Macroflash (Cup Cryostat)

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.

The Cryostat-500 provides laboratory measurement of the steady-state thermal transmission properties of thermal insulation systems under conditions below ambient temperature. Liquid nitrogen is used as a direct measure of the energy going through the test specimen. Thermal insulation systems may be composed of one or more materials that may be homogeneous or non-homogeneous at boundary conditions from 77 K to 373 K and in environments from high vacuum (10E-7 torr) to ambient pressure (10E+3 torr). The Cryostat-500 provides a much wider range of thermal performance and covers the full range of environmental conditions for applications below ambient temperature. The instrument has been proven through extensive testing of foams, composite panels, multilayer insulation (MLI) systems, aerogel blankets, fiberglass, and many other types of materials. Both the quality and quantity of the thermal performance data for insulation materials and systems have increased even as the process and method has become more time efficient and cost effective. Further guidelines on the test method and equipment for the Cryostat-500 are given in ASTM C1774, Annex A3.

Space and ground launch support related hardware often operate under extreme pressure, temperature, and corrosive conditions. When dealing with this type of equipment, it is frequently necessary to run wiring, tubes, or fibers through a barrier separating one process from another with one or both operating in extreme environments. Feedthroughs used to route the wiring, tubes, or fibers through these barriers must meet stringent sealing and leak tightness requirements. This affordable NASA feedthrough meets or exceeds all sealing and leak requirements utilizing easy-to-assemble commercial-off-the-shelf hardware with no special tooling. The feedthrough is a fully reconfigurable design; however, it can also be produced as a permanent device. Thermal cycling and helium mass spectrometer leak testing under extreme conditions of full cryogenic temperatures and high vacuum have proven the sealing capability of this feedthrough with or without potting (epoxy fill) on the ends. Packing material disks used in the construction of the device can be replaced as needed for rebuilding a given feedthrough for another job or a different set of feeds if potting is not used for the original feedthrough build. (Potting on one or both sides of the sleeve provides double or triple leak sealing protection). Variable Compression Ratio (VCR) connectors were adapted for the pressure seal on the feedthrough; however, any commercial connector can be similarly adapted. The design can easily be scaled up to larger (2" diameter) and even very large (12" or more) sizes.

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.

This technology was developed to improve Armstrong's multi-patented FOSS system, which has long been used to measure temperature and liquid levels in cryogenic environments. When the sensing system's fibers trapped humidity from the surrounding environment before their submersion into cryogenic liquids, the moisture adversely affected outputs. A new manufacturing process solves this problem, increasing reliability and accuracy not only of NASA's FOSS but also any fiber optic sensing system. How It Works Armstrong has developed a two-step process to assemble the sensors. First, the bare sensor fiber is inserted into an oven to expel all moisture from the fiber coating. Then, the moisture-free fiber is placed inside a humidity-controlled glove box to prevent it from absorbing any new moisture. While inside the glove box, the fiber is inserted into a loose barrier tubing that isolates the fiber yet is still thin enough to provide adequate thermal transfer. The tubing can be further purged with various gases while it is inside the glove box to provide additional moisture isolation. This innovation is particularly useful for fiber optic systems that measure temperature and that identify any temperature stratifications within cryogenic liquids. Why It Is Better This process seals sensor fibers from environmental moisture, enabling fiber optic sensing systems to operate reliably in humid environments. The innovation eliminates erroneous readings that can occur due to moisture collection on the fiber sensors. For more information about the full portfolio of FOSS technologies, see DRC-TOPS-37 or visit https://technology-afrc.ndc.nasa.gov/featurestory/fiber-optic-sensing