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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

On the design of nonlinear controllers for flight control systems

A method of approximate input-output linearization by dynamic state feedback is presented, with the flight control of VTOL aircraft used as an example. It is shown that the closed loop system has a graceful degradation of performance as the moment-to-force coupling is increased. It is also demonstrated that the approach proposed here leads to an asymptotically stable closed loop system with guaranteed bounds on the tracking error caused by the nonminumum phase character of the system.

Hauser, John↗
NASA NTRS1992

Beyond the cockpit: The visual world as a flight instrument

The use of cockpit instruments to guide flight control is not always an option (e.g., low level rotorcraft flight). Under such circumstances the pilot must use out-the-window information for control and navigation. Thus it is important to determine the basis of visually guided flight for several reasons: (1) to guide the design and construction of the visual displays used in training simulators; (2) to allow modeling of visibility restrictions brought about by weather, cockpit constraints, or distortions introduced by sensor systems; and (3) to aid in the development of displays that augment the cockpit window scene and are compatible with the pilot's visual extraction of information from the visual scene. The authors are actively pursuing these questions. We have on-going studies using both low-cost, lower fidelity flight simulators, and state-of-the-art helicopter simulation research facilities. Research results will be presented on: (1) the important visual scene information used in altitude and speed control; (2) the utility of monocular, stereo, and hyperstereo cues for the control of flight; (3) perceptual effects due to the differences between normal unaided daylight vision, and that made available by various night vision devices (e.g., light intensifying goggles and infra-red sensor displays); and (4) the utility of advanced contact displays in which instrument information is made part of the visual scene, as on a 'scene linked' head-up display (e.g., displaying altimeter information on a virtual billboard located on the ground).

Johnson, W. W.↗
NASA NTRS1990

Risk and value analysis of SETI

This paper attempts to apply a traditional risk and value analysis to the Search for Extraterrestrial Intelligence--SETI. In view of the difficulties of assessing the probability of success, a comparison is made between SETI and a previous search for extraterrestrial life, the biological component of Project Viking. Our application of simple Utility Theory, given some reasonable assumptions, suggests that SETI is at least as worthwhile as the biological experiment on Viking.

NASA Program Exobiology↗
NASA NTRS2011

ELaNa - Educational Launch of Nanosatellite Enhance Education Through Space Flight

One of NASA's missions is to attract and retain students in the science, technology, engineering and mathematics (STEM) disciplines. Creating missions or programs to achieve this important goal helps strengthen NASA and the nation's future work force as well as engage and inspire Americans and the rest of the world. During the last three years, in an attempt to revitalize educational space flight, NASA generated a new and exciting initiative. This initiative, NASA's Educational Launch of Nanosatellite (ELaNa), is now fully operational and producing exciting results. Nanosatellites are small secondary satellite payloads called CubeSats. One of the challenges that the CubeSat community faced over the past few years was the lack of rides into space. Students were building CubeSats but they just sat on the shelf until an opportunity arose. In some cases, these opportunities never developed and so the CubeSat never made it to orbit. The ELaNa initiative is changing this by providing sustainable launch opportunities for educational CubeSats. Across America, these CubeSats are currently being built by students in high school all the way through graduate school. Now students know that if they build their CubeSat, submit their proposal and are selected for an ELaNa mission, they will have the opportunity to fly their satellite. ELaNa missions are the first educational cargo to be carried on expendable launch vehicles (ELY) for NASA's Launch Services Program (LSP). The first ELaNa CubeSats were slated to begin their journey to orbit in February 2011 with NASA's Glory mission. Due to an anomaly with the launch vehicle, ELaNa II and Glory failed to reach orbit. This first ELaNa mission was comprised of three IU CubeSats built by students at Montana State University (Explorer Prime Flight 1), the University of Colorado (HERMES), and Kentucky Space, a consortium of state universities (KySat). The interface between the launch vehicle and the CubeSat, the Poly-Picosatellite Orbital Deployer (P-POD), was developed and built by students at California Polytechnic State University (Cal Poly). Integrating a P-POD on a NASA ELV was not an easy task. The creation of new processes and requirements as well as numerous reviews and approvals were necessary within NASA before the first ELaNa mission could be attached to a NASA launch vehicle (LV). One of the key objectives placed on an ELaNa mission is that the CubeSat and PPOD does not increase the baseline risk to the primary mission and launch vehicle. The ELaNa missions achieve this objective by placing a rigorous management and engineering process on both the LV and CubeSat teams. So, what is the future of ELaNa? Currently there are 16 P-POD missions manifested across four launch vehicles to support educational CubeSats selected under the NASA CubeSat Initiative. From this initiative, a rigorous selection process produced 22-student CubeSat missions that are scheduled to fly before the end of 2012. For the initiative to continue, organizations need to submit proposals to the annual CubeSat initiative call so they have the opportunity to be manifested and launched.

