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At least 721 records · Page 40

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DOE OSTI2023

The Bikinians

On March 29, 1944, a small contingent of Marines invaded Bikini Atoll. Their mission was to wrest control of the atoll from Japan and, at the same time, prevent the Bikinians from interfering with the ongoing war effort. The Marines found only five Japanese, all dead by suicide, and about 150 starving islanders who also were suffering from such diseases as the Yaws. The Marines fed the Bikinians and secured medical treatment for them. The Bikinians, like all Marshallese, were extremely grateful to be rescued by Americans. Two years later, the Navy landed on Bikini to send the islanders into exile so that their ancestral homeland could be used for Operation Crossroads. On March 7 th , the Bikinians were relocated to uninhabited Rongerik Atoll, where the Navy had built a village complete with twenty-six homes, canvas water tanks, screened toilets, and nine concrete cisterns. Although the accommodations were adequate, the Navy did not understand that uninhabited Marshallese atolls cannot sustain native life. Within two years, the Bikinians would have to be rescued from starvation again.

99 GENERAL AND MISCELLANEOUS↗

NASA NTRS1996

Design of a mixer for the thrust-vectoring system on the high-alpha research vehicle

One of the advanced control concepts being investigated on the High-Alpha Research Vehicle (HARV) is multi-axis thrust vectoring using an experimental thrust-vectoring (TV) system consisting of three hydraulically actuated vanes per engine. A mixer is used to translate the pitch-, roll-, and yaw-TV commands into the appropriate TV-vane commands for distribution to the vane actuators. A computer-aided optimization process was developed to perform the inversion of the thrust-vectoring effectiveness data for use by the mixer in performing this command translation. Using this process a new mixer was designed for the HARV and evaluated in simulation and flight. An important element of the Mixer is the priority logic, which determines priority among the pitch-, roll-, and yaw-TV commands.

Pahle, Joseph W.↗

DOE OSTI2023

Progress in the validation of rotor aerodynamic codes using field data

Within the framework of the fourth phase of the International Energy Agency (IEA) Wind Task 29, a large comparison exercise between measurements and aeroelastic simulations has been carried out featuring three simulation cases in axial, sheared and yawed inflow conditions. Results were obtained from more than 19 simulation tools originating from 12 institutes, ranging in fidelity from blade element momentum (BEM) to computational fluid dynamics (CFDs) and compared to state-of-the-art field measurements from the 2 MW DanAero turbine. More than 15 different variable types ranging from lifting-line variables to blade surface pressures, loads and velocities have been compared for the different conditions, resulting in over 250 comparison plots. The result is a unique insight into the current status and accuracy of rotor aerodynamic modeling. For axial flow conditions, a good agreement was found between the various code types, where a dedicated grid sensitivity study was necessary for the CFD simulations. However, compared to wind tunnel experiments on rotors featuring controlled conditions, it remains a challenge to achieve good agreement of absolute levels between simulations and measurements in the field. For sheared inflow conditions, uncertainties due to rotational and unsteady effects on airfoil data result in the CFD predictions standing out above the codes that need input of sectional airfoil data. However, it was demonstrated that using CFD-synthesized airfoil data is an effective means to bypass this shortcoming. For yawed flow conditions, it was observed that modeling of the skewed wake effect is still problematic for BEM codes where CFD and free vortex wake codes inherently model the underlying physics correctly. The next step is a comparison in turbulent inflow conditions, which is featured in IEA Wind Task 47. Doing this analysis in cooperation under the auspices of the IEA Wind Technology Collaboration Program (TCP) has led to many mutual benefits for the participants. The large size of the consortium brought ample manpower for the analysis where the learning process by combining several complementary experiences and modeling techniques gave valuable insights that could not be found when the analysis is carried out individually.

