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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Peculiar Behavior of He II Disturbances due to Sloshing Dynamics Driven by Jitter Accelerations Associated with Slew Motion in Microgravity

The mathematical formulation of Dewar container sloshing dynamics when partially filled with superfluid liquid He 11 driven by the gravity jitter acceleration associated with slew motion in a microgravity environment is studied. Numerical computation of the sloshing dynamics is based on the non-inertia container bound co-ordinate, and solving time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. This study discloses the capillary effect of the sloshing dynamics governing the liquid-vapour interface fluctuations driven by the gravity jitter acceleration associated with slew motion, which affects the stability of the fluid system in a microgravity environment. The peculiar behaviour of superfluid helium when reacting to the sloshing dynamics driven by the gravity jitter acceleration associated with slew motion in a microgravity environment is also investigated.

Hung, R. J.↗
NASA NTRS1997

Dynamical Models for Sloshing Dynamics of Helium 2 Under Low-G Conditions

Coupling of sloshing dynamics within a partially filled rotating dewar of superfluid helium 2 with spacecraft dynamics are investigated in response to the realistic environmental disturbance forces and torques acting on the spacecraft during normal operation. This study investigates: (1) the rotating bubble of superfluid helium 2 reacting to combined environmental disturbances, including gravity gradient, aerodynamic, and magnetic forces and torques; (2) characteristics of slosh reaction forces and torques coupling with spacecraft dynamics; (3) the contribution of slosh dynamics to over-all spacecraft dynamics; and (4) activating of attitude and translation control system. The numerical computation of sloshing dynamics is based on the rotational frame, while the spacecraft dynamics is associated with non-rotational frame. Results show that the contributions of spacecraft dynamics are driven by the environmental disturbances coupling with slosh dynamics. Without considering the effects of environmental disturbances-driven slosh dynamics acting on spacecraft coupling with the spacecraft dynamics may lead to the wrong results for the development of spacecraft system guidance and attitude control techniques.

Hung, R. J.↗
NASA NTRS1999

T(sub lambda) Depression by a Heat Current Along the lambda-Line

We report measurements of the depression of the superfluid transition temperature by a heat current (1 less than or = Q less than or = 100 microW/sq cm) along the lambda-line (SVP less than or = P less than or = 21.6 bar). At P = 21.6 bar, measurements were also performed in a reduced gravity (0.2g). Experimental results show that the pressure dependence of the depression and the gravity effect on the measurements are small, in qualitative agreement with theoretical predictions. Keywords: superfluid helium; Lambda transition; heat current

Liu, Yuanming↗
NASA NTRS2003

Ground-Based Investigations with the Cryogenic Hydrogen Maser

The cryogenic hydrogen maser (CHM) developed at the Smithsonian Astrophysical Observatory (SAO) was designed to be functionally similar to SAO room temperature hydrogen masers with appropriate modifications made for operation at cryogenic temperatures. A schematic of the SAO CHM is shown in Figure 1, and a description of this device and its operation follows. A beam of molecular hydrogen is dissociated into atoms at room temperature. The resultant beam of atomic hydrogen is then cooled, magnetically state selected, and focused into a quartz storage bulb centered inside of a microwave cavity resonant with the hydrogen hyperfine transition at 1420 MHz. The quartz storage bulb is coated with a superfluid He-4 film, and both the bulb and cavity are maintained near 0.5 K. The maser signal is coupled out inductively and carried to room temperature via semi-rigid coaxial cable. After passing through a room temperature isolator and preamp, the maser signal is detected with a low-noise heterodyne receiver as used in the room temperature SAO hydrogen masers. The maser temperature is lowered to 0.5 K using a recirculating He-3 refrigerator. This refrigerator consists of several cooling stages: a liquid nitrogen stage at 77 K, a liquid 4He bath at 4.2 K, a pumped He-4 pot at approximately 1.7 K, and the pumped, recirculating He-3 stage at 0.5 K. The atomic hydrogen beam, state selector, storage bulb and cavity are all connected inside a single, maser vacuum chamber (MVC). This space is pumped out from below by a turbo pump. Above the MVC, an inlet to the space allows for the input of flowing superfluid 4He film. External to the MVC is a second, outer vacuum chamber (OVC), maintained for operation of the cryostat and also pumped by a turbo pump. Inside the OVC, there is radiation shielding at 77 K and 1.7 K.