Skrobot, Garrett Lee↗
NASA NTRS1985

Fluid and electrolyte control in simulated and actual spaceflight

Effects of microgravity on body fluid distribution and electrolyte and hormonal levels of astronauts have been studied since the early manned space missions. Bedrested subjects have been used as controls to separate effects of microgravity from those of hypokinesia. These investigations have led to documentation of the physiological effects of spaceflight and to a unified theory of response to microgravity. During flight, crewmembers have decreased thirst and a net loss of body water, sodium, and potassium. These changes seem to be initiated by passive transfer of extracellular fluid resulting in increased central venous pressure (CVP), to which the homeostatic mechanisms respond. A new equilibrium state is maintained during flight; it does not change in response to negative calcium and nitrogen balances during flight. On reexposure to gravity, profound water and salt retention occurs to replete extracellular fluid. Attempts to avoid cardiac deconditioning by repleting water and salt before leaving microgravity have somewhat ameliorated postural hypotension but have had little effect on CVP, cardiac chamber size or electrolyte dynamics.

Leach, C. S.↗
NASA NTRS1981

A decoupled control system for improved flight performance in wind shear

A fixed-base simulation study has been made to compare the approach and landing performance of a decoupled longitudinal control system and the velocity-vector control-wheel steering (VCWS) system that currently exists on the NASA Terminal Configured Vehicle (TCV). The decoupled control system employed constant prefilter and feedback gains to provide steady-state decoupling of flight-path angle, pitch angle, and forward velocity using symmetric spoilers, throttle, and elevator as active control elements. In severe wind shear, of the Kennedy-type, the decoupled control system improved both approach performance and touchdown performance even when the spoiler deflection was limited to 16 deg. On a 10-point rating scale, three research pilots rated the approach and landing task with decoupled controls as much as 3 to 4 increments better than the use of the VCWS system in severe winds

Miller, G. K., Jr.↗
NASA NTRS1974

Fixed-base simulation study of decoupled controls during approach and landing of a STOL transport airplane

A fixed-base visual simulation study has been conducted to evaluate the use of decoupled controls as a means for reducing pilot workload during approach and landing of an externally blown jet-flap short take-off and landing (STOL) transport. All six rigid-body degrees of freedom were employed with the aerodynamic characteristics based on wind-tunnel data. The primary piloting task was to use a flight director to capture and maintain a two-segment glide slope, with a closed-circuit television display of a STOL airport used during simulations of the flare and landing. The decoupled longitudinal controls used constant prefilter and feedback gains to provide steady-state decoupling of flight-path angle, pitch angle, and forward velocity. The pilots were enthusiastic about the decoupled longitudinal controls but believed the decoupled concept offered no significant advantage over conventional controls in the lateral mode.

