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NASA NTRS2014

Controllable Multi-Functional Heat Exchanger for Space Applications

Team Spacering will design SpaceRing, a cooling and waste heat recycling system that addresses NASA’s interest for a cooling and power-generating unit in its prototype deep space habitat[1]. The merits of this system are as follows: - Controllable cooling is critical in maintaining a habitable environment and in the functionality of life support systems, powering electronics and other devices in a spacecraft. - Power is expensive to produce in a space environment. Converting wasted thermal energy into electricity will save energy and money for the space station. Space habitation is a highly complex endeavor. Consequently, the SpaceRing must adhere to additional constraints, which include: - Lack of natural fluid or gas convection due to micro-gravity environment - Limited range for heat source and cold sink temperature - Subject to high fluctuations of incoming thermal energy - Minimal weight due to the high cost of transporting items into space After consulting with NASA and experts in thermal studies, several design objectives were identified and are listed below in order of importance: - High cooling capacity - Reliable safety control and alert system - Maximization of energy generation from wasted heat - Optimization of cooling capability and power generation - Long operational life and minimization of maintenance In space, conventional cooling systems utilize passive heat pipe systems for small-scale heat rejection and pumped pipes with heat exchangers for large-scale heat rejection. Thermal power generation in space is mainly achieved by using thermoelectric material that produces electric energy from temperature differentials. We propose a design that combines cooling and thermoelectric power generation. Using a hot pipe connected to a heat source, a cold pipe connected to a radiator, a heat exchanger in contact with both pipes, and a pump in each pipe to move the fluid, we make an active cooling system. The thermoelectric material is inserted in the heat exchanger between the hot and cold pipes to extract energy from the maximum temperature difference coming from the two pipes. It also provides controllable cooling capacity through the use of the thermoelectric material as cooling modules. We have tested our system under target heat source and sink conditions and measured the temperatures and flow rates. Our preliminary results are promising, demonstrating the output of 25 Watts of power on average. We are in the process of running control tests to compare the heat transfer performance without the thermoelectric generators, which is vital in determining whether or not the generators introduce an unacceptable amount of thermal resistance. While some control tests have been run already, the results have been noisy. We have modified our testing environment and data acquisition methods to allow for simple comparison between the control test results and thermoelectric performance results. Lastly, we have modified the heat exchanger design slightly to include acrylic baffles. This will allow the heat to flow through the heat exchanger more efficiently. We have presented our preliminary results to NASA and will deliver the final product by the end of May 2014.

Lee Xiong↗

NASA NTRS1993

A giant X-ray flare on Lambda Eridani (B2e)

A 30 ks observation with the ROSAT PSPC distributed over 39 hr shows that the putatively single, mild B2e star Lambda Eri emits at most times a soft X-ray flux at a rate and temperature consistent with other B stars. However, during the middle of our observations, this star's X-ray flux increased by a factor of 6 before returning to the basal level. This brightening, due entirely to photon energies of 0.7 keV or greater, can be fitted well to a Raymond-Smith temperature parameter of 14 MK and luminosity 4 x 10 exp 31 ergs/s; these are characteristics of giant stellar flares. With an estimated duration of about 50,000 s, this event is arguably the strongest X-ray flare yet observed. We consider several possible scenarios for the site of the flare, including several with an active cool secondary or degenerate companion. We find that IUE and optical spectra do not support a binary picture and that it is most probable that the flare site is on or related to Lambda Eri itself. This supports other evidence for violent magnetic activity on some B-type stars.

Smith, Myron A.↗

NASA NTRS2015

Zero Boil-Off System Testing

Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration plans due to their high specific impulse for rocket motors of upper stages. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for long duration missions. These losses can be eliminated by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and modulating the cryocooler temperature to control tank pressure. The technology being developed by NASA is the reverse turbo-Brayton cycle cryocooler and its integration to the propellant tank through a distributed cooling tubing network coupled to the tank wall. This configuration was recently tested at NASA Glenn Research Center in a vacuum chamber and cryoshroud that simulated the essential thermal aspects of low Earth orbit, its vacuum and temperature. This test series established that the active cooling system integrated with the propellant tank eliminated boil-off and robustly controlled tank pressure.

