Conflict Resolution in Autonomous Operations Area airspace

A paradigm shift is at hand with the planned redesign of the Air Traffic Management and Air Traffic Control systems. The concept for the future air traffic system foresees that aircraft will monitor and maintain separation to each other by themselves in Autonomous Operations Area airspace. With this shift of responsibility for separation assurance from Air Traffic Control to the flight deck crews a more flexible and better airspace usage is expected. Furthermore, through the more flexible airspace usage, a gain in flight efficiency is also anticipated. In order to operate in this airspace area, aircraft are required to be equipped with a system enabling them to detect and resolve air traffic conflicts. Upon detection of a conflict with another aircraft, the system is expected to compute an alternative trajectory which guides the aircraft around the conflict and back to its original trajectory. The alternative trajectory needs to adhere to several requirements, such as being clear of conflicts and being flyable. Further requirements that are often stated are to minimise the additional fuel and time required for the resolution. This thesis is concerned with such a Conflict Detection & Resolution system. Primary focus lies on the resolution of air traffic conflicts while guaranteeing flyability and respecting the Cost Index. The Cost Index is nowadays used by the Flight Management System to optimise the flight profile in respect to the operators prioritisation of fuel-related to time-related costs. This paramter is included into the Conflict Resolution process which is based on Artificial Force Fields. Flyability of the trajectory is intended to be guaranteed through integration of a flight mechanics model. The algorithm devised in this work is validated in fast time simulations with varying Cost Index. Objects of study are the distance at the Closest Point of Approach, the integration of the Cost Index and the flyability of the resulting trajectory. The first two objects of this study will be validated through comparison of the original and updated trajectory. The new trajectory is considered conflict free if the distance at the Closest Point of Approach is sufficiently large. The lateral, vertical and temporal differences between the two trajectories are used as measures for time- and fuel-related costs. Flyability of the resulting trajectory is validated by confirming adherence to the flight envelope and the constraints given by the flight mechanics model used. The evaluation of the algorithm showed that by integration of a flight mechanics model flyability of the resulting trajectory could be assured. Regarding resolution of the conflicts, the algorithm could compute a trajectory which prevented the initially set up Mid-Air Collision between the aircraft. Though, the minimum required separation could not be achieved in all cases. The approach of integrating the Cost Index into the resolution process showed to be feasible, whereas especially regarding the speed resolution further enhancements have been found to be necessary

Multi-Trajectory Automatic Ground Collision Avoidance System with Flight Tests (Project Have ESCAPE)

Multi-trajectory automatic collision avoidance techniques for heavy-type aircraft are explored to increase aviation safety procedures and decrease losses due to controlled flight into terrain. Additionally, this research includes flight test results from the United States Test Pilot School’s Test Management Project (TMP) titled Have Emergency Safe Calculated Autonomous Preplanned Exit (ESCAPE). Currently, the heavy aircraft community lacks an automatic collision avoidance system that has proven to save lives in fighter-type aircraft. The tested algorithm includes both a 3-path and a 5-path avoidance technique that is compared to an optimal solution which minimizes aircraft control to avoid terrain. The research utilizes Level 1 Digital Terrain Elevation Data (DTED) to analyze the terrain and a 3-Degrees of Freedom (DOF) Equations of Motion (EOM) model to predict potential terrain avoidance paths for the aircraft based on current location. The algorithm then waits until all paths collide and automatically activates the path with the longest time until collision with an appropriate time safety margin. The research also characterizes terrain based on changing slope and presents a new classification of aircraft based on performance capabilities. The result was used for algorithm parameter specification of path execution times and pre-planned maneuver creation so that the system can be modified for a wide variety of aircraft. Finally, the algorithm was flight tested against DTED in a simulated environment using the Calspan Learjet to determine actual 3 and 5- path performance, parameter specification, and comparison to the optimal solution. The important recommendations include a need for flexible entry parameters based on current aircraft state, continued evaluation of the terrain during avoidance maneuver execution, and more precise control of the aircraft flight path angle. Finally, due to comparison with the optimal solution, it is concluded that an acceptable terrain avoidance algorithm is possible using only a 3-path solution given that all three paths include a climbing maneuver

SAM-2 ground-truth plan: Correlative measurements for the Stratospheric Aerosol Measurement-2 (SAM 2) sensor on the Nimbus G satellite

The SAM-2 will fly aboard the Nimbus-G satellite for launch in the fall of 1978 and measure stratospheric vertical profiles of aerosol extinction in high latitude bands. The plan gives details of the location and times for the simultaneous satellite/correlative measurements for the nominal launch time, the rationale and choice of the correlative sensors, their characteristics and expected accuracies, and the conversion of their data to extinction profiles. The SAM-2 expected instrument performance and data inversion results are presented. Various atmospheric models representative of polar stratospheric aerosols are used in the SAM-2 and correlative sensor analyses

