Flight Configuration Research Articles

Analysis of helicopter blade vortex structure by laser velocimetry

In descent flight, helicopter external noise is mainly generated by the Blade Vortex Interaction (BVI). To under-stand the dynamics of this phenomenon, the vortex must be characterized before its interaction with the blade, which means that its viscous core radius, its strength and its distance to the blade have to be determined by non-intrusive measurement techniques. As part of the HART program (Higher Harmonic Control Aeroacoustic Rotor Test, jointly conducted by US Army, NASA, DLR, DNW and ONERA), a series of tests have been made in the German Dutch Wind Tunnel (DNW) on a helicopter rotor with 2 m long blades, rotating at 1040 rpm; several flight configurations, with an advance ratio of 0.15 and a shaft angle of 5.3°, have been studied with different higher harmonic blade pitch angles superposed on the conventional one (corresponding to the baseline case). The flow on the retreating side has been analyzed with an especially designed 3D laser velocimeter, and, simultaneously, the blade tip attitude has been determined in order to get the blade-vortex miss distance, which is a crucial parameter in the noise reduction.

Pressure sensitive paint in transonic wind-tunnel testing of the F-15

The pressure sensitive paint (PSP) technique has been used to measure surface static pressures on a 4.7% scale F-15E model with complex store loadings during a high-speed wind-tunnel test. Successful employment of the technique required an integrated process of paint formulation, model preparation, test procedure, data acquisition, and data reduction. Testing a total of 107 different combinations of configuration s and flight conditions has provided an invaluable database. The data have immediate qualitative utility as surface flow visualization. Details of the measured pressure distribution were readily correlated with specific geometric features of the model. Absolute accuracy, and hence, quantitative utility is determined presently by the paint calibration. The digital data can be processed readily by appropriate software to provide pressure distribution plots, pressure increments, and integrated loads. This test's combination of duration, variety of flight conditions and configurations, and quick data turnaround represent a milestone in the practical application of PSP in aerospace testing.

Characteristics of flight nursing practice

Introduction: The purpose of this study was to describe the roles, levels of responsibility and backgrounds of flight nurses employed in flight programs across the country and to determine if the role of the flight nurse varied as a function of crew configuration or size of program. Methods: In 1991, a retrospective statistical questionnaire was sent to 105 programs with 50 or more flights per month. Results: This survey provides national data regarding description of programs, evidence of the critical-care environment, professional profiles of flight nurses and practice differences between nurse and paramedic personnel. A difference in the practice for nurses existed in the larger programs (≥ 1,100 flights) with nurse/paramedic flight configurations. Nurses more frequently performed interventions regarding initiating and discontinuing medications ( p = 0.00023)—especially paralyzing agents ( p = 0.012) and blood ( p = 0.0016)—and recognizing by physical exam the need for interventions to decrease intracranial pressure ( p = 0.0194). In the larger programs, nurses also were more responsible for decision making regarding titration of medications ( p = 0.027). Conclusions: Flight nurses practice in advanced autonomous roles, performing duties and skills consistent with critical care and emergency medicine in air medical transport.

A spacecraft for the Earth observing system

The space segment of NASA's Earth observing system (EOS) includes three series of intermediate-sized spacecraft, plus two smaller spacecraft. The EOS-AM spacecraft is the first of the intermediate-sized spacecraft. EOS-AM accommodates sensors that measure cloud and aerosol radiative properties, and that provide data to study the water and energy cycles. Scheduled for launch in the late 1990s, the EOS-AM spacecraft is designed for a 5-year mission. The spacecraft will be launched from the Western Space and Missile Center (California) into a polar, Sun-synchronous, low-Earth orbit with a 16-day repeat cycle. In its flight configuration, the spacecraft is almost 20 ft long (including instruments mounted at the fore end of the spacecraft) and 6 ft wide (in its widest dimension), has a mass of about 13,000 Ibs and uses about 3000 W of electrical power. The spacecraft is compatible with the Atlas IIAS launch vehicle. EOS-AM has on-board storage for at least two orbits of science data. These data will be transmitted to the ground via the tracking and data relay satellite system (using data structures and protocols in compliance with the recommendations of the Consultative Committee for Space Data Systems). A direct downlink system to support distributed users will also be available.