Reverse turbo-Brayton cycle↗

NASA NTRS2001

Silicon Nitride Plates for Turbine Blade Application: FEA and NDE Assessment

Engine manufacturers are continually attempting to improve the performance and the overall efficiency of internal combustion engines. The thermal efficiency is typically improved by raising the operating temperature of essential engine components in the combustion area. This reduces the heat loss to a cooling system and allows a greater portion of the heat to be used for propulsion. Further improvements can be achieved by diverting part of the air from the compressor, which would have been used in the combustor for combustion purposes, into the turbine components. Such a process is called active cooling. Increasing the operating temperature, decreasing the cooling air, or both can improve the efficiency of the engine. Furthermore, lightweight, strong, tough hightemperature materials are required to complement efficiency improvement for nextgeneration gas turbine engines that can operate with minimum cooling. Because of their low-density, high-temperature strength, and thermal conductivity, ceramics are being investigated as potential materials for replacing ordinary metals that are currently used for engine hot section components. Ceramic structures can withstand higher operating temperatures and other harsh environmental factors. In addition, their low densities relative to metals helps condense component mass (ref. 1). The objectives of this program at the NASA Glenn Research Center are to develop manufacturing technology, a thermal barrier coating/environmental barrier coating (TBC/EBC), and an analytical modeling capability to predict thermomechanical stresses, and to do minimal burner rig tests of silicon nitride (Si3N4) and SiC/SiC turbine nozzle vanes under simulated engine conditions. Furthermore, and in support of the latter objectives, an optimization exercise using finite element analysis and nondestructive evaluation (NDE) was carried out to characterize and evaluate silicon nitride plates with cooling channels.

Abdul-Aziz, Ali↗

NASA NTRS1988

Thermostructural analysis of simulated cowl lips

Three dimensional finite element analyses using MSC/NASTRAN and MARC are performed to predict the thermal and structural response of various cooling schemes under high heat loads. Steady state heat transfer analyses and elastic stress analyses are performed using MSC/NASTRAN. Elastic/plastic analyses are done using MARC. To help verify these analyses experimentally, a hydrogen-oxygen rocket engine was modified to use the exhaust stream as a high enthalpy, high heat flux source to evaluate various actively cooled, simulated cowl lip (leading edges) segments as well as flat structural segments. Cross flow and parallel flow cooling configurations were tested and analyzed using cooling fluids of water and gaseous hydrogen. In addition, various material types, including high conductivity copper, nickel, and a copper and graphite metal matrix composite were tested and compared.

Melis, Matthew E.↗

NASA NTRS1979

Cooling a radioisotope power source in the Space Shuttle Orbiter

Radioisotope thermoelectric generators (RTG's), used to generate electrical power on outer planetary spacecraft, are presently planned for a January 1982 launch of Galileo and later for a February 1983 launch. The RTG's will be externally located on a spacecraft to be deployed from the Space Shuttle Orbiter. Each RTG rejects nearly 2.5 kW (8500 Btu/hr) of thermal energy. From the time the RTG's are loaded into the payload bay until the doors are opened one to three hours after launch, active cooling will maintain proper temperature limits. This paper includes a description of two types of RTG's and the various cooling concepts considered. The payload cooling capability of the Shuttle Orbiter and modifications required to accommodate the RTG's are discussed. The analytical technique for determining the heat load split between the orbiter environment and RTG coolant is also presented.

