Development of a Nitrous Oxide-Based Monopropellant Propulsion System for Small Satellites

As the demand for highly capable microsatellite missions continues to grow, so too does the need for small yet effective satellite technologies. One area which needs to be addressed is compact propulsion systems capable of performing on-orbit maneuvers, station keeping, and de-orbit impulses with good efficiency. Another important consideration for propulsion systems is the safety and ease in handling, integrating, and testing the propulsion system. This is particularly important for small satellites in order to maintain simplicity by avoiding toxic propellants such as hydrazine. In response to this demand, the Space Flight Laboratory has developed its next generation propulsion system which builds on the experience of the Canadian Nanospace Advanced Propulsion System (CNAPS), a cold gas system that enabled the successful CanX-4/CanX-5 formation flying mission in 2014. The new propulsion system uses nitrous oxide (N2O) as the propellant. The benefits of nitrous oxide are that it is safe to handle, non toxic, cheap, and much easier to access and transport than traditional propellants. Nitrous oxide also self pressurizes to 50.5 bar (733 psi) at 20 °C and thus does not require the addition of a pump or pressurant gas to move the propellant; this allows the tank and feed system design to be much simpler than for liquid propellants. Nitrous oxide can also be used as monopropellant, that is to say that it can be exothermically decomposed to provide an increase in efficiency from an input power point of view. This paper summarizes SFL\u27s effort in the development of this system. A 100 mN resistojet was initially developed. The performance using nitrous oxide was verified with a specific impulse of 100 s and input power ofdevelopment, a monopropellant version of the thruster was developed. The 100 mN monopropellant thruster has successfully demonstrated sustainable nitrous oxide decomposition with a specific impulse of 148 s and operational endurance of greater than 50 hours. Current research focuses on evaluating different catalysts and further extending the operational lifetime of the system

Generation of a Convalescent Model of Virulent Francisella tularensis Infection for Assessment of Host Requirements for Survival of Tularemia

Francisella tularensis is a facultative intracellular bacterium and the causative agent of tularemia. Development of novel vaccines and therapeutics for tularemia has been hampered by the lack of understanding of which immune components are required to survive infection. Defining these requirements for protection against virulent F. tularensis, such as strain SchuS4, has been difficult since experimentally infected animals typically die within 5 days after exposure to as few as 10 bacteria. Such a short mean time to death typically precludes development, and therefore assessment, of immune responses directed against virulent F. tularensis. To enable identification of the components of the immune system that are required for survival of virulent F. tularensis, we developed a convalescent model of tularemia in C57Bl/6 mice using low dose antibiotic therapy in which the host immune response is ultimately responsible for clearance of the bacterium. Using this model we demonstrate αβTCR+ cells, γδTCR+ cells, and B cells are necessary to survive primary SchuS4 infection. Analysis of mice deficient in specific soluble mediators shows that IL-12p40 and IL-12p35 are essential for survival of SchuS4 infection. We also show that IFN-γ is required for survival of SchuS4 infection since mice lacking IFN-γR succumb to disease during the course of antibiotic therapy. Finally, we found that both CD4+ and CD8+ cells are the primary producers of IFN-γand that γδTCR+ cells and NK cells make a minimal contribution toward production of this cytokine throughout infection. Together these data provide a novel model that identifies key cells and cytokines required for survival or exacerbation of infection with virulent F. tularensis and provides evidence that this model will be a useful tool for better understanding the dynamics of tularemia infection

Drug discovery: Insights from the invertebrate Caenorhabditis elegans

Therapeutic drug development is a long, expensive, and complex process that usually takes 12–15 years. In the early phases of drug discovery, in particular, there is a growing need for animal models that ensure the reduction in both cost and time. Caenorhabditis elegans has been traditionally used to address fundamental aspects of key biological processes, such as apoptosis, aging, and gene expression regulation. During the last decade, with the advent of large-scale platforms for screenings, this invertebrate has also emerged as an essential tool in the pharmaceutical research industry to identify novel drugs and drug targets. In this review, we discuss the reasons why C. elegans has been positioned as an outstanding cost-effective option for drug discovery, highlighting both the advantages and drawbacks of this model. Particular attention is paid to the suitability of this nematode in large-scale genetic and pharmacological screenings. High-throughput screenings in C. elegans have indeed contributed to the breakthrough of a wide variety of candidate compounds involved in extensive fields including neurodegeneration, pathogen infections and metabolic disorders. The versatility of this nematode, which enables its instrumentation as a model of human diseases, is another attribute also herein underscored. As illustrative examples, we discuss the utility of C. elegans models of both human neurodegenerative diseases and parasitic nematodes in the drug discovery industry. Summing up, this review aims to demonstrate the impact of C. elegans models on the drug discovery pipeline.Fil: Giunti, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Andersen, Natalia Denise. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Rayes, Diego Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: de Rosa, Maria Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; Argentin

