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All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Analysis of Control Strategies for Aircraft Flight Upset Recovery

This paper proposes a framework for studying the ability of a control strategy, consisting of a control law and a command law, to recover an aircraft from ight conditions that may extend beyond the normal ight envelope. This study was carried out (i) by evaluating time responses of particular ight upsets, (ii) by evaluating local stability over an equilibrium manifold that included stall, and (iii) by bounding the set in the state space from where the vehicle can be safely own to wings-level ight. These states comprise what will be called the safely recoverable ight envelope (SRFE), which is a set containing the aircraft states from where a control strategy can safely stabilize the aircraft. By safe recovery it is implied that the tran- sient response stays between prescribed limits before converging to a steady horizontal ight. The calculation of the SRFE bounds yields the worst-case initial state corresponding to each control strategy. This information is used to compare alternative recovery strategies, determine their strengths and limitations, and identify the most e ective strategy. In regard to the control law, the authors developed feedback feedforward laws based on the gain scheduling of multivariable controllers. In regard to the command law, which is the mechanism governing the exogenous signals driving the feed- forward component of the controller, we developed laws with a feedback structure that combines local stability and transient response considera- tions. The upset recovery of the Generic Transport Model, a sub-scale twin-engine jet vehicle developed by NASA Langley Research Center, is used as a case study.

Crespo, Luis G.↗
NASA NTRS2012

NASA Human Health and Performance Strategy

In May 2007, what was then the Space Life Sciences Directorate, issued the 2007 Space Life Sciences Strategy for Human Space Exploration. In January 2012, leadership and key directorate personnel were once again brought together to assess the current and expected future environment against its 2007 Strategy and the Agency and Johnson Space Center goals and strategies. The result was a refined vision and mission, and revised goals, objectives, and strategies. One of the first changes implemented was to rename the directorate from Space Life Sciences to Human Health and Performance to better reflect our vision and mission. The most significant change in the directorate from 2007 to the present is the integration of the Human Research Program and Crew Health and Safety activities. Subsequently, the Human Health and Performance Directorate underwent a reorganization to achieve enhanced integration of research and development with operations to better support human spaceflight and International Space Station utilization. These changes also enable a more effective and efficient approach to human system risk mitigation. Since 2007, we have also made significant advances in external collaboration and implementation of new business models within the directorate and the Agency, and through two newly established virtual centers, the NASA Human Health and Performance Center and the Center of Excellence for Collaborative Innovation. Our 2012 Strategy builds upon these successes to address the Agency's increased emphasis on societal relevance and being a leader in research and development and innovative business and communications practices. The 2012 Human Health and Performance Vision is to lead the world in human health and performance innovations for life in space and on Earth. Our mission is to enable optimization of human health and performance throughout all phases of spaceflight. All HH&P functions are ultimately aimed at achieving this mission. Our activities enable mission success, optimizing human health and productivity in space before, during, and after the actual spaceflight experience of our crews, and include support for ground-­‐ based functions. Many of our spaceflight innovations also provide solutions for terrestrial challenges, thereby enhancing life on Earth. Our strategic goals are aimed at leading human exploration and ISS utilization, leading human health and performance internationally, excelling in management and advancement of innovations in health and human system integration, and expanding relevance to life on Earth and creating enduring support and enthusiasm for space exploration.

Davis, Jeffrey R.↗
NASA NTRS2013

Mixed-Strategy Chance Constrained Optimal Control

This paper presents a novel chance constrained optimal control (CCOC) algorithm that chooses a control action probabilistically. A CCOC problem is to find a control input that minimizes the expected cost while guaranteeing that the probability of violating a set of constraints is below a user-specified threshold. We show that a probabilistic control approach, which we refer to as a mixed control strategy, enables us to obtain a cost that is better than what deterministic control strategies can achieve when the CCOC problem is nonconvex. The resulting mixed-strategy CCOC problem turns out to be a convexification of the original nonconvex CCOC problem. Furthermore, we also show that a mixed control strategy only needs to "mix" up to two deterministic control actions in order to achieve optimality. Building upon an iterative dual optimization, the proposed algorithm quickly converges to the optimal mixed control strategy with a user-specified tolerance.