17 WIND ENERGY↗

NASA NTRS1972

Space shuttle: Longitudinal and lateral aerodynamic characteristics of the 0.0035-scale GD/C aerospace booster (B-15B-1)

Force tests on a 0.0035-scale model of the General Dynamics/Convair space shuttle B-15B-1 booster were conducted in the MSFC trisonic wind tunnel during February and March 1971. Longitudinal and lateral characteristics were obtained at Mach numbers from 0.6 to 4.96. The configuration tested had a low delta wing, all-movable canard controls of delta planform, and a single vertical tail. Most of the test was devoted to obtaining data relevant to the transition from atmospheric reentry to subsonic cruise. In that portion of the test the angles of attack ranged from 6 degrees to 60 degrees, and yaw runs were made at angles of attack of 15 and 35 degrees. The rest of the test was devoted to obtaining booster-alone buildup data relevant to the launch phase. For the launch phase, the Mach number range was from 0.6 to 2.0, the angles of attack were from -10 to +10 degrees, and yaw runs were made at zero angle of attack.

Debevoise, J. M.↗

NASA NTRS1976

Theoretical Stability and Control Characteristics of Wings With Various Amounts of Taper and Twist

Stability derivatives have been computed for twisted wings of different planforms that include variations in both the wing taper and the aspect ratio. Taper ratios of 1.0, 0.50, and 0.25 are considered for each of three aspect ratios: 6, 10, and 16. The specific derivatives for which results are given are the rolling moment and the yawing moment derivatives with respect to rolling velocity, yawing velocity, and angle of sideslip. In addition to the stability derivatives, results are included for determining the theoretical rolling moment due to aileron deflection and a series of influence lines is given by which the loading across the span may be determined for any angle-of-attack distribution that may occur on the wing planforms considered.

Henry A Pearson↗

NASA NTRS1991

Guideline requirements for serviceable spacecraft grasping/berthing/docking interfaces based on simulations and flight experience (survey paper)

As space vehicles and structures become larger and more complex, the development of systems to assist humans in assembling, operating, maintaining, and performing space rescue or retrieval of these vehicles and structures becomes increasingly important. With the diversity of international spacecraft, both manned and unmanned, planned to be in orbit in the future, a set of guidelines for berthing and docking subsystems is mandatory if servicing, resupply, and retrieval is to become practical on an international level. Successful interaction between these space systems and ground and/or space-based humans requires standardized and effective operational interface designs, particularly with respect to space grasping/berthing/docking interface mechanisms. This paper defines the spacecraft mechanical interfaces necessary to create a standard dynamic envelope for joining two free-flying spacecraft in a 'hard' berth or dock with each other in space. A review was made of past space flights and dynamics simulations dating back to 1962 to obtain necessary parameters and their values for successful manually controlled and autonomous spacecraft docking/berthing. The various spacecraft docking/berthing mechanisms and concepts are illustrated along with their dynamic capture and impact tolerances including maximum contact velocity along the approach axis and in the y-z plane; capture linear misalignment tolerances; and maximum capture roll, pitch, and yaw angles. From this data sets of recommended guidelines parameters were developed for autonomous and manual impact docking tolerances, non-impact grasping/berthing tolerances (end effectors), berthing contact conditions, and alignment tolerances after rigidizing. Also, detailed requirements were developed for mechanical design interface features, as well as latching, unlatching, and separation tolerances. This data was drafted in the form of a proposed ANSI Standard guideline, reviewed, and added to by members of the committee representing several spacecraft manufacturers, NASA, and the USAF, and a consensus was reached.

Thompson, Allen B.↗

NASA NTRS1950

Yawed-Landing Investigation of a Model of the Convair Y2-2 Airplane, TED No. NACA DE 363

A model of the Convair Y2-2 airplane was tested in Langley tank no. 2 to determine whether satisfactory stability in yawed landings was possible with a certain ventral fin. Free-body landings were made in smooth and rough water at two speeds and two rates of descent with the model yawed 15deg. The behavior of the model was determined by visual observations and from motion-picture re.cords. It was concluded that satisfactory stability was possible with the ventral fin as tested but that the characteristics of the model shock absorbers and the settings of the elevon control surfaces had an appreciable influence on behavior.

