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NASA NTRS1974

Thermal characteristics of Apollo 16 lunar fines

The vacuum thermal conductivity of the Apollo 16 fines is presented as a function of temperature for the approximate range of diurnal temperatures on the moon. The density used is 1500 kg/cu m, which is approximately the density of the core tube samples returned from the landing site. The thermal diffusivity was calculated from the conductivity, density and specific heat and is also presented. These properties along with the reflectance and emittance are used in a calculation of temperature in the lunar surface layer.

Cremers, C. J.↗

NASA NTRS2013

High-Strength, Superelastic Compounds

In a previous disclosure, the use of 60- NiTiNOL, an ordered intermetallic compound composed of 60 weight percent nickel and 40 weight percent titanium, was investigated as a material for advanced aerospace bearings due to its unique combination of physical properties. Lessons learned during the development of applications for this material have led to the discovery that, with the addition of a ternary element, the resulting material can be thermally processed at a lower temperature to attain the same desirable hardness level as the original material. Processing at a lower temperature is beneficial, not only because it reduces processing costs from energy consumption, but because it also significantly reduces the possibility of quench cracking and thermal distortion, which have been problematic with the original material. A family of ternary substitutions has been identified, including Hf and Zr in various atomic percentages with varying concentrations of Ni and Ti. In the present innovation, a ternary intermetallic compound consisting of 57.6 weight percent Ni, 39.2 weight percent Ti, and 3.2 weight percent Hf (54Ni-45Ti-1Hf atomic percent) was prepared by casting. In this material, Hf substitutes for some of the Ti atoms in the material. In an alternate embodiment of the innovation, Zr, which is close in chemical behavior to Hf, is used as the substitutional element. With either substitution, the solvus temperature of the material is reduced, and lower temperatures can be used to obtain the necessary hardness values. The advantages of this innovation include the ability to solution-treat the material at a lower temperature and still achieve the required hardness for bearings (at least 50 Rockwell C) and superelastic behavior with recoverable strains greater than 2%. Most structural alloys will not return to their original shape after being deformed as little as 0.2% (a tenth of that possible with superelastic materials like 60 NiTiNOL). Because lower temperatures can be used in the heat treatment process, less energy will be consumed, and there will be less dimensional distortion and quench cracking. This results in fewer scrap parts, less material waste from large amounts of material removal, and fewer machining steps to rework parts that are out of specification. This material has a combination of properties that have been previously unobtainable. The material has a Young s modulus of approximately 95 GPa (about half that of conventional steels), moderate density (10 to 15% lower than conventional steels), excellent corrosion resistance, and high hardness (58 to 62 HRC). These properties make this material uniquely suited for advanced bearings.

Stanford, Malcolm↗

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 NTRSDate not supplied

Mercury Lander: A Planetary Mission Concept Study for the 2023–2032 Decadal Survey

Mercury holds unique clues to the distribution of elements at the birth of the solar system and how planets form and evolve in close proximity to their host stars. The Mercury Lander mission concept returns in situ measurements to: understand Mercury’s unique mineralogy and geochemistry; characterize the massive core’s structure; measure the planet’s active and ancient magnetic fields at the surface; investigate the processes that alter the surface and produce the exosphere; and provide groundtruth for remote datasets. The mission concept achieves one Mercury year (~88 Earth days) of surface operations with an 11-instrument, high-heritage payload delivered to a landing site within Mercury’s widely distributed low-reflectance material, and addresses science goals encompassing geochemistry, geophysics, the Mercury space environment, and geology. The spacecraft launches on an expendable SpaceX Falcon Heavy in 2035. The four-stage flight system uses a solar-electric propulsion cruise stage to reach Mercury in2045. The orbital stage brings the spacecraft into a thermally safe orbit, then performs orbital maneuvers to prepare for descent. During the orbital phase, a narrow-angle camera acquires images for selecting a low-hazard landing zone within our region of interest. The descent stage begins the braking burn ~120 s before landing. The lander continues to touchdown, using continuous LIDAR operations to support hazard detection and safely deliver the payload to the surface. Landing is at dusk to meet thermal requirements, permitting ~30 hours of sunlight for initial observations. The radioisotope-powered lander continues operations through the Mercury night. Direct-to-Earth communication is possible for the initial three weeks of landed operations, drops out for six weeks, and resumes for the final month. Thermal conditions exceed lander operating temperatures shortly after sunrise, ending operations. A total of ~11 GB of data are returned to Earth. The Phase A–D mission cost estimate (50% unencumbered reserves, excluding launch vehicle) is $1.2 B(FY25$), comparing favorably with past New Frontiers missions and to the cost cap in the New Frontiers4 call(~$1.1B FY25$). This cost estimate shows that a Mercury Lander mission is feasible and compelling as a New Frontiers-class mission in the coming decade.