Levine, D. I.↗

NASA NTRS2018

Using Liquid Natural Gas Fuel to Cryogenically Cool and Enhance a Hybrid Electric Aircraft Power System

A previous system study identified significant increases in range and number of urban air mobility (UAM) missions by replacing the all battery power system of a notional UAM vehicle with an advanced diesel hybrid using conventional diesel or liquid natural gas (LNG) fuels (at constant vehicle design gross weight). Some benefits were realized using the LNG's cryogenic properties to reduce some electrical component losses and cooling requirements. Significant questions were raised concerning volume and thermal management considerations for all studied systems. The notional, baseline vehicle was a hybrid helicopter / airplane design capable of vertical take-off and landing (VTOL), balancing high cruise efficiency with reasonable hover capability. A subsequent power system assessment using the same notional vehicle and mission was performed that identified increased volume and power requirements for the active cooling required. The cooling airflow could also generate additional drag on the vehicle during operation. For the notional vehicle studied, the additional volume identified by the subsequent study would not affect vehicle mold line and therefore drag. However, the additional drag from cooling airflow and the power to circulate it as needed would impact power system and vehicle mission performance. Vehicle and mission models were updated and rerun. Updated results still indicated significant benefits in range and number of UAM missions, but reduced the benefit by 12-15%. Hold time for the hybrid systems also generally increased a few minutes because of reduced power available for charging from the power for required cooling flows. Vehicle weights, thermal loads, and cooling airflows from the updated analyses were similar to previous results.

systems analysis↗

NASA NTRS2000

X-ray Emission from Pre-Main-Sequence Stars - Testing the Solar Analogy

This LTSA award funded my research on the origin of stellar X-ray emission and the validity of the solar-stellar analogy. This research broadly addresses the relevance of our current understanding of solar X-ray physics to the interpretation of X-ray emission from stars in general. During the past five years the emphasis has been on space-based X-ray observations of very young stars in star-forming regions (T Tauri stars and protostars), cool solar-like G stars, and evolved high-mass Wolf-Rayet (WR) stars. These observations were carried out primarily with the ASCA and ROSAT space-based observatories (and most recently with Chandra), supplemented by ground-based observations. This research has focused on the identification of physical processes that are responsible for the high levels of X-ray emission seen in pre-main-sequence (PMS) stars, active cool stars, and WR stars. A related issue is how the X-ray emission of such stars changes over time, both on short timescales of days to years and on evolutionary timescales of millions of years. In the case of the Sun it is known that magnetic fields play a key role in the production of X-rays by confining the coronal plasma in loop-like structures where it is heated to temperatures of several million K. The extent to which the magnetically-confined corona interpretation can be applied to other X-ray emitting stars is the key issue that drives the research summarized here.

Skinner, Stephen L.↗

NASA NTRSDate not supplied

Expanding the Capability of A Legacy Combustion Flametube to Test High Temperature Engine Materials in Relevant Environments

New materials and component designs are needed to advance gas turbine engine technology and provide the performance and efficiency needs for future applications. In order to advance these materials, testing in combustion environments is a critical step prior to engine testing. In this work, we detail the design and the fabrication of a materials test sector in a flametube combustor facility. The facility simulates a combustion environment similar to that experienced by components in gas turbine engines. The flow regime is characterized by a combination of high-temperature, high-velocity, high-heat flux, and high-velocity that components experience in gas turbine engines. Exposure of components in this facility allows for the study of combined environmental effects and the impact on both coating and substrate durability. The test facility may operate across a wide range of pressures from 275-400 psig (1,896-2,758 kPa) and an air flow rate of 5 lb/s (2.27 kg/s). While combustion gas temperature is expected in excess of 3,000°F (1,649°C), 900°F (482°C) cooling air may be supplied to the backside of components or test articles. The flametube combustor was previously used to evaluate fuel injectors and combustion products, and the new test configuration will also allow for materials exposure to complex, engine-like conditions. The interior of the Test Section was additively manufactured from GRCop-84 and cryogenically fit and brazed to a stainless steel 304 housing. The use of a copper liner minimizes welds and with active cooling, is expected to provide better durability over traditional hardware using stainless steel or Inconel with a ceramic liner. The Test Section has two opposing removable windows approximately 230 mm x 80 mm that can accommodate articles up to 85 mm tall. This modular design allows for custom platforms to hold coupons, panels, or airfoil shapes to be tested with minimal re-engineering or fabrication. The bolted joint and sealing remains consistent, so any new testing only needs to work within the existing design footprint. This paper will provide an overview of the facility capabilities, design considerations, as well as thermal and structural analysis of the hardware. Future testing of ceramic matrix composite (CMC) airfoils and advanced environmental barrier coatings (EBCs) will also be discussed.

