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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6

PCM Passive Cooling System Containing Active Subsystems

A multistage system has been proposed for cooling a circulating fluid that is subject to intermittent intense heating. The system would be both flexible and redundant in that it could operate in a basic passive mode, either sequentially or simultaneously with operation of a first, active cooling subsystem, and either sequentially or simultaneously with a second cooling subsystem that could be active, passive, or a combination of both. This flexibility and redundancy, in combination with the passive nature of at least one of the modes of operation, would make the system more reliable, relative to a conventional cooling system. The system would include a tube-in-shell heat exchanger, within which the space between the tubes would be filled with a phase-change material (PCM). The circulating hot fluid would flow along the tubes in the heat exchanger. In the basic passive mode of operation, heat would be conducted from the hot fluid into the PCM, wherein the heat would be stored temporarily by virtue of the phase change.

Blanding, David E.↗

Thermostructural analysis with experimental verification in a high heat flux facility of a simulated cowl lip

Three-dimensional FEM analyses using the NASTRAN and MARC codes have been used to predict the thermal and structural response of active cooling schemes proposed for a hypersonic vehicle's propulsion system cowl lip under high aerothermodynamic heating loads. In order to experimentally verify these analyses, a hydrogen/oxygen rocket engine has been modified to employ the exhaust stream as a high enthalpy/high heat flux source for the evaluation of various actively cooled, simulated cowl lip segments as well as flat structural segments.

Melis, Matthew E.↗

Structures technology development for hypersonic vehicles

This paper summarizes some of the efforts to advance hypersonic structures technology through the National Aero-Space Plane (NASP) Structures Technology Maturation Program. The ranges of expected structural loads and results from analysis and test activities are described. Topics briefly covered include shock impingement effects on aerothermal loads, actively-cooled structures concepts and test results to date for leading edges and panels, design and fabrication of a carbon-carbon control surface, a program for predicting performance of metal matrix composites, an analysis and sizing procedure for thermal structures, and some recently-developed test fixtures for seals, thermal insulation, and actively-cooled panels.

Camarda, Charles J.↗

UV Observations of Prominence Activation and Cool Loop Dynamics

In this paper we investigate the thermal and dynamic properties of dynamic structures in and around a prominence channel observed on the limb on 17 April 2003. Observations were taken with the Solar and Heliospheric Observatory's Solar Ultraviolet Measurements of Emitted Radiation (SOHO/SUMER) in lines formed at temperatures from 80,000 to 1.6 MK. The instrument was pointed to a single location and took a series of 90 s exposures. Two-dimensional context was provided by the Transition Region and Coronal Explorer (TRACE) in the UV and EUV and the Kanzelhohe Solar Observatory in H-alpha. Two dynamic features were studied in depth: an activated prominence and repeated motions in a loop near the prominence. We calculated three-dimensional geometries and trajectories, differential emission measure, and limits on the mass, pressure, average density, and kinetic and thermal energies. These observations provide important tests for models of dynamics in prominences and cool (approx. 10(exp 5) K)loops, which will ultimately lead to a better understanding the mechanism(s) leading to energy and mass flow in these solar features.

Kucera, Therese A.↗

UV Chromospheric Activity in Cool, Short-Period Contact Binaries

We have completed our analysis of the IUE spectra of the short-period contact binary OO Aql. OO Aql is a rare W UMa-type eclipsing binary in which the two solar-type stars may have only recently evolved into contact. The binary has an unusually high mass ratio (0.84), and a relatively long orbital period (0.506 d) for its spectral type (mid-G). Twelve ultraviolet spectra of OO Aql were obtained in 1988 with the IUE satellite, including a series of consecutive observations that cover nearly a complete orbital cycle. Chromospheric activity is studied by means of the Mg II h+k emission at 2800 A. The Mg II emission is found to vary, even when the emission is normalized to the adjacent continuum flux. This variation may be correlated with orbital phase in the 1988 observations. It also appears that the normalized Mg H emission varies with time, as seen in spectra obtained at two different epochs in 1988 and when compared with two spectra obtained several years earlier. The level of chromospheric activity in OO Aql is less than that of other W UMa-type binaries of similar colors, but this is attributed to its early stage of contact binary evolution. Ultraviolet light curves were composed from measurements of the ultraviolet continuum in the spectra. These were analyzed along with visible light curves of OO Aql to determine the system parameters. The large wavelength range in the light curves enabled a well-constrained fit to a cool spot in the system. A paper on these results is scheduled for publication in the February 2001 issue of the Astronomical Journal.

