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At least 379 records · Page 21

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NASA NTRS1986

Performance testing of lidar receivers

In addition to the considerations about the different types of noise sources, dynamic range, and linearity of a lidar receiver, one requires information about the pulse shape retaining capabilities of the receiver. For this purpose, relatively precise information about the height resolution as well as the recovery time of the receiver, due both to large transients and to fast changes in the received signal, is required. As more and more analog receivers using fast analog to digital converters and transient recorders will be used in the future lidar systems, methods to test these devices are essential. The method proposed for this purpose is shown. Tests were carried out using LCW-10, LT-20, and FTVR-2 as optical parts of the optical pulse generator circuits. A commercial optical receiver, LNOR, and a transient recorder, VK 220-4, were parts of the receiver system.

Shams, M. Y.↗

NASA NTRS1987

Challenges in modeling the X-29 flight test performance

Presented are methods, instrumentation, and difficulties associated with drag measurement of the X-29A aircraft. The initial performance objective of the X-29A program emphasized drag polar shapes rather than absolute drag levels. Priorities during the flight envelope expansion restricted the evaluation of aircraft performance. Changes in aircraft configuration, uncertainties in angle-of-attack calibration, and limitations in instrumentation complicated the analysis. Limited engine instrumentation with uncertainties in overall in-flight thrust accuracy made it difficult to obtain reliable values of coefficient of parasite drag. The aircraft was incapable of tracking the automatic camber control trim schedule for optimum wing flaperon deflection during typical dynamic performance maneuvers; this has also complicated the drag polar shape modeling. The X-29A was far enough off the schedule that the developed trim drag correction procedure has proven inadequate. However, good drag polar shapes have been developed throughout the flight envelope. Preliminary flight results have compared well with wind tunnel predictions. A more comprehensive analysis must be done to complete performance models. The detailed flight performance program with a calibrated engine will benefit from the experience gained during this preliminary performance phase.

John W Hicks↗

NASA NTRS1987

Challenges in modeling the X-29A flight test performance

The paper presents the methods, instrumentation, and difficulties associated with drag measurement of the X-29A aircraft. The initial performance objective of the X-29A program emphasized drag polar shapes rather than absolute drag levels. Priorities during the flight envelope expansion restricted the evaluation of aircraft performance. Changes in aircraft configuration, uncertainties in angle-of-attack calibration, and limitations in instrumentation complicated the analysis. Limited engine instrumentation with uncertainties in overall in-flight thrust accuracy made it difficult to obtain reliable values of coefficient of parasite drag. The aircraft was incapable of tracking the automatic camber control trim schedule for optimum wing flaperon deflection during typical dynamic performance maneuvers; this has also complicated the drag polar shape modeling. The X-29A was far enough off the schedule that the developed trim drag correction procedure has proven inadequate. Despite these obstacles, good drag polar shapes have been developed throughout the flight envelope. Preliminary flight results have compared well with wind tunnel predictions. A more comprehensive analysis must be done to complete the performance models. The detailed flight performance program with a calibrated engine will benefit from the experience gained during this preliminary performance phase.

Hicks, John W.↗

NASA NTRS1987

Performance test of a laboratory pump liquid transfer based on the fountain effect

A laboratory scale pump has been tested in detail in order to determine the flow characteristics of a heater-activated all-metal thermomechanical pump (fountain effect pump, FEP). The emphasis is on the functional dependence of the fountain pressure difference versus mass throughput. A modified Vote et al. (1971) power law approximation is employed for a simplified description of the flow rate as a function of the driving force. Flow rates of up to 10 liters/(hr/sq cm) have been obtained despite a large nominal pore size of the porous plug of 2 microns (filtration rating) used for the FEP.

Chen, W. E. W.↗

NASA NTRS1988

Performance test of a laboratory pump for liquid transfer based on the fountain effect

A laboratory scale pump which determines the flow characteristics of a heater-activated all-metal thermomechanical fountain-effect pump (FEP) is evaluated. Results are presented on the functional dependence of the fountain pressure difference versus mass throughput. A modified Vote et al. (1971) power law approximation is used to obtain the flow rate as a function of the driving force. Despite a large nominal pore size of the porous plug used for the FEP, flow rates of up to 10 liter/hr sq cm have been obtained.

Chen, W. E. W.↗

NASA NTRS1988

Jitter performance test for the Hubble Space Telescope - Method and results

The types of on-board equipment on the Hubble Space Telescope (HST) that can cause jitter are identified. Tests designed and conducted to measure the motion of the focal plane due to disturbances from the on-board equipment are then described. Test results are presented for two types of jitter-producing equipment: the reaction wheel assemblies and the engineering/science tape recorders.

Blair, Mark A.↗

NASA NTRS1988