The CanX-4&5 Formation Flying Mission: A Technology Pathfinder for Nanosatellite Constellations

Future nano- and microsatellite constellations will require highly precise absolute and relative position knowledge and control; intersatellite communications; high-performance attitude determination and control systems; and advanced, compact propulsion systems for orbit maintenance. The dual spacecraft CanX-4&5 mission - slated to launch in the late 2013 / early 2014 timeframe on India’s Polar Satellite Launch Vehicle (PSLV) - will demonstrate all of these capabilities at the nanosatellite scale: both as standalone subsystems, and in concert, to accomplish autonomous formation flight with sub-meter relative position control and centimeter-level relative position determination. CanX-4 and CanX-5 are individual spacecraft based on the SFL Generic Nanosatellite Bus (GNB). Each spacecraft is identical, and formation flight is enabled by each satellite having a GPS receiver, on-board propulsion system, S-Band inter-satellite link, and fine guidance and control (GNC) computer. The two spacecraft will share on-board position, velocity, and attitude data wirelessly over their intersatellite link, and one of the two spacecraft will perform propulsive maneuvers to achieve and maintain a series of autonomous formations. The technologies and algorithms used on CanX-4&5 are extensible to a broad range of missions and satellites at the nano- and microsatellite scale, and this ambitious technology demonstration will serve as a pathfinder for several formation flight and constellation applications

GPS Relative Navigation for the CanX-4 and CanX-5 Formation Flying Nanosatellites

In November 2014 the CanX-4 and CanX-5 spacecraft became the first nanosatellites to demonstrate autonomous formation control with error less than 1 m. This feat was accomplished both in along-track formations at 1000 and 500 m range and projected circular orbit formations at 100 and 50 m. This control performance was enabled through carrier-phase differential GPS navigation techniques, providing online relative state estimates typically accurate to better than 10 cm. It was an important milestone on the road to regular and fully operational formation-flying missions. This paper provides an overview of the relative positioning algorithm design, presents an independent assessment of the receiver performance, and assesses the absolute and relative navigation results. The mission’s on-orbit results are compared with an independently determined orbit solution computed using the GPS High Precision Orbit Determination Software Tools at the German Aerospace Centre

CanX–4 and CanX–5 Precision Formation Flight: Mission Accomplished!

In November 2014, only four months following launch, the CanX–4 and CanX–5 dual-spacecraft formation-flying mission achieved what has never been accomplished before, and successfully completed all of its mission goals with unprecedented precision and speed. This achievement—a series of autonomous formations with sub-metre control and centimetre-level relative position knowledge at the nanosatellite scale—was preceded by a rapid commissioning phase and orbit acquisition manoeuvres, which brought the two satellites from a maximum range of 2300 km to a closest controlled range of 50m during formation flight. Launched on 30 June 2014 from Sriharikota, India on board the Polar Satellite Launch Vehicle (PSLV), CanX–4 and CanX–5 were deployed separately following launch, after which a series of drift recovery manoeuvres were executed to bring the spacecraft within communications range of each other. Subsequently, the spacecraft used onboard propulsion, an S-band intersatellite communications link, and relative navigation using carrier-phase differential GPS techniques to perform a series of precise, controlled, autonomous formations from 1km range down to 50m separation. The achievements of CanX–4 and CanX–5 have set the high mark for small satellite formation flight, and the technologies and algorithms developed for this mission enable a number of future applications, from on-orbit inspection and repair to sparse aperture sensing, interferometry, and ground-moving target indication. This paper describes the CanX–4 and CanX–5 mission and its exciting results, with an emphasis on launch, commissioning, relative orbit acquisition and phasing, and autonomous formation flight

Three new seabird species recorded at Tristan da Cunha archipelago.

The Tristan da Cunha archipelago comprises three main islands: Tristan, Inaccessible and Nightingale at 37ºS 12ºW, with Gough Island (40ºS 10ºW) the only other temperate oceanic island in the South Atlantic Ocean (Ryan 2007). Tristan and Gough are important breeding sites for 25 species of seabirds (Ryan 2008; Ryan et al. 2014; 2015; Robertson et al. 2016), and a further 30 species of non-breeding seabirds have been reported from the islands (Ryan 2007; Visser et al. 2009; Ryan 2010). We report three additional species from the islands based on observations from 2017 to 2019