Ono, Masahiro↗
NASA NTRS2014

Fault Management Design Strategies

Development of dependable systems relies on the ability of the system to determine and respond to off-nominal system behavior. Specification and development of these fault management capabilities must be done in a structured and principled manner to improve our understanding of these systems, and to make significant gains in dependability (safety, reliability and availability). Prior work has described a fundamental taxonomy and theory of System Health Management (SHM), and of its operational subset, Fault Management (FM). This conceptual foundation provides a basis to develop framework to design and implement FM design strategies that protect mission objectives and account for system design limitations. Selection of an SHM strategy has implications for the functions required to perform the strategy, and it places constraints on the set of possible design solutions. The framework developed in this paper provides a rigorous and principled approach to classifying SHM strategies, as well as methods for determination and implementation of SHM strategies. An illustrative example is used to describe the application of the framework and the resulting benefits to system and FM design and dependability.

systems engineering↗
NASA NTRS2016

A COTS-Style Acquisition Strategy for Human Exploration Beyond LEO

The Evolvable Mars Campaign presents a long term strategy for NASA's Journey to Mars within a capability driven framework. By comparing each element to a set of criteria, this paper reviews the potential of acquiring those capabilities using a strategy similar to the Commercial Orbital Transportation Services program. The paper presents the criteria, assesses the elements against those criteria, and then discusses the suitability of each element to being developed using this acquisition strategy. Throughout the campaign, certain capabilities are well suited to being developed in this manner while others are not. This assessment is a snapshot in time, and should be revisited as the campaign and/or commercial capabilities change. This paper will explore each of these elements in the campaign and discuss how the COTS development andacquisition strategy could or could not be applied to those elements. This assessment will be based on theservices or functionality required in the campaign, and will use the best practices discussed above to create acase for or against a COTS-style acquisition strategy for each given element.

Arney, Dale↗
NASA NTRS2011

Navigation Strategies for Primitive Solar System Body Rendezvous and Proximity Operations

A wealth of scientific knowledge regarding the composition and evolution of the solar system can be gained through reconnaissance missions to primitive solar system bodies. This paper presents analysis of a baseline navigation strategy designed to address the unique challenges of primitive body navigation. Linear covariance and Monte Carlo error analysis was performed on a baseline navigation strategy using simulated data from a· design reference mission (DRM). The objective of the DRM is to approach, rendezvous, and maintain a stable orbit about the near-Earth asteroid 4660 Nereus. The outlined navigation strategy and resulting analyses, however, are not necessarily limited to this specific target asteroid as they may he applicable to a diverse range of mission scenarios. The baseline navigation strategy included simulated data from Deep Space Network (DSN) radiometric tracking and optical image processing (OpNav). Results from the linear covariance and Monte Carlo analyses suggest the DRM navigation strategy is sufficient to approach and perform proximity operations in the vicinity of the target asteroid with meter-level accuracy.

Getzandanner, Kenneth M.↗
NASA NTRS2021

NASA Strategy for Technology Development

The National Aeronautics and Space Administration (NASA) Office of the Chief Technologist (OCT) provides the strategy and leadership that integrates NASA’s technology development and open innovation activities to advance American aeronautic, science, and space exploration objectives. OCT performs an agency-level technology coordination role, coordinating with the NASA Mission Directorates, field centers, and other government agencies to align the agency’s technology investments to meet mission requirements while filling gaps, anticipating future needs, and minimizing duplication of effort. OCT provides the strategy and coordination that guide NASA's technology and innovation activities through Strategic Technology Integration, Digital Transformation, the Science and Technology Partnership Forum, and Innovation. The Strategic Technology Integration team informs policy, requirements, and strategy for NASA’s technology development activities in support of the Chief Technologist by coordinating with NASA mission directorates, other government agencies, and external organizations. As part of these efforts, OCT develops the NASA Technology Taxonomy and the NASA Strategic Space Technology Investment Plan. Digital Transformation will increasingly change the way NASA operates and will enable the agency’s missions to be completed more efficiently and effectively. It will allow current and future employees to use their talents in more innovative ways. The Science and Technology Partnership Forum is a strategic forum, with principal partners at the United States Space Force and the National Reconnaissance Office. It was established to identify synergistic efforts and technologies in order to leverage those synergies and influence portfolios across space agencies in areas deemed pervasive and ready for collaboration. NASA's Innovation efforts are designed to transform diverse ideas into value and are guided by a framework that is focused on the agency’s people, processes, partnerships and portfolio. The innovation framework is used to connect the workforce to tools, strategies and activities to increase the pace of innovation. OCT translates National space policies into NASA technology strategies and coordination across the agency and interagency communities to guide NASA's technology and innovation activities to achieve capabilities needed for future missions. This chapter provides insight into the value of analyzing future states to inform technology developments to plot the strategic direction of NASA’s space technology program.

Erica Rodgers↗
NASA NTRS1972

Maneuver strategies for multi-planet missions.

This paper compares a number of maneuver strategies for five multi-planet missions, including the single planet strategy of nulling the aim-plane and flight-time errors at the immediate target. Significant differences were found among the strategies in the amount of corrective propellant required and the residual miss at each target. In general, nulling or minimization of the residual miss at the next target was found to be superior to that at the immediate target, when error growth is not nulled early. The best strategy corrects aim-plane and flight-time errors at the next target.