Walsworth, Ronald L.↗
NASA NTRS2003

Qualifying the Sunpower M-87N Cryocooler for Operation in the AMS-02 Magnetic Field

The Alpha Magnetic Spectrometer-02 (AMs-02) experiment consists of a superfluid helium dewar. The outer vapor cooled shields of the dewar are to be held at 77 K by four Sunpower M87N cryocoolers. These cryocoolers have magnetic components that might interact with the external applied field generated by the superconducting magnet, thereby degrading the cryocoolers' performance. Engineering models of the Sunpower M87N are being tested at NASA Goddard Space Flight in order to qualify them to operate in a magnetic environment similar to the AMS-02 magnetic environment. AMS-02 will be a space station based particle detector studying the properties and origin of cosmic particles including antimatter and dark matter. It uses a superconducting magnet that is cooled by the superfluid helium dewar. Highly sensitive detector plates inside the magnet will measure a particle's momentum and charge.

Mustafi, Shuvo↗
NASA NTRS2004

Changes in the X-Ray Emission from the Magnetar Candidate 1E 2259+586 During its 2002 Outburst

An outburst of more than 80 individual bursts, similar to those seen from Soft Gamma Repeaters (SGRs), was detected from the anomalous X-ray pulsar (AXP) 1E 2259+586 in 2002 June. Coincident with this burst activity were gross changes in the pulsed flux, persistent flux, energy spectrum, pulse profile, and spin-down of the underlying X-ray source. We present Rossi X-Ray Timing Explorer and X-Ray Multi-Mirror Mission observations of 1E 2259+586 that show the evolution of the aforementioned source parameters during and following this episode and identify recovery timescales for each. Specifically, we observe an X-ray flux increase (pulsed and phase-averaged) by more than an order of magnitude having two distinct components. The first component is linked to the burst activity and decays within approx. 2 days, during which the energy spectrum is considerably harder than during the quiescent state of the source. The second component decays over the year following the glitch according to a power law in time with an exponent -0.22 +/- 0.01. The pulsed fraction decreased initially to approx. 15% rms but recovered rapidly to the preoutburst level of approx. 23% within the first 3 days. The pulse profile changed significantly during the outburst and recovered almost fully within 2 months of the outburst. A glitch of size Delta(sib (nu)max) = (4.24 +/- 0.11) x 10(exp -6) was observed in 1E 2259+586, which preceded the observed burst activity. The glitch could not be well fitted with a simple partial exponential recovery. An exponential rise of approx. 20% of the frequency jump with a timescale of approx. 14 days results in a significantly better fit to the data; however, contamination from a systematic drift in the phase of the pulse profile cannot be excluded. A fraction of the glitch (approx. 19%) was recovered in a quasi-exponential manner having a recovery timescale of approx. 16 days. The long-term postglitch spin-down rate decreased in magnitude relative to the preglitch value. The changes in the source properties of 1E 2259+586 during its 2002 outburst are shown to be qualitatively similar to changes seen during or following burst activity in two SGRs, thus further solidifying the common nature of SGRs and AXP's as magnetars. The changes in persistent emission properties of 1E 2259+586 suggest that the star underwent a plastic deformation of the crust that simultaneously impacted the superfluid interior (crustal and possibly core superfluid) and the magnetosphere. Finally, the changes in persistent emission properties coincident with burst activity in 1E 2259+586 enabled us to infer previous burst-active episodes from this and other AXP's. The nondetection of these outbursts by all-sky gamma-ray instruments suggests that the number of active magnetar candidates in our Galaxy is larger than previously thought.

