Cryogenic-coolant He4-superconductor dynamic and static interactions

A composite superconducting material (NbTi-Cu) was evaluated with emphasis on post quench solid cooling interaction regimes. The quasi-steady runs confirm the existence of a thermodynamic limiting thickness for insulating coatings. Two distinctly different post quench regimes of coated composites are shown to relate to the limiting thickness. Only one regime,, from quench onset to the peak value, revealed favorable coolant states, in particular in He2. Transient recovery shows favorable recovery times from this post quench regime (not drastically different from bare conductors) for both single coated specimens and a coated conductor bundle

Cryogenic-coolant He-4-superconductor interaction

The thermodynamic and thermal interaction between a type 2 composite alloy and cryo-coolant He4 was studied with emphasis on post quench phenomena of formvar coated conductors. The latter were investigated using a heater simulation technique. Overall heat transfer coefficients were evaluated for the quench onset point. Heat flux densities were determined for phenomena of thermal switching between a peak and a recovery value. The study covered near saturated liquid, pressurized He4, both above and below the lambda transition, and above and below the thermodynamic critical pressure. In addition, friction coefficients for relative motion between formvar insulated conductors were determined

Decay of first year sea ice : A second season of field measurements : Interim report

This report describes a field program that was undertaken to characterize the seasonal ice decay process using a second year of measurements. Ice property measurements were made and a borehole jack assembly was used to measure the in situ confined compressive strength (borehole strength) of the ice. The project was conducted from 14 May to 28 June 2001 during which time the ice thickness ranged from 1.45 to 1.30 m. More than one hundred borehole jack tests were conducted at depths 0.3, 0.6, 0.9 and 1.2 m. No significant ice ablation occurred during the time that the borehole jack tests were conducted. Over the period mid-May to early June, the ice strength decreased by 50% in the top 0.50 m of ice. Measurements showed that the surface layer of ice decreased from a strength of 22 MPa to 10 MPa between mid May and early June. In comparison, the strength in the bottom layer of ice (depth 1.20 m) remained relatively constant (10 to 13 MPa) during that time.NRC publication: Ye

SIRTF Telescope Instrument Changeout and Cryogen Replenishment (STICCR) Study

The Space Infrared Telescope Facility (SIRTF) is a long-life cryogenically cooled space-based telescope for infrared astronomy from 2 to 700 micrometers. SIRTF is currently under study by NASA-ARC (Reference AP) and planned for launch in approximately the mid 1990s. SIRTF will operate as a multiuser facility, initially carrying three instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and baseline is currently to be 2 years. The telescope changes required to allow in-space replenishment of the 4,000-L superfluid helium tank was investigated. A preliminary design for the space services equipment was also developed. The impacts of basing the equipment and servicing on the space station were investigated. Space replenishment and changeout of instruments required changes to the telescope design. Preliminary concepts are presented

Elastic moduli of sea ice and lake ice calculated from in-situ and laboratory experiments

The effective elastic modulus of ice is an important physical parameter for the calculation of ice stresses in different situations when ice deformations are small. In the present paper the review of methods used for the calculation of the elastic modulus of ice is performed, new tests for the calculation of the elastic modulus are described, and their results are discussed. Field experiments with floating vibrating ice beams with fixed ends were performed in March and November 2019 on sea ice of the Van Mijen Fjord and fresh-water ice of a lake near Longyearbyen. Laboratory experiments with vibrating cantilever beams were performed in the cold laboratory of UNIS in November 2019. The results are compared with the values of the effective elastic modulus obtained in quasi-static tests with floating cantilever beams, and with in-situ dynamic tests where the effective elastic modulus was measured by the speed of sound waves

Influence of vibrations on indentation and compression strength of sea ice

Indentation and compression strengths of floating sea ice subjected to vibrations is discussed. The experiments were performed on the land fast ice of the Van-Mijen Fjord in March of 2018 and 2019. The ice thickness was around 70 cm, and the ice salinity was 4-5 ppt. Vibrations were introduced in the ice by the vibration plate with weight of 400 kg before the tests during 10-15 min. The vibration plate was standing and vibrating on the ice surface. The spectrum of vibrations was recorded with accelerometers. Analysis of thin sections of ice was performed on the place of the field works. Indentation tests were performed with the original hydraulic rig on natural ice and ice subjected to the action of vibrating plate. It was discovered that stroke rates tests were higher in the tests performed on the ice subjected to vibrations. Uniaxial compression tests were also performed on ice cores taken from the natural ice and from the ice subjected to the vibrations. Uniaxial compression strength of ice cores taken from the ice subjected to vibrations was higher than in the tests with natural ice

Review of standards for ice forces on port structures

Port structures in cold regions generally take the form of large caisson structures or piled structures. There are limited standards for such structures, so the following standards for highway bridges and offshore structures were assessed for application in specifying ice forces on port structures; CSA-S6 Canadian Highway Bridge Design Code, ISO 19906 Arctic offshore structures, CSA-S471 General requirements, design criteria, the environment, and loads, API Recommended Practice 2N Planning, Designing, and Constructing Structures and Pipelines for Arctic Conditions (1995), and Russia\u2019s SNiP 2.06.04-82* Loads and Effects on Hydrotechnical Structures. The ice condition considered was level ice 0.2 to 2 m thick. Three typical structures were evaluated; 1 m diameter pile, 4 m diameter structure and a 50 m wide structure. CSA S6 was found to be best suited for small pile structures (~1 m dia.). For slightly larger structures (~4 m dia.), CSA S6 was the best choice, but ISO 19906 and CSA S471 could be used for ice thickness greater than 1.2 m. Finally, for wide structures CSA S471 was most suitable, but ISO 19906 or API RP 2N could be used for ice thickness greater than 0.6 m and up to 2 m.Peer reviewed: YesNRC publication: Ye

Large scale hull loading of first-year ice, preliminary analysis of stress distributions

A finite element analysis of various geometries of on ice edge was carried out. The analysis showed that high tensile stresses were generated at interior corners which would lead to tensile failure of the ice at those locations before compressive failure under the indentor. Suggestions were made on the positioning of a stress relief slot to encourage compressive failure of the ice under the indentor.NRC publication: Ye