C M Ernst↗

NASA NTRS1982

Experiments on fuel heating for commercial aircraft

An experimental jet fuel with a -33 C freezing point was chilled in a wing tank simulator with superimposed fuel heating to improve low temperature flowability. Heating consisted of circulating a portion of the fuel to an external heat exchanger and returning the heated fuel to the tank. Flowability was determined by the mass percent of unpumpable fuel (holdup) left in the simulator upon withdrawal of fuel at the conclusion of testing. The study demonstrated that fuel heating is feasible and improves flowability as compared to that of baseline, unheated tests. Delayed heating with initiation when the fuel reaches a prescribed low temperature limit, showed promise of being more efficient than continuous heating. Regardless of the mode or rate of heating, complete flowability (zero holdup) could not be restored by fuel heating. The severe, extreme-day environment imposed by the test caused a very small amount of subfreezing fuel to be retained near the tank surfaces even at high rates of heating. Correlations of flowability established for unheated fuel tests also could be applied to the heated test results if based on boundary-layer temperature or a solid index (subfreezing point) characteristic of the fuel.

Friedman, R.↗

NASA NTRS1984

Heating experiments for flowability improvement of near-freezing aviation fuel

Friedman, R.↗

NASA NTRS2007

Bayesian Analysis of the Cosmic Microwave Background

There is a wealth of cosmological information encoded in the spatial power spectrum of temperature anisotropies of the cosmic microwave background! Experiments designed to map the microwave sky are returning a flood of data (time streams of instrument response as a beam is swept over the sky) at several different frequencies (from 30 to 900 GHz), all with different resolutions and noise properties. The resulting analysis challenge is to estimate, and quantify our uncertainty in, the spatial power spectrum of the cosmic microwave background given the complexities of "missing data", foreground emission, and complicated instrumental noise. Bayesian formulation of this problem allows consistent treatment of many complexities including complicated instrumental noise and foregrounds, and can be numerically implemented with Gibbs sampling. Gibbs sampling has now been validated as an efficient, statistically exact, and practically useful method for low-resolution (as demonstrated on WMAP 1 and 3 year temperature and polarization data). Continuing development for Planck - the goal is to exploit the unique capabilities of Gibbs sampling to directly propagate uncertainties in both foreground and instrument models to total uncertainty in cosmological parameters.

methods - statistical↗

NASA NTRSDate not supplied

207Pb-206Pb Geochronology and Microstructures of Phosphates From Apollo 14 and 15 Soils

Phosphates (apatite and merrillite) are common accessory minerals in many Apollo basalt and regolith samples. Phosphates typically have lower closure temperatures than their companion accessory phase zircon for their U-Pb and (U-Th)/He geochronologic systems [e.g., 1, 2]. As such, the ages of phosphates in impact melt-bearing breccias have typically been used to constrain the ages of impact events [3]. Phosphates have also served as anchors for 207Pb-206Pb isochrons allowing for precise ages of basaltic samples to be determined [4]. Apatite is also a reservoir for volatile species (e.g., F, Cl, OH, S) [e.g., 5, 6] which are important for investigating the formation and evolution of the lunar interior [7-11]. Recent work by [11] and [12] has shown that deformation and exposure to high temperatures, especially those in impact environments, can influence both apatite chronology and chemistry. Here we present the first chronology and microstructure results of a large consortium study aimed at unraveling the impact and endogenous volatile record of phosphates extracted from lunar soils. These soils potentially sample a larger range of lithologies than the rocks returned by Apollo astronauts, and should, therefore, represent a more global phosphate record. For more information on low temperature (U-Th)/He thermochronology, please see the companion abstract [13].

