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NASA NTRS1995

Sensitivity Analysis of Wing Aeroelastic Responses

Design for prevention of aeroelastic instability (that is, the critical speeds leading to aeroelastic instability lie outside the operating range) is an integral part of the wing design process. Availability of the sensitivity derivatives of the various critical speeds with respect to shape parameters of the wing could be very useful to a designer in the initial design phase, when several design changes are made and the shape of the final configuration is not yet frozen. These derivatives are also indispensable for a gradient-based optimization with aeroelastic constraints. In this study, flutter characteristic of a typical section in subsonic compressible flow is examined using a state-space unsteady aerodynamic representation. The sensitivity of the flutter speed of the typical section with respect to its mass and stiffness parameters, namely, mass ratio, static unbalance, radius of gyration, bending frequency, and torsional frequency is calculated analytically. A strip theory formulation is newly developed to represent the unsteady aerodynamic forces on a wing. This is coupled with an equivalent plate structural model and solved as an eigenvalue problem to determine the critical speed of the wing. Flutter analysis of the wing is also carried out using a lifting-surface subsonic kernel function aerodynamic theory (FAST) and an equivalent plate structural model. Finite element modeling of the wing is done using NASTRAN so that wing structures made of spars and ribs and top and bottom wing skins could be analyzed. The free vibration modes of the wing obtained from NASTRAN are input into FAST to compute the flutter speed. An equivalent plate model which incorporates first-order shear deformation theory is then examined so it can be used to model thick wings, where shear deformations are important. The sensitivity of natural frequencies to changes in shape parameters is obtained using ADIFOR. A simple optimization effort is made towards obtaining a minimum weight design of the wing, subject to flutter constraints, lift requirement constraints for level flight and side constraints on the planform parameters of the wing using the IMSL subroutine NCONG, which uses successive quadratic programming.

Issac, Jason Cherian↗

NASA NTRS2000

ISS Payload Operations: The Need for and Benefit of Responsive Planning

International Space Station (ISS) payload operations are controlled through implementation of a payload operations plan. This plan, which represents the defined approach to payload operations in general, can vary in terms of level of definition. The detailed plan provides the specific sequence and timing of each component of a payload's operations. Such an approach to planning was implemented in the Spacelab program. The responsive plan provides a flexible approach to payload operations through generalization. A responsive approach to planning was implemented in the NASA/Mir Phase 1 program, and was identified as a need during the Skylab program. The current approach to ISS payload operations planning and control tends toward detailed planning, rather than responsive planning. The use of detailed plans provides for the efficient use of limited resources onboard the ISS. It restricts flexibility in payload operations, which is inconsistent with the dynamic nature of the ISS science program, and it restricts crew desires for flexibility and autonomy. Also, detailed planning is manpower intensive. The development and implementation of a responsive plan provides for a more dynamic, more accommodating, and less manpower intensive approach to planning. The science program becomes more dynamic and responsive as the plan provides flexibility to accommodate real-time science accomplishments. Communications limitations and the crew desire for flexibility and autonomy in plan implementation are readily accommodated with responsive planning. Manpower efficiencies are accomplished through a reduction in requirements collection and coordination, plan development, and maintenance. Through examples and assessments, this paper identifies the need to transition from detailed to responsive plans for ISS payload operations. Examples depict specific characteristics of the plans. Assessments identify the following: the means by which responsive plans accommodate the dynamic nature of science programs and the crew desire for flexibility; the means by which responsive plans readily accommodate ISS communications constraints; manpower efficiencies to be achieved through use of responsive plans; and the implications of responsive planning relative to resource utilization efficiency.

Nahay, Ed↗

NASA NTRS1996

Efficient Low-Speed Flight in a Wind Field

A new software tool was needed for flight planning of a high altitude, low speed unmanned aerial vehicle which would be flying in winds close to the actual airspeed of the vehicle. An energy modeled NLP (non-linear programming) formulation was used to obtain results for a variety of missions and wind profiles. The energy constraint derived included terms due to the wind field and the performance index was a weighted combination of the amount of fuel used and the final time. With no emphasis on time and with no winds the vehicle was found to fly at maximum lift to drag velocity, V(sub md). When flying in tail winds the velocity was less than V(sub md), while flying in head winds the velocity was higher than V(sub md). A family of solutions was found with varying times of flight and varying fuel amounts consumed which will aid the operator in choosing a flight plan depending on a desired landing time. At certain parts of the flight, the turning terms in the energy constraint equation were found to be significant. An analysis of a simpler vertical plane cruise optimal control problem was used to explain some of the characteristics of the vertical plane NLP results.

