Microscale combustion: Technology development and fundamental research

New energetic materials (EMs) are the key to great advances in microscale energy-demanding systems as actuation part, igniter, propulsion unit, and power. Nanoscale EMs (nEMs) particularly offer the promise of much higher energy densities, faster rate of energy release, greater stability, and more security (sensitivity to unwanted initiation). nEMs could therefore give response to microenergetics challenges. This paper provides a comprehensive review of current research activities in nEMs for microenergetics application. While thermodynamic calculations of flame temperature and reaction enthalpies are tools to choose desirable EMs, they are not sufficient for the choice of good material for microscale application where thermal losses are very penalizing. A strategy to select nEM is therefore proposed based on an analysis of the material diffusivity and heat of reaction. Finally, after a description of the different nEMs synthesis approaches, some guidelines for future investigations are provided.

https://homepages.laas.fr/rossi/Publi/Nanoenergetics-Review-JMEMS-2.pdf

Nanoenergetic Materials for MEMS: A Review

A gas generator for an air bag according to the present invention comprising a cylindrical housing, an inner cylindrical member disposed inside the housing, a central cylindrical member disposed inside the inner cylindrical member, a gas generating agent packed in an annular space between the central cylindrical member and the inner cylindrical member and an ignition means for igniting the gas generating agent, wherein the ignition means comprises in turn a transfer charge disposed at one end of the central cylindrical member, an igniter for igniting the transfer charge and a fire transfer member disposed close to the transfer charge at a central portion of the central cylindrical member, and wherein the fire transfer member is constituted by a non-explosive material and comprises a stick-like member extending along almost the full length of the central cylindrical member. The gas generator for an air bag according to the present invention is provided with an ignition structure which can generate uniform ignition energy in a longitudinal direction thereof.

Gas generator for air bag

At present, no Cubesat has flown in space featuring propulsion. This was acceptable as long as CubeSats were flown mostly as university experiments. As CubeSats become of interest to other users in the government and industry communities as well, a larger range of capabilities may be required than exhibited so far, while maintaining the uniqueness of the Cubesat platform. Propulsion capability is crucial in increasing mission capabilities of future CubeSats, such as orbit change and raising, formation flying, proximity operations, fine attitude control, or drag-make-up and de-orbit. While some of these tasks may be accomplished with propellantless devices, their applications are limited, applicable mostly to a single task, and bear their own risks. In this study, a survey was conducted of propulsion technologies applicable to CubeSats. Only few off-the-shelf design solutions exist today. The survey was thus expanded to such devices as well that are under significant development, and are approaching the required design envelope for CubeSats with respect to mass, volume, and power. In some cases, such as electric propulsion devices, CubeSat architectures themselves may need to be adapted, required to feature deployable solar arrays to increase power capabilities. Given the vast scope of this survey, only thruster technologies could be surveyed. However, valves and other feed system components, as well as their integration, are equally important, but have to be left to a future survey. Three major propulsion technology areas applicable to CubeSats emerged when conducting this review: (1) Existing technologies, such as butane systems, pulsed plasma thrusters, and vacuum arc thrusters are applicable to CubeSats today with no or only minor changes, (2) New thruster technologies under significant development, such as hydrazine monopropellant systems, ion engines, or colloid thrusters could be adapted to CubeSats with some further development, especially also in other subsystem areas such as feed systems and power processing units. They will also require increased power capabilities, and (3) emerging technologies, such as micro electrospray arrays and micro cavity discharge arrays that offer even higher flexibility due to scalability for CubeSats, and enable compact integration.

Survey of Propulsion Technologies Applicable to Cubesats

Techniques for preconditioning an oilfield reservoir including heavy oil and/or bitumen prior to production of a petroleum product are described. A preconditioning agent can be injected into a mobile water film included in the oilfield reservoir. The preconditioning agent preconditions the reservoir prior to production of the petroleum product.

Preconditioning an oilfield reservoir

Small satellites flying in clusters require periodic “stationkeeping” to keep them in place. The required impulse is very small – the goal is not to keep the individual satellites in rigid formation, but only to keep them in well-defined orbitals with respect to one another. The necessary impulse, therefore, is only the amount needed to overcome the difference in drag between the most-affected and the least-affected satellites in the cluster. Estimates are that the differential drag can be overcome by providing ~1 μNsec (micro-Newton second) to ~1 mN sec (milli-Newton second) every 10 to 100 seconds throughout each satellite’s mission. The system we are developing will do that. The thrusters have very low power and energy thresholds for ignition (~10 mWatts, ~100 μJoules), and no moving parts so they are expected to be highly reliable. A single thruster array contains a quarter of a million separate thrusters.

/pdf/mems-mega-pixel-micro-thruster-arrays-for-small-satellite-1iadunoutb.pdf

MEMS Mega-pixel Micro-thruster Arrays for Small Satellite Stationkeeping

A multi-level output inflator (10) for inflating an air bag in the event of a vehicle crash, comprising a housing, a wall section disposed in the housing to define separate primary and secondary combustion chambers (18,20) therein. A primary initiator (30) and primary propellant are disposed within the primary combustion chamber (18), and a secondary initiator (32) and secondary propellant are disposed with the secondary combustion chamber (20). The housing comprises a primary nozzle (22) in communication with the primary combustion chamber (18), and a secondary nozzle (32) in communication with the secondary combustion chamber (20). The primary and secondary initiators (30,32) may be fired separately, simultaneously, or in a timed sequence to inflate the air bag at different rates and levels depending on the nature of the vehicle crash. A method of assembling the components of the inflator is also described and covered.

Compact dual nozzle air bag inflator

Fire suppressant compositions which are substantially free of ammonium nitrate and which comprise potassium nitrate in an amount sufficient to generate at least about 10 wt. % potassium carbonate when combusted. Most preferably, a guanidine salt, such as guanidine nitrate, is used in combination with the potassium nitrate. The compositions employed in the present invention have low pressure exponents, high burning rates and low flame temperatures.

Fire suppressant compositions

A gas generator capable of quickly producing a large quantity of substantially solids-free nontoxic gas useful as a propellant in halon replacement fire suppression systems is provided. The double base castable propellant composition is formulated from a major amount of ammonium nitrate, a minor amount of nitrocellulose, at least one selected high energy nitrate ester plasticizer, a thermal scavenger, and at least one burning rate modification and control additive to achieve a burning rate of 0.2 inches per second or greater at 1000 psia. The burning rate is further enhanced by the configuration of the solid propellant, which is formed to have dimensions selected to enhance the burning rate. The gas generator composition and physical arrangement synergistically produce an optimally rapid burning rate.

Gas generator for expelling halon replacements

A gas generating propulsion system includes an igniter containing an igniter propellant and an auto igniter. A rocket motor is coupled to the igniter and has a housing containing a main propellant, a rocket motor throat and a nozzle. A release port extends through a portion of the rocket motor. This gas release port has a variable diameter through bore in fluid communication with the main propellant. In this way, the through bore has a variable area that forms an unobstructed open area with a cross-section effective to discharge gas generated by the main propellant such that a pressure increase within the housing remains below a safety value for the housing.

Slow cook off rocket igniter

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