C A Crow↗

NASA NTRS2016

A Hybrid Mars Ascent Vehicle Design and FY 2016 Technology Development

Hybrid propulsion is currently favored for a Mars Ascent Vehicle (MAV) concept from a thermal performance and Gross Lift Off Mass standpoint. However, it is at a relatively low level of maturity compared to conventional propulsion options. Technology development efforts are currently underway to bring hybrid propulsion to a technology readiness level that would enable its infusion into potential Mars Sample Return. A new propellant combination is being considered for this design that has excellent low temperature behavior. Preliminary results of two ground test campaigns are currently underway to characterize this propellant combination. Hotfire testing is being carried out in parallel at Parabilis Space Technologies and Space Propulsion Group. In addition to the new propellant combination, several other technologies are being pursued for a potential hybrid MAV: hypergolic ignition and Liquid Injection Thrust Vector Control. Both of these technologies have been applied in other rocket applications, e.g. liquid propulsion commonly uses hypergolic propellants and missiles, such as the Minuteman II, have used LITVC in the past. Hypergolic ignition, when oxidizer and fuel combust upon contact, is highly desirable for multiple starts required by the MAV concept. Therefore, testing at Penn State and Purdue is being completed in this area. An updated hybrid propulsion system design for a Mars Ascent Vehicle concept based on JPL’s current understanding of potential Mars Sample Return requirements will be presented, leveraging the advances in technology development as well as updated understanding of how requirements may evolve.

Karp, Ashley C.↗

NASA NTRS2019

Titan's Neutral Atmosphere Seasonal Variations up to the End of the Cassini Mission

In this paper we report new results concerning the seasonal atmospheric evolution near Titan's poles and equator using the Cassini Composite Infrared Spectrometer (CIRS). In previous papers (Coustenis et al. 2016 and 2018), after the 2010 equinox, we have monitored Titan's stratosphere since the beginning of the mission and reported recently on the observed strong temperature decrease and compositional enhancement above Titan's southern polar latitudes since 2012 of several trace species such as complex hydrocarbons and nitriles, which were previously observed only at high northern latitudes. This effect followed the transition of Titan's seasons from northern winter in 2002 to northern summer in 2017, while at that latter time, the southern hemisphere was entering winter. From 2013 until 2016, the northern polar region has shown a temperature increase of 10 K, while the south has shown a more significant decrease (up to 25 K) in a similar period of time. The stratosphere over the south pole of Titan shows a change in shape with a steeper positive slope and an increase in temperature in 2017 with respect to 2014, by 10-50 K in the 0.5 mbar-0.05 mbar pressure range, the larger 2017 temperatures observed in the higher atmospheric levels around 0.05 mbar, while in average the 70Â°S values return closer to the warmer ones found in 2012. While the south polar region is continuously enhanced since 2012, the chemical content in the north is showing a clear depletion for all molecules only since 2015 (Coustenis et al., 2018). We present here a complementary analysis of nadir spectra acquired by Cassini/CIRS at high resolution during the last year of the Cassini mission in 2017 and describe the temperature and composition variations near Titan's poles and at the equator over almost two Titan seasons. The 2017 data we have acquired and analyzed here are important because they are the only nadir ones afforded since 2014 close to the south pole at high resolution. They show no significant changes in the north with respect to 2016, but a large temperature increase in the southern polar stratosphere and a change in the temperature profiles shape while the South is also finally showing a related significant decrease in most of the abundances.

Coustenis, A.↗

DOE OSTI2015

A numerical study on bow shocks around the lightning return stroke channel

Bow shock structures are important to various hydrodynamics and magnetohydrodynamics (MHD) phenomena in geophysics and astrophysics. The formation and propagation of bow shocks around the lightning return stroke channel are investigated based on the self-similar motion theory and simulated with a two-dimensional Eulerian finite volume resistive radiation MHD code. In this framework, as verification of theoretical models, the evolving structures of many quantities, such as the plasma density, temperature, pressure, shock velocity, and magnetic field, can be obtained, which present all the characteristics of bow shocks in the lightning return stroke processes. The evolution characteristics and the configuration of the curved return stroke channels, e.g., the non-ideal effects and the scaling laws, are discussed in detail. The results may have applications for some observed features of the return stroke channels and other phenomena in the lightning discharge plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS2021