Combustion↗

NASA NTRS1973

Shuttle active thermal control system development testing. Volume 6: Water ejector plume tests

Results are given of vacuum testing of nozzles designed to eject water vapor away from the space shuttle to prevent contamination of the spacecraft surfaces and payload. The water vapor is generated by an active cooling system which evaporates excess fuel cell water to supplement a modular radiator system (MRS). The complete heat rejection system including the MRS, flash evaporator or sublimator and nozzle were first tested to demonstrate the system operational characteristics. The plume tests were performed in two phases and the objectives of this test series were: (1) to determine the effectiveness of a supersonic nozzle and a plugged nozzle in minimizing impingement upon the spacecraft of water vapor exhausted by an active device (flash evaporator or sublimator); and (2) to obtain basic data on the flow fields of exhaust plumes generated by these active devices, both with and without nozzles installed.

Mcginnis, F. K.↗

NASA NTRS2009

CRYOTE (Cryogenic Orbital Testbed) Concept

Demonstrating cryo-fluid management (CFM) technologies in space is critical for advances in long duration space missions. Current space-based cryogenic propulsion is viable for hours, not the weeks to years needed by space exploration and space science. CRYogenic Orbital TEstbed (CRYOTE) provides an affordable low-risk environment to demonstrate a broad array of critical CFM technologies that cannot be tested in Earth's gravity. These technologies include system chilldown, transfer, handling, health management, mixing, pressure control, active cooling, and long-term storage. United Launch Alliance is partnering with Innovative Engineering Solutions, the National Aeronautics and Space Administration, and others to develop CRYOTE to fly as an auxiliary payload between the primary payload and the Centaur upper stage on an Atlas V rocket. Because satellites are expensive, the space industry is largely risk averse to incorporating unproven systems or conducting experiments using flight hardware that is supporting a primary mission. To minimize launch risk, the CRYOTE system will only activate after the primary payload is separated from the rocket. Flying the testbed as an auxiliary payload utilizes Evolved Expendable Launch Vehicle performance excess to cost-effectively demonstrate enhanced CFM.

Gravlee, Mari↗

NASA NTRS2011

Disinfection of Spacecraft Potable Water Systems by Photocatalytic Oxidation Using UV-A Light Emitting Diodes

Ultraviolet (UV) light has long been used in terrestrial water treatment systems for photodisinfection and the removal of organic compounds by several processes including photoadsorption, photolysis, and photocatalytic oxidation/reduction. Despite its effectiveness for water treatment, UV has not been explored for spacecraft applications because of concerns about the safety and reliability of mercury-containing UV lamps. However, recent advances in ultraviolet light emitting diodes (UV LEDs) have enabled the utilization of nanomaterials that possess the appropriate optical properties for the manufacture of LEDs capable of producing monochromatic light at germicidal wavelengths. This report describes the testing of a commercial-off-the-shelf, high power Nichia UV-A LED (250mW A365nnJ for the excitation of titanium dioxide as a point-of-use (POD) disinfection device in a potable water system. The combination of an immobilized, high surface area photocatalyst with a UV-A LED is promising for potable water system disinfection since toxic chemicals and resupply requirements are reduced. No additional consumables like chemical biocides, absorption columns, or filters are required to disinfect and/or remove potentially toxic disinfectants from the potable water prior to use. Experiments were conducted in a static test stand consisting of a polypropylene microtiter plate containing 3mm glass balls coated with titanium dioxide. Wells filled with water were exposed to ultraviolet light from an actively-cooled UV-A LED positioned above each well and inoculated with six individual challenge microorganisms recovered from the International Space Station (ISS): Burkholderia cepacia, Cupriavidus metallidurans, Methylobacterium fujisawaense, Pseudomonas aeruginosa, Sphingomonas paucimobilis and Wautersia basilensis. Exposure to the Nichia UV-A LED with photocatalytic oxidation resulted in a complete (>7-log) reduction of each challenge bacteria population in <180 minutes of contact time. With continued advances in the design and manufacture of UV-A LEDs and semi-conducting photocatalysts, LED activated photochemical process technology promises to extend its application to spacecraft environmental systems.

