Mechanical Components

Binding Causes of Printed Wiring Assemblies With Card-Loks

A document discusses a study that presents the first documented extraction loads, both nominal and worstcase, and presents the first comprehensive evaluation of extraction techniques, methodologies, and tool requirements relating to extracting printed wiring assemblies (PWAs) with Card-Loks during EVA (extra vehicular activity). This task was performed for the first time during HST (Hubble Space Telescope) Servicing Mission 4.

Posted in: Mechanics, Mechanical Components, Briefs

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A Reversible Thermally Driven Pump for Use in a Sub-Kelvin Magnetic Refrigerator

A document describes a continuous magnetic refrigerator that is suited for cooling astrophysics detectors. This refrigerator has the potential to provide efficient, continuous cooling to temperatures below 50 mK for detectors, and has the benefits over existing magnetic coolers of reduced mass because of faster cycle times, the ability to pump the cooled fluid to remote cooling locations away from the magnetic field created by the superconducting magnet, elimination of the added complexity and mass of heat switches, and elimination of the need for a thermal bus and single crystal paramagnetic materials due to the good thermal contact between the fluid and the paramagnetic material.

Posted in: Mechanics, Mechanical Components, Briefs

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Coring Sample Acquisition Tool

A sample acquisition tool (SAT) has been developed that can be used autonomously to sample drill and capture rock cores. The tool is designed to accommodate core transfer using a sample tube to the IMSAH (integrated Mars sample acquisition and handling) SHEC (sample handling, encapsulation, and containerization) without ever touching the pristine core sample in the transfer process.

Posted in: Mechanics, Mechanical Components, Briefs

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Robust Tensioned Kevlar Suspension Design

A suite of compact design elements improves the reliability of Kevlar suspension systems. One common but challenging problem in cryogenic engineering is to produce a mount that has excellent thermal isolation but is also rigid. Such mounts can be achieved by suspending the load from a network of fibers or strings held in tension. Kevlar fibers are often used for this purpose owing to their high strength and low thermal conductivity. However, Kevlar presents challenges since it expands on cooling and tends to creep after initial tensioning, causing reductions in the resonant frequencies and a shift in the position of the suspended element, which can lead to misalignment and thermal short circuits. With existing designs, such as the Kevlar suspension used on the Herschel SPIRE instrument, it is difficult to re-tension the Kevlar or measure the tension because parts of the Kevlar string are staked with epoxy. Non-cryogenic designs used on a larger scale, such as tensioning reels on sailboats, use turnbuckles and fixed eyebolts that cannot be scaled down to a small-scale structure without a significant addition of mass.

Posted in: Mechanics, Mechanical Components, Briefs

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Focal Plane Alignment Utilizing Optical CMM

This approach will eliminate all requirements on positional tolerances. In many applications, an optical detector has to be located relative to mechanical reference points. One solution is to specify stringent requirements on (1) mounting the optical detector relative to the chip carrier, (2) soldering the chip carrier onto the printed circuit board (PCB), and (3) installing the PCB to the mechanical structure of the subsystem. Figure 1 shows a sketch of an optical detector mounted relative to mechanical reference with high positional accuracy. The optical detector is typically a fragile wafer that cannot be physically touched by any measurement tool.

Posted in: Mechanics, Mechanical Components, Briefs

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Long-Life, Lightweight, Multi-Roller Traction Drives for Planetary Vehicle Surface Exploration

These drives can be used for Earth-based applications where extreme temperatures are involved. NASA’s initiative for Lunar and Martian exploration will require long lived, robust drive systems for manned vehicles that must operate in hostile environments. The operation of these mechanical drives will pose a problem because of the existing extreme operating conditions. Some of these extreme conditions include operating at a very high or very cold temperature, operating over a wide range of temperatures, operating in very dusty environments, operating in a very high radiation environment, and operating in possibly corrosive environments.

Posted in: Mechanics, Mechanical Components, Briefs

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Wavefront Compensation Segmented Mirror Sensing and Control

Six degrees of freedom can be sensed at each segment edge. The primary mirror of very large submillimeter-wave telescopes will necessarily be segmented into many separate mirror panels. These panels must be continuously co-phased to keep the telescope wavefront error less than a small fraction of a wavelength, to ten microns RMS (root mean square) or less. This performance must be maintained continuously across the full aperture of the telescope, in all pointing conditions, and in a variable thermal environment.

Posted in: Mechanics, Mechanical Components, Briefs

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