Global Intercomparison of hyper-resolution ECOSTRESS coastal sea surface temperature measurements from the Space Station with VIIRS-N20

The ECOSTRESS multi-channel thermal radiometer on the Space Station has an unprecedented spatial resolution of 70 m and a return time of hours to 5 days. It resolves details of oceanographic features not detectable in imagery from MODIS or VIIRS, and has open-ocean coverage, unlike Landsat. We calibrated two years of ECOSTRESS sea surface temperature observations with L2 data from VIIRS-N20 (2019–2020) worldwide but especially focused on important upwelling systems currently undergoing climate change forcing. Unlike operational SST products from VIIRS-N20, the ECOSTRESS surface temperature algorithm does not use a regression approach to determine temperature, but solves a set of simultaneous equations based on first principles for both surface temperature and emissivity. We compared ECOSTRESS ocean temperatures to well-calibrated clear sky satellite measurements from VIIRS-N20. Data comparisons were constrained to those within 90 min of one another using co-located clear sky VIIRS and ECOSTRESS pixels. ECOSTRESS ocean temperatures have a consistent 1.01 ◦C negative bias relative to VIIRS-N20, although deviation in brightness temperatures within the 10.49 and 12.01 µm bands were much smaller. As an alternative, we compared the performance of NOAA, NASA, and U.S. Navy operational split-window SST regression algorithms taking into consideration the statistical limitations imposed by intrinsic SST spatial autocorrelation and applying corrections on brightness temperatures. We conclude that standard bias-correction methods using already validated and well-known algorithms can be applied to ECOSTRESS SST data, yielding highly accurate products of ultra-high spatial resolution for studies of biological and physical oceanography in a time when these are needed to properly evaluate regional and even local impacts of climate change.

Nicolas Weidberg↗

NASA NTRS1988

Core temperature is regulated, although at a lower temperature, in rats exposed to hypergravic fields

1. In rats acclimated to 23 degrees C (RT rats) or 5 degrees C (CA rats), core temperature (Tc), tail temperature (Tt) and oxygen consumption (VO2) were measured during exposure to a hypergravic field. 2. Rats were exposed for 5.5 h to a 3 g field while ambient temperature (Ta) was varied. For the first 2 h, Ta was 25 degrees C; then Ta was raised to 34 degrees C for 1.5 h. During this period of warm exposure, Tc increased 4 degrees C in both RT and CA rats. Finally, Ta was returned to 25 degrees C for 2 h, and Tc decreased toward the levels measured prior to warm exposure. 3. In a second experiment at 3 g, RT and CA rats were exposed to cold (12 degrees C) after two hours at 25 degrees C. During the one hour cold exposure, Tc fell 1.5 degrees C in RT and 0.5 degree C in CA rats. After cold exposure, when ambient temperature was again 25 degrees C, Tc of RT and CA rats returned toward the levels measured prior to the thermal disturbance. 4. Rats appear to regulate their temperature, albeit at a lower level, in a 3 g field.

NASA Discipline Number 40-30↗

DOE OSTI2020

Harnessing biomimetic cryptic bonds to form self-reinforcing gels

Cryptic sites, which lay hidden in folded biomolecules, become exposed by applied force and form new bonds that reinforce the biomaterial. While these binding interactions effectively inhibit mechanical deformation, there are few synthetic materials that harness mechano-responsive cryptic sites to forestall damage. Here, we develop a computational model to design polymer gels encompassing cryptic sites and a lower critical solution temperature (LCST). LCST gels swell with a decrease in temperature, thereby generating internal stresses within the sample. The gels also encompass loops held together by the cryptic sites, as well as dangling chains with chemically reactive ends. A decrease in temperature or an applied force causes the loops to unfold and expose the cryptic sites, which then bind to the dangling chains. We show that these binding interactions act as “struts” that reinforce the network, as indicated by a significant decrease in the volume of the gel (from 44% to 80%) and shifts in the volume phase transition temperature. Once the temperature is increased or the deformation is removed, the latter “cryptic bonds” are broken, allowing the loops to refold and the gel to return to its original state. These findings provide guidelines for designing polymer networks with reversible, mechano-responsive bonds, which allow gels to undergo a self-stiffening behavior in response to a temperature-induced internal stress or external force. When applied as a coating, these gels can prevent the underlying materials from undergoing damage and thus, extend the lifetime of the system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2000

