pdf/516642main_NASA_FY12_Budget_
Estimates-Aeronautics.pdf, accessed July 27, 2011. The current hypersonics budget figure is from J.L. Pittman, "Hypersonics Project Flight
Research Fundamental Aeronautics Program," briefing to the National Research Council Committee to Assess NASA's Aeronautics Flight
Research Capabilities, June 13, 2011, Washington, D.C.
38 Executive Office of the President of the United States, National Science and Technology Council, Committee on Technology, Aeronautics
Science and Technology Subcommittee, "Biennial Update: National Aeronautics Research and Development Plan," available at http://www.
whitehouse.gov/sites/default/files/microsites/ostp/aero-rdplan-2010.pdf, February 2010.
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40 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
TABLE 2.2 National Aeronautics Plan Hypersonics Research Goal
Goal Near Term (10 years)
Goal 5 Demonstrate sustained, Ground test scramjet Demonstrate scramjets operable to
Demonstrate sustained, controlled flight at Mach 5-7 propulsion systems to 10× Mach 10 on hydrocarbon fuel and
controlled, hypersonic for a duration greater than 5 airflow of today's scramjet to Mach 14 on hydrogen fuel
flight minutes using an expendable technology
airframe and hydrocarbon fuel Increase effective heat capacity
of endothermically cracked
hydrocarbon fuel to extend
vehicle thermal balance point
beyond Mach 8
Ground test hypersonic vehicle Flight test air-breathing vehicle Validate an optimum air vehicle
component technologies, technologies beyond Mach solution that demonstrates an
including high-temperature 7 and durations greater than efficient thermal management
structures, thermal protection 10 minutes for application approach to accommodate the
systems, adaptive guidance to space launch systems and combined thermal loads of
and control, and health possible reconnaissance/strike the aero-thermal environment,
management technologies systems integrated engines and internal
vehicle subsystems
Demonstrate a lightweight,
durable airframe capable of
global reach
SOURCE: Executive Office of the President of the United States, National Science and Technology Council, Committee on Technology, Aero-
nautics Science and Technology Subcommittee, "Biennial Update: National Aeronautics Research and Development Plan," February 2010,
available at http://www.whitehouse.gov/sites/default/files/microsites/ostp/aero-rdplan-2010.pdf, accessed July 27, 2011.
several critical shortfalls in the nation's infrastructure required to meet the National Aeronautics R&D Plan goals,
including the lack of adequate hypersonic test ranges required for hypersonic flight research. 39
The milestones to meet Goal 5 of the National Aeronautics R&D Plan require significant ground and flight
tests as well as substantial work in modeling and simulation and cannot possibly be met by the NASA Hypersonics
project alone. The current budget request and projections for the project make it difficult to see how the project
can develop or sustain partnerships to help meet Goal 5. Table 2.3 illustrates the precipitous drop in support of the
flight research planned by the project because of the current budgets. Flight research funding is expected to drop to
zero within 2 years. This effectively leaves only ground test and modeling and simulation. The low yearly budgets
for NASA hypersonics will also significantly curtail these two remaining efforts and make it difficult to maintain
the "competencies relied upon by other agencies"40 and attract partners for any type of hypersonics research. This
erosion of NASA's hypersonics competencies will also undermine hypersonics research and development efforts
at other NASA mission directorates and other U.S. government agencies. The dire budget situation for hypersonics
is somewhat mitigated by the shift of flight test research responsibility for planetary entry, descent, and landing
technology from the ARMD Hypersonics project to the NASA Office of Chief Technologist, which arguably
can properly shoulder some of the burden for this research.41 But recent failures during flight tests of both the
DARPA HTV-2 and the Air Force X-51 indicate the need for more involvement by NASA experts in the nation's
atmospheric hypersonic flight research efforts, contrary to current NASA Hypersonics project budget projections.
In September 2011, NASA Administrator Charles Bolden spoke at the New Horizons in Aviation Forum
and stated that NASA was currently working with the Air Force on hypersonics research, specifically scramjet
propulsion, trying to extend the operations time of hypersonic vehicles as opposed to simply increasing speeds.
39 Executive Office of the President of the United States, National Science and Technology Council, Committee on Technology, Aeronautics
Science and Technology Subcommittee, "National Aeronautics Research, Development, Test and Evaluation (RDT&E) Infrastructure Plan,"
available at http://www.whitehouse.gov/sites/default/files/microsites/ostp/NSTC-Approved-IPlan-04Jan2011.pdf, January 2011.
