Search NASA⌕ Search

SEARCH · Search NASA

Results for “Test Techniques”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Evaluation of nondestructive testing techniques for the space shuttle nonmetallic thermal protection system

A program was conducted to evaluate nondestructive analysis techniques for the detection of defects in rigidized surface insulation (a candidate material for the Space Shuttle thermal protection system). Uncoated, coated, and coated and bonded samples with internal defects (voids, cracks, delaminations, density variations, and moisture content), coating defects (holes, cracks, thickness variations, and loss of adhesion), and bondline defects (voids and unbonds) were inspected by X-ray radiography, acoustic, microwave, high-frequency ultrasonic, beta backscatter, thermal, holographic, and visual techniques. The detectability of each type of defect was determined for each technique (when applicable). A possible relationship between microwave reflection measurements (or X-ray-radiography density measurements) and the tensile strength was established. A possible approach for in-process inspection using a combination of X-ray radiography, acoustic, microwave, and holographic techniques was recommended.

Tiede, D. A.↗
NASA NTRS1979

An impulse test technique with application to acoustic measurements

A method has been presented for measuring the acoustic properties of an absorbent material and a duct/nozzle system (with or without airflow) using a high voltage spark discharge as an impulse source of sound. The cross-spectra of the incident, reflected and transmitted acoustic pressure transients are analyzed by way of a FFT digital processor in the form of complex transfer functions. These transfer functions have a direct relationship to the termination impedance and radiation directivity. The impulse method has been justified by comparisons, with data obtained from existing methods (both experimental and theoretical), that show excellent agreement. Reflection coefficients and radiation impedances of various duct-nozzle systems and their associated far-field directivities are also presented as some of the applications of the impulse technique.

Salikuddin, M.↗
NASA NTRS1981

Irrigated lands assessment for water management: Technique test

A procedure for estimating irrigated land using full frame LANDSAT imagery was demonstrated. Relatively inexpensive interpretation of multidate LANDSAT photographic enlargements was used to produce a map of irrigated land in California. The LANDSAT and ground maps were then linked by regression equations to enable precise estimation of irrigated land area by county, basin, and statewide. Land irrigated at least once in California in 1979 was estimated to be 9.86 million acres, with an expected error of less than 1.75% at the 99% level of confidence. To achieve the same level of error with a ground-only sample would have required 3 to 5 times as many ground sample units statewide. A procedure for relatively inexpensive computer classification of LANDSAT digital data to irrigated land categories was also developed. This procedure is based on ratios of MSS band 7 and 5, and gave good results for several counties in the Central Valley.

Wall, S. L.↗
NASA NTRS1983

A system study for the application of microcomputers to research flight test techniques

The onboard simulator is a three degree of freedom aircraft behavior simulator which provides parameters used by the interception procedure. These parameters can be used for verifying closed loop performance before flight. The air to air intercept mode is a software package integrated in the simulation process that generates a target motion and performs a tracking procedure that predicts the most likely next target position, for a defined time step. This procedure also updates relative position parameters and gives adequate fire commands. A microcomputer based on an aircraft spin warning system periodically samples the assymetric thrust and yaw rate of an airplane and then issues voice synthesized warnings and /or suggests to the ilot how to respond to the situation.

Smyth, R. K.↗
NASA NTRS1983

Aircraft lightning-induced voltage test technique developments

High voltage safety, fuels safety, simulation, and response/measurement techniques are discussed. Travelling wave transit times, return circuit conductor configurations, LC ladder network generators, and repetitive pulse techniques are also discussed. Differential conductive coaxial cable, analog fiber optic link, repetitive pulse sampled data instrumentation system, flash A/D optic link system, and an FM telemetry system are considered.

Crouch, K. E.↗
NASA NTRS1986

Comparative Thermal-Conductivity Test Technique

Approximate thermal conductivities determined rapidly. Two specimens, to be compared, placed in assembly with insulation. One end of assembly placed in furnace. Temperature of furnace, of each end, and of center of each specimen recorded. Procedure used to rate quickly candidate materials for applications in which thermal conductivity prime consideration.

Webster, C. N.↗
NASA NTRS1986

The use of flight test techniques in aircraft accident investigations

Wind shear is a serious safety hazard to commercial aviation. Low level wind shear (downburst) was the cause of the takeoff accident in New Orleans, July 9, 1982, and the landing accident in Dallas, Aug. 2, 1985. Shear layer instability is a common cause of clear air turbulence (CAT) at cruising altitudes. A number of encounters with severe CAT, in which passengers were injured, have recently occurred (Hannibal, MO, April 1981; Morton, WY, July 1982; etc.). Improved accident investigation techniques can lead to a better understanding of the nature of the wind environment associated with downbursts and CAT and to better detection and avoidance procedures. For the past several years, NASA-Ames has worked closely with the National Transportation Safety Board in the investigation of wind related accidents.

Parks, E. K.↗
NASA NTRS1989

New test techniques to evaluate near field effects for supersonic store carriage and separation

Store separation and store carriage drag studies were conducted. A primary purpose is to develop new experimental methods to evaluate near field effects of store separation and levels of store carriage drag associated with a variety of carriage techniques for different store shapes and arrangements. Flow field measurements consisting of surface pressure distributions and vapor screen photographs are used to analyze the variations of the store separation characteristics with cavity geometry. Store carriage drag measurements representative of tangent, semi-submerged, and internal carriage installations are presented and discussed. Results are included from both fully metric models and models with only metric segments (metric pallets) and the relative merits of the two are discussed. Carriage drag measurements for store installations on an aircraft parent body are compared both with prediction methods and with installations on a generic parent body.

Sawyer, Wallace C.↗
NASA NTRS1990

Mechanical system diagnostics using vibration testing techniques

The 'Cepstrum' technique of vibration-path identification allows the recovery of the transfer function of a system with little knowledge as to its excitation force, by means of a mathematical manipulation of the system output in conjunction with subtraction of part of the output and suitable signal processing. An experimental program has been conducted to evaluate the usefulness of this technique in the cases of simple, cantilever-beam and free-free plate structures as well as in that of a complex mechanical system. On the basis of the transfer functions thus recovered, it was possible to evaluate the shifts in the resonance frequencies of a structure due to the presence of defects.

Mcleod, Catherine D.↗
NASA NTRS1993

Test techniques for evaluating flight displays

The rapid development of graphics technology allows for greater flexibility in aircraft displays, but display evaluation techniques have not kept pace. Historically, display evaluation has been based on subjective opinion and not on the actual aircraft/pilot performance. Existing electronic display specifications and evaluation techniques are reviewed. A display rating technique analogous to handling qualities ratings was developed and is recommended for future evaluations. The choice of evaluation pilots is also discussed and the use of a limited number of trained evaluators is recommended over the use of a large number of operational pilots.

Haworth, Loran A.↗