Tech Briefs

Miniature Free-Space Electrostatic Ion Thrusters

A miniature electrostatic ion thruster is proposed for maneuvering small spacecraft. In a thruster based on this concept, one or more propellant gases would be introduced into an ionizer based on the same principles as those of the device described in the earlier article, “Miniature Bipolar Electrostatic Ion Thruster” (NPO-21057). On the front side, positive ions leaving an ionizer element would be accelerated to high momentum by an electric field between the ionizer and an accelerator grid around the periphery of the concave laminate structure. On the front side, electrons leaving an ionizer element would be ejected into free space by a smaller accelerating field. The equality of the ion and electron currents would eliminate the need for an additional electron- or ion-emitting device to keep the spacecraft charge-neutral. In a thruster design consisting of multiple membrane ionizers in a thin laminate structure with a peripheral accelerator grid, the direction of thrust could then be controlled (without need for moving parts in the thruster) by regulating the supply of gas to specific ionizer. This work was done by Frank T. Hartley and James B. Stephens of Caltech for NASA’s Jet Propulsion Laboratory.

Posted in: Briefs, TSP, Physical Sciences, Downsizing, Performance upgrades, Gases, Rocket engines, Spacecraft

Read More >>

Miniature Oxidizer Ionizer for a Fuel Cell

A proposed miniature device for ionizing the oxygen (or other oxidizing gas) in a fuel cell would consist mostly of a membrane ionizer using the same principles as those of the device described in the earlier article, “Miniature Bipolar Electrostatic Ion Thruster” (NPO-21057). The oxidizing gas would be completely ionized upon passage through the holes in the membrane ionizer. The resulting positively charged atoms or molecules of oxidizing gas could then, under the influence of the fringe fields of the ionizer, move toward the fuel-cell cathode that would be part of a membrane/electrode assembly comprising the cathode, a solid-electrolyte membrane, and an anode. The electro- oxidized state of the oxidizer atoms and molecules would enhance transfer of them through the cathode, thereby reducing the partial pressure of the oxidizer gas between the ionizer and the fuelcell cathode, thereby, in turn, causing