Design and development of ionic liquid dual-mode spacecraft propellants

Energetic ionic liquids capable of dual-mode chemical monopropellant or bipropellant and electric electrospray rocket propulsion are investigated. Following an extensive literature review, ionic liquids [Bmim][dca], [Bmim][NO₃], and [Emim][EtSO₄] are selected for study since their physical properties align well with the current state-of-the-art in chemical and electrospray propellants. Simulations show that these liquids will not be useful for monopropellant propulsion due to the prediction of solid carbon formation in the exhaust and performance 13-23% below that of hydrazine. Considering these ionic liquids as a fuel component in a binary monopropellant mixture with hydroxyl ammonium nitrate shows 1-4% improved specific impulse over some \u27green\u27 monopropellants, while avoiding volatility issues and reducing the number of electrospray emitters by 18-27% and power required by 9-16%, with oxidizing ionic liquid fuels providing the greatest savings. Mixtures of HAN with ionic liquid fuels [Bmim][NO₃] and [Emim][EtSO₄] are synthesized and tested for catalytic decomposition in a micro-reactor to investigate their potential for use as monopropellants. Two unsupported catalyst materials were tested with the novel propellants: rhenium and iridium. For the [Bmim][NO₃]/HAN propellant, 30 µL droplets on rhenium preheated to 160⁰C yielded a pressure rise rate of 26 mbar/s, compared to 14 mbar/s for iridium and 12 mbar/s for no catalyst. [Emim][EtSO₄]/HAN propellant shows slightly less activity at 160⁰C preheat temperature, yielding a pressure rise rate of 20 mbar/s, 4 mbar/s, and 2.5 mbar/s for injection onto rhenium, iridium, and the thermal plate, respectively --Abstract, page iv

Electrical/Chemical Thruster using the Same Monopropellant and Method

A thruster operable in a chemical mode or in an electrospray mode using the same liquid monopropellant for operation in both modes is described having a multiplicity of a microthrusters made of a catalytic material having a bore therethrough, where, when operated in the chemical mode, the microthrusters are heated to decompose the monopropellant the monopropellant flows therethrough to generate relatively high thrust. An extractor is positioned downstream of the outlet ends of the microthrusters, such that when the system is operated in its electrospray mode the flowrate of the monopropellant through the microthrusters is substantially lower than in the chemical mode and the extractor is energized with an electric field so that ions and droplets are discharged from the microthrusters and accelerated so as to yield a relatively high specific impulse

Design and Development of a Multi-Mode Monopropellant Electrospray Mircropropulsion System

Multi-mode spacecraft propulsion is the use of two or more types of propulsive devices on a spacecraft that share some commonality in terms of either hardware or propellant. An example is the Mars Global Surveyor, which made use of hydrazine as both a monopropellant for attitude control and a bipropellant for primary maneuvering. Specific to this study is a multi-mode propulsion system making use of a high-thrust chemical mode and a high-specific impulse electric mode. Using these two modes can be beneficial in two primary ways. One way is by designing a mission such that the high-thrust and high-specific impulse maneuvers are conducted in such a way that it provides a more optimum trajectory over a single chemical or single electric maneuver. The second is to increase the mission flexibility of a single spacecraft architecture in that both high-thrust and high-specific impulse maneuvers are available to mission designers at will, perhaps even allowing for drastic changes in the mission plan while on-orbit or with a relatively short turnaround from concept to launch. For the second method, it is extremely beneficial to utilize a shared propellant for both modes as this provides the highest flexibility in terms of mission design choices. 9 Previous research has investigated a multi-mode system utilizing a single ionic liquid propellant for chemical monopropellant and electrospray modes. Two propellants were developed that may not only function, but theoretically perform well in both modes. These propellants, based on binary mixtures of ionic liquid fuels [Emim][EtSO4] and [Bmim][NO3] with ionic liquid oxidizer hydroxylammonium nitrate (HAN), have been previously synthesized and tested for thermal and catalytic decomposition in a microreactor and electrosprayed in a capillary emitter. This paper will present the design of a multi-mode micropropulsion system for nano- and picosatellites. The system uses a shared propellant, as described above, and shared hardware including tanks, feed lines, valves, and thruster to provide both monopropellant and electrospray propulsive capabilities. The thruster is a catalytic microtube integrated with a capillary electrospray emitter. Using experimental results investigating operation of each mode separately, power, mass, and flow control requirements are developed and scale favorably for small satellite systems. For a 6U cubesat, the system has a three times larger mission design space compared to a system using completely separate, state-of-the-art monopropellant and electrospray thrusters. The effect of using a fully integrated thruster is shown to increase delta-V capability at a given mission duration time by 40% compared to using separate, state-of-the-art thrusters. The final paper will include potential mission applications of the final propulsion system design for a cubesat system