Feldman, Michael A.↗

NASA NTRS2007

Access to Space for Technology Validation Missions: A Practical Guide

Space technology experiments and validation missions share a common dilemma with the aerospace industry in general: the high cost of access to space. Whether the experiment is a so-called university cubesat, a university measurement experiment, or a NASA New Millennium Program (NMP) technology validation mission, the access to space option can be scaled appropriately for the particular constraints. A cubesat might fly as one of a number of cubesats that negotiate a flight on an experimental vehicle. A university experiment might do the same. A NASA flight validation might partner with an Air Force experimental mission.

access to space↗

NASA NTRS2012

The WFIRST Interim Design Reference Mission: Capabilities, Constraints, and Open Questions

The Project Office and Science Definition Team for the Wide-Field Infrared Survey Telescope (WFIRST) are in the midst of a pre-Phase A study to establish a Design Reference Mission (DRM). An Interim report was released in June 2011, with a final report due later in 2012. The predicted performance of the Interim DRM Observatory will be described, including optical quality, observing efficiency, and sensitivity for representative observing scenarios. Observing constraints and other limitations on performance will also be presented, with an emphasis on potential Guest Observer programs. Finally, a brief status update will be provided on open trade studies of interest to the scientific community. The final DRM may differ from the Interim DRM presented here. However, the underlying requirements of the scientific programs are not expected to change, hence the capabilities of the IDRM are likely to be maintained even if the implementation changes in significant ways.

Kruk, Jeffrey W.↗

NASA NTRS2010

Investing American Recovery and Reinvestment Act Funds to Advance Capability, Reliability, and Performance in NASA Wind Tunnels

The National Aeronautics and Space Administration's (NASA) Aeronautics Test Program (ATP) is implementing five significant ground-based test facility projects across the nation with funding provided by the American Recovery and Reinvestment Act (ARRA). The projects were selected as the best candidates within the constraints of the ARRA and the strategic plan of ATP. They are a combination of much-needed large scale maintenance, reliability, and system upgrades plus creating new test beds for upcoming research programs. The projects are: 1.) Re-activation of a large compressor to provide a second source for compressed air and vacuum to the Unitary Plan Wind Tunnel at the Ames Research Center (ARC) 2.) Addition of high-altitude ice crystal generation at the Glenn Research Center Propulsion Systems Laboratory Test Cell 3, 3.) New refrigeration system and tunnel heat exchanger for the Icing Research Tunnel at the Glenn Research Center, 4.) Technical viability improvements for the National Transonic Facility at the Langley Research Center, and 5.) Modifications to conduct Environmentally Responsible Aviation and Rotorcraft research at the 14 x 22 Subsonic Tunnel at Langley Research Center. The selection rationale, problem statement, and technical solution summary for each project is given here. The benefits and challenges of the ARRA funded projects are discussed. Indirectly, this opportunity provides the advantages of developing experience in NASA's workforce in large projects and maintaining corporate knowledge in that very unique capability. It is envisioned that improved facilities will attract a larger user base and capabilities that are needed for current and future research efforts will offer revenue growth and future operations stability. Several of the chosen projects will maximize wind tunnel reliability and maintainability by using newer, proven technologies in place of older and obsolete equipment and processes. The projects will meet NASA's goal of integrating more efficient, environmentally safer, and less energy consuming hardware and processes into existing tunnel systems. These include Environmental Protection Agency-approved refrigerants, energy efficient motors, and faster, flexible tunnel data systems.

Sydnor, Goerge H.↗

NASA NTRS1988

Structural Tailoring of Advanced Turboprops (STAT)

This interim report describes the progress achieved in the structural Tailoring of Advanced Turboprops (STAT) program which was developed to perform numerical optimizations on highly swept propfan blades. The optimization procedure seeks to minimize an objective function, defined as either direct operating cost or aeroelastic differences between a blade and its scaled model, by tuning internal and external geometry variables that must satisfy realistic blade design constraints. This report provides a detailed description of the input, optimization procedures, approximate analyses and refined analyses, as well as validation test cases for the STAT program. In addition, conclusions and recommendations are summarized.