Hoffman, Edward L.↗

DOE OSTI2023

Bivalent molecular mimicry by ADP protects metal redox state and promotes coenzyme B 12 repair

Control over transition metal redox state is essential for metalloprotein function and can be achieved via coordination chemistry and/or sequestration from bulk solvent. Human methylmalonyl-Coenzyme A (CoA) mutase (MCM) catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA using 5′-deoxyadenosylcobalamin (AdoCbl) as a metallocofactor. During catalysis, the occasional escape of the 5′-deoxyadenosine (dAdo) moiety leaves the cob(II)alamin intermediate stranded and prone to hyperoxidation to hydroxocobalamin, which is recalcitrant to repair. In this study, we have identified the use of bivalent molecular mimicry by ADP, coopting the 5′-deoxyadenosine and diphosphate moieties in the cofactor and substrate, respectively, to protect against cob(II)alamin overoxidation on MCM. Crystallographic and electron paramagnetic resonance (EPR) data reveal that ADP exerts control over the metal oxidation state by inducing a conformational change that seals off solvent access, rather than by switching five-coordinate cob(II)alamin to the more air stable four-coordinate state. Subsequent binding of methylmalonyl-CoA (or CoA) promotes cob(II)alamin off-loading from MCM to adenosyltransferase for repair. This study identifies an unconventional strategy for controlling metal redox state by an abundant metabolite to plug active site access, which is key to preserving and recycling a rare, but essential, metal cofactor.

Science & Technology - Other Topics↗

NASA NTRS1971

Self-rotation of animate beings.

Consideration of the ability of both animals and humans to perform well-controlled self-rotation maneuvers while falling freely for short periods of time in the neighborhood of the earth's surface. Specifically, an analytical theory dealing with the righting movements of falling cats is constructed, and the validity of this theory is tested by reference to photographs. Pitch, yaw, and roll motions generated by arm and leg motions of humans are studied analytically and, in the case of yaw motions, experimentally.

Kane, T. R.↗

NASA NTRS1984

SCOLE dynamic analysis and frequency response using DISTEL software

The distributed element dynamic analysis package DISTEL is used to analyze the NASA/Institute of Electrical and Electronics Engineers' Spacecraft Control Laboratory Experiment (SCOLE). In this configuration, the Space Shuttle motion is coupled to the motion of a large dish antenna through a Shuttle-deployed flexible mast of 40 m long. Due to the high asymmetry of the system, the motions about the different axes (roll, pitch, yaw) are severely coupled. A general purpose software like DISTEL is especially suited for this kind of analysis. Modal frequencies of the complete spacecraft and impulse response (modal gains) to excitations at different locations are obtained. Mode-shape plots of the deformations of the entire system are given. Finally, results obtained at NASA and at Purdue University are compared to those found by the European space technology center, ESTEC.

Poelaert, D.↗

NASA NTRS1992

Digital resolver for helicopter model blade motion analysis

The paper reports the development and initial testing of a digital resolver to replace existing analog signal processing instrumentation. Radiometers, mounted directly on one of the fully articulated blades, are electrically connected through a slip ring to analog signal processing circuitry. The measured signals are periodic with azimuth angle and are resolved into harmonic components, with 0 deg over the tail. The periodic nature of the helicopter blade motion restricts the frequency content of each flapping and yaw signal to the fundamental and harmonics of the rotor rotational frequency. A minicomputer is employed to collect these data and then plot them graphically in real time. With this and other information generated by the instrumentation, a helicopter test pilot can then adjust the helicopter model's controls to achieve the desired aerodynamic test conditions.

