R. John Hansman

Nonlinear fluid slosh coupled to the dynamics of a spacecraft

The dynamics of a linear spacecraft mode coupled to the nonlinear low-gravity slosh of a fluid in a cylindrical tank is investigated. Coupled, nonlinear equations of motion for the fluid-spacecraft system are derived through an assumed mode Lagrangian method. Unlike a linear model, this nonlinear model retains two fundamental slosh modes and three secondary slosh modes. An approximate perturbation solution of the equations of motion indicates that the nonlinear coupled system response involves fluid-spacecraft modal resonances not predicted by either a linear, or a nonlinear, uncoupled slosh analysis. An experiment was developed to verify and complement this analysis. Scale model fluid tanks were coupled to an electromechanical analog for the second-order oscillatory spacecraft mode. Moderate and low gravity were simulated in 1 g using capillary scale models, and zero gravity was simulated in parabolic flight tests on the NASA KC-135 Reduced Gravity Test Facility. The experimental results substantiated the analytical predictions. The dependence of the coupled nonlinear response on the coupled system parameters and the gravity level is illustrated and discussed.

Investigation of surface water behavior during glaze ice accretion

A series of experimental investigations that focused on isolating the primary factors that control the behavior of unfrozen surface water during glaze ice accretion were conducted. Detailed microvidco observations were made of glaze ice accretions on 2.54 cm diam cylinders in a closed-loop refrigerated wind tunnel. Distinct zones of surface water behavior were observed; a smooth wet zone in the stagnation region with a uniform water film, a rough zone where surface tension effects caused coalescence of surface water into stationary beads, and a zone where surface water run back as rivulets. The location of the transition from the smooth to the-rough zone was found to migrate towards the stagnation point with time. Comparative tests were conducted to study the effect of the substrate thermal and roughness properties on ice accretion. The importance of surface water behavior was evaluated by the addition of a surface tension reducing agent to the icing tunnel water supply, which significantly altered the accreted glaze ice shape. Measurements were made to determine the contact angle behavior of water droplets on ice. A simple multizone modification to current glaze ice accretion models was proposed to include the observed surface roughness behavior.

Research agenda for an integrated approach to infrastructure planning, design and management

Building on broad discussions between many universities, this paper presents a research agenda based on a holistic, comprehensive view of the issues. It proposes that our infrastructure is a system of systems involving different technical manifestations and social organisations. The implication is that we need a fundamental reconsideration of how we look at system design, away from traditional disciplinary considerations and toward a multi-domain, multi-disciplinary effort. To this end, it proposes an agenda of: comparative analyses across infrastructures and political structures, that would identify commonalities and larger lessons; creation of integrated socio-technical models that usefully describe the interactions between the technical infrastructure and its social context; methodological efforts, aimed largely at capturing the network characteristics, both technical and social, of the infrastructure system of systems; explicit testing and evaluation of the research through programs of collaboration with practitioners and governmental organisations.

Modeling of surface roughness effects on glaze ice accretion

A series of experimental investigations focused on studying the cause and effect of surface roughness on accreting glaze ice surfaces were conducted. Detailed microvideo observations were made of glaze ice accretions on 1- to 4-in.-diam cylinders in three icing wind tunnels (the Data Products of New England 6-in. test facility, the NASA Lewis Icing Research Tunnel, and the B. F. Goodrich Ice Protection Research Facility). Infrared thermal video recordings were made of accreting ice surfaces in the Goodrich facility. Distinct zones of surface water behavior were observed: a smooth wet zone in the stagnation region with a uniform water film, a rough zone where surface tension effects caused coalescence of surface water into stationary beads, a horn zone where roughness elements grow into horn shapes, a runback zone where surface water ran back as rivulets, and a dry zone where rime feathers formed. The location of the transition from the smooth to the rough zone was found to migrate with time towards the stagnation point. The behavior of the transition appeared to be controlled by boundary-laye r transition and bead formation mechanisms at the interface between the smooth and rough zones. Regions of wet ice growth and enhanced heat transfer were clearly visible in the infrared video recordings of glaze ice surfaces. A simple multizone modification to the current glaze ice accretion model was proposed to include spatial variability in surface roughness. A preliminary version of this model was implemented on the LEWICE ice accretion code and compared with experimental ice shapes. For one of the cases, running the multizone model significantly improved the prediction of the glaze ice shapes.

