Experimental investigation of stability and stall flutter of a free-floating wing V/STOL model

An experimental investigation was made of the static and dynamic stability characteristics of a one-fourth scale model of a tilt-propeller free-wing V/STOL aircraft. The effects of wing pivot location, wing chord, trailing-edge angle, propeller tilt angle, and thrust were studied, and a limited evaluation was made of high-lift devices. A dynamically similar wing was used to measure frequency and damping ratio from transient response data in the linear aerodynamic regime and the results were compared to quasi-steady and unsteady aerodynamic theory. It was found that at high trim angles of attack, in the nonlinear aerodynamic regime, stall flutter oscillations occurred with typical amplitudes ranging from 15 to 20 deg. Wing control tab deflection was effective in initiating and terminating stall flutter but variations in configuration or operating conditions did not greatly influence the occurrence of characteristics of the oscillations

Development of an external ceramic insulation for the space shuttle orbiter. Part 3: Development of stabilized aluminum phosphate fibers

The development of reusable surface insulation materials that are thermal shock resistant and highly refractory is discussed. A stabilized, high-cristobalite, aluminum orthophosphate fiber was developed and found to possess the desired qualities. The application of such a material to heat shielding for space shuttles is examined

Tomanek Hall: Letter, to President Edward Hammond, from Kathy Ormiston of Senator Bob Dole\u27s office, February 26, 1990

Letter thanking President Hammond for her tour of Fort Hays State University and telling him that Senator Dole is behind the project of getting a new physical sciences building.https://scholars.fhsu.edu/tomanek/1037/thumbnail.jp

A Look Back at the 1974 AHS/NASA Ames Specialists' Meeting and the Rotor Loads Comparison

International audienceThe paper looks back on the 1974 Specialists' Meeting on Rotorcraft Dynamics and the paper on Loads Comparison, and reflects broadly on the ensuing 40 years of aeromechanics R&D and the changes that have taken place. How the 1974 Specialists' Meeting came about and the process of how the Loads Comparison effort was initiated and organized is described, involving as it did, a cooperative effort of disparate industry analysts and government researchers. How these events influenced emerging Army rotorcraft R&D in the Ames environment, and the birth of the AHS San Francisco Bay Area chapter are recalled. To bridge the 40-year span of loads prediction, then and now, new results from today's evolved codes are compared with the original 1974 results. Modern results from RCAS, UMARC, along with CFD/CSD results from the HELIOS/RCAS and GT-Hybrid/DYMORE are presented. Suggestions are offered to address rotorcraft aeromechanics R&D in the future. * Preface The theme of the Fifth Decennial AHS Aeromechanics Specialists' Conference is " Current Challenges and Future Directions in Rotorcraft Aeromechanics. " As we aim toward these challenges and plan future research it is appropriate to look back on the origins of this unique series of five meetings and conferences. Although the technical environment was quite different and the rotorcraft world was of another era, today's challenges trace back to that time. Thus we may draw insight from past approaches and results therefrom and planners of today's research may perhaps benefit from understanding past approaches and lessons learned in the intervening four decades

The capillary circulation in dehydration

A short synopsis is given of previous investigation of the capillaries of children and infants in health and disease as seen under the microscope.A satisfactory method of examination of the capillaries of infants is described,and also the normal capillary formation and blood flow in these subjects.Observations on the abnormal state of the capillary circulation in dehydrated infants are set down in detail,and in addition the effect of the intravenous injection of whole blood and of dextrose solution.A discussion follows on the significance of the observations

Wind tunnel tests of four flexible wing ultralight gliders

The aerodynamic lift, drag, and pitching moment characteristics of four full scale, flexible wing, ultralight gliders were measured in the settling chamber of a low speed wind tunnel. The gliders were tested over a wide range of angle of attack and at two different velocities. Particular attention was devoted to the lift and pitching moment behavior at low and negative angles of attack because of the potential loss of longitudinal stability of flexible wing gliders in this regime. The test results were used to estimate the performance and longitudinal control characteristics of the gliders

Hingeless helicopter rotor with improved stability

Improved stability was provided in a hingeless helicopter rotor by inclining the principal elastic flexural axes and coupling pitching of the rotor blade with the lead-lag bending of the blade. The primary elastic flex axes were inclined by constructing the blade of materials that display non-uniform stiffness, and the specification described various cross section distributions and the resulting inclined flex axes. Arrangements for varying the pitch of the rotor blade in a predetermined relationship with lead-lag bending of the blade, i.e., bending of the blade in a plane parallel to its plane of rotation were constructed

A Comparison of PID and Sliding Mode Controllers When Applied to the Orbit Raising of a Satellite Using Solar Sail Propulsion

Solar Sail spacecraft have become increasingly popular due to their ability to perform long term missions without the need for propellant. Because solar sail propulsion is so unique, most research has been focused on developing new mechanical control techniques. However, it can be argued that more advanced control algorithms can be used to mitigate the shortcomings of commonly used control actuators, specifically reaction wheels, when applied to solar sails. This thesis will research how a sliding mode controller compares to a PID controller with respect to settling time and state response error over a range of maximum reaction wheel torque values. The actuator saturation and actuator energy are then compared for two different sliding mode controllers and a PID controller. It was found that the sliding mode controller performed at minimum 14% better in terms of settling time and 7.7% better in terms of state response error, however the PID controller performed 24% better in terms of actuator saturation and energy. Further research should be done to study the potential benefits of sliding mode controllers in terms of their benefits to reduce actuator saturation and energy