Miller, G. K., Jr.↗
NASA NTRS2006

New Air-Launched Small Missile (ALSM) Flight Testbed for Hypersonic Systems

A new testbed for hypersonic flight research is proposed. Known as the Phoenix air-launched small missile (ALSM) flight testbed, it was conceived to help address the lack of quick-turnaround and cost-effective hypersonic flight research capabilities. The Phoenix ALSM testbed results from utilization of two unique and very capable flight assets: the United States Navy Phoenix AIM-54 long-range, guided air-to-air missile and the NASA Dryden F-15B testbed airplane. The U.S. Navy retirement of the Phoenix AIM-54 missiles from fleet operation has presented an excellent opportunity for converting this valuable flight asset into a new flight testbed. This cost-effective new platform will fill an existing gap in the test and evaluation of current and future hypersonic systems for flight Mach numbers ranging from 3 to 5. Preliminary studies indicate that the Phoenix missile is a highly capable platform. When launched from a high-performance airplane, the guided Phoenix missile can boost research payloads to low hypersonic Mach numbers, enabling flight research in the supersonic-to-hypersonic transitional flight envelope. Experience gained from developing and operating the Phoenix ALSM testbed will be valuable for the development and operation of future higher-performance ALSM flight testbeds as well as responsive microsatellite small-payload air-launched space boosters.

Bui, Trong T.↗
NASA NTRS1996

Effects of microgravity on osteoblast growth activation

Space flight is an environmental condition where astronauts can lose up to 19% of weight-bearing bone during long duration missions. We used the MC3T3-E1 osteoblast to investigate bone cell growth in microgravity (10(-6) to 10(-9)g). Osteoblasts were launched on the STS-56 shuttle flight in a quiescent state with 0.5% fetal calf serum (FCS) medium and growth activation was initiated by adding fresh medium with 10% FCS during microgravity exposure. Four days after serum activation, the cells were fixed before return to normal Earth gravity. Ground controls were treated in parallel with the flight samples in identical equipment. On landing, cell number, cell cytoskeleton, glucose utilization, and prostaglandin synthesis in flight (n = 4) and ground controls (n = 4) were examined. The flown osteoblasts grew slowly in microgravity with total cell number significantly reduced (55 +/- 6 vs 141 +/- 8 cells per microscopic field). The cytoskeleton of the flight osteoblasts had a reduced number of stress fibers and a unique abnormal morphology. Nuclei in the ground controls were large and round with punctate Hoechst staining of the DNA nucleosomes. The flight nuclei were 30% smaller than the controls (P < 0.0001) and oblong in shape, with fewer punctate areas. Due to their reduced numbers, the cells activated in microgravity used significantly less glucose than ground controls (80.2 +/- 0.7 vs 50.3 +/- 3.7 mg of glucose/dl remaining in the medium) and had reduced prostaglandin E2 (PGE2) synthesis when compared to controls (57.3 +/- 17 vs 138.3 +/- 41 pmol/ml). Cell viability was normal since, on a per-cell basis, glucose use and prostaglandin synthesis were comparable for flight and ground samples. Taken together, these data suggest that growth activation in microgravity results in reduced growth, causing reduced glucose utilization and reduced prostaglandin synthesis, with significantly altered actin cytoskeleton in osteoblasts.

NASA Program Flight↗
NASA NTRS1975

Moving-base visual simulation study of decoupled controls during approach and landing of a STOL transport aircraft

The simulation employed all six rigid-body degrees of freedom and incorporated aerodynamic characteristics based on wind-tunnel data. The flight instrumentation included a localizer and a flight director which was used to capture and to maintain a two-segment glide slope. A closed-circuit television display of a STOLport provided visual cues during simulations of the approach and landing. The decoupled longitudinal controls used constant prefilter and feedback gains to provide steady-state decoupling of flight-path angle, pitch angle, and forward velocity. The pilots were enthusiastic about the decoupled longitudinal controls and believed that the simulator motion was an aid in evaluating the decoupled controls, although a minimum turbulence level with root-mean-square gust intensity of 0.3 m/sec (1 ft/sec) was required to mask undesirable characteristics of the moving-base simulator.