Brown, Kenneth W.↗

NASA NTRS2012

Mixed Integer Programming and Heuristic Scheduling for Space Communication Networks

We developed framework and the mathematical formulation for optimizing communication network using mixed integer programming. The design yields a system that is much smaller, in search space size, when compared to the earlier approach. Our constrained network optimization takes into account the dynamics of link performance within the network along with mission and operation requirements. A unique penalty function is introduced to transform the mixed integer programming into the more manageable problem of searching in a continuous space. The constrained optimization problem was proposed to solve in two stages: first using the heuristic Particle Swarming Optimization algorithm to get a good initial starting point, and then feeding the result into the Sequential Quadratic Programming algorithm to achieve the final optimal schedule. We demonstrate the above planning and scheduling methodology with a scenario of 20 spacecraft and 3 ground stations of a Deep Space Network site. Our approach and framework have been simple and flexible so that problems with larger number of constraints and network can be easily adapted and solved.

Mixed Integer Programming↗

NASA NTRS2006

START Analysis for ESAS Capability Needs Prioritization

START is a tool to optimize research and development primarily for NASA missions. It was developed within the Strategic Systems Technology Program Office, a division of the Office of the Chief Technologist at NASA's Jet Propulsion Laboratory. START is capable of quantifying and comparing the risks, costs, and potential returns of technologies that are candidates for funding. START can be enormously helpful both in selecting technologies for development -- within the constraints of budget, schedule, and other resources -- and in monitoring their progress. START's methods are applicable to everything from individual tasks to multiple projects comprising entire programs of investigation. They can address virtually any technology assessment and capability prioritization issue. In this report, START is used to analyze the capability needs using data from NASA's Exploration Systems Architecture Study (ESAS).

optimization↗

NASA NTRS2008

PrismTech Data Distribution Service Java API Evaluation

My internship duties with Launch Control Systems required me to start performance testing of an Object Management Group's (OMG) Data Distribution Service (DDS) specification implementation by PrismTech Limited through the Java programming language application programming interface (API). DDS is a networking middleware for Real-Time Data Distribution. The performance testing involves latency, redundant publishers, extended duration, redundant failover, and read performance. Time constraints allowed only for a data throughput test. I have designed the testing applications to perform all performance tests when time is allowed. Performance evaluation data such as megabits per second and central processing unit (CPU) time consumption were not easily attainable through the Java programming language; they required new methods and classes created in the test applications. Evaluation of this product showed the rate that data can be sent across the network. Performance rates are better on Linux platforms than AIX and Sun platforms. Compared to previous C++ programming language API, the performance evaluation also shows the language differences for the implementation. The Java API of the DDS has a lower throughput performance than the C++ API.

Riggs, Cortney↗

NASA NTRS1993

Workshop on advanced technologies for planetary instruments

NASA's robotic solar system exploration program requires a new generation of science instruments. Design concepts are now judged against stringent mass, power, and size constraints--yet future instruments must be highly capable, reliable, and, in some applications, they must operate for many years. The most important single constraint, however, is cost: new instruments must be developed in a tightly controlled design-to-cost environment. Technical innovation is the key to success and will enable the sophisticated measurements needed for future scientific exploration. As a fundamental benefit, the incorporation of breakthrough technologies in planetary flight hardware will contribute to U.S. industrial competitiveness and will strengthen the U.S. technology base. The Workshop on Advanced Technologies for Planetary Instruments was conceived to address these challenges, to provide an open forum in which the NASA and DoD space communities could become better acquainted at the working level, and to assess future collaborative efforts. Over 300 space scientists and engineers participated in the two-and-a-half-day meeting held April 28-30, 1993, in Fairfax, Virginia. It was jointly sponsored by NASA's Solar System Exploration Division (SSED), within the Office of Space Science (OSS); NASA's Office of Advanced Concepts and Technology (OACT); DoD's Strategic Defense Initiative Organization (SDIO), now called the Ballistic Missile Defense Organization (BMDO); and the Lunar and Planetary Institute (LPI). The meeting included invited oral and contributed poster presentations, working group sessions in four sub-disciplines, and a wrap-up panel discussion. On the first day, the planetary science community described instrumentation needed for missions that may go into development during the next 5 to 10 years. Most of the second day was set aside for the DoD community to inform their counterparts in planetary science about their interests and capabilities, and to describe the BMDO technology base, flight programs, and future directions. The working group sessions and the panel discussion synthesized technical and programmatic issues from all the presentations, with a specific goal of assessing the applicability of BMDO technologies to science instrumentation for planetary exploration.

Appleby, J.↗

NASA NTRS2015

Level-Set Topology Optimization with Aeroelastic Constraints

Level-set topology optimization is used to design a wing considering skin buckling under static aeroelastic trim loading, as well as dynamic aeroelastic stability (flutter). The level-set function is defined over the entire 3D volume of a transport aircraft wing box. Therefore, the approach is not limited by any predefined structure and can explore novel configurations. The Sequential Linear Programming (SLP) level-set method is used to solve the constrained optimization problems. The proposed method is demonstrated using three problems with mass, linear buckling and flutter objective and/or constraints. A constraint aggregation method is used to handle multiple buckling constraints in the wing skins. A continuous flutter constraint formulation is used to handle difficulties arising from discontinuities in the design space caused by a switching of the critical flutter mode.

