Enabling High-Power SmallSats with Advanced Thermal Management

High-power Small Satellites have the potential to provide new and advanced capabilities; however, significant challenges prevent wide-spread use. Of these, thermal management of high-heat loads is significant. Although advances in thermal acquisition, transport, and storage are available; thermal dissipation technologies for high-power systems are lacking. Several design concepts are presented focused on high-efficiency, lightweight deployable radiating technologies. Analysis showed that realistic deployable radiator designs offer 220% more thermal dissipation than body-mounted radiator designs, which directly correlates to the same amount of increase in feasible total bus power. Using deployable radiators, a nominal 6U Small Satellite can realistically dissipate around 200 W

PRELIMINARY MULTI-VARIABLE EXPERIMENTAL ANALYSIS TO DETERMINE THE START UP CRITERIA OF PULSATING HEAT PIPES

Pulsating Heat Pipes (PHP) are passive two-phase heat transfer devices characterized by a simple structure and high heat transfer capabilities. Despite this, their large-scale application is still hindered by the actual unpredictability of their dynamic behavior during the start-up and the thermal crisis phases, that are crucial to define their operational limits. This is due to the complex phenomena involving the thin liquid film evaporation at the triple line (tube wall/liquid/vapor) during the start-up and dry-out process. An innovative experimental apparatus is designed to address the above open issues. It consists in a square loop made of four borosilicate transparent glass tubes (2mm inner diameter; 5 external diameter) joined at corners by means of brass connectors. The external tube surface is coated by means of series of transparent Indium Tin Oxide (ITO) heaters (16 patches of 30 mm length). The device is used to topologically reproduce a 8 turn PHP with an 2 mm inner diameter tube, filled with pure ethanol (FR = 50% vol.) and tested in horizontal position. The use of transparent heaters allows a complete knowledge of initial fluid distribution and fluid dynamics. The device is tested for 10°C and 20°C condenser temperatures, from 10W to 40W. In the 10 °C condenser temperature test, the device starts up at 10 W and shows an intermittent functioning up to 30W; increasing input power leads to self-sustained oscillations and partial dry-out. In the 20 °C condenser temperature test, the device shows a better performance. No intermittent operation is present, and the average evaporators temperature is ~6°C lower than the one of previous case. Further tests with different configurations will be fundamental for the understanding of the PHP governing phenomena

Preliminary Multi-Variable Experimental Analysis To Determine The Startup Criteria of Pulsating Heat Pipes

Pulsating Heat Pipes (PHP) are passive two-phase heat transfer devices characterized by a simple structure and high heat transfer capabilities. Despite this, their large-scale application is still hindered by the actual unpredictability of their dynamic behavior during the start-up and the thermal crisis. An innovative experimental apparatus is designed to systematically investigate the above phenomena. It consists in a square loop made of four borosilicate transparent glass tubes joined at corners by means of brass connectors. The external tube surface is coated with several transparent Indium Tin Oxide heaters. The device is used to topologically reproduce 5, 7, and 11 turns (i.e., heated sections in the evaporator) PHPs with an 2 mm inner diameter tube, filled with pure ethanol and tested in horizontal position. The condenser temperature is varied from 10°C to 40°C; the input power goes from 10 W to 40W. It is observed that the startup occurrence does not depend only on the number of heating sections but also on the condenser temperature. Increasing condenser temperature lowers the critical number of heated sections. At the same time, with the increase of the condenser temperature the startup time increases. Moreover, thanks to the direct fluid visualization, the increase of condenser temperature is linked to the formation of long liquid plugs that are found to be detrimental in terms of startup time

Inhalational anthrax (Ames aerosol) in naive and vaccinated New Zealand rabbits: characterizing the spread of bacteria from lung deposition to bacteremia.

There is a need to better understand inhalational anthrax in relevant animal models. This understanding could aid risk assessment, help define therapeutic windows, and provide a better understanding of disease. The aim here was to characterize and quantify bacterial deposition and dissemination in rabbits following exposure to single high aerosol dose (>100LD50) of Bacillus anthracis (Ames) spores immediately following exposure through 36 hours. The primary goal of collecting the data was to support investigators in developing computational models of inhalational anthrax disease. Rabbits were vaccinated prior to exposure with the human vaccine (Anthrax Vaccine Adsorbed, AVA) or were sham-vaccinated, and were then exposed in pairs (1 sham and 1 AVA) so disease kinetics could be characterized in equally-dosed hosts where one group is fully protected and is able to clear the infection (AVA-vaccinated), while the other is susceptible to disease, in which case the bacteria are able to escape containment and replicate uncontrolled (sham-vaccinated rabbits). Between 4-5% of the presented aerosol dose was retained in the lung of sham- and AVA-vaccinated rabbits as measured by dilution plate analysis of homogenized lung tissue or bronchoalveolar lavage (BAL) fluid. After 6 and 36 hours, >80% and >96%, respectively, of the deposited spores were no longer detected in BAL, with no detectable difference between sham- or AVA-vaccinated rabbits. Thereafter, differences between the two groups became noticeable. In sham-vaccinated rabbits the bacteria were detected in the tracheobronchial lymph nodes (TBLN) 12 hours post exposure and in the circulation at 24 hours, a time point which was also associated with dramatic increases in vegetative CFU in the lung tissue of some animals. In all sham-vaccinated rabbits, bacteria increased in both TBLN and blood through 36 hours at which point in time some rabbits succumbed to disease. In contrast, AVA-vaccinated rabbits showed sm

Whole exome sequencing in patients with white matter abnormalities

Here we report whole exome sequencing (WES) on a cohort of 71 patients with persistently unresolved white matter abnormalities with a suspected diagnosis of leukodystrophy or genetic leukoencephalopathy. WES analyses were performed on trio, or greater, family groups. Diagnostic pathogenic variants were identified in 35% (25 of 71) of patients. Potentially pathogenic variants were identified in clinically relevant genes in a further 7% (5 of 71) of cases, giving a total yield of clinical diagnoses in 42% of individuals. These findings provide evidence that WES can substantially decrease the number of unresolved white matter cases