Miller, G. K., Jr.↗
NASA NTRS2018

Incremental States for Precise On-Orbit Relative Knowledge in Formation Flight

High precision and close proximity formation flight is an enabling technology for future space missions and requires an on-board relative navigation capability that is accurate to the mm-level and robust to formation parameters. Common estimation techniques linearize the entire formation about one spacecraft’s position, resulting in degraded accuracy due to linearization errors when separation distances become large. Additionally, methods which decouple absolute and relative state estimates usually require ad-hoc methods to incorporate the estimates together. This work discusses an alternative ”incremental” formulation of the relative navigation problem which is in variant to formation size, robust to coupling between absolute and relative dynamics, and can undergo similarity transformations to smoothly incorporate either absolute or relative information without numerical issues. A specific example of this architecture is presented in the context of formation navigation using Carrier-Differential Global Positioning System measurements, and is compared to a traditional leader-linearized filter. In the presence of accurate measurements, the incremental architecture is shown to reduce linearization errors and mean estimate errors by up to three orders of magnitude without the incorporation of new sensor information.

Seubert, Carl↗
NASA NTRS2021

A Machine Learning Approach to Predict Aircraft Landing Times using Mediated Predictions from Existing Systems

We developed a novel approach for predicting the landing time of airborne flights in real-time operations. The first step predicts a landing time by using mediation rules to select from among physics-based predictions (relying on the expected flight trajectory) already available in real time in the Federal Aviation Administration System Wide Information Management system data feeds. The second step uses a machine learning model built upon the mediated predictions. The model is trained to predict the error in the mediated prediction, using features describing the current state of an airborne flight. These features are calculated in real time from a relatively small number of data elements that are readily available for airborne flights. Initial results based on five months of data at six large airports demonstrate that incorporating a machine learning model on top of the mediated physics-based prediction can lead to substantial additional improvements in prediction quality.

Machine learning↗
NASA NTRS2021

A Machine Learning Approach to Predict Aircraft Landing Times using Mediated Predictions from Existing Systems

We developed a novel approach for predicting the landing time of airborne flights in real-time operations. The first step predicts a landing time by using mediation rules to select from among physics-based predictions (relying on the expected flight trajectory) already available in real time in the Federal Aviation Administration System Wide Information Management system data feeds. The second step uses a machine learning model built upon the mediated predictions. The model is trained to predict the error in the mediated prediction, using features describing the current state of an airborne flight. These features are calculated in real time from a relatively small number of data elements that are readily available for airborne flights. Initial results based on five months of data at six large airports demonstrate that incorporating a machine learning model on top of the mediated physics-based prediction can lead to substantial additional improvements in prediction quality.

Machine learning↗
NASA NTRS1979

NASA/Princeton digital avionics flight test facility

This paper describes a general-aviation digital avionics flight-test facility being jointly developed by the Flight Dynamics Laboratory of Princeton University and NASA/Langley Research Center. This facility consists of the Princeton avionics research aircraft (ARA) and NASA/Langley's digital avionics research (DARE) system. The ARA is a fully instrumented five-degree-of-freedom fly-by-wire aircraft. The DARE system contains a state-of-the-art flight computer system and receiving equipment that permits use of the NASA/Wallops Flight Center's position-tracking ground-based display-generation and ground-to-air digital-data-link equipment. The DARE/ARA system will be used for flight evaluation of advanced control, guidance, and display concepts developed as part of NASA/Langley Research Center's general aviation terminal area operations program.

Downing, D. R.↗
NASA NTRS1982

LANDSAT Digital Data Base Preparation for the Pennsylvania Defoliation Application Pilot Test

A LANDSAT digital mosaic data base for the State of Pennsylvania was prepared for use in the development of an automated system to annually estimate the extent and severity of Gypsy Moth defoliation of hardward forests. The techniques for detecting the defoliation and development of a geographic information system (GIS) to assess damage is being developed jointly by NASA/Goddard Space Flight Center and Pennsylvania State University using the JPL prepared mosaic base. The JPL processing involved the use of ground control points from the Master Data Processor for planimetric control, resampling of the LANDSAT data to 57 x 57 meter pixels, realignment to north, and reprojection to the Universal Transverse Mercator (UTM) projection in UTM zones 17 and 18. The completed mosaic for each UTM zone was subdivided into 1 degree of latitude by 2 degrees of longitude quadrangles for easy data handling. Consideration is given to the issues of mapping standards, sensor and spacecraft platform characteristics, and their implication to geographic information systems operation. Methods for obtaining measures of accuracy for LANDSAT mosaics are reviewed.