Hrivnak, Bruce J.↗

The evolution of chromospheric activity of cool giant and subgiant stars

IUE spectra for a large sample of cool subgiant stars are examined, and evidence is found that subgiants in the mass range 1.2-1.6 solar masses undergo a sudden decline in UV transition region emission near B - V = 0.6, which corresponds to spectral type G0 IV. The decline in UV emission coincides with a sharp decrease in stellar rotation rates, and it is suggested that this decay in activity and rotation marks a transformation from acoustic heating in the early F stars to magnetic dynamo-driven activity in the cooler stars, resulting in a strong rotational braking action by stellar wind. For more massive giant stars, there is a similar transformation in the nature of chromospheric activity near B - V = 0.7, or spectral type G0 III, from acoustic heating in the F-type giants to a solarlike dynamo mechanism in the cooler giants. No sign of an abrupt drop in activity near spectral type G5 III at the location of Gray's proposed rotational boundary line is seen.

Simon, Theodore↗

Development of Advanced Multizone Facilities for Microgravity Processing

NASA has been interested in experimental ground based study to investigate the fundamental processes involved in phase transformation processes during growth of metallic, nonmetallic and electronic materials. Solidification, vapor growth and solution growth techniques of growing crystals are of special interest because of the inherent importance of convection in the nutrient solution. Convection enhances the mass transport through the nutrient and results in faster growth rates. Availability of low gravity environment of space has provided scientists a new variable to control the extent of convection and thus isolate the diffusive phenomena for their better understanding. The thermal gradient at the liquid-solid interface is determined by the alloy characteristics, the hot zone temperature, cold zone temperature and the width of the insulating zone. The thermal profiles get established by the existing material and geometrical constraints of the experimental set up. The major effort under this research was devoted to designing a programmable furnace which can be used to obtain thermal profiles along the length of the sample as per the demands of the scientists. The furnace did not have active cooling of the zones. Only active heating and passive cooling were utilized.

Source record↗

A second-generation supersonic transport

Ever since the advent of commercial flight vehicles, one goal of designers has been to develop aircraft that can fly faster and carry more passengers than before. After the development of practical supersonic military aircraft, this desire was naturally manifested in a search for a practical supersonic commercial aircraft. The first and, to date, only supersonic civil transport is the Concorde, manufactured by a consortium of British and French aerospace companies. Unfortunately, due to a number of factors, including low passenger capacity and limited range, the Concorde has not been an economic success. It is for this reason that there is considerable interest in developing a design for a supersonic civil transport that addresses some of the inadequacies of the Concorde. For the design of such an aircraft to be feasible in the near term, certain guidelines must be established at the outset. Based upon the experience with the Concorde, whose 100- passenger capacity is not large enough for profitable operation, a minimum capacity of 250 passengers is desired. Second, to date, because of the limited range of the Concorde, supersonic commercial flight has been restricted to trans-Atlantic routes. In order to broaden the potential market, any new design must have the capability of trans-Pacific flight. A summary of the potential markets involved is presented in Fig. 1. Also, because of both the cost and complexity involved with actively cooling an entire aircraft, an additional design constraint is that the aircraft as a whole be passively cooled. One additional design constraint is somewhat less quantitative in nature but of great importance nonetheless. Any time a new design is attempted, the tendency is to assume great strides in technology that serve as the basis for actual realization of the design. While it is not always possible to avoid this dependence on "enabling technology," since this design is desired for the near term, it is prudent, wherever possible, to rely on already existing technology. This is of particular importance with respect to support technology such as airport terminals and runways. Based on the above introductory remarks, a possible approach to the design of a second-generation supersonic civil transport is presented below. The design Mach number for this aircraft is 3.5. This value was chosen as it represents the limiting Mach number in the absence of active cooling. The ensuing design attempts to deal with the particular problems that are the most demanding, while relying on proven technology where it is adequate. The report clearly does not solve, or even deal with, every aspect of the aircraft design. Rather, a general direction is suggested and supported with initial, approximate calculations.