The point spread function of the soft X-ray telescope aboard Yohkoh

The point spread function of the SXT telescope aboardYohkoh has been measured in flight configuration in three different X-ray lines at White Sands Missile Range. We have fitted these data with an elliptical generalization of the Moffat function. Our fitting method consists of χ2 minimizationin Fourier space, especially designed for matching of sharply peaked functions. We find excellent fits with a reduced χ2 of order unity or less for single exposure point spread functions over most of the CCD. Near the edges of the CCD the fits are less accurate due to vignetting. From fitting results with summation of multiple exposures we find a systematic error in the fitting function of the order of 3% near the peak of the point spread function, which is close to the photon noise for typical SXT images in orbit. We find that the full width to half maximum and fitting parameters vary significantly with CCD location. However, we also find that point spread functions measured at the same location are consistent to one another within the limit determined by photon noise. A ‘best’ analytical fit to the PSF as function of position on the CCD is derived for use in SXT image enhancement routines. As an aside result we have found that SXT can determine the location of point sources to about a quarter of a 2.54 arc sec pixel.

Further Theoretical Studies on Rotary Drying Processes Represented By Distributed Systems

ABSTRACT Mathematical tools for studying panicle transpon in rotary drying and cooling processes are developed in this paper. In contrast to conventional approaches aimed at deriving empirical or xmi-empirical correlations, a rigorous mathematical analysis which employs dilferential calculus and analytical geometry is emphasis4 in the current research. These developments allow accurale computations of solid flowrate, retention time and particle holdup in rotary dryers with arbilrary flight configurations. Consequently, optimal dryer configuration design in terms of drum dimension, flight number and geometry can be achieved through a better understanding of the mathematical insight of rotary drum performance. Techniques developed using this method are applied to the distributed parameter model eslablished earlier by the authors (Wang el al., 1993) to replace out-dated correlations for the determination of retention Lime and solid holdup. As a result of the new developments, the distributed parameter approach to the dynamics of rotary drying processes becomes more general and more reliable.

Two-phase experiment for the in-orbit demonstration of two-phase heat transport system technology

As two-phase flow and heat transfer depends on gravity, a Two-Phase eXperiment has been developed for ESA to demonstrate two-phase heat transport system technology in orbit. TPX, a two-phase ammonia system, has flown in the 5ft 3 nitrogen gas filled Get Away Special canister G557, aboard STS60. The system, a reduced-scale capillary pumped two-phase loop with a flat and a cylindrical capillary evaporator and an actively controlled reservoir for loop temperature setpoint control, included downscaled components of a mechanically pumped loop: multichannel condensers, vapour quality sensors, and a controllable 3-way valve for control exercises. The flight configuration of the autonomous experiment (own power supply, data handling, experiment control) is presented. Preliminary results of a comparison between pre-flight, flight and post-flight data are discussed.

Experimental modeling of central axis and jet-ring turbine disk cooling

The test facility, experimental methods, and summary results are presented from a study modeling turbine disk cooling with multiple impinging jets, such as employed on the Space Shuttle Main Engine oxygen turbopump. The study was designed to provide a comparison of detailed local convection heat transfer information obtained with a single center-supply of disk coolant, as opposed to the present flight configuration where disk coolant is supplied through an array of 19 radially outboard jets. Specially constructed turbine disk models were used in a program to evaluate possible benefits and tradeoffs of employing an alternate disk cooling scheme. The study involved the design, construction, and testing of two full-scale rotating model disks, one plane and smooth for baseline testing and the second contoured to the present flight configuration, together with the corresponding plane and contoured stators. Local heat transfer rates are determined from the color display of encapsulated liquid crystals coated on the disk in conjunction with use of a computer vision system. The test program was composed of a wide variety of disk speeds, flow rates, and geometrical configurations, including testing for the effects of bolt heads and hot gas entrainment into the disk cavity.

