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At least 235 records · Page 13

Air traffic management evaluation tool

Methods for evaluating and implementing air traffic management tools and approaches for managing and avoiding an air traffic incident before the incident occurs. A first system receives parameters for flight plan configurations (e.g., initial fuel carried, flight route, flight route segments followed, flight altitude for a given flight route segment, aircraft velocity for each flight route segment, flight route ascent rate, flight route descent route, flight departure site, flight departure time, flight arrival time, flight destination site and/or alternate flight destination site), flight plan schedule, expected weather along each flight route segment, aircraft specifics, airspace (altitude) bounds for each flight route segment, navigational aids available. The invention provides flight plan routing and direct routing or wind optimal routing, using great circle navigation and spherical Earth geometry. The invention provides for aircraft dynamics effects, such as wind effects at each altitude, altitude changes, airspeed changes and aircraft turns to provide predictions of aircraft trajectory (and, optionally, aircraft fuel use). A second system provides several aviation applications using the first system. Several classes of potential incidents are analyzed and averted, by appropriate change en route of one or more parameters in the flight plan configuration, as provided by a conflict detection and resolution module and/or traffic flow management modules. These applications include conflict detection and resolution, miles-in trail or minutes-in-trail aircraft separation, flight arrival management, flight re-routing, weather prediction and analysis and interpolation of weather variables based upon sparse measurements. The invention combines these features to provide an aircraft monitoring system and an aircraft user system that interact and negotiate changes with each other.

Sridhar, Banavar↗

Ventilation during simulated altitude, normobaric hypoxia and normoxic hypobaria

To investigate the possible effect of hypobaria on ventilation (VE) at high altitude, we exposed nine men to three conditions for 10 h in a chamber on separate occasions at least 1 week apart. These three conditions were: altitude (PB = 432, FIO2 = 0.207), normobaric hypoxia (PB = 614, FIO2 = 0.142) and normoxic hypobaria (PB = 434, FIO2 = 0.296). In addition, post-test measurements were made 2 h after returning to ambient conditions at normobaric normoxia (PB = 636, FIO2 = 0.204). In the first hour of exposure VE was increased similarly by altitude and normobaric hypoxia. The was 38% above post-test values and end-tidal CO2 (PET(CO2) was lower by 4 mmHg. After 3, 6 and 9 h, the average VE in normobaric hypoxia was 26% higher than at altitude (p < 0.01), resulting primarily from a decline in VE at altitude. The difference between altitude and normobaric hypoxia was greatest at 3 h (+ 39%). In spite of the higher VE during normobaric hypoxia, the PET(CO2) was higher than at altitude. Changes in VE and PET(CO2) in normoxic hypobaria were minimal relative to normobaric normoxia post-test measurements. One possible explanation for the lower VE at altitude is that CO2 elimination is relatively less at altitude because of a reduction in inspired gas density compared to normobaric hypoxia; this may reduce the work of breathing or alveolar deadspace. The greater VE during the first hour at altitude, relative to subsequent measurements, may be related to the appearance of microbubbles in the pulmonary circulation acting to transiently worsen matching. Results indicate that hypobaria per se effects ventilation under altitude conditions.

NASA Discipline Environmental Health↗

Results of a remote multiplexer/digitizer unit accuracy and environmental study

A remote multiplexer/digitizer unit (RMDU), a part of the airborne integrated flight test data system, was subjected to an accuracy study. The study was designed to show the effects of temperature, altitude, and vibration on the RMDU. The RMDU was subjected to tests at temperatures from -54 C (-65 F) to 71 C (160 F), and the resulting data are presented here, along with a complete analysis of the effects. The methods and means used for obtaining correctable data and correcting the data are also discussed.

Wilner, D. O.↗

Effects of Flight Conditions at Booster Separation on Payload Weight in Orbit

A study of the principal flight parameters at booster separation was conducted to find the effect of each on the weight of the payload boosted into an earth orbit along a zero drag gravity turn trajectory. The parameters considered include Mach number (3 to 9), flight-path angle (10 deg to 55 deg), altitude (90,000 and 350,000 ft), inert weight ratio (0.05 to 0.15), and thrust-weight ratio (1.5 to 2.5), with a specific impulse of 289 seconds. Both transfer ellipse and direct orbit trajectories were considered. With either trajectory method, payload weight was highest for low initial flight-path angles and high initial Mach numbers. Of course, high initial Mach numbers require greater energy expenditures from the booster. Changes in initial altitude had little effect on payload weight, and only small gains were evident when thrust-weight ratio was increased.

Nelson, Richard D.↗

On the energy deposition of photoelectrons in the atmosphere of Venus

Vertical components of photoelectron fluxes in the atmosphere of Venus are computed by solving an appropriate form of the Boltzmann equation in the cases where there is no flux of either photoelectrons or solar-wind particles across the ionopause and where photoelectrons are free to escape from the atmosphere. It is assumed that Venus has no magnetic field and that the atmosphere is composed of carbon dioxide, atomic oxygen, and helium. The results are plotted as a function of altitude for several energies in the range from 100 eV to a cutoff of the order of 1 eV. Heating rates for the two upper boundary conditions and the case of no spatial transport are determined which show that transport effects dominate at altitudes greater than about 200 km. Electron temperatures are calculated for the adopted model atmosphere and ionosphere by solving the pertinent conservation equation, and excitation rates are computed for the CO Cameron band as well as the CO2(+) A and B bands.

