Test & Measurement

Rangefinder for Measuring Volume of Cryogenic or Caustic Turbulent Fluids

A non-intrusive laser rangefinder yields extremely accurate fluid height measurements. Stennis Space Center, Mississippi Specific impulse (ISP), or simply impulse (change in momentum) per unit amount of propellant consumed, is a measure of rocket and jet engine efficiency. The amount of propellant, or in the case of engine testing at the Stennis Space Center (SSC), cryogen consumed during rocket engine testing must be measured to accurately quantify ISP. One way to determine the amount of cryogen used is to measure the change in cryogen fluid height within a storage/feed tank during testing and then relate the change in height to volume of cryogen consumed. A float system coupled with discrete vertically positioned Reed switches is currently used at the SSC to determine cryogen fluid height and then determine cryogen consumed during a rocket motor test firing. However, the cryogen fluid level within a run tank varies continuously and the switches are placed at discrete locations, limiting the accuracy of this method. If individual switch failures occur, the error increases due to the increased distance between switches/measurement locations. In addition, since pressurized gas is used to force the significantly cooler liquid cryogen out of the tank during a test, the liquid cryogen surface is turbulent and not flat or smooth, which can also affect accuracy.

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Micro-Force Sensing Nanoprobe

Goddard Space Flight Center, Greenbelt, Maryland The NGXO (Next Generation X-Ray Optics) project has several problems relating to how to bond a very thin glass mirror to a metallic structure without distortion. One problem is that all epoxies shrink (at the micron level) when they cure. This shrinkage distorts the optical quality of the mirror unacceptably. Another problem is how to correlate finite element models of thin glass mirrors to verify that they are accurately predicting the distortions that a real glass will see due to enforced displacements, such as those applied by epoxy shrinkage. The forces required to simulate epoxy shrinkage and to balance a mirror on a bed of actuators are in the 100-1000 micro-newton range. The displacements are on the order of a few microns. These tiny forces and displacements cannot be easily measured or actuated with typical lab equipment.

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High-Channel-Count, High-Scan-Rate Data Acquisition System for the NASA Langley Transonic Dynamics Tunnel

Langley Research Center, Hampton, Virginia The NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) has been operational since 1960, investigating a wide range of aeroelastic and non-aeroelastic phenomena. A dedicated aeroelastic test facility, the TDT is a large, variable-pressure, transonic wind tunnel. To support unique types of aeroelastic and dynamic tests, the TDT possesses a dynamic data acquisition system (DAS) with synchronous scanning of all analog channels. Steady (static) values are simply computed as the mean of any signal. The existing TDT DAS is referred to as the Open Architecture Data Acquisition System (OA-DAS). An effort was initiated to replace OA-DAS in order to increase the scan rate, increase the channel count, increase the reliability, increase user friendliness, and improve upon some features while maintaining synchronous scanning and other unique abilities. This effort has been spearheaded by researchers within the Aeroelasticity Branch (AB) co-located with the TDT; hence, the new data system has been named AB-DAS. The new data system will serve as the primary data system and will substantially increase the scan rate capabilities and analog channel count. This synchronous and dynamic system enables high-channel-count buffet and aeroacoustic tests in addition to the range of other testing done at TDT.

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Fusible Alloy Thermometer

Goddard Space Flight Center, Greenbelt, Maryland This work was based on the need for a relatively small passive detector of maximum temperature reached by an object that can be visually inspected. The device requirements are to be hermetically sealed for contamination control, give a clear indication of maximum temperature achieved (non-reversible) with a ~10 °C resolution, have an essentially unlimited shelf-life and insensitivity to radiation, be passive without any electronics or mechanisms, provide good thermal conductivity, and be low-cost. Prior detectors have an unclear lifetime, contamination outgassing properties, and radiation tolerance. These could be used at much higher temperatures than plastic methods (>>100 °C), though out of scope for the tests performed to date.

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Small-Volume Pressurized Sample Handling System

NASA’s Jet Propulsion Laboratory, Pasadena, California A method was developed for effective, efficient, non-destructive, in-situ sample processing. Pressure vessels are used for sample delivery and collection, a shaker is used to keep the particles suspended, a back pressure of argon gas is used to keep the system under pressure to regulate the flow, and flow restrictors and frits are used that never come into contact with the sample slurry to avoid clogs.

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Live-Cell Microscopy and Traction Force Measurements with Simulated Microgravity “Clinochip”

Goddard Space Flight Center, Greenbelt, Maryland The deleterious effects of microgravity are undeniable: reduced bone mineral density, muscle atrophy, vascular remodeling, etc. These health issues may derive from both systemic factors, and from direct alterations to intracellular components and in the local microenvironment around cells. To understand the biological mechanisms at play, detailed studies have been performed in spaceflight. However, because experiments on the International Space Station (ISS) can be prohibitively expensive, clinostats are an alternative ground-based analogue for cellular studies. Clinostats “randomize” the orientation of gravity with respect to the cell fixed-frame, thereby simulating microgravity by eliminating a preferential gravity direction.

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Comparison of Three Methods for Measuring Distortion in Optical Windows

A new method for quantifying distortion based on phase-shifting interferometry has been developed. John F. Kennedy Space Center, Florida The primary function of a window is to allow observation of, and protection from, a potentially hazardous environment. Yet, from the window designer’s point of view, ensuring protection from weather conditions in home windows; from wind, temperature, and airborne debris in automotive windows; and from extreme pressures and temperatures in aircraft and spacecraft windows has almost always taken precedence over image quality. It is more important to protect an astronaut from the vacuum of space than to provide clear imagery, yet these are not exclusive requirements. Advances in materials and material processing allow the designer to attain better optical performance while not sacrificing important material specifications such as strength. In addition, increased performance demands on spacecraft windows — which are now used for photography, telescope observation, and laser communications — require greater consideration of optical clarity.

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