Daniels, T. S.↗

NASA NTRS2020

U.S. Coast Guard Boat Recovery Simulation at the NASA Ames Vertical Motion Simulator

The U.S. Coast Guard routinely uses the Over-The-Horizon (OTH-IV), a cutter deployed, rigid-hulled inflatable boat for rescue and law enforcement operations. The term "cutter" refers to a Coast Guard vessel 65 feet in length or greater with accommodations for crew to live aboard and the ability to deploy smaller boats including the OTH-IV. A deployment method employed by some cutter class vessels is a davit crane system and specialized hook mechanism to connect the smaller boat. The launch and recovery operation requires several crewmembers, where one is tasked with releasing and connecting the hook to the small boat. Manipulating the hook can pose a risk to the crewmember depending on sea conditions combined with fatigue level or task expertise. Equipment and crewmembers are tested extensively due to the inherent risk of the task, but the sea conditions cannot be controlled. To address the sea condition variable, the U.S. Coast Guard and NASA leveraged the Vertical Motion Simulator (VMS) as a platform to test new equipment or train crewmembers in varying sea conditions. With 6 degrees of freedom and a vertical displacement of +/- 22ft, the VMS is capable of simulating conditions up to sea-state 5. The proof of concept experiment took place in September 2018 and demonstrated that the VMS can accurately simulate varying sea-states, collect performance data, and design a reliable and safe system for participants. The U.S. Coast Guard provided boat displacement data from the Large Amplitude Motion Program (LAMP). The program generates multi-directional waves with a cosine squared spreading function which produced a time history response of displacement data (surge, sway, heave, roll, pitch, yaw) of the OTH-IV's center of gravity (C.G). The displacement data was differentiated into acceleration evaluated at the crewmember's position at the front (bow) of the boat. Those accelerations were transformed to the VMS coordinate system and used as command inputs to the motion system's washout filters. The VMS uses Interchangeable Cabs (ICab) to perform flight simulations on a variety of aircraft or spacecraft configurations. An ICab typically contains seats, restraints, pilot controls, instrument panel, and out-the-window projectors all enclosed in a familiar cockpit configuration. To replicate the launch and recovery of a small boat, all the conventional features of a flight simulator and canopy were removed to be replaced with a to-scale OTH-IV bow mockup. The bow section was constructed from aluminum, and a connection point known as the davit ring. Additionally, a hook replica was suspended by a cable from the ceiling as if it were hanging from a davit crane aboard a cutter vessel. The last step was providing an auxiliary control to close the distance between suspended hook and the davit ring on the bow mockup. Without control the boat would simulate the wave motion, but with no guarantee that the crewmember will be in reach of the hook. Since the wave motion was repeatable, an additional acceleration command sent to the washout filters to move the simulator in the surge, sway, and heave directions, independently. The commands were rate limited such that the additional movement was not detectable with respect to the wave motion. The results showed that for each wave profile, a unique set of acceleration commands provided opportunities for crewmembers to gain control of the hook and connect it to the davit ring.

Riccobono, Nicholas S.↗

NASA NTRS1994

Controlling forebody asymmetries in flight: Experience with boundary layer transition strips

The NASA Dryden Flight Research Center has an ongoing program to investigate aircraft flight characteristics at high angles of attack. As part of this investigation, longitudinal boundary layer transition strips were installed on the F-18 HARV forebody, a preproduction F/A-18 radome with a nose-slice tendency, and the X-31 aircraft forebody and noseboom to reduce asymmetric yawing moments at high angles of attack. The transition strips were effective on the F-18 HARV at angles of attack above 60 deg. On the preproduction F/A-18 radome at an angle of attack near 50 deg the strips were not effective. When the transition strips were installed on the X-31 noseboom, a favorable effect was observed on the yawing moment dynamics but the magnitude of the yawing moment was not decreased.

David F Fisher↗

NASA NTRS1938

Theoretical stability and control characteristics of wings with various amounts of taper and twist

Stability derivatives have been computed for twisted wings of different plan forms that include variations in both the wing taper and the aspect ratio. Taper ratios of 1.0, 0,50, and 0.25 are considered for each of three aspect ratios: 6, 10, and 16. The specific derivatives for which results are given are the rolling-moment and the yawing-moment derivatives with respect to (a) rolling velocity, (b) yawing velocity, and (c) angle of sideslip. These results are given in such a form that the effect of any initial symmetrical wing twist (such as may be produced by flaps) on the derivatives may easily be taken into account. In addition to the stability derivatives, results are included for determining the theoretical rolling moment due to aileron deflection and a series of influence lines is given by which the loading across the span may be determined for any angle-of-attack distribution that may occur on the wing plan forms considered. The report also includes incidental references to the application of the results.