W. Humphrey↗

Nickel-hydrogen battery state of charge during low rate trickle charging

The NASA AXAF-I program requires high battery state of charge at launch. Traditional approaches to providing high state of charge, during prelaunch operations, require significant battery cooling. The use of active cooling, in the AXAF-I prelaunch environment, was considered and proved to be difficult to implement and very expensive. Accordingly alternate approaches were considered. An approach utilizing adiabatic charging and low rate trickle charge, was investigated and proved successful.

Lurie, C.↗

Multiphysics Simulation of Active Hypersonic Lip Cooling

This article describes the application of the Multidisciplinary Analysis (MDA) solver, Spectrum, in analyzing a hydrogen-cooled hypersonic cowl leading-edge structure. Spectrum, a multiphysics simulation code based on the finite element method, addresses compressible and incompressible fluid flow, structural, and thermal modeling, as well as the interactions between these disciplines. Fluid-solid-thermal interactions in a hydrogen impingement-cooled leading edge are predicted using Spectrum. Two- and semi-three-dimensional models are considered for a leading edge impingement coolant, concept under either specified external heat flux or aerothermodynamic heating from a Mach 5 external flow interaction. The solution accuracy is demonstrated from mesh refinement analysis. With active cooling, the leading edge surface temperature is drastically reduced from 1807 K of the adiabatic condition to 418 K. The internal coolant temperature profile exhibits a sharp gradient near channel/solid interface. Results from two different cooling channel configurations are also presented to illustrate the different behavior of alternative active cooling schemes.

Melis, Matthew E.↗

Fuel injection assembly for gas turbine engine combustor

A fuel injection assembly for a gas turbine engine combustor, including at least one fuel stem, a plurality of concentrically disposed tubes positioned within each fuel stem, wherein a cooling supply flow passage, a cooling return flow passage, and a tip fuel flow passage are defined thereby, and at least one fuel tip assembly connected to each fuel stem so as to be in flow communication with the flow passages, wherein an active cooling circuit for each fuel stem and fuel tip assembly is maintained by providing all active fuel through the cooling supply flow passage and the cooling return flow passage during each stage of combustor operation. The fuel flowing through the active cooling circuit is then collected so that a predetermined portion thereof is provided to the tip fuel flow passage for injection by the fuel tip assembly.

Candy, Anthony J.↗

CFD evaluation of an advanced thrust vector control concept

A potential concept that can offer an alternate method for thrust vector control of the Space Shuttle Solid Rocket Booster is the use of a cylindrical probe that is inserted (on demand) through the wall of the rocket nozzle. This Probe Thrust Vector Control (PTVC) concept is an alternate to that of a gimbaled nozzle or a Liquid Injection Thrust Vector (LITVC) system. The viability of the PTVC concept can be assessed either experimentally and/or with the use of CFD. A purely experimental assessment can be time consuming and expensive, whereas a CFD assessment can be very time- and cost-effective. Two key requirements of the proposed concept are PTVC vectoring performance and the active cooling requirements for the probe to maintain its thermal and structural integrity. An active thermal cooling method is the injection of coolant around the pheriphery of the probe. How much coolant is required and how this coolant distributes itself in the flow field is of major concern. The objective of the work reported here is the use of CFD to answer these question and in the design of test hardware to substantiate the results of the CFD predictions.