Approaches to mitigating complexity-driven issues in commercial autoflight systems

Abstract There appears to be broad consensus in the aviation community that increased automation in the cockpit has changed the task of flying commercial aircraft. The changes have been both beneficial, through the increase of capabilities and efficiencies, and detrimental, as indicated by accidents implicating automation as a contributory factor. It is hypothesized that the constraining factor on automation design has changed from technological to human. The evolutionary growth of the automation has increased complexity which is thought to have led to the lack of a global model of the automation upon which the training material and operator feedback can be designed. Based on these analyses, three classes of complexity mitigation management techniques are explored. The first is to train pilots to understand and work within the current automation system. The second is to enhance feedback to allow more effective monitoring of aircraft systems, and to allow a reduction in the apparent order of the system to the pilot. Finally, a modified development process is suggested which explicitly considers the pilot in early design stages. It is believed that a process-oriented solution will be necessary for future automation systems. This process uses an explicit automation model as a basis for training material and for software requirement specification.

Investigating conformance monitoring issues in air traffic control using fault detection techniques

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, February 2004.

An Integrated Approach to Evaluating Risk Mitigation Measures for UAV Operational Concepts in the NAS

*† An integrated approach is outlined in this paper to evaluate risks posed by operating Unmanned Aerial Vehicles in the National Airspace System. The approach supports the systematic evaluation of potential risk mitigation measures recognizing key issues in creation of regulatory and safety policy, including public perception and UAV market forces. Risk mitigation measures are examined for two example concepts of operation: High Altitude Long Endurance UAV and small, local UAV operations. Primary hazards of ground impact and midair collision are considered. The examples illustrate three major areas of risk mitigation: exposure, recovery, and effects mitigation. The different mitigation possibilities raise key issues on how to determine appropriate UAV policies to ensure that an acceptable level of safety is achieved.

Identification of Important "Party Line" Information Elements and the Implications for Situational Awareness in the Datalink Environment

This work was supported by National Aeronautics and Space Administration/Ames Research Center and the Federal Aviation Administration under grant NAG 2-716.

Low Reynolds number tests of NACA 64-210, NACA 0012, and Wortmann FX67-K170 airfoils in rain

Wind-tunnel experiments were conducted on Wortmann FX67-K170, NACA 0012, and NACA 64-210 airfoils at a simulated rain rate of 1000 mm/h and Reynolds number of 3.1 X105 to compare the aerodynamic performance degradation of the airfoils in heavy rain conditions and to identify the various mechanisms that affect airfoil performance in rain conditions. Lift and drag were measured in both dry and wet conditions, and a variety of flow-visualiz ation techniques were employed. At low angles of attack, the lift degradation in wet conditions varied significantly between the airfoils. The Wortmann section had the greatest lift degradation (-25%) and the NACA 64-210 airfoil had the least (-5%). At high angles of attack, the NACA 64-210 and NACA 0012 airfoils were observed to have improved aerodynamic performance in rain conditions due to a reduction of boundary-layer separation. Performance degradation in heavy rain for all three airfoils at low angles of attack could be emulated by forced boundary-layer transition near the leading edge. Time-resolved measurements indicate two primary mechanisms are responsible for the observed performance degradation. The initial effect of rain is to cause premature boundary-layer transition at the leading edge. The second effect occurs at time scales consistent with top surface water runback (1-10 s). The runback layer is thought to alter the airfoil geometry effectively, but this effect is most likely exaggerated in these tests due to the small scale. The severity of the performance degradation for the airfoils varied. The relative differences appeared to be related to the susceptibility of each airfoil to premature boundary-layer transition.

Anomaly detection in onboard-recorded flight data using cluster analysis

A method has been developed to support Flight Operations Quality Assurance (FOQA) by identifying anomalous flights based on onboard-recorded flight data using cluster analysis techniques. Unlike current techniques, the method does not require pre-defined thresholds of particular parameters, but detects data patterns which differ from the majority of flights by considering all the available flight parameters. The method converts time series data from multiple flight parameters into a high dimensional data vector. Each vector captures all the available information for a single flight. Cluster analysis of the vectors is performed to identify nominal flights which are associated with large clusters and anomalous flights that do not belong to a specific cluster. The method was applied to a representative Digital Flight Fata Recorder (DFDR) dataset from an international airline. Detailed analysis was performed on takeoff and approach for 365 B777 flights. Abnormal flights were detected using the cluster technique which was able to identify anomalous behaviors including: high and low energy states, unusual pitch excursions, abnormal flap settings, high wind conditions. In addition, data clusters representing nominal conditions were also detected. Three distinct takeoff clusters were identified in the B777 data: one represented a majority of the takeoff cases, one correlated with a specific high altitude airport, one correlated with reduced power takeoffs. This initial evaluation indicates that cluster analysis is a promising approach for the identification of anomalous flights from onboard-recorded flight data.