Dunning, Peter D.↗

NASA NTRS2017

Fixed Base Modal Survey of the MPCV Orion European Service Module Structural Test Article

Recently, the MPCV Orion European Service Module Structural Test Article (E-STA) underwent sine vibration testing using the multi-axis shaker system at NASA GRC Plum Brook Station Mechanical Vibration Facility (MVF). An innovative approach using measured constraint shapes at the interface of E-STA to the MVF allowed high-quality fixed base modal parameters of the E-STA to be extracted, which have been used to update the E-STA finite element model (FEM), without the need for a traditional fixed base modal survey. This innovative approach provided considerable program cost and test schedule savings. This paper documents this modal survey, which includes the modal pretest analysis sensor selection, the fixed base methodology using measured constraint shapes as virtual references and measured frequency response functions, and post-survey comparison between measured and analysis fixed base modal parameters.

modal testing↗

NASA NTRS2007

Low Velocity Airdrop Tests of an X-38 Backup Parachute Design

The NASA Johnson Space Center's X-38 program designed a new backup parachute system to recover the 25,000 lb X-38 prototype for the Crew Return Vehicle spacecraft. Due to weight and cost constraints, the main backup parachute design incorporated rapid and low cost fabrication techniques using off-the-shelf materials. Near the vent, the canopy was constructed of continuous ribbons, to provide more damage tolerance. The remainder of the canopy was a constructed with a continuous ringslot design. After cancellation of the X-38 program, the parachute design was resized, built, and drop tested for Natick Soldiers Center's Low Velocity Air Drop (LVAD) program to deliver cargo loads up to 22,000 lbs from altitudes as low as 500 feet above the ground. Drop tests results showed that the 500-foot LVAD parachute deployment conditions cause severe skirt inversion and inflation problems for large parachutes. The bag strip occurred at a high angle of attack, causing skirt inversion before the parachute could inflate. The addition of a short reefing line prevented the skirt inversion. Using a lower porosity in the vent area, than is normally used in large parachutes, improved inflation. The drop testing demonstrated that the parachute design could be refined to meet the requirements for the 500-foot LVAD mission.

Stein, Jenny M.↗

NASA NTRS2011

A Generalized Framework for Constrained Design Optimization of General Supersonic Configurations Using Adjoint Based Sensitivity Derivatives

The Aeronautics Research Mission Directorate (ARMD) sent out an NASA Research Announcement (NRA) for proposals soliciting research and technical development. The proposed research program was aimed at addressing the desired milestones and outcomes of ROA (ROA-2006) Subtopic A.4.1.1 Advanced Computational Methods. The second milestone, SUP.1.06.02 Robust, validated mesh adaptation and error quantification for near field Computational Fluid Dynamics (CFD), was addressed by the proposed research. Additional research utilizing the direct links to geometry through a CAD interface enabled by this work will allow for geometric constraints to be applied and address the final milestone, SUP2.07.06 Constrained low-drag supersonic aerodynamic design capability. The original product of the proposed research program was an integrated system of tools that can be used for the mesh mechanics required for rapid high fidelity analysis and for design of supersonic cruise vehicles. These Euler and Navier-Stokes volume grid manipulation tools were proposed to efficiently use parallel processing. The mesh adaptation provides a systematic approach for achieving demonstrated levels of accuracy in the solutions. NASA chose to fund only the mesh generation/adaptation portion of the proposal. So this report describes the completion of the proposed tasks for mesh creation, manipulation and adaptation as it pertains to sonic boom prediction of supersonic configurations.

Karman, Steve L., Jr.↗

NASA NTRS1990

A computer program for the design of optimum catalytic monoliths for CO2 lasers

Pulsed CO2 lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers is hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalysts and design methods for implementation of catalysts inside lasers. The performance criteria and constraints involved in the design of catalyst configurations for use in a closed-cycle laser are discussed, and several design studies performed with a computerized design program that was written are presented. Trade-offs between catalyst activity and dimensions, flow channel dimensions, pressure drop, O2 conversion and other variables are discussed.