Tiarn, Weihnurng↗

Review of convectively cooled structures for hypersonic flight

Resurgent interest in development of Aerospace Plane and Orient Express type vehicles promises to stretch structural technology for hypersonic flight vehicles to the uppermost limits. Significant portions of the structure may require active cooling of some type to survive hostile environments. Despite a lack of recent research activity for cooled structures, a significant body of unclassified knowledge exists concerning such structures. Contractual and in-house research conducted mainly by NASA's Langley Research Center during the 60's and 70's on vehicles very similar to the proposed Orient Express has provided a substantial data base for convectively cooled hypersonic flight structures. Specifically, results are presented for regeneratively cooled structural concepts which have a relatively high heat flux capability and use the hydrogen fuel directly as a coolant; and for structural concepts which use a secondary coolant loop to absorb incident heating and then transfer the absorbed heat to the liquid hydrogen fuel as it flows to the engines. Results are presented to indicate application regions in terms of heat flux capability for various concepts and benefits for each concept. Experience gained and costs are discussed in terms of heat flux capability for various concepts and benefits for each concept. Additionally, experience gained and cost involved with design, fabrication, and testing of full-scale convectively cooled structures are discussed.

Shore, Charles P.↗

Internal convective cooling systems for hypersonic aircraft

Parametric studies were conducted to investigate the relative merits of construction materials, coolants, and cooled panel concepts for internal convective cooling systems applied to airframe structures of hydrogen-fueled hypersonic aircraft. These parametric studies were then used as a means of comparing various cooled structural arrangements for a hypersonic transport and a hypersonic research airplane. The cooled airplane studies emphasized weight aspects as related to the choice of materials, structural arrangements, structural temperatures, and matching of the cooling system heat load to the available hydrogen fuel-flow heat sink. Consideration was given to reliability and to fatigue and fracture aspects, as well. Even when auxiliary thermal protection system items such as heat shielding, insulation, and excess hydrogen for cooling are considered the more attractive actively cooled airframe concepts indicated potential payload increases of from 40 percent to over 100 percent for the hypersonic transport as compared to the results of previous studies of the same vehicle configuration with an uncooled airframe.

Anthony, F. M.↗

A Multi-Center Controlled Study of the Acute and Chronic Effects of Cooling Therapy for MS

To determine the acute and chronic effects of cooling therapy on patients with MS using objective functional performance measures and self-assessed measures of fatigue. Cooling demyelinated nerves can reduce conduction block, potentially improving symptoms of MS. Significant acute and chronic effects of cooling have not been demonstrated in a multi-center, controlled, blinded study using objective measures of neurologic function. Patients (N=84) with definite MS, mild to moderate disability (EDSS less than 6.0), and self-reported heat sensitivity were enrolled at 5 study sites. Acute effects of cooling were assessed by randomly assigning subjects to high-dose or low-dose cooling for one hour using an active cooling vest and cap (Life Enhancement Technologies, Santa Clara, CA). Settings were individualized to maintain the cooling garments at 55 F for the high-dose treatment and 70 F for the low-dose treatment. Both patients and examining investigators were blinded to treatment assignments. The MSFC and visual acuity/contrast sensitivity were assessed before and 30 minutes after treatment. The following week, subjects had an identical visit with the alternate cooling treatment. Chronic effects of cooling were assessed by randomly assigning the same subjects to unblinded daily home cooling or observation for 4 weeks. All subjects completed the Rochester Fatigue Diary (RFD) twice weekly and subjective measures of strength, cognition, and energy level daily. At the end of the period, subjects completed the Modified Fatigue Impact Scale (MFIS) and underwent another high-dose cooling session with assessment of the MSFC and vision. After a one-week washout period, subjects crossed over to the alternate 4-week treatment. Oral temperatures were reduced with both acute treatments (0.8 +/- .06 F, high and 0.5 +/- .06 F, low). While mean MSFC did not change significantly during individual cooling sessions, post hoc analysis pooling the 3 high-dose cooling sessions revealed an improvement in MSFC scores (acute phase 0.064 +/- 0.020, p = 0.0013; chronic phase 0.044 +/- 0.021, p = 0.0368) from before to after cooling. The change in MSFC scores during the acute cooling sessions was not related to the extent of change in oral temperatures. Both the RFD score and the MFIS indicate a significantly lower fatigue level during the cooling month compared to observation (RFD, 2.53 +/- 0.83,p = 0.0033; MFIS 7.63 +/- 1.56, p = 0.0001).