Birmele, Michele N.↗

NASA NTRS2015

Radioisotope Power System Pool Concept

Advanced Radioisotope Power Systems (RPS) for NASA deep space science missions have historically used static thermoelectric-based designs because they are highly reliable, and their radioisotope heat sources can be passively cooled throughout the mission life cycle. Recently, a significant effort to develop a dynamic RPS, the Advanced Stirling Radioisotope Generator (ASRG), was conducted by NASA and the Department of Energy, because Stirling based designs offer energy conversion efficiencies four times higher than heritage thermoelectric designs; and the efficiency would proportionately reduce the amount of radioisotope fuel needed for the same power output. However, the long term reliability of a Stirling based design is a concern compared to thermoelectric designs, because for certain Stirling system architectures the radioisotope heat sources must be actively cooled via the dynamic operation of Stirling converters throughout the mission life cycle. To address this reliability concern, a new dynamic Stirling cycle RPS architecture is proposed called the RPS Pool Concept.

Power↗

NASA NTRS2004

Cryogenic Technology: Ongoing Developments for the Next Decade

To obtain optimum sensitivity a submillimeter space observatory will require low temperature mirrors (approx. 3K) and very low temperature detectors (< or approx. 0.1 K). Both of these temperatures have been achieved by space cryogenic systems, but neither for a 10 year duration. Past systems used superfluid helium to provide direct cooling in the 1 to 2 K range (IRAS, COBE, IRTS, ISO) or as an upper stage for an adiabatic demagnetization refrigerator to achieve temperatures down to 0.06 K (Astro-E/XRS). Boiloff vapor may be used to cool an otherwise warm telescope as in the Space InfraRed Telescope Facility (SIRTF). In SIRTF a 0.85 m telescope is cooled to 5.5 K by absorbing about 6 mW in the cold vapor. This residual heat is due to both radiation from a helium vapor cooled outer shield at about 20 K and from conduction through a structure mounting the cold telescope and instruments to the warm spacecraft. The boil off rate required to cool the telescope results in a 2.6 to 5 year lifetime, depending on whether other parasitic heat sources such as thermoacoustic oscillations are also present. A helium dewar results in a very heavy system to achieve 2 to 5 year lifetimes. For example it takes roughly 400 kg for XRS to achieve 0.06 K for two year life with a 250 K boundary temperature, and approx. 300 kg (including thermal shielding) for SIRTF to achieve 1.3 K for 5 year life with a 35 K boundary temperature. To go to longer duration and to lower the weight, active cooling methods are required combined with more aggressive passive cooling techniques. It is possible, with some development, to provide cooling for detectors to 0.05 K and telescopes and instruments to < 4 K for a 10 year mission with a 100 kg system including power sources, structural support, and vacuum enclosures for critical portions of the instruments.

DiPirro, Michael↗

NASA NTRS2013

Acoustic and Thermal Testing of an Integrated Multilayer Insulation and Broad Area Cooling Shield System

A Multilayer Insulation (MLI) and Broad Area Cooling (BAC) shield thermal control system shows promise for long-duration storage of cryogenic propellant. The NASA Cryogenic Propellant Storage and Transfer (CPST) project is investigating the thermal and structural performance of this tank-applied integrated system. The MLI/BAC Shield Acoustic and Thermal Test was performed to evaluate the MLI/BAC shield's structural performance by subjecting it to worst-case launch acoustic loads. Identical thermal tests using Liquid Nitrogen (LN2) were performed before and after the acoustic test. The data from these tests was compared to determine if any degradation occurred in the thermal performance of the system as a result of exposure to the acoustic loads. The thermal test series consisted of two primary components: a passive boil-off test to evaluate the MLI performance and an active cooling test to evaluate the integrated MLI/BAC shield system with chilled vapor circulating through the BAC shield tubes. The acoustic test used loads closely matching the worst-case envelope of all launch vehicles currently under consideration for CPST. Acoustic test results yielded reasonable responses for the given load. The thermal test matrix was completed prior to the acoustic test and successfully repeated after the acoustic test. Data was compared and yielded near identical results, indicating that the MLI/BAC shield configuration tested in this series is an option for structurally implementing this thermal control system concept.