Pearson, Henry A↗

NASA NTRS1991

Progress in multirate digital control system design

A new methodology for multirate sampled-data control design based on a new generalized control law structure, two new parameter-optimization-based control law synthesis methods, and a new singular-value-based robustness analysis method are described. The control law structure can represent multirate sampled-data control laws of arbitrary structure and dynamic order, with arbitrarily prescribed sampling rates for all sensors and update rates for all processor states and actuators. The two control law synthesis methods employ numerical optimization to determine values for the control law parameters. The robustness analysis method is based on the multivariable Nyquist criterion applied to the loop transfer function for the sampling period equal to the period of repetition of the system's complete sampling/update schedule. The complete methodology is demonstrated by application to the design of a combination yaw damper and modal suppression system for a commercial aircraft.

Berg, Martin C.↗

NASA NTRS1993

Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF) calibration of the Upper Atmosphere Research Satellite (UARS) sensors

Flight Dynamics Facility (FDF) responsibilities for calibration of Upper Atmosphere Research Satellite (UARS) sensors included alignment calibration of the fixed-head star trackers (FHST's) and the fine Sun sensor (FSS), determination of misalignments and scale factors for the inertial reference units (IRU's), determination of biases for the three-axis magnetometers (TAM's) and Earth sensor assemblies (ESA's), determination of gimbal misalignments of the Solar/Stellar Pointing Platform (SSPP), and field-of-view calibration for the FSS's mounted both on the Modular Attitude Control System (MACS) and on the SSPP. The calibrations, which used a combination of new and established algorithms, gave excellent results. Alignment calibration results markedly improved the accuracy of both ground and onboard Computer (OBC) attitude determination. SSPP calibration results allowed UARS to identify stars in the period immediately after yaw maneuvers, removing the delay required for the OBC to reacquire its fine pointing attitude mode. SSPP calibration considerably improved the pointing accuracy of the attached science instrument package. This paper presents a summary of the methods used and the results of all FDF UARS sensor calibration.

Hashmall, J.↗

NASA NTRS1973

Low-speed wind-tunnel investigation of the longitudinal characteristics of a large-scale variable wing-sweep fighter model in the high-lift configuration

The low-speed characteristics of a large-scale model of the U. S. Navy/Grumman F-14A aircraft were studied in tests conducted in the Ames Research Center 40- by 80-Foot Wind Tunnel. The primary purpose of the program was the determination of lift and stability levels and landing approach attitude of the aircraft in its high-lift configuration. Tests were conducted at wing angles of attack between minus 2 deg and 30 deg with zero yaw. Data were taken at Reynolds numbers ranging from 3.48 million to 9.64 million based on a wing mean aerodynamic chord of 7.36 ft. The model configuration was changed as required to show the effects of glove slat, wing slat leading-edge radius, cold flow ducting, flap deflection, direct lift control (spoilers), horizontal tail, speed brake, landing gear and missiles.

Eckert, W. T.↗

NASA NTRS1982

Applications of system identification methods to the prediction of helicopter stability, control and handling characteristics

A set of results on rotorcraft system identification is described. Flight measurements collected on an experimental Puma helicopter are reviewed and some notable characteristics highlighted. Following a brief review of previous work in rotorcraft system identification, the results of state estimation and model structure estimation processes applied to the Puma data are presented. The results, which were obtained using NASA developed software, are compared with theoretical predictions of roll, yaw and pitching moment derivatives for a 6 degree of freedom model structure. Anomalies are reported. The theoretical methods used are described. A framework for reduced order modelling is outlined.

Padfield, G. D.↗