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Kurtz, D. W.

Publications and source records attributed to Kurtz, D. W..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

The high-overtone p-mode spectrum of the rapidly oscillating Ap star HR 1217 (HD 24712) - Results of a frequency analysis of 324 hr of multi-site photometric observations obtained during a 46-d time-span in 1986

The present high-speed photometry for the rapidly oscillating Ap star HR 1217 indicates that the 6-min light variations are amplitude-modulated, in phase with the magnetic variations. Amplitude and magnetic maxima coincide, while the mean light minimum occurs at a perhaps significantly different time. It is established that HR 1217 is an oblique rotator with a centered dipole magnetic field, as well as an oblique pulsator whose pulsation and magnetic axes are aligned. There are six principal frequencies of pulsation; the secondary frequencies indicate that the principal ones are amplitude-modulated on a time-scale of months.

Kurtz, D. W.↗
NASA NTRS1986

Systems Engineering of Electric and Hybrid Vehicles

Technical paper notes systems engineering principles applied to development of electric and hybrid vehicles such that system performance requirements support overall program goal of reduced petroleum consumption. Paper discusses iterative design approach dictated by systems analyses. In addition to obvious peformance parameters of range, acceleration rate, and energy consumption, systems engineering also considers such major factors as cost, safety, reliability, comfort, necessary supporting infrastructure, and availability of materials.

Kurtz, D. W.↗
NASA NTRS1985

Aerodynamic Design of Road Vehicles

Guidebook discusses design of road vehicles to reduce aerodynamic drag. Book presents strategy for integrating aerodynamic design into vehicle design. Book written for readers lacking experience in aerodynamics.

Kurtz, D. W.↗
NASA NTRS1984

The Ground Based Photometric Limitations to the Search for Light Variations Due to 5-minute Solar-type Oscillations in Other Stars

High speed photometric observations obtained with a single channel photometer on the South African Astronomical Observatory 0.5-m and 1.9-m telescopes are presented. It is argued that the dominant source of noise at periods near 5 minutes is sky transparency variation rather than scintillation. For bright stars this means that, at this period, increased telescope aperture does not improve photometric accuracy. It is claimed that ground based photometric observations cannot reach accuracies sufficient to study solar-type oscillations in other stars. Such observations must be made from space. Recommendations for improving ground based observations are made.

Kurtz, D. W.↗
NASA NTRS1983

EHV systems technology - A look at the principles and current status

An examination of the basic principles and practices of systems engineering is undertaken in the context of their application to the component and subsystem technologies involved in electric and hybrid vehicle (EHV) development. The limitations of purely electric vehicles are contrasted with hybrid, heat engine-incorporating vehicle technology, which is inherently more versatile. A hybrid vehicle concept assessment methodology is presented which employs current technology and yet fully satisfies U.S. Department of Energy petroleum displacement goals.

Kurtz, D. W.↗
NASA NTRS1980

Aerodynamic design of electric and hybrid vehicles: A guidebook

A typical present-day subcompact electric hybrid vehicle (EHV), operating on an SAE J227a D driving cycle, consumes up to 35% of its road energy requirement overcoming aerodynamic resistance. The application of an integrated system design approach, where drag reduction is an important design parameter, can increase the cycle range by more than 15%. This guidebook highlights a logic strategy for including aerodynamic drag reduction in the design of electric and hybrid vehicles to the degree appropriate to the mission requirements. Backup information and procedures are included in order to implement the strategy. Elements of the procedure are based on extensive wind tunnel tests involving generic subscale models and full-scale prototype EHVs. The user need not have any previous aerodynamic background. By necessity, the procedure utilizes many generic approximations and assumptions resulting in various levels of uncertainty. Dealing with these uncertainties, however, is a key feature of the strategy.

Kurtz, D. W.↗
NASA NTRS1979

Aerodynamic characteristics of sixteen electric, hybrid, and subcompact vehicles

An elementary electric and hybrid vehicle aerodynamic data base was developed using data obtained on sixteen electric, hybrid, and sub-compact production vehicles tested in the Lockheed-Georgia low-speed wind tunnel. Zero-yaw drag coefficients ranged from a high of 0.58 for a boxey delivery van and an open roadster to a low of about 0.34 for a current four-passenger proto-type automobile which was designed with aerodynamics as an integrated parameter. Vehicles were tested at yaw angles up to 40 degrees and a wing weighting analysis is presented which yields a vehicle's effective drag coefficient as a function of wing velocity and driving cycle. Other parameters investigated included the effects of windows open and closed, radiators open and sealed, and pop-up headlights. Complete six-component force and moment data are presented in both tabular and graphical formats. Only limited commentary is offered since, by its very nature, a data base should consist of unrefined reference material. A justification for pursuing efficient aerodynamic design of EHVs is presented.

Kurtz, D. W.↗
NASA NTRS1978

Weight propagation and equivalent horsepower for alternate-engined cars

In order to evaluate properly the consequences of replacing conventional Otto-cycle engines with alternate power systems, comparisons must be carried out at the vehicle level with functionally equivalent cars. This paper presents the development and application of a procedure for establishing equivalent vehicles. A systematic weight propagation methodology, based on detailed weight breakdowns and influence factors, yields the vehicle weight impacts due to changes in engine weight and power. Performance-matching criteria, utilizing a vehicle simulation program, are then employed to establish Otto-engine-equivalent vehicles, whose characteristics can form the basis for alternative engine evaluations.

Klose, G. J.↗
NASA NTRS1976

Aerodynamics as a subway design parameter

A parametric sensitivity study has been performed on the system operational energy requirement in order to guide subway design strategy. Aerodynamics can play a dominant or trivial role, depending upon the system characteristics. Optimization of the aerodynamic parameters may not minimize the total operational energy. Isolation of the station box from the tunnel and reduction of the inertial power requirements pay the largest dividends in terms of the operational energy requirement.

Kurtz, D. W.↗
NASA NTRS1975

Experimental aerodynamic characteristics of vehicles traveling in tubes

A simplified theoretical model for a vehicle traveling through an unvented tube under equilibrium incompressible conditions was used to guide the test program, reduce the data, and determine the self-consistency of the results. The results were then used to establish values for the arbitrary coefficients in the theoretical model. Substantial progress was made in understanding the aerodynamic characteristics of vehicles traveling in tubes as exemplified by the good agreement of the theoretical model predictions with the experimental data throughout the Reynolds number range (three orders of magnitude, up to that for an actual full-scale system) and the many geometric variables tested.

Kurtz, D. W.↗
NASA NTRS1972

Search for coronal line emission from the Cygnus Loop.

The flux from the edges of the Cygnus Loop in the forbidden Fe XIV coronal line at 5303 A is measured to be less than 5 nanoergs per sq cm per sterad per sec (0.017 R) in a 3 A band centered on the line. This upper limit is an order of magnitude lower than the predicted total flux in the line and implies that there must be substantial broadening of the line profile by mass motion or that the temperature is somewhat higher than the present best estimate from X-ray data.

Kurtz, D. W.↗