Dwivedi, N. P.↗
NASA NTRS1977

Outer planets exploration - A mission strategy for the 1980's

This paper presents a mission strategy for exploring the outer planets in the 1980s. The strategy is based on the anticipated findings of the 1977 Voyager Jupiter/Saturn Mission, and the 1982 Jupiter Orbiter Probe (JOP) Mission, recently approved as a new project start, beginning in October 1977. The JOP Mission then becomes a principal element in the strategy presented here. Characteristics (launch energy, trajectory parameters, etc.) of other mission opportunities to the outer planets in the 1980s are developed and presented. The need for and benefits from advanced propulsion systems, which can enable the more difficult missions to the outer planets, also are cited. The overall mission strategy, including a description of the options, is evolved in consideration of scientific rationale and return, and technical and programmatic coupling factors.

Moore, J. W.↗
NASA NTRS1986

Voyager 2 Uranus targeting strategy

One of the major challenges involved in the Voyager 2 Uranus flyby is to deliver the spacecraft to an appropriate aimpoint at the optimum time, so as to maximize the science return of the mission, while yet keeping propellant expenditure low. An unusual targeting strategy has been devised to satisfy these requirements. Its complexity arises from the great distance of the planet Uranus and the limited performance capabilities of Voyager. This selected strategy is developed in relation to a set of candidate strategies, mission requirements and shifting science objectives. The analysis of these candidates is conducted via a Monte Carlo simulation, the results of which yield data for the comparative evaluation and eventual and selection of the actual targeting strategy to be employed.

Cesarone, R. J.↗
NASA NTRS1988

A computational strategy for making complicated structural problems simple

An effective computational strategy is presented for the analysis of large and complex structures. The strategy is based on generating the response of the complex structure using large perturbations from that of a lower-order (simpler) model associated with a simpler structure (or a simpler mathematical/discrete model of the original structure). The three key elements of the strategy are: (a) mixed (or primitive variable) formulation with the fundamental unknowns consisting of generalized displacements and stress parameters; (2) operator splitting, or a reduction method to relate the arrays and degrees of freedom of the original complex structure ot those of the simpler system; and (3) efficient iterative process for the generation of the response of the complex structure starting from that of the simpler system. The effectiveness of the proposed strategy is demonstrated by means of two numerical examples.

Noor, Ahmed K.↗
NASA NTRS1988

Strategies for adding adaptive learning mechanisms to rule-based diagnostic expert systems

Rule-based diagnostic expert systems can be used to perform many of the diagnostic chores necessary in today's complex space systems. These expert systems typically take a set of symptoms as input and produce diagnostic advice as output. The primary objective of such expert systems is to provide accurate and comprehensive advice which can be used to help return the space system in question to nominal operation. The development and maintenance of diagnostic expert systems is time and labor intensive since the services of both knowledge engineer(s) and domain expert(s) are required. The use of adaptive learning mechanisms to increment evaluate and refine rules promises to reduce both time and labor costs associated with such systems. This paper describes the basic adaptive learning mechanisms of strengthening, weakening, generalization, discrimination, and discovery. Next basic strategies are discussed for adding these learning mechanisms to rule-based diagnostic expert systems. These strategies support the incremental evaluation and refinement of rules in the knowledge base by comparing the set of advice given by the expert system (A) with the correct diagnosis (C). Techniques are described for selecting those rules in the in the knowledge base which should participate in adaptive learning. The strategies presented may be used with a wide variety of learning algorithms. Further, these strategies are applicable to a large number of rule-based diagnostic expert systems. They may be used to provide either immediate or deferred updating of the knowledge base.

Stclair, D. C.↗
NASA NTRS1990

Relative merits of reactive and forward-look detection for wind-shear encounters during landing approach for various microburst escape strategies

The goal was to quantify the benefits of airborne forward-look windshear detection and to develop and test a candidate set of strategies for recovery from inadvertent microburst encounters during the landing approach, given the utilization of both reactive-only and forward-look windshear detection. Candidate strategies were developed and evaluated using a non-piloted simulation consisting of a simple point-mass performance model of a transport-category airplane flying through an analytical microburst model. The results indicate that the factor which most strongly effects a microburst recovery is the time at which the recovery is initiated. Forward-look alerts given 10 seconds prior to microburst entry permitted recoveries to be made with negligible altitude loss. The results also show that no single microburst scenario can be used to evaluate the relative merits of various recovery strategies. The type of alert used to initiate the recovery (reactive or forward-look) and the altitude of the microburst encounter had an effect on the type of recovery strategy that performed best. These factors may have serious implications for the design and certification of windshear systems.