40 "FY2012 Aeronautics Research Budget Estimate," available at http://www.nasa.gov/pdf/516642main_NASA_FY12_Budget_Estimates-
Aeronautics.pdf, accessed July 27, 2011.
41 J. Pittman, "Hypersonics Project Flight Research," briefing to the National Research Council Committee to Assess NASA's Aeronautics
Flight Research Capabilities, June 13, 2011, Washington, D.C.
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FOCUS FOR ARMD--CASE STUDIES 41
TABLE 2.3 NASA Hypersonics Project Projected Support of Flight Research
FY2011 FY2012 FY2013 FY2014a FY2015b
Hypersonic Flight Research Funding $4.7 million $2.4 million $0.7 million -- --
Hypersonic Flight Research Workforce 21.0 EP 11.9 EP 3.0 EP -- --
NOTE: EP, equivalent person (civil service employee + contractor); FY, fiscal year.
a No funding or workforce is expected in FY2014.
b No funding or workforce is expected in FY2015.
SOURCE: J. Pittman. "Hypersonics Project Flight Research," briefing to the National Research Council Committee to Assess NASA's Aero-
nautics Flight Research Capabilities, June 13, 2011, Washington, D.C.
As Bolden stated, work was continuing on developing a "practical hypersonic vehicle, with more sophisticated
technology flight experiments planned in the next few years." 42 The committee agrees with the administrator's
comments. Although some hypersonics research is currently under way, in the committee's view it lacks focus.
The committee concluded that in order to focus the currently unfocused project, the NASA Hypersonics project
could establish the specific goal of development and demonstration of the technologies for a hypersonic vehicle
in coordination with other U.S. government agencies. This approach will make better use of available funds and
make progress toward the National Aeronautics R&D Plan mid- and far-term hypersonics goals.
It will be up to NASA and its partners to determine the steps necessary to achieve this goal and the funding
levels required. The goal does not necessarily require hypersonic "cruise vehicles," a specific combined-cycle
propulsion system, travel at velocities higher than Mach 6, or even air-breathing propulsion. It also does not neces-
sarily mean a vehicle capable of carrying humans and could include trans-atmospheric vehicles that spend part of
their flight above the atmosphere. Because these vehicles would still fly hypersonically, they could provide a focus
for the research. While there may not be an immediate commercial application, further research might identify
one. Such a goal would logically start with simpler flight experiments and move on to testbed-type vehicles to
test a variety of technologies, eventually leading to a "flagship"-type vehicle integrating multiple technologies.
The recommended focus on a hypersonic vehicle capable of point-to-point flights from any spot on the globe,
rather than a hypersonic reusable vehicle for space access or a reconnaissance/strike vehicle, is chosen because the
air vehicle and propulsion system technologies are, in general, common to all three missions. With the appropriate
design requirements and constraints, such a vehicle could form the basis for either of the other vehicles, whereas
the converse is not as likely. In addition, this choice is more in line with the other ARMD programs that are aimed
at expanding and opening new commercial aeronautics markets. This focus eliminates the political questions about
NASA aeronautics focusing on DOD missions. (This focus also appears to be in line with recent statements by Jaiwon
Shin, NASA Associate Administrator for Aeronautics, and Marion Blakey, Aerospace Industries Association president,
advocating development of hypersonic vehicles at a September 15, 2011, meeting of the House Aerospace Caucus. 43)
Summary
NASA's Hypersonics project has until now been able to maintain a strong flight research program in the face
of declining budgets through ad hoc cooperation with other U.S. government agencies and NASA mission direc-
torates. However, the current plans show these flight research efforts coming to an end within 2 years because
ofsevere budget reductions. This ad hoc approach to flight research through partnering has also resulted in a rather
unfocused effort, attacking a number of problems depending more on the interest of the partner than on the needs
of a specific long-range mission goal. As several presenters to the committee indicated, contributing to the overall
problem in hypersonics research is the lack of a coordinated plan by the various U.S. government agencies charged
with implementing the hypersonics research goal outlined in the National Aeronautics R&D Plan. Each agency
42 "Remarks for Administrator Bolden, New Horizons in Aviation Forum," September 22, 2011, available at http://www.nasa.gov/
pdf/595570main_11%200922%20Bolden%20Final%20New%20Horizons%20Forum.pdf.