The Low Temperature Microgravity Physics Experiments Project

The Low Temperature Microgravity Physics Facility (LTMPF) is being developed by NASA to provide long duration low temperature and microgravity environment on the International Space Station (ISS) for performing fundamental physics investigations. Currently, six experiments have been selected for flight definition studies. More will be selected in a two-year cycle, through NASA Research Announcement. This program is managed under the Low Temperature Microgravity Physics Experiments Project Office at the Jet Propulsion Laboratory. The facility is being designed to launch and returned to earth on a variety of vehicles including the HII-A and the space shuttle. On orbit, the facility will be connected to the Exposed Facility on the Japanese Experiment Module, Kibo. Features of the facility include a cryostat capable of maintaining super-fluid helium at a temperature of 1.4 K for 5 months, resistance thermometer bridges, multi-stage thermal isolation system, thermometers capable of pico-Kelvin resolution, DC SQUID magnetometers, passive vibration isolation, and magnetic shields with a shielding factor of 80dB. The electronics and software architecture incorporates two VME buses run using the VxWorks operating system. Technically challenging areas in the design effort include the following: 1) A long cryogen life that survives several launch and test cycles without the need to replace support straps for the helium tank. 2) The minimization of heat generation in the sample stage caused by launch vibration 3) The design of compact and lightweight DC SQUID electronics. 4) The minimization of RF interference for the measurement of heat at pico-Watt level. 5) Light weighting of the magnetic shields. 6) Implementation of a modular and flexible electronics and software architecture. The first launch is scheduled for mid-2003, on an H-IIA Rocket Transfer Vehicle, out of the Tanegashima Space Center of Japan. Two identical facilities will be built. While one facility is onboard the ISS, the other is re-integrated on the ground with new experiments. When the cryogen of the facility in space are exhausted, it will be swapped with the other facility with the new experiment. A total of 20 science missions are envisioned over the next 20 years.

Holmes, Warren↗

NASA NTRS1973

Relaxation times of remanent magnetisation in lunar fines

On the basis of an analysis of the magnetic parameters, it appears that the bulk of metallic Fe particles in the lunar fines are essentially spherical and have a short remanent relaxation time. These spherical metallic Fe particles could account for the apparently low blocking temperature observed for the unstable components of the natural remanent magnetization detected in the returned lunar samples.

Tsay, F.-D.↗

NASA NTRS1980

Venus nighttime hydrogen bulge

The concentration of atomic hydrogen in the Venus thermosphere near 165 km altitude and approximately 18 deg north latitude has been derived from Pioneer Venus in situ measurements of H(+), O(+), O and CO2 concentrations, under the assumption of chemical equilibrium. Altitude profiles of derived H concentration suggest that chemical equilibrium prevails to an altitude of at least 200 km on the dayside and to 165 km on the nightside. Measurements below these limits were made by the ion and neutral mass spectrometers on the orbiter spacecraft between December 1978 and July 1979, while periapsis traversed a complete diurnal cycle. The hydrogen concentration is found to rise sharply at both terminators from a dayside value of approximately 50,000/cu cm, and to exhibit an asymmetric nightside distribution with a peak density in the predawn sector approximately 400 times greater than the dayside value. Analysis suggests that wind-induced diffusion, combined with exospheric return flow, can account for the observed hydrogen behavior. The large day-night temperature contrast enhances advective transport, which produces the large H concentration diurnal variation; the shift of the H concentration nighttime maximum toward dawn is caused by atmospheric superrotation.

Brinton, H. C.↗

NASA NTRS1985

Kidney Cell Electrophoresis

Materials and procedures for microgravity electrophoresis of living human embryonic kidney cells were evaluated, ground support in the form of analytical cell electrophoresis and flow cytometry was provided and cells returned from space flight were analyzed. Preflight culture media, electrophoresis buffer, fraction collection media, temperature profiles, and urokinase assay procedures were tested prior to flight. Electrophoretic mobility distributions of aliquots of the cell population to be fractionated in flight were obtained. The protocol established and utilized is given.

Todd, P.↗