Hinton, David A.↗
NASA NTRS1989

Technology and task parameters relating to the effectiveness of the bracing strategy

The bracing strategy has been proposed in various forms as a way to improve robot performance. One version of the strategy employs independent stages of motion. The first stage, referred to as the large or bracing arm, carries the second stage of motion. After the first stage has completed its motion it is braced to provide a more rigid base of motion with a more accurate relationship to the parts to be manipulated. The hypothesis is that more rapid completion of certain tasks is possible with lighter arms using the bracing strategy. While it is easy to make conceptual arguments why this should be so, it is less easy to specify even approximately when this will be true for some reasonably generic situation. There is no relevant experience base with bracing arms to be compared to non-bracing arms. Furthermore, if one were interested in obtaining such practical experience, there would be no methodical guidance on the selection of an interesting case, one in which the unproven approach, bracing, can show its superiority. If one such case exists, only the extent of applicability of the new approach is in question. One set of interesting cases is likely to be applications in which a large workspace must be covered, but where a series of small accurate moves will remain within a smaller region of the total workspace. A prototype application with these characteristics is set up and a skeleton design of arms using the competing strategies are compared.

Book, Wayne J.↗
NASA NTRS1990

Asteroid mission departure strategies from a precessing Space Station orbit

In using the Space Station as a point of departure for interplanetary missions, the precission of its orbit complicates the process of determining the available departure period. The constantly changing ascending node of the Space Station orbit defines the departure geometry. Severe Delta V penalties occur if favorable departure opportunities are missed and a plane change is required at departure. This paper compares two strategies to reduce the cost of the plane change maneuver, and increase the available departure opportunities. A 3-impulse injection strategy is compared to a deep space plane change for two asteroid rendezvous missions. Results indicate that the deep space plane change strategy has lower propellant mass requirements for the two missions studied. The difference in propellant requirements for the two strategies is a function of the departure geometry.

Sharma, Jayant↗
NASA NTRS1990

MALEO: Modular Assembly in Low Earth Orbit. A strategy for an IOC lunar base

Modular Assembly in Low Earth Orbit (MALEO) is a new strategy for building an initial operational capability lunar habitation base. In this strategy, the modular lunar base components are brought up to Low Earth Orbit by the Space Transportation System/Heavy Lift Launch Vehicle fleet, and assembled there to form a complete lunar base. Modular propulsion systems are then used to transport the MALEO lunar base, complete and intact, all the way to the moon. Upon touchdown on the lunar surface, the MALEO lunar habitation base is operational. An exo-skeletal truss superstructure is employed in order to uniformly absorb and distribute the rocket engine thrusting forces incurred by the MALEO lunar base during translunar injection, lunar orbit insertion, and lunar surface touchdown. The components, configuration, and structural aspects of the MALEO lunar base are discussed. Advantages of the MALEO strategy over conventional strategies are pointed out. It is concluded that MALEO holds promise for lunar base deployment.

Thangavelu, M.↗
NASA NTRS1991

An evaluation of the total quality management implementation strategy for the advanced solid rocket motor project at NASA's Marshall Space Flight Center

An evaluation of the NASA's Marshall Space Flight Center (MSFC) strategy to implement Total Quality Management (TQM) in the Advanced Solid Rocket Motor (ASRM) Project is presented. The evaluation of the implementation strategy reflected the Civil Service personnel perspective at the project level. The external and internal environments at MSFC were analyzed for their effects on the ASRM TQM strategy. Organizational forms, cultures, management systems, problem solving techniques, and training were assessed for their influence on the implementation strategy. The influence of ASRM's effort was assessed relative to its impact on mature projects as well as future projects at MSFC.

Schramm, Harry F.↗
NASA NTRS1990

Connectivity strategies for higher-order neural networks applied to pattern recognition

Different strategies for non-fully connected HONNs (higher-order neural networks) are discussed, showing that by using such strategies an input field of 128 x 128 pixels can be attained while still achieving in-plane rotation and translation-invariant recognition. These techniques allow HONNs to be used with the larger input scenes required for practical pattern-recognition applications. The number of interconnections that must be stored has been reduced by a factor of approximately 200,000 in a T/C case and about 2000 in a Space Shuttle/F-18 case by using regional connectivity. Third-order networks have been simulated using several connection strategies. The method found to work best is regional connectivity. The main advantages of this strategy are the following: (1) it considers features of various scales within the image and thus gets a better sample of what the image looks like; (2) it is invariant to shape-preserving geometric transformations, such as translation and rotation; (3) the connections are predetermined so that no extra computations are necessary during run time; and (4) it does not require any extra storage for recording which connections were formed.

Spirkovska, Lilly↗