43 J.A. Tirpak, Advocating hypersonics, Daily Report, Airforce-magazine.com, September 16, 2011, available at http://www.airforce-
magazine.com/DRArchive/Pages/2011/September%202011/September%2016%202011/ AdvocatingHypersonics.aspx.
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42 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
has its own plans, and while there is some coordination on specific projects, the current situation leaves little hope
that anything beyond the near-term hypersonics goal (see Table 2.2) will be met. In order to meet the mid-term
and far-term goals, much more significant coordination between the agencies will be required.
Finding: Better understanding of the hypersonic flight regime is critical to both NASA's aeronautics and
its space missions and can enable new military and civil transport capabilities.
Finding: Because of the limitations of hypersonic ground test facilities and computational tools, flight
research is critical to progress in hypersonics research, development, and design.
Finding: The NASA hypersonics budget has fallen from ~$82 million per year in FY2006 to ~$25 million
per year in FY2012, significantly threatening the continued viability of hypersonics research and severely
limiting the possibility of future development efforts.
Finding: If NASA determines that progress in hypersonics research is a priority, then the agency could
reform the hypersonics project with the specific goal of development and demonstration of the technolo-
gies for a Hypersonic vehicle within 25 years to enable point-to-point flights from any point on Earth to
any other point in a few hours. NASA could coordinate development plans with DARPA and other DOD
organizations in order to make the program affordable and enhance its development.
COMMON ISSUES IN THE CASE STUDIES
As the committee noted in Chapter 1, one of the problems facing NASA's aeronautics program is that it is
spread too thin, trying to accomplish numerous objectives with a limited budget. These case studies demonstrate
that even within the major projects that NASA aeronautics is pursuing, agency personnel are addressing multiple
technologies with small-scale efforts. NASA is undertaking multiple, small flight research projects and failing
to focus on a few, achievable goals. In none of these cases is NASA flying a dedicated, system-level (i.e., "flag-
ship") research aircraft or performing visible, or even moderately ambitious, research. At the moment, the agency
has only a single aircraft designated as an "X-plane" (the X-48), and this is a sub-scale vehicle with limited util-
ity. UAVs can offer substantial benefits for flight research, although they are not entirely a substitute for piloted
aircraft (see Box 2.1).
One of the consistent themes for these projects is that they rarely resulted from strategic planning. The indi-
vidual programs were not given guidance to actually consider flight research. Instead, they were given guidance
to conduct research, which was parceled into projects too small to actually lead to flight. In the committee's view,
NASA aeronautics was being forced to do more with less, but decentralized the strategic planning that was neces-
sary to actually achieve that goal.
The committee concluded that these projects could make better progress if NASA Headquarters issued
stronger strategic direction. By doing so, the small-scale, loosely coordinated efforts can either be eliminated or
consolidated in favor of more ambitious and technically challenging efforts, including flagship programs. Major
flagship programs capture the public's imagination and bring multiple centers together to innovate and inspire not
only the next generation of aircraft, but also the newest and brightest minds that will make up the U.S. aviation
industry's workforce in the days ahead.44 The committee was expressly requested to consider the role of technol-
ogy vehicles and/or X-planes as they relate to advancing NASA's mission. Because existing flight assets cannot
achieve sustained supersonic flight or low-boom design goals or demonstrate the systems-level capabilities of a
highly fuel-efficient, low-noise aircraft, this type of programmatic approach is necessary if the agency is going
to make substantive progress. Without budget increases, performing flagship demonstrations may require more
than just changing NASA's focus from many small research efforts to fewer focused ones; it will likely require
substantial cooperative activities with other government agencies, industry, and perhaps other countries.
44 D. McBride, "Dryden Flight Research Center Flight Projects and Perspectives," briefing to National Research Council Committee to
Assess NASA Aeronautics Flight Research Capabilities, April 20, 2011, Edwards, Calif.
