Feedthrough for Severe Environments and Temperatures

Dusty, dirty environments can be very tough on connectors. The abrasive nature of dust and dirt particles can rub and wear down connector surfaces through friction, and have a negative effect on coatings used on gaskets to seal equipment. Dust on umbilical connections can also make mating and de-mating electrical and fluid connections difficult, hazardous, and unreliable. NASA's Quick Disconnect (QD) design uses the gas supplied by the umbilical to spray the connector surfaces prior to mating to remove dust and debris. The QD uses a novel dual-poppet design and springs that balance forces on umbilical components. This allows a controlled release of gas to clear away dust from the end of the connector before it it inserted in the supply umbilical. The connector assembly is capable of mating and de-mating under 3500 psi fluid/gas. One poppet seals the QD while de-mated and automatically cleans the front surface of the QD during mating. A second poppet seals the QD while de-mated and automatically cleans the cylindrical surface of the QD during mating. The internal cavity of the QD is specifically designed such that the pressure in the line is reduced from 3500 psi to 450 psi while surface cleaning occurs. Finally, all exterior connector surfaces are designed to minimize the entrapment of dust while in the de-mated position.

Cryostat-100 combines the best features of previous cryostats developed by NASA, while offering new features and conveniences. This unit can readily handle the full range of cryogenic-vacuum conditions over several orders of magnitude of heat flux. Guide rings, handling tools, and other design items make insulation change-out and test measurement verification highly reliable and efficient to operate. The new apparatus requires less ancillary equipment (it is not connected to storage tank, phase separator, subcooler, etc.) to operate properly. It is top-loading, which makes disassembly, change-out, and instrumentation hook-up much faster. The thermal stability is improved because of internal vapor plates, a single-tube system of filling and venting, bellows feed-throughs, Kevlar thread suspensions, and heavy-wall stainless-steel construction. The cold mass of Cryostat-100 is 1m long, with a diameter of 168 mm. The test articles can therefore be of a corresponding length and diameter, with a nominal thickness of 25.4 mm. Shorter lengths are acceptable, and thicknesses may be from 0 mm to 50 mm. Tests are conducted from ambient pressure (760 torr) to high vacuum (below 110-4 torr) and at any vacuum pressure increment between these two extremes. The residual gas (and purge gas) is typically nitrogen but can be any purge gas, such as helium, argon, or carbon dioxide. Typically, eight cold vacuum pressures are performed for each test series. The warm boundary temperature is approximately 293 K, and the cold boundary temperature is approximately 78 K. The delta temperature for the cryogenic testing is therefore approximately 215 K. A unique lift mechanism provides for change-out of the insulation test specimens. It also provides for maintenance and other operations in the most effective and time-efficient ways. The lift mechanism is also a key to the modularity of the overall system.

Dusty, dirty environments can be very tough on connectors. The abrasive nature of dust and dirt particles can rub and wear down connector surfaces through friction, and have a negative effect on coatings used on gaskets to seal equipment. Dust on umbilical connections can also make mating and de-mating electrical and fluid connections difficult, hazardous, and unreliable. NASA's Quick Disconnect (QD) design consists of columnar arrays of parallel filaments. All the pins of the electrical connector easily penetrate the barriers when the umbilicals are brought together. They are wiped clean of dust when they penetrate the barrier and mate cleanly and reliably. Likewise, the male end of a fluid connector penetrates the filament arrays of both connector ends. Since the filament arrays are oriented perpendicular to each other, the entire circumference of the connector is contacted by the filaments that stretch around, conform to, and sweep off dust from the mating surface ensuring a clean and secure connection.

Advances in new polymers and composites along with growing industrial needs in below-ambient temperature applications have brought about the Macroflash development. Accurate thermal performance information, including effective thermal conductivity data, are needed under relevant end-use conditions. The Macroflash is a practical tool for basic testing of common materials or research evaluation of advanced materials/systems. The Macroflash can test solids, foams, or powders that are homogeneous or layered in composition. Test specimens are typically 75mm in diameter and 6mm in thickness. The cold side is maintained by liquid nitrogen at 77 K while a heater disk maintains a steady warm-side temperature from ambient up to 373 K. The steady boiloff of the liquid nitrogen provides a direct measure of the heat energy transferred through the thickness of the test specimen. Nitrogen or other gas is supplied to the instrument to establish a stable, moisture-free, ambient pressure environment. Different compression loading levels can also be conveniently applied to the test specimen as needed for accurate, field-representative thermal performance data. The Macroflash is calibrated from approximately 10 mW/m-K to 800 mW/m-K using well-characterized materials.

Efficient thermal management has long been an issue in both commercial systems and in the extreme environments of space. In space exploration and habitation, significant challenges are experienced in providing fluid support systems such as cryogenic storage, life support, and habitats; or thermal control systems for launch vehicle protection, environmental heat management, or electronic instruments. Furthermore, these systems operate in dynamic, transient modes and often under extremes of temperature or pressure. The current technical requirements associated with the thermal management of these systems result in control issues as well as significant life-cycle costs. To combat these issues, the Adaptive Thermal Management System (ATMS) was developed to help provide the capability for tanks, structural walls, or composite substrate materials to switch functionality (conductive or insulative) depending on environmental conditions or applied stimuli. As a result, the ATMS provides the ability to adapt between both heating and cooling modes within a single system. For example, shape memory alloy (SMA) elements are used to actuate at certain design temperatures to create a conductive bridge between two metal plates allowing broad-area heat rejection from the hotter surface. Upon cooling to the lower design set-point, the SMA elements return to their original shapes, thereby breaking the conductive path and returning the system to its overall insulative state. This technology has the potential to be applied to any system that would have the need for a self-regulating thermal management system that allows for heat transfer from one side to another.