Non-isothermal and Non-Newtonian Flow Analysis for the Non-intermeshing Counter-rotating Twin Screw Extruder Based on FAN Method

On the basis of the flow analysis network (FAN) method, a two-dimensional simulation for the non-isothermal flow of non-Newtonian fluid was developed and applied to the flow of polypropylene (PP) melt in a non-intermeshing counter-rotating twin screw extruder. The constitutive model for the PP melt we used was the Cross model with an Arrhenius-type function for temperature dependence. Calculating the movement of fluid particles permitted us to represent not only streamlines them-selves but internal residence time profiles in the flow field. Then, the energy equation was able to be successfully solved along the streamlines after replacing it in the convected coordinates.Taking into accunt back flow and leakage flow, flux fields and streamlines in the flow field clearly showed the difference of conditions between staggered and matched screw flight configurations. The profiles of pressure, shear rate, shear viscosity, temperature and residence time also told us the mechanism of this complicating flow in the extruder. The non-isothermal flow of non-Newtonian fluid in the extruder was differentiated from the isothermal flow of non-Newtonian fluid and the isothermal flow of Newtonian fluid in terms of screw characteristics. The effects of several geometrical and operating conditions, including staggering angle, helix angle of screw flight, screw rotational speed and set temperature, on the screw characteristics were also investigated. Furthermore, some simulated results were compared with experiments using a model twin screw extruder and they demonstrated good agreements in pressure profiles and screw characteristics.

Adaptive attitude control and momentum management for large-angle spacecraft maneuvers

The fully coupled equations of motion are systematically linearized around an equilibrium point of a gravity gradient stabilized spacecraft, controlled by momentum exchange devices. These equations are then used for attitude control system design of an early Space Station Freedom flight configuration, demonstrating the errors caused by the improper approximation of the spacecraft dynamics. A full state feedback controller, incorporating gain-scheduled adaptation of the attitude gains, is developed for use during spacecraft on-orbit assembly or operations characterized by significant mass properties variations. The feasibility of the gain adaptation is demonstrated via a Space Station Freedom assembly sequence case study. The attitude controller stability robustness and transient performance during gain adaptation appear satisfactory.

Consort 1 flight results: A synopsis

Consort 1 was the first low gravity materials processing payload to be launched by a commercially licensed rocket in the U.S.A. It carried six experiments which operated as planned during approx. 7 min of suborbital, low gravity flight (10 −5 g) and were returned in excellent condition to the investigators within 4h of launch. Nearly 150 physical samples supported by measurements and photographs made during the flight were obtained for analysis. In addition to the experimental data returned, the success of Consort 1 demonstrated the ability of industry, working with university centers and government agencies, to rapidly prepare and launch payloads. A brief description of the rocket flight and payload configuration is given. Experiment objectives and methods are described and preliminary results and conclusions are presented.

U.S. space station freedom: Orbital assembly and early mission opportunities

This paper describes the U.S. Space Station launch and assembly sequence and the mission support capabilities available in man-tended and permanently manned modes. Design and operational constraints affecting launch package configurations and orbital deployment and assembly are defined. The resulting flight configurations and associated payload accommodations are described with emphasis on the early flights through man-tended capability. The initial mission objectives will emphasize engineering data collection (structural, thermal, power, control, propulsion, etc.) to verify design and to calibrate system models and simulation tools. On-board information will be used to characterize the microgravity, electromagnetic, particulate, and other environmental features for the benefit of Space Station users. Early flight configurations will provide accommodation for attached payloads which may include experimentation in materials exposure, solar physics, and Earth and stellar observations. These mission payloads, once installed and initialized by the Shuttle flight crews, will be operated by ground control from their mission specialists. When the pressurized laboratory is added, the mission emphasis will shift to microgravity experimentation including material processing and manufacturing research, life sciences, and supporting technology research and development. These missions will be operated in a man-tended mode. Installation, real-time operation, and servicing will be performed by Shuttle during periodic visits; a combination of ground control and automatic modes will be used between Shuttle flights. As Station build-up continues, resources available for payloads will also increase. With the achievement of the permanently manned capability, continuous crew support will be available for mission activities. This paper summarizes each step of this build-up process and the capabilities available for Station operation and payload activities versus time.