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FOCUS FOR ARMD--CASE STUDIES 43
BOX 2.1
UAVs--Their Role in Flight Research, Their
Cost-Effectiveness, and Their Complexity
The impressive advances in unmanned aerial vehicles (UAVs, also referred to as unpiloted aerial
systems, or UASs) lead to the obvious question of whether such aircraft can be used effectively at both
subscale and full-scale for the Environmentally Responsible Aviation (ERA) project and supersonics re-
search (current hypersonics research vehicles do not carry a pilot). NASA is already flying a subscale
UAV, the X-48 for ERA research, and uses other UAVs such as Global Hawk and Ikhana for science and
other missions. UAVs offer many advantages for research and for NASA's science missions, and this is
currently a highly dynamic aspect of military and civilian aeronautics. But although UAVs offer promise for
flight research, they also have limitations.
Small and Geometrically Scaled UAVs
Currently the Department of Defense is the predominant user of UAVs, although many other govern-
ment agencies and civil groups are looking to UAVs to perform tasks currently done by piloted aircraft.
Flight research ultimately will be required for sense-and-avoid and certification of vehicles piloted from the
ground as well as autonomous vehicles. The current process for getting authorization to fly a UAV in the
National Airspace System from the Federal Aviation Administration is quite difficult. The NASA Aeronautics
Research Mission Directorate (ARMD) has recognized this issue and has responded by forming the UAS
in the National Airspace System project within the Integrated Systems Research Program. Another use of
UAVs, which is now starting to be realized, is in fundamental aeronautics research. UAVs offer the ability of
performing high-risk flight test without the need to jeopardize a pilot. They can also greatly reduce the cost
of flight research by reducing the size of the research vehicle when the area of research is not dependent
on vehicle size constraints.
ARMD is currently active in the flight testing of UAVs for rotorcraft, primarily at the NASA Dryden
Flight Research Center and, to a lesser extent, at NASA Langley and NASA Ames. NASA's Science Mis-
sion Directorate also uses UAVs such as the agency's Global Hawk aircraft for science research. Most of
the UAVs that have been or are currently being flight tested by ARMD were designed and built to operate
as geometrically scaled (smaller than full-scale) air vehicles. The software that controls the aerodynamic
surfaces on these UAVs was designed for the specific vehicle in which the software is applied. Appropriate
authorization to flight test these UAVs has been obtained by ARMD.
Lockheed Martin Aeronautics Company in Palmdale ("The Skunk Works") recently conducted funda-
mental research on flutter prediction and suppression using a number of small 10-pound, 10-foot-span
remotely piloted vehicles. Because the cost of the vehicle structure was less than $20,000 and the on-board
electronics could be reused, four of the five original aircraft were flown up to and beyond their structural
limits. The research, including the construction and flight test of the five vehicles, cost approximately one-
quarter of the amount of a flutter wind tunnel model of a similar configuration. Because the wind tunnel
model must be suspended in the tunnel, sources of error are introduced that make the data collected
questionable. These sources of error are not present in a free-flight vehicle. The flight test of these vehicles
was conducted within the small UAV test area at the NASA Dryden Flight Research Center with support
from NASA Dryden personnel.1 (See Figure 2.1.1.)
The initial research using these very small UAVs led to a U.S. Air Force Research Laboratory (AFRL)
contract to build and flight test two additional vehicles. Of the seven vehicles built, two remain in flyable
condition and have been used for additional research. Because these vehicles are small, realistic aircraft
structure and construction techniques were not used in their design (this is typical for small UAVs to reduce
costs, although realistic techniques can be used in some cases if they are required for flight research).
The size of the vehicle and construction techniques used were specially chosen to reduce the cost of the
program; this is sometimes referred to as cost as an independent variable design. With the fundamental
understanding from these flight tests, a larger aircraft is being designed and built by Lockheed Martin under
contract to AFRL that will have realistic aircraft structure and construction methods. This new vehicle is in
the 500-pound class, still too small to carry a pilot but low cost enough to risk at the edge of the envelope.2
continued
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44 RECAPTURING NASA'S AERONAUTICS FLIGHT RESEARCH CAPABILITIES
BOX 2.1 Continued
Lockheed Martin is not unique in its development of UAVs. All of the major aerospace companies, including
Boeing, Northrop Grumman, Aurora Flight Sciences, Aerovironment, General Atomics, and Lockheed Martin,
are developing UAVs across all weight classes. Because the cost of the development of a small UAV can be
relatively low, many smaller companies are entering the UAV market. These companies are developing UAVs
for research, science, and for operational utility.
In this environment of constrained budgets, NASA is considering how it can make greater use of small
UAVs for fundamental research. NASA also has the opportunity to be a resource center to industry and other
government agencies for the safe flight testing of UAVs within the NASA Dryden range.