Luna, Bernadette↗

Cryogenic Curation of Lunar Samples Returned to Earth

Future lunar missions may collect samples that have been preserved at sub-freezing or even cryogenic temperatures. For such samples, the study of volatiles and temperature-sensitive minerals will have high priority. Valuable geochemical and mineralogical information will be lost if such samples are allowed to reach ambient temperatures on Earth. The ability to store, document, subdivide, and transport extraterrestrial geologic samples while maintaining sub-freezing or cryogenic temperatures, possibly as low as 40 K, is required for the complete scientific study of samples from cold environments. A lunar cryogenic sample return mission might require a combination of passive cooling during collection and cruise and active cooling during and after re-entry for maintaining desired temperatures. Once on Earth, cryocontainment must be maintained through delivery to a cryogenic chamber in the curatorial facility. This cryogenic curation chamber would include cameras and robotic manipulators for preliminary examination, subdivision of samples, and specialized sample allocation containers for shipment to laboratories world-wide. This presentation describes the planning and feasibility of cryogenic curation with current technologies developed for the superconductor industry. In addition, significant advanced research and development would be required to tailor some of these technologies to the task of sample return and long term curation of lunar samples at low temperatures in order to preserve their scientific integrity.

Calaway, Michael J.↗

Cooled Ceramic Matrix Composite Panel Successfully Tested in Rocket Exhaust

Actively cooled ceramic matrix composite (CMC) components are enabling or enhancing for a broad range of hypersonic and reusable launch vehicle propulsion systems. Teaming with other NASA centers, the Air Force, and industry, the Glenn Ceramics Branch has successfully tested multiple cooled CMC panel concepts in high-heat-flux, high-pressure, flowing rocket engine combustion gas environments. Sub-element components survived multiple cycles and the severe thermal gradients imposed by combustion gas temperatures in excess of 5500 F and cryogenic hydrogen or ambient temperature water internal coolants. These demonstrations are critical for the continued development of this class of materials, and the research is expected to continue with additional concepts and increasingly larger and more complex geometries being fabricated and tested in a broad range of engine operating conditions.

Eckel, Andrew J.↗

Lessons Learned During Instrument Testing for the Thermal Infrared Sensor (TIRS)

The Themal InfraRed Sensor (TIRS) instrument, set to launch on the Landsat Data Continuity Mission in 2013, features a passively cooled telescope and IR detectors which are actively cooled by a two stage cryocooler. In order to proceed to the instrument level test campaign, at least one full functional test was required, necessitating a thermal vacuum test to sufficiently cool the detectors and demonstrate performance. This was fairly unique in that this test occurred before the Pre Environmental Review, but yielded significant knowledge gains before the planned instrument level test. During the pre-PER test, numerous discrepancies were found between the model and the actual hardware, which were revealed by poor correlation between model predictions and test data. With the inclusion of pseudo-balance points, the test also provided an opportunity to perform a pre-correlation to test data prior to the instrument level test campaign. Various lessons were learned during this test related to modeling and design of both the flight hardware and the Ground Support Equipment and test setup. The lessons learned in the pre-PER test resulted in a better test setup for the nstrument level test and the completion of the final instrument model correlation in a shorter period of time. Upon completion of the correlation, the flight predictions were generated including the full suite of off-nominal cases, including some new cases defined by the spacecraft. For some of these ·new cases, some components now revealed limit exceedances, in particular for a portion of the hardware that could not be tested due to its size and chamber limitations.. Further lessons were learned during the completion of flight predictions. With a correlated detalled instrument model, significant efforts were made to generate a reduced model suitable for observatory level analyses. This proved a major effort both to generate an appropriate network as well as to convert to the final model to the required format and yielded additional lessons learned. In spite of all the challenges encountered by TIRS, the instrument was successfully delivered to the spacecraft and will soon be tested at observatory level in preparation for a successful mission launch.

Peabody, Hume L.↗