Material management at the Ideal Shipbuilding Company

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Optimisation of laser assisted forming conditions for improved formability of aerospace materials

ISF technology was gradually considered as a manufacturing technology for fabricating sheet metal parts for both commercial and military aircraft. However, many challenges remain with respect to improving the consistency of the process, such as part thinning and springback. This is especially critical for two phase titanium alloy Ti-6AL-4V which has limited formability at room temperature. Therefore, understanding the correlation of laser system parameters and material properties is a key aspect for successful ISF of non-fractured Ti-6AL-4V. The laser heating is modelled to find the relationships between laser power, beam radius, scan speed, and the resultant temperature. The analysis shows that the temperature from laser heating increases with an increase in power, decreases significantly with an increase in beam radius, and decreases slightly with an increase in scan speed

Thermal Conductivity and Specific Heat Measurements of Candidate Structural Materials for the JWST Optical Bench

The James Webb Space Telescope will include an optical bench known as the integrated science instrument module (ISIM). Candidate structural materials for the ISIM must have low density, high stiffness, high thermal conductivity, and low thermal expansion coefficient at the operating temperature of 30 Kelvin. The specific heat is also important in modeling the on-orbit cooldown. We built two different systems for measuring the thermal conductivity and specific heat of samples between 4 Kelvin and 290 Kelvin. Both experiments were carefully designed to minimize potential errors due to radiative heat transfer. We chose the cooling system and instrumentation to allow long-term unattended operation. Software was developed to automate each experiment. It used an algorithm designed to ensure that each system was in thermal equilibrium before a measurement was taken. We describe the two experiments and present the data

Thermal and Electrical Conductivity Measurements of CDA 510 Phosphor Bronze

Many cryogenic systems use electrical cables containing phosphor bronze wire. While phosphor bronze's electrical and thermal conductivity values have been published, there is significant variation among different phosphor bronze formulations. The James Webb Space Telescope (JWST) will use several phosphor bronze wire harnesses containing a specific formulation (CDA 510, annealed temper). The heat conducted into the JWST instrument stage is dominated by these harnesses, and approximately half of the harness conductance is due to the phosphor bronze wires. Since the JWST radiators are expected to just keep the instruments at their operating temperature with limited cooling margin, it is important to know the thermal conductivity of the actual alloy being used. We describe an experiment which measured the electrical and thermal conductivity of this material between 4 and 295 Kelvin

Cryogenic Thermal Emittance Measurements on Small-Diameter Stainless Steel Tubing

The Mid Infrared Instrument aboard the James Webb Space Telescoep includes a mechanical cryocooler which cools its detectors to their 6 K operating temperature. The refrigerant flows through several meters of approximately 2 mm diameter 304L stainless steel tubing, with some sections gold plated, and some not, which are exposed to their environment. An issue of water freezing onto the tube surfaces is mitigated by a running a warm gas through the lines to sublimate the water. To model the effect of this process on nearby instruments, an accurate measure of the tube emittance is needed. Previously we reported the abosprtance of the gold plated stainless steel tubing as a function of source temperature (i.e. its environment). In this work the thermal emittance of the uncoated tubing is measured as a function of its temperature between 100 and 300 K. This value leads to an accurate prediction of the minimum length of time required to thermally recycle the system. We report the technique and present the results

Cryogenic System for the Origins Space Telescope: Cooling a Large Space Telescope to 4K with Today's Technology

The Origins Space Telescope (OST) concept is one of four NASA Science Mission Directorate, Astrophysics Division, observatory concepts being studied for launch in the mid 2030's. OST's wavelength coverage will be from the midinfrared to the sub-millimeter, 6-600 microns. To enable observations at the zodiacal background limit the telescope must be cooled to about 4 K. Combined with the telescope size (currently the primary is 9 m in diameter) this appears to be a daunting task. However, simple calculations and thermal modeling have shown the cooling power required is met with several currently developed cryocoolers. Further, the telescope thermal architecture is greatly simplified, allowing simpler models, more thermal margin, and higher confidence in the final performance values than previous cold observatories. We will describe design principles to simplify modeling and verification. We will argue that the OST architecture and design principles lower its integration and test time and reduce its ultimate cost

The potential for biological control on cryptic plant invasions

Cryptic invasions can be defined as ‘the occurrence of an invasive species or genotype that was not previously recognised as alien in origin or not distinguished from other aliens’. Such invasions can result in negative impacts on the recipient ecosystems and disturb the evolutionary history of native plant populations. Many cryptic invasions have become so problematic that there is a need to implement control measures. This paper explores the potential for biological control to be implemented as a means of managing cryptic invasions. Firstly, the paper defines the different forms of cryptic invasion, differentiating between interspecific and intraspecific invasions; this hierarchy influences how to detect, study and ultimately implement biological control when cryptic invasions occur. Secondly, unique challenges associated with biological control programmes for cryptic invasions are addressed, including: the need for intraspecific level host specificity in agents, the occurrence of hybridisation between native species/lineages and the target weed, the role of enemy release in cryptic invasions in the presence of closely related native plant species/lineages, and a review of potential stakeholder conflicts of interest and legislation. Biological control of cryptic invasions has been shown to be possible, however the process will be more difficult and complex than controlling traditional targets and will likely take up more time and resources. If these challenges are overcome, then biological control programmes against cryptic invasions should be able to proceed and maintain the same standards as traditional biological control programmes

Cooling the Origins Space Telescope

The NASA Astrophysics Division has commissioned 4 studies for consideration by the 2020 Decadal Survey to be the next flagship mission following WFIRST (Wide Field Infrared Survey Telescope). One of the four studies is the Origins Space Telescope (OST), which will cover wavelengths from 6 microns to 600 microns. To perform at the level of the zodiacal, galactic, and cosmic background, the telescope must be cooled to 4 degrees Kelvin. 4 degrees Kelvin multi-stage mechanical cryocoolers will be employed along with a multilayer sunshield/thermal shield to achieve this temperature with a manageable parasitic heat load. Current state-of-the-art cryocoolers can achieve close to 4 degrees Kelvin, providing about 50 megawatts of cooling at 4 degrees Kelvin with an input power of 500 watts. Multiple coolers at this power level will be used in parallel. These coolers also provide extra cooling power at intermediate temperature stages of 15-20 degrees Kelvin and 50-70 degrees Kelvin . This upper stage cooling will be used to limit the heat conducted to 4 degrees Kelvin . The multi-layer sunshield will limit the radiated thermal energy to the 4 degrees Kelvin volume. This paper will describe the architecture of the cryogenic system for OST along with preliminary thermal models