Woods, P. M.↗
NASA NTRS2003

Numerical Studies of Properties of Confined Helium

We carry out state of the art simulations of properties of confined liquid helium near the superfluid transition to a degree of accuracy which allows to make predictions for the outcome of fundamental physics experiments in microgravity. First we report our results for the finite-size scaling behavior of heat capacity of superfluids for cubic and parallel-plate geometry. This allows us to study the crossover from zero and two dimensions to three dimensions. Our calculated scaling functions are in good agreement with recently measured specific heat scaling functions for the above mentioned geometries. We also present our results of a quantum simulation of submonolayer of molecular hydrogen deposited on an ideal graphite substrate using path-integral quantum Monte Carlo simulation. We find that the monolayer phase diagram is rich and very similar to that of helium monolayer. We are able to uncover the main features of the complex monolayer phase diagram, such as the commensurate solid phases and the commensurate to incommensurate transition, in agreement with the experiments and to find some features which are missing from the experimental analysis.

Manousakis, Efstratios↗
NASA NTRS2003

Low Temperature Microgravity Physics Facility Payload for the ISS

The LTMPF Payload is a 182-liter superfluid-helium dewar that will be attached to the JEM-EF facility of the International Space Station after launch in the cargo bay of the Space Shuttle. The LTMPF Payload will provide a major low-temperature research laboratory for Fundamental Physics experiments on the International Space Station. The LTMPF payload will provide instrument temperatures below superfluid helium temperatures and the ISS will provide microgravity to allow the experiments to study condensed matter and gravitational physics. Each flight will be allocated to one condensed matter instrument and one gravitation instrument.

Langford, Don↗
NASA NTRS1995

(abstract) Production and Levitation of Free Drops of Liquid Helium

We are interested in the nucleation and behavior of quantized vorticies and surface excitations in free drops of superfluid helium. We have constructed an apparatus to maintain liquid helium drops isolated from any material container in the Earth's gravitational field, and have investigated two techniques for generating and introducing liquid drops into the region of confinement. The levitation apparatus utilizes the electrostatic force acting upon a charged liquid drop to counteract the gravitational force, with drop position stability provided by a static magnetic field acting upon the helium diamagnetic moment. Electrically neutral superfluid drops have been produced with a miniature thermomechanical pump; for a given configuration the liquid initial velocity has been varied up to several centimeters per second. Liquid drops carrying either net positive or negative charge are produced by an electrode which generates a flow of ionized liquid from the bulk liquid surface. Potentials of less than one thousand volts to several thousand volts are required. The mass flow is controlled by varying duration of the ionizing voltage pulse; drops as small as 30 micrometers diameter, charged to near the Rayleigh limit, have been observed.

quantized vorticity levitation liquid helium↗
NASA NTRS2011

Design of a 3-Stage ADR for the Soft X-Ray Spectrometer Instrument on the Astro-H Mission

The Japanese Astro-H mission will include the Soft X-ray Spectrometer (SXS) instrument, whose 36-pixel detector array of ultra-sensitive x-ray microcalorimeters requires cooling to 50 mK. This will be accomplished using a 3-stage adiabatic demagnetization refrigerator (ADR). The design is dictated by the need to operate with full redundancy with both a superfluid helium dewar at 1.3 K or below, and with a 4.5 K Joule-Thomson (JT) cooler. The ADR is configured as a 2-stage unit that is located in a well in the helium tank, and a third stage that is mounted to the top of the helium tank. The third stage is directly connected through two heat switches to the JT cooler and the helium tank, and manages heat flow between the two. When liquid helium is present, the 2-stage ADR operates in a single-shot manner using the superfluid helium as a heat sink. The third stage may be used independently to reduce the time-average heat load on the liquid to extend its lifetime. When the liquid is depleted, the 2nd and 3rd stages operate as a continuous ADR to maintain the helium tank at as low a temperature as possible - expected to be 1.2 K - and the 1st stage cools from that temperature as a single-stage, single-shot ADR. The ADR s design and operating modes are discussed, along with test results of the prototype 3-stage ADR.