Mcleod, R. G.↗
NASA NTRS2014

Assessing V and V Processes for Automation with Respect to Vulnerabilities to Loss of Airplane State Awareness

Automation has contributed substantially to the sustained improvement of aviation safety by minimizing the physical workload of the pilot and increasing operational efficiency. Nevertheless, in complex and highly automated aircraft, automation also has unintended consequences. As systems become more complex and the authority and autonomy (A&A) of the automation increases, human operators become relegated to the role of a system supervisor or administrator, a passive role not conducive to maintaining engagement and airplane state awareness (ASA). The consequence is that flight crews can often come to over rely on the automation, become less engaged in the human-machine interaction, and lose awareness of the automation mode under which the aircraft is operating. Likewise, the complexity of the system and automation modes may lead to poor understanding of the interaction between a mode of automation and a particular system configuration or phase of flight. These and other examples of mode confusion often lead to mismanaging the aircraftâ€"TM"s energy state or the aircraft deviating from the intended flight path. This report examines methods for assessing whether, and how, operational constructs properly assign authority and autonomy in a safe and coordinated manner, with particular emphasis on assuring adequate airplane state awareness by the flight crew and air traffic controllers in off-nominal and/or complex situations.

Whitlow, Stephen↗
NASA NTRS1992

Pre-flight risk assessment in Emergency Medical Service (EMS) helicopters

The Emergency Medical Service (EMS) industry has been the subject of several television and newspaper articles (Harvey and Jensen, 1987) which emphasized the negative aspects, (e.g., fatalities and high accident rates), rather than the life saving services performed. Until recently, the accident rate of the EMS industry has been five times as high as that of other civil helicopters. This high accident rate has been coupled with the dramatic rise in the number of programs. The industry has built from a single service at its inception in 1972, to over 180 in 1987 (Spray, 1987), to the point that 93 percent of the contiguous U.S. is now covered by some type of EMS service. These factors prompted the National Transportation Safety Board (NTSB) to study the accidents that occurred between May 11, 1978 and December 3, 1986 (NTSB, 1988). The NTSB report concluded that 'Sound pilot judgment is central to safe flight operations.' They further stated that '... factors unique to EMS helicopter operations--such as the influence of the mission itself, program competition, and EMS program management perspectives--can drastically influence pilot judgment during the EMS mission.' One of the most difficult decisions that a pilot must make is whether to accept or decline a mission. A pre-flight risk assessment system (SAFE) was developed at NASA-Ames Research Center for civil EMS operations to aid pilots in making this decision objectively. The ability of the SAFE system to predict mission risk profiles was tested at an EMS facility. The results of this field study demonstrated that the usefulness of SAFE was highly dependent on the type of mission flown. SAFE is now being modified so that it can 'learn' with each mission flown. For example, after flying a mission to a particular site, an EMS pilot would input information about this mission into the system, such as new buildings, wires, or approach procedures. Then, the next time a pilot flew a similar mission or one to the same area, this additional information would be taken into account in computing a risk assessment.

Shively, R. J.↗
NASA NTRS2018

Component-Level Selection and Qualification for the Global Ecosystem Dynamics Investigation (GEDI) Laser Altimeter Transmitter

Flight quality solid-state lasers require a unique and extensive set of testing and qualification processes, both at the system and component levels to insure the laser's promised performance. As important as the overall laser transmitter design is, the quality and performance of individual subassemblies, optics, and electro-optics dictate the final laser unit's quality. The Global Ecosystem Dynamics Investigation (GEDI) laser transmitters employ all the usual components typical for a diode-pumped, solid-state laser, yet must each go through their own individual process of specification, modeling, performance demonstration, inspection, and destructive testing. These qualification processes and results for the laser crystals, laser diode arrays, electro-optics, and optics, will be reviewed as well as the relevant critical issues encountered, prior to their installation in the GEDI flight laser units.

Frese, Erich A.↗