Combinatorial Markov chains on linear extensions

We consider generalizations of Schuetzenberger's promotion operator on the set L of linear extensions of a finite poset of size n. This gives rise to a strongly connected graph on L. By assigning weights to the edges of the graph in two different ways, we study two Markov chains, both of which are irreducible. The stationary state of one gives rise to the uniform distribution, whereas the weights of the stationary state of the other has a nice product formula. This generalizes results by Hendricks on the Tsetlin library, which corresponds to the case when the poset is the anti-chain and hence L=S_n is the full symmetric group. We also provide explicit eigenvalues of the transition matrix in general when the poset is a rooted forest. This is shown by proving that the associated monoid is R-trivial and then using Steinberg's extension of Brown's theory for Markov chains on left regular bands to R-trivial monoids.Comment: 35 pages, more examples of promotion, rephrased the main theorems in terms of discrete time Markov chain

Investigation of Current Spike Phenomena During Heavy Ion Irradiation of NAND Flash Memories

A series of heavy ion and laser irradiations were performed to investigate previously reported current spikes in flash memories. High current events were observed, however, none matches the previously reported spikes. Plausible mechanisms are discussed

Temporal Experiment for Storms and Tropical Systems Technology Demonstration (TEMPEST-D) Mission: Enabling Time-Resolved Cloud and Precipitation Observations from 6U-Class Satellite Constellations

The Temporal Experiment for Storms and Tropical Systems Technology Demonstration (TEMPEST-D) mission is to demonstrate the capability of 6U-Class satellite constellations to perform repeat-pass radiometry to measure clouds and precipitation with high temporal resolution on a global basis. The TEMPEST mission concept is to improve understanding of clouds and precipitation by providing critical information on their time evolution in different climatic regimes. Measuring at five frequencies from 89 to 182 GHz, TEMPEST-D millimeter-wave radiometers are capable of penetrating into the cloud to observe changes as precipitation begins or ice accumulates inside the storm. The TEMPEST-D flight model radiometer instrument has been completed, passed functional testing, vibration testing and self-compatibility testing with the XB1 spacecraft bus. The next steps for the TEMPEST-D millimeter-wave radiometer are thermal vacuum testing and antenna pattern measurements. The complete TEMPEST-D flight system will be delivered to NanoRacks for launch integration in the autumn of 2017, in preparation for launch to the ISS in the second quarter of 2018, with deployment shortly thereafter into a nominal orbit at 400-km altitude and 51.6° inclination

Lysosomal Disorders Drive Susceptibility to Tuberculosis by Compromising Macrophage Migration.

A zebrafish genetic screen for determinants of susceptibility to Mycobacterium marinum identified a hypersusceptible mutant deficient in lysosomal cysteine cathepsins that manifests hallmarks of human lysosomal storage diseases. Under homeostatic conditions, mutant macrophages accumulate undigested lysosomal material, which disrupts endocytic recycling and impairs their migration to, and thus engulfment of, dying cells. This causes a buildup of unengulfed cell debris. During mycobacterial infection, macrophages with lysosomal storage cannot migrate toward infected macrophages undergoing apoptosis in the tuberculous granuloma. The unengulfed apoptotic macrophages undergo secondary necrosis, causing granuloma breakdown and increased mycobacterial growth. Macrophage lysosomal storage similarly impairs migration to newly infecting mycobacteria. This phenotype is recapitulated in human smokers, who are at increased risk for tuberculosis. A majority of their alveolar macrophages exhibit lysosomal accumulations of tobacco smoke particulates and do not migrate to Mycobacterium tuberculosis. The incapacitation of highly microbicidal first-responding macrophages may contribute to smokers' susceptibility to tuberculosis.This work was supported by the National Institutes of Health (R37AI054503, LR, R01NS082567, CBM, 5F30HL110455, RB, 1DP2-OD008614, DMT), the Wellcome Trust (LR), the National Institute of Health Research Cambridge Biomedical Research Centre (LR), the Health Research Board of Ireland (HRA_POR/2013/387, MO’S and CSA/2012/16, JK), and The Royal City of Dublin Hospital Trust (Grant 146, JK).This is the final version of the article. It first appeared from Cell Press via http://dx.doi.org/10.1016/j.cell.2016.02.034