Shirron, Peter J.↗
NASA NTRS2017

Mechanical Design of a 4-Stage ADR for the PIPER mission

The four 1,280 bolometer detector arrays that will fly on the balloon borne PIPER mission will be cooled by a 4-stage adiabatic demagnetization refrigerator (ADR). Two of the three mechanically independent ADR assemblies provide thermal isolation to their salt pills through Kevlar suspensions while the other provides thermal isolation to its salt pill through the use of bellows and Vespel material. The ADR integrates with the detector arrays and it sits in a large bucket Dewar containing superfluid liquid helium. This paper will describe the complex mechanical design of the PIPER ADR, and summarize the mechanical analysis done to validate the design.The four 1,280 bolometer detector arrays that will fly on the balloon borne PIPER mission will be cooled by a 4-stage adiabatic demagnetization refrigerator (ADR). Two of the three mechanically independent ADR assemblies provide thermal isolation to their salt pills through Kevlar suspensions while the other provides thermal isolation to its salt pill through the use of bellows and Vespel material. The ADR integrates with the detector arrays and it sits in a large bucket Dewar containing superfluid liquid helium. This paper will describe the complex mechanical design of the PIPER ADR, and summarize the mechanical analysis done to validate the design.

Cryogenics↗
NASA NTRS2019

Anti-Glitches in the Ultraluminous Accreting Pulsar NGC 300 ULX-1 Observed with NICER

We present evidence for three spin-down glitches (or “anti-glitches”) in the ultraluminous accreting X-ray pulsar NGC 300 ULX-1, in timing observations made with the Neutron Star Interior Composition Explorer. Our timing analysis reveals three sudden spin-down events of magnitudes Δν=−23, −30, and −43 μHz (fractional amplitudes Δν/ν=−4.4, −5.5, and −7.7×10−4). We determined fully phase-coherent timing solutions through the first two glitches, giving us high confidence in their detection, while the third candidate glitch is somewhat less secure. These are larger in magnitude (and opposite in sign) than any known radio pulsar glitch. This may be caused by the prolonged rapid spin up of the pulsar, causing a sudden transfer of angular momentum between the superfluid and non-superfluid components of the star. We find no evidence for profile or spectral changes at the epochs of the glitches, supporting the conclusion that these are due to the same process as in normal pulsar glitches, but in reverse.

Paul S Ray↗
NASA NTRS1999

Second Sound Measurements Very Near the Lambda Point

The sound was generated by wire-wound heaters embedded in the end opposite the sensor in each cavity. The superfluid density was determined from second sound measurements and the critical exponent v was obtained from fits to the data. The results from the exponent were found to be very sensitive to the treatment of systematic effects in the data.

sound measurements Lambda point superfluid↗
NASA NTRS1994

DYNAMX: A Low Temperature Microgravity Investigation of Phase Transitions

The Critical Dynamics in Microgravity Experiment, DYNAMX, will investigate the effects on the superfluid transition in 4 He of currents generated by heat flow, measuring the thermal conductivity in the fluid as a function of applied heat. DYNAMX will also take advantage of the weightless environment to measure the conductivity properties in the region of the interface between the two phases. Thus, DYNAMX represents an experiment that will explore a system driven far from equilibrium. This paper will describe the science objectives, the current design of the experiment apparatus, the steps being taken to prepare this experiment for flight, and the results of ground-based feasibility demonstrations now underway.

superfluid↗
NASA NTRS1995

Cryogenic Design of the Liquid Helium Experiment "Critical Dynamics in Microgravity"

Although many well controlled experiments have been conducted to measure the static properties of systems near criticality, few experiments have explored the transport properties in systems driven far away from equilibrium as a phase transition occurs. The cryogenic design of an experiment to study the dynamic aspect of critical phenomena is reported here. Measurements of the thermal gradient across the superfluid (He II)Юormal fluid (He I) interface in helium under microgravity conditions will be performed as a heat flux holds the system away from equilibrium. New technologies are under development for this experiment, which is in the definition phase for a space shuttle flight.

superfluid↗