Wood, J. J.↗

NASA NTRS2013

Acoustic and Thermal Testing of an Integrated Multilayer Insulation and Broad Area Cooling Shield System

Wood, Jessica J.↗

NASA NTRS2009

Long-Lived Venus Lander Conceptual Design: How To Keep It Cool

Surprisingly little is known about Venus, our neighboring sister planet in the solar system, due to the challenges of operating in its extremely hot, corrosive, and dense environment. For example, after over two dozen missions to the planet, the longest-lived lander was the Soviet Venera 13, and it only survived two hours on the surface. Several conceptual Venus mission studies have been formulated in the past two decades proposing lander architectures that potentially extend lander lifetime. Most recently, the Venus Science and Technology Definition Team (STDT) was commissioned by NASA to study a Venus Flagship Mission potentially launching in the 2020- 2025 time-frame; the reference lander of this study is designed to survive for only a few hours more than Venera 13 launched back in 1981! Since Cytherean mission planners lack a viable approach to a long-lived surface architecture, specific scientific objectives outlined in the National Science Foundation Decadal Survey and Venus Exploration Advisory Group final report cannot be completed. These include: mapping the mineralogy and composition of the surface on a planetary scale determining the age of various rock samples on Venus, searching for evidence of changes in interior dynamics (seismometry) and its impact on climate and many other key observations that benefit with time scales of at least a full Venus day (Le. daylight/night cycle). This report reviews those studies and recommends a hybrid lander architecture that can survive for at least one Venus day (243 Earth days) by incorporating selective Stirling multi-stage active cooling and hybrid thermoacoustic power.

Dyson, Ridger W.↗

NASA NTRS2005

Coronal Structures in Cool Stars

We have extended our study of the structure of coronas in cool stars to very young stars still accreting from their surrounding disks. In addition we are pursing the connection between coronal X-rays and a powerful diagnostic line in the infrared, the He I 10830Angstrom transition of helium. Highlights of these are summarized below including publications during this reporting period and presentations. Spectroscopy of the infrared He I (lambda10830) line with KECK/NIRSPEC and IRTF/CSHELL and of the ultraviolet C III (lambda977) and O VI (lambda1032) emission with FUSE reveals that the classical T Tauri star TW Hydrae exhibits P Cygni profiles, line asymmetries, and absorption indicative of a continuous, fast (approximately 400 kilometers per second), hot (approximately 300,000 K) accelerating outflow with a mass loss rate approximately 10(exp -11)-10(exp -12) solar mass yr(sup -1) or larger. Spectra of T Tauri N appear consistent with such a wind. The source of the emission and outflow seems restricted to the stars themselves. Although the mass accretion rate is an order of magnitude less for TW Hya than for T Tau, the outflow reaches higher velocities at chromospheric temperatures in TW Hya. Winds from young stellar objects may be substantially hotter and faster than previously thought. The ultraviolet emission lines, when corrected for absorption are broad. Emission associated with the accretion flow and shock is likely to show turbulent broadening. We note that the UV line widths are significantly larger than the X-ray line widths. If the X-rays from TW Hya are generated at the accretion shock, the UV lines may not be directly associated with the shock. On the other hand, studies of X-ray emission in young star clusters, suggest that the strength of the X-ray emission is correlated with stellar rotation, thus casting doubt on an accretion origin for the X-rays. We are beginning to access the infrared spectral region where the He I 108308Angstroms transition occurs. This line is particularly useful as a diagnostic of coronal radiation since it is formed by recombination following photoionization of neutral helium by coronal X-rays. Because the lower level of the transition is metastable, infrared radiation from the stellar photosphere is absorbed which provides a diagnostic of atmospheric dynamics. This transition is useful both in young stars in the T Tauri phase and in active cool star binaries. We will investigate the influence of coronal x-rays on the strength of this transition.

Oliversen, Ronald↗