Guinn, K.↗

NASA NTRS1992

A 6 degree-of-freedom Lorentz force vibration isolator with nonlinear controller

This program demonstrated the technical feasibility of constructing large-stroke magnetic suspensions that can meet the active vibration isolation requirements of Space Station. These requirements include: (1) strokes over 1 cm in all directions, (2) actuator bandwidths over 100 Hz, (3) isolator roll-off frequencies below 10(exp -2) Hertz, and (4) force capability over 1 Newton in all axes. The 100 Hz actuator bandwidth allows the suspension to reject any direct force disturbances that act on the microgravity experiment, for example forces created by cable connections. The low isolator roll-off frequency and large stroke allow the magnetic suspension to isolate the microgravity experiment from Space Station vibrations above the roll-off frequency. The capability to meet these requirements was demonstrated by designing, constructing and testing a six-degree-of-freedom, prototype magnetic suspension system that featured high-performance, Lorentz-force actuators and full multi-input, multi-output control. This prototype suspension is designed to isolate large orbiter locker experiments under typical spacecraft constraints of size, weight, and power. Suspension in the full six-degrees-of-freedom was successfully demonstrated in this program while using a gravity-force unload mechanism to simulate a space environment. The prototype isolator is capable of space-based isolation service with relatively minor modification. The use of advanced, nonlinear control algorithms were investigated on a specially designed single-degree-of-freedom testbed. This low acceleration test facility simulates the Space Station vibration isolation problem in a single horizontal axis with low-friction, air-slide support. This allowed testing at the desired microgravity levels, without the gravity bias effects that are seen in a full six-degrees-of-freedom suspension. Precision components were used to reduce residual accelerations to microgravity levels so that the effects of sensor, actuator, and electronic noise could be evaluated. During the Phase 2 program, this testbed was used to demonstrate the advantages of nonlinear control algorithms to provide increased vibration isolation performance.

Fenn, Ralph↗

NASA NTRS2000

The New Millenium Program: Serving Earth and Space Sciences

NASA has exciting plans for space science and Earth observations during the next decade. A broad range of advanced spacecraft and measurement technologies will be needed to support these plans within the existing budget and schedule constraints. Many of these technology needs are common to both NASA's Office of Earth Science (OES) and Office of Space Sciences (OSS). Even though some breakthrough technologies have been identified to address these needs, project managers have traditionally been reluctant to incorporate them into flight programs because their inherent development risk. To accelerate the infusion of new technologies into its OES and OSS missions, NASA established the New Millennium Program (NMP). This program analyzes the capability needs of these enterprises, identifies candidate technologies to address these needs, incorporates advanced technology suites into validation flights, validates them in the relevant space environment, and then proactively infuses the validated technologies into future missions to enhance their capabilities while reducing their life cycle cost. The NMP employs a cross-enterprise Science Working Group, the NASA Enterprise science and technology roadmaps to define the capabilities needed by future Earth and Space science missions. Additional input from the science community is gathered through open workshops and peer-reviewed NASA Research Announcement (NRAs) for advanced measurement concepts. Technology development inputs from the technology organizations within NASA, other government agencies, federally funded research and development centers (FFRDC's), U.S. industry, and academia are sought to identify breakthrough technologies that might address these needs. This approach significantly extends NASA's technology infrastructure. To complement other flight test programs that develop or validate of individual components, the NMP places its highest priority on system-level validations of technology suites in the relevant space environment. This approach is not needed for all technologies, but it is usually essential to validate advanced system architectures or new measurement concepts. The NMP has recently revised its processes for defining candidate validation flights, and selecting technologies for these flights. The NMP now employs integrated project formulation teams, 'Which include scientists, technologists, and mission planners, to incorporate technology suites into candidate validation flights. These teams develop competing concepts, which can be rigorously evaluated prior to selection for flight. The technology providers for each concept are selected through an open, competitive, process during the project formulation phase. If their concept is selected for flight, they are incorporated into the Project Implementation Team, which develops, integrates, tests, launches, and operates the technology validation flight. Throughout the project implementation phase, the Implementation Team will document and disseminate their validation results to facilitate the infusion of their validated technologies into future OSS and OES science missions. The NMP has successfully launched its first two Deep Space flights for the OSS, and is currently implementing its first two Earth Orbiting flights for the OES. The next OSS and OES flights are currently being defined. Even though these flights are focused on specific Space Science and Earth Science themes, they are designed to validate a range of technologies that could benefit both enterprises, including advanced propulsion, communications, autonomous operations and navigation, multifunctional structures, microelectronics, and advanced instruments. Specific examples of these technologies will be provided in our presentation. The processes developed by the NMP also provide benefits across the Space and Earth Science enterprises. In particular, the extensive, nation-wide technology infrastructure developed by the NMP enhances the access to breakthrough technologies for both enterprises.

Li, Fuk K.↗