Mccormick, P. T.↗

Relative effects on atmospheric ozone of latitude and altitude of supersonic flight

Three calculations are reported of the potential depletion of ozone by supersonic aircraft. These calculations utilized a two-dimensional model and a three-dimensional photochemical-dynamical model of the atmosphere in which ozone and the dynamical variables of the atmosphere were derived simultaneously. All calculations were based on a continuous atmospheric injection of 1.8 million tons/yr of NO2. Injections of 45 deg N and 20 km, at equilibrium, resulted in a 36% increase in total odd nitrogen between 8 and 38 km and in global ozone depletion of approximately 12%. Injection at 45 deg N and 17 km produced a 27% increase in odd nitrogen, but, because much of this increase occurred below 20 km, the ozone depletion amounted to only 6%. Injection at 10 deg N and 29 km resulted in a 55% increase of odd nitrogen; however, although there was more depletion above 20 km altitude, there was less below that altitude, and the ozone depletion was only 12.5%. In all three calculations, at least half as much ozone depletion occurred in the Southern Hemisphere as in the Northern Hemisphere.

Cunnold, D. M.↗

Effects of growth, diving history, and high altitude on blood oxygen capacity in harbor seals

Blood volume and body composition for diving and nondiving harbor seals were measured at six-week intervals during a 10-month period of captitivity. Whole body hematocrit, red cell volume per kg of lean body mass, and total circulating hemoglobin per kg lean body mass were significantly higher in the diving group, but relatively large blood volumes expressed in terms of body weight (11-12%) were found in both groups. A pair of harbor seals exposed to high altitude for about three months registered significant increases in red cell volume, blood hemoglobin levels, and blood volume expressed in terms of body weight; results of alveolar gas analyses indicate that hyperventilation also occurred. These typical mammalian responses to hypoxia suggest that the harbor seal's large blood volume and high hemoglobin content are an expression of phylogenetic control, and that in spite of its adaptability to apnea during its diving life, the animal cannot be considered preacclimatized to high altitude.

Kodama, A. M.↗

Comparison between calculated and measured photoelectron fluxes from Atmosphere Explorer C and E

The two-stream method has been used to calculate photoelectron fluxes. These results have been compared to those obtained by the photoelectron spectrometer on Atmosphere Explorers C and E. At both low altitudes, and higher altitudes (where transport effects are significant) the calculated and measured photoelectron fluxes yield good agreement. It is suggested that (1) better photoionization and scattering cross-section data will yield improved flux calculations, and (2) measurements of the pitch angle distribution are necessary for better high-altitude comparisons.

Nagy, A. F.↗

Considering Turbofan Operability in Hybrid Electric Aircraft Propulsion System Design

This paper explores the design of a hybrid electric aircraft propulsion system that uses a turbofan to power an electric system. In such a system, the gas turbine will experience a loss of power generation as altitude increases, however the electric system will not. This difference results in designs that may over size the electric system at high altitude or under size at low altitude. Two studies are performed within this paper. The first looks at extracting power from the engine for use with electric aircraft propulsion at cruise and the second reviews a design of an engine that uses thrust assist for takeoff. Both studies look at the effects of changing altitude on the amount of power extraction or insertion that can be taken from the turbofan as dictated by operability limits. Results of the paper show that low-pressure compressor surge margin and high-pressure compressor speed can be pushed to unaccepted limits with large scale power extraction or insertion, however these issues can be mitigated by adding power extraction or insertion at off design operating points to compensate. Additionally, the benefits of thrust assist are quantified for this configuration demonstrating a reduction in thrust specific fuel consumption at cruise of over 5%.

Gas Turbine↗

Considering Turbofan Operability in Hybrid Electric Aircraft Propulsion System Design

This paper explores the design of a hybrid electric aircraft propulsion system that uses a turbofan to power an electric system. In such a system, the gas turbine will experience a loss of power generation as altitude increases, however the electric system will not. This difference results in designs that may over size the electric system at high altitude or under size at low altitude. Two studies are performed within this paper. The first looks at extracting power from the engine for use with electric aircraft propulsion at cruise and the second reviews a design of an engine that uses thrust assist for takeoff. Both studies look at the effects of changing altitude on the amount of power extraction or insertion that can be taken from the turbofan as dictated by operability limits. Results of the paper show that low-pressure compressor surge margin and high-pressure compressor speed can be pushed to unaccepted limits with large scale power extraction or insertion, however these issues can be mitigated by adding power extraction or insertion at off design operating points to compensate. Additionally, the benefits of thrust assist are quantified for this configuration demonstrating a reduction in thrust specific fuel consumption at cruise of over 5%.