Full-Scale UAVs
Several challenges must be addressed for the effective use of full-scale UAVs in flight research. Full-scale,
as used in this discussion, refers to a vehicle with energy levels similar to that of a piloted aircraft. This energy
may be a result of mass, airspeed, or a combination of the two. Because of the higher energy of these vehicles
there is a requirement for greater safety oversight. Therefore, the primary challenges are (1) authorization to
use specific airspace, (2) development of control software, and (3) logistical support personnel for remote guid-
ance and control. These three challenges determine the cost profile of full-scale flight research with UAVs and,
hence, the cost advantage of full-scale UAVs versus full-scale piloted aircraft in flight-testing.
The demands for safety in testing full-scale UAVs expand the size of the restricted airspace required over
that of small UAVs. Because of the substantially greater energy levels of full-scale UAVs, elaborate very-high-
reliability flight termination systems are required to ensure that the vehicle does not depart the cleared flight test
range and endanger the general public. Remote, government-owned and -operated restricted ranges are likely
airspaces for full-scale UAV testing and operation. However, these airspaces are also in demand for the flight
test of piloted aircraft. This is the case with NASA Dryden's airspace within the larger Edwards Air Force Base
restricted range, known as the R2515 complex, and the R2505 range operated by the U.S. Navy Western Test
Range and China Lake Naval Air Station. The net systems cost for the use of other remote, government-owned
and -operated airspaces may be comparable to or less than the cost for airspaces such as Dryden or Edwards.
The cost of developing control software is driven by the unique requirement of the control mechanisms of
the full-scale aircraft. For example, control software for a stable, conventional control system is fundamentally
different from that for an unstable fly-by-wire feedback control system. The cost advantages of developing
modular control software are not present if the full-scale fleet of test aircraft is a mix of different types of control
mechanisms. Developing, testing, verifying, and validating software remain a major cost in the development of
aircraft systems. A complete hazard analysis must be performed on both the unpiloted aircraft and the piloted
aircraft to understand if a reduction in the level of redundancy of the UAV may reduce the hardware cost and
software development cost sufficiently to warrant the use of a full-scale UAV. The scale of the vehicle also af-
fects the redundancy levels required and thus the complexity. The larger the vehicle, the greater the amount of
energy in the vehicle, and therefore the greater the hazard.
NASA is currently working to develop processes and procedures to allow greater access of UAVs into the
National Airspace System; however, greater access will most likely be applicable only to vehicles on opera-
tional missions, not vehicles for research flight testing. There is also a considerable amount of work ongoing in
government and industry to develop controls software for UAVs that include autonomous capability on top of
the vehicle stability control. The final hurdle is cost: Will the use of a full-scale UAV be cost-efficient relative to
a piloted aircraft, and what value is assigned to the risk to the pilot of the aircraft as this tradeoff is performed?
1 E. Burnett, C. Atkinson, J. Beranek, B. Sibbitt, B. Holm-Hansen, and L. Nicolai, NDOF Simulation Model for Flight Control
Development with Flight Test Correlation, paper presented at AIAA Modeling and Simulation Technologies Conference, August
2-5, 2010, AIAA 2010-7780, American Institute of Aeronautics and Astronautics, Reston, Va.
2 J. Beranek, L. Nicolai, M. Buonanno, E. Burnett, C. Atkinson, B. Holm-Hansen, and P. Flick, Conceptual Design of a Multi-
utility Aeroelastic Demonstrator, paper presented at 10th AIAA Aviation Technology, Integration, and Operations Conference,
September 13-15, 2010, AIAA-2010-9350, American Institute of Aeronautics and Astronautics, Reston, Va.
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FOCUS FOR ARMD--CASE STUDIES 45
FIGURE 2.1.1Lockheed Martin/Air Force Research Laboratory's Body Freedom Flutter aircraft, built by Lockheed
Martin. This vehicle was designed to test the limits of aircraft structures, including the point of destructive flutter. The
crash is therefore not an accident, but the end result of this test. This kind of flight research cannot be conducted with
piloted vehicles and is cost prohibitive with full-scale R02196
vehicles. SOURCE: Courtesy of Jeff Beranek, Lockheed Martin.
Figure 2-1-1
collage of 5 bitmapped images, rescalable and re-arrangeable