IMAGE QUALITY ON THE KUIPER AIRBORNE OBSERVATORY. I. RESULTS OF THE FIRST FLIGHT SERIES

ABSTRACT The NASA Kuiper Airborne Observatory (KAO) was flown three times during June and July, 1984 in order to study the causes of the poor seeing obtained with the 0.9-m telescope. High-speed pressure and temperature sensors were placed in the telescope cavity. Several thousand stellar images were recorded under various flight and optical configurations. It is found that the long-exposure image size is affected by telescope tracking errors, imperfect optics, poor optical alignment, telescope and instrument vibration, thermal fluctuations in the telescope cavity, and density fluctuations in the shear layer that forms the boundary between the cavity air and outside air. Possible ways to improve the quality of the images are discussed.

Finite element modeling of a counter‐rotating, non‐intermeshing twin screw extruder

AbstractThis paper is concerned with Newtonian flow in a counter‐rotating non‐intermeshing twin‐screw extruder. Both the matched and the mismatched screw flight configurations are considered. A three‐dimensional analysis of the pressure flow through the complete extruder cross‐section is included. The model predictions agree well with the experimental data. Computed examples are given to illustrate the utility of this work.

Cometary dust particles detected by the DIDSY-IPM-P sensor on board GIOTTO

The IMP-P sensor of GIOTTO's Dust Impact Detection System (DIDSY) was covered by three Kapton films of a total thickness of 22.5 μm in order to protect it against contamination during launch. This cover failed to open prior to the encounter with Halley's comet. Nevertheless, during the cometary approach phase, IPM-P recorded about 1000 impacts of particles which penetrated this cover. Extensive laboratory experiments allowed us to recalibrate the instrument in its flight configuration. The impact rates are in good agreement with those from other dust experiments on board GIOTTO. Radial flux profiles measured by IPM-P before encounter are presented. The data support the notion that small particles are swept to the nightside of the nucleus by a lateral breeze. Dielectric properties are attributed to the first detected particles.

Acoustic and Thermal Test Facility Construction and Validation

A requirement was developed to expose the upper stage of the Centaur in the final flight configuration to intense acoustic and thermal environments. To satisfy this requirement a large state-of-the-art acoustic and thermal test facility was constructed. The facility consists of a 1840.8 m3 (65,000 ft3) reverberation chamber and a 1316.9 m3 (46,500 ft3) thermal chamber housed in a single clean environment facility. The acoustic chamber has an overall sound pressure capability of 154 dB with uniformity within -2 to +4 dB. The sound intensity is created by a four-horn matrix with a frequency range of 25 to 10,000 Hz. The thermal chamber has a temperature range capability of -35 to +185° F with a uniformity of ±5°. The thermal chamber air is humidity controlled and filtered to maintain cleanliness standards. Both chambers are supported by modern digital data acquisition and control systems located in a 175.2 m2 (1886 ft2) control room. The facility has the capability to store and transfer cryogenic liquids into the Centaur vehicle. Problems encountered during the design and construction are discussed along with the test program that was performed to validate the facility. Suggestions are made to future builders of large acoustic or thermal test facilities.

MBB‐ERNO Starts Detail Definition for COLUMBUS

THE smallest will be first: according to present plans, the Polar Platform is to be the first flight configuration from the European COLUMBUS programme to take up work in 1995. An ARIANE 5 will launch the platform whose task will be earth observation. The large COLUMBUS laboratory that is to form an integral part of the international space station of NASA will follow in 1996, launched with the US space shuttle.

The European Columbus Programme

This paper describes the current status of the COLUMBUS Programme, Europe's contribution to the U.S. Space Station, which is being studied under contract to the European Space Agency. Twelve European nations are involved in and are contributing to this new space undertaking. The elements of the COLUMBUS Space Segment presently being considered by ESA are a Pressurized Laboratory Module (4 segment), permanently attached to the U.S. Space Station, dedicated to materials science, fluid physics and compatible life sciences, and a Polar Platform, configured to accommodate Earth observation, meteorology, communications and space science payloads. The reference launch vehicles are the Space Shuttle for the attached Module and Ariane 5 for the Polar Platform. The more recently added COLUMBUS flight configuration, the Man-Tended Free Flyer (MTFF), consists of a combination of two programme elements, the Resource Module and a 2-segment Pressurized Module. It is designed to provide all required resources and services to the various payloads in a continuous microgravity environment to perform material science, fluid physics and compatible life sciences experiments. The MTFF is carried into orbit by the European launcher Ariane 5. As an option, studies of an enhanced ground based EURECA carrier as a small co-orbiting platform, launched by the Space Shuttle, will be initiated. The primary function would be to accommodate space science and/or micro-g payloads. These EURECA studies are performed currently outside the COLUMBUS programme scope, and this option is therefore not addressed in detail in this paper.

Data Processing and Calibration for an Airborne Scatterometer

The ERASME radar system has been designed to be easily mounted on small helicopters or aircraft. As it is used for research investigations on radar remote-sensing applications, it has to be well calibrated in every configuration, both absolutely and relatively for comparisons at different points of the swath. The data processing is described, which allows for antenna pattern correction and for flight parameters correction (pitch, roll, altitude), as an introduction for the calibration procedures: internal calibration, external calibration on corner reflectors for absolute calibration (within 1 dB), and a statistical approach, which uses experimental data itself and analyzes the correlation between processed data and recorded flight parameters. This method provides a way to check or adjust calibration for specific flight configurations, and allows a relative accuracy of better than 0.5 dB for data comparison within the radar swath. Such a method could be used to calibrate any airborne or spaceborne scatterometer when accurate antenna measurement is not feasible.

Universality of node-avoiding and path-avoiding Levy flights

The real space renormalisation group theory is applied to the self-avoiding Levy flight problem with Levy exponent g on a two-dimensional square lattice. A finite-lattice renormalisation transformation is used to derive the critical behaviour exhibited by two classes of self-avoiding Levy processes: the node-avoiding Levy flight ( NALF) and the path-avoiding Levy flight (PALF). It is found that the NALF and the PALF belong to the same universality class. Random walks in which the step length is a random variable with an infinite mean- squared displacement per step are called Levy flights (Levy 1937, Montroll and West 1979, Mandelbrot 1977). The Levy flight process is characterised by the Levy exponent p which parametrises the single-step probability T,,(/) of taking a step of length 1. Asymptotically, T, (I) - Z-(F+d) in d dimensions. If 0 < p < 2, then the second moment (1') is infinite and the corresponding Levy process is 'superdiffusive'. If p 22, then (I2) is finite and thus, via the central limit theorem, leads to ordinary diffusive behaviour. The self-similar structure of the Levy flight has been characterised by a fractal dimension D= p for p <2 (Mandelbrot 1977, Hughes er a1 1981, Seshadri and West 1982). The connection between the Levy flight and the long-range interacting spherical model of critical phenomena has been noted (Joyce 1972, Hioe 1984). There exist two distinct types of self-avoiding interactions that can be imposed on the Levy flight process (Halley and Nakanishi 1985). For a Levy flight on a lattice, th.= unequal step lengths provide the opportunity for a Levy flight configuration to contain path intersections in addition to the ordinary node intersections. The path- avoiding Levy flight (PALF) is defined as a Levy flight that must avoid any part (nodes and bonds) of its entire path. Path-avoidance is a stronger constraint than node- avoidance and thus PALP represent a subset of the class of node-avoiding Levy flights (NALF). PALF would be very difficult to simulate on the computer because the path- avoiding constraint represents a long-range (non-Markovian) interaction that requires the memorisation of a set of paths, rather than a set of points.