Gas turbine↗

Considering Turbofan Operability in Hybrid Electric Aircraft Propulsion System Design

This paper explores the design of a hybrid electric aircraft propulsion system that uses a turbofan to power an electric system. In such a system, the gas turbine will experience a loss of power generation as altitude increases, however the electric system will not. This difference results in designs that may over size the electric system at high altitude or under size at low altitude. Two studies are performed within this paper. The first looks at extracting power from the engine for use with electric aircraft propulsion at cruise and the second reviews a design of an engine that uses thrust assist for takeoff. Both studies look at the effects of changing altitude on the amount of power extraction or insertion that can be taken from the turbofan as dictated by operability limits. Results of the paper show that low-pressure compressor surge margin and high-pressure compressor speed can be pushed to unaccepted limits with large scale power extraction or insertion, however these issues can be mitigated by adding power extraction or insertion at off design operating points to compensate. Additionally, the benefits of thrust assist are quantified for this configuration demonstrating a reduction in thrust specific fuel consumption at cruise of over 5%.

Gas turbine↗

Considering Turbofan Operability in Hybrid Electric Aircraft Propulsion System Design

This paper explores the design of a hybrid electric aircraft propulsion system that uses a turbofan to power an electric system. In such a system, the gas turbine will experience a loss of power generation as altitude increases, however the electric system will not. This difference results in designs that may over size the electric system at high altitude or under size at low altitude. Two studies are performed within this paper. The first looks at extracting power from the engine for use with electric aircraft propulsion at cruise and the second reviews a design of an engine that uses thrust assist for takeoff. Both studies look at the effects of changing altitude on the amount of power extraction or insertion that can be taken from the turbofan as dictated by operability limits. Results of the paper show that low-pressure compressor surge margin and high-pressure compressor speed can be pushed to unaccepted limits with large scale power extraction or insertion, however these issues can be mitigated by adding power extraction or insertion at off design operating points to compensate. Additionally, the benefits of thrust assist are quantified for this configuration demonstrating a reduction in thrust specific fuel consumption at cruise of over 5%.

Gas Turbine↗

Determination of vertical ozone distributions by spacecraft measurements using a limb-scan technique

The principle of a new inversion technique which uses multiple wavelength-solar UV radiation satellite measurements for determining vertical ozone profiles is described, and examples of computer simulations for 280, 300, 320, and 340 nm are discussed. Weighting functions corresponding to the sensitivity of the limb radiance to the relative ozone density at each altitude are the basis for the inversion equation, which is then solved by an iteration technique. The use of multiple wavelengths can provide more information of higher accuracy over a wider height range than those profiles recovered at a single wavelength. It is indicated that an effective range of altitude of approximately 20-70 km with a vertical resolution of 1-2 km is feasible for determining ozone profiles with an inferred profile error about three to four times larger than the measurement error within that altitude region. Ozone profile accuracy of the highest altitude region may be improved using wavelengths down to 260 nm, and inferred ozone profiles above 70 km are possible, but with a larger error.

Aruga, T.↗

Retrieval of HCl and HNO3 Profiles from Ground-Based FTIR Data Using SFIT2

A recently developed algorithm, SFIT2, is used to assess profile information available in ground-based FTIR measurements of HCl and HNO3 and to analyze spectra recorded at Lauder, New Zealand, and Arrival Heights, Antarctica. It is shown that the altitude range of HCI retrievals may be extended by using multiple spectral lines. A preliminary analysis of a five year record of HNO3 at Lauder shows that the Pinatubo aerosol caused a large increase of HNO3 in a layer at about 20-30 km while having little effect at lower altitude.

Connor, Brian↗

Math modeling for helicopter simulation of low speed, low altitude and steeply descending flight

A math model was formulated to represent some of the aerodynamic effects of low speed, low altitude, and steeply descending flight. The formulation is intended to be consistent with the single rotor real time simulation model at NASA Ames Research Center. The effect of low speed, low altitude flight on main rotor downwash was obtained by assuming a uniform plus first harmonic inflow model and then by using wind tunnel data in the form of hub loads to solve for the inflow coefficients. The result was a set of tables for steady and first harmonic inflow coefficients as functions of ground proximity, angle of attack, and airspeed. The aerodynamics associated with steep descending flight in the vortex ring state were modeled by replacing the steady induced downwash derived from momentum theory with an experimentally derived value and by including a thrust fluctuations effect due to vortex shedding. Tables of the induced downwash and the magnitude of the thrust fluctuations were created as functions of angle of attack and airspeed.

Sheridan, P. F.↗

Auroral effects in the D region of the ionosphere

Physical phenomena associated with the interaction between auroral particles and electromagnetic fields, auroral energy flow, and the propagation of auroral effects to low altitudes are discussed in detail. It is concluded that energy deposition of soft auroral X-rays would be negligible at stratospheric altitudes. New data from incoherent backscatter measurements of neutral winds in the auroral region indicate a lack of correlation between stratospheric winds and winds in the auroral ionosphere. Magnetograms are used to show that sector boundary crossings with a time scale of approximately one hour (as opposed to the sector structure itself with a time scale of several days) do not couple effectively with the magnetosphere and are not significant energy inputs to it.

Akasofu, S. I.↗