A new control technology for the development of an air-to-air refueling system

Air to Air Refueling (AAR) was first performed over 100 years ago and until now it has almost exclusively been used in military applications. This is due to the prohibitive cost of maintaining a tanker fleet to enable refueling operations as well as the amount of training required by both tanker and receiver pilots to mitigate the risk involved with operating aircraft in close proximity. There are two methods of performing AAR operations: probe-drogue and flying boom. This work investigates the feasibility of converting a civilian tanker into a probe-drogue tanker for use in civilian applications. The aircraft chosen for this work is FuelBoss AT-802 as a fuel hauler. The first objective of this thesis is to model the AT-802 and explore its potential role as an AAR tanker. The second objective of this thesis is to address the issue of risk in AAR by modeling a hose-drogue and proposing a new control technology to stabilize a drogue in flight. As no drogue system is available for experimental testing, a flexible smart structure lab workstation will be used to investigate control strategies for vibration suppression under variable system dynamics. A Deep Deterministic Policy Gradient (DDPG) algorithm is proposed in conjuncture with Domain Randomization for reinforcement training of the controller. The effectiveness of the proposed control technique and learning algorithm is verified by experimental tests, with comparison to other related control methods such as the built-in PD controller and an intelligent NF controller. Dynamic conditions of the flexible structure are simulated by placing magnetic mass blocks at different positions on the beam. Experimental results show that the proposed DDPG controller outperforms other related control methods in terms of settling time, overshoot, and mean error, without sacrificing robustness and stability. It can learn a decision-making policy in environments with large action spaces such as in vibration suppression and has potential to used for hose-drogue system control

The Use of Coincident Synthetic Aperture Radar and Visible Imagery to Aid in the Analysis of Photon-Counting Lidar Data Sets Over Complex Ice/Snow Surfaces

Qualitative and quantitative analysis of multi-sensor data is becoming increasingly useful as a method of improving our understanding of complex environments, and can be an effective tool in the arsenal to help climate scientists to predict sea level rise due to change in the mass balance of large glaciers in the Arctic and Antarctic. A novel approach to remote sensing of the continuously changing polar environment involves the use of coincident RADARSAT-2 synthetic aperture radar (SAR) imagery and Landsat 7 visible/near-infrared imagery, combined with digital elevation models (DEM) developed from Multiple Altimeter Beam Experimental Lidar (MABEL) data sets. MABEL is a scaled down model of the lidar altimeter that will eventually be flown on ICESat-2, and provides dense along-track and moderate slope (cross-track) elevation data over narrow (~198 m) aircraft transects. Because glacial terrain consists of steep slopes, crevices, glacial lakes, and outflow into the sea, accurate slope information is critical to our understanding of any changes that may be happening in the ice sheets. RADARSAT-2 operates in the C-band, at a wavelength of 5.55 cm, and was chosen partly for its ability to image the Earth under all atmospheric conditions, including clouds. The SAR images not only provide spatial context for the elevation data found using the lidar, but also offer key insights into the consistency of the snow and ice making up the glacier, giving us some idea of mean temperature and surface conditions on the ice sheet. Finally, Landsat 7 images provide us with information on the extent of the glacier, and additional understanding of the state of the glacial surface. To aid in the analysis of the three data sets, proper preparation of each data set must first be performed. For the lidar data, this required the development of a new data reduction technique, based on statistical analysis, to reduce the number of received photons to those representing only the surface return. Accordingly, the raw SAR images require calibration, speckle reduction, and geocorrection, before they can be used. Landsat 7 bands are selected to provide the most contrast between rock, snow, and other surface features, and compiled into a three-band red, green, blue (RGB) image. By qualitatively analyzing images and data taken only a short time apart using multiple imaging modalities, we are able to accurately compare glacial surface features to elevation provided by MABEL, with the goal of increasing our understanding of how the glacier is changing over time. Quantitative analysis performed throughout this thesis has indicated that there is a strong correlation between top-of-the-atmosphere reflectance (Landsat 7), σ,0-calibrated HH and HV polarized backscatter coefficients (RADARSAT-2), elevation (MABEL), and various surface features and glacial zones on the ice sheet. By comparing data from unknown or mixed surfaces to known quantities scientists can effectively estimate the type of glacial zone the area of interest occurs in. Climate scientists can then use this data, along with long-term digital elevations models, as a measure of predicting climate change

Aeronautical engineering: A continuing bibliography with indexes (supplement 291)

This bibliography lists 757 reports, articles, and other documents introduced into the NASA scientific and technical information system in May. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Earth Resources: A continuing bibliography with indexes, Issue 35

This bibliography list 587 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System between July 1, and September 30, 1982. Emphasis is placed on the use of remote sensing and geophysical instrumentation in spacecraft and aircraft to survey and inventory natural resources and urban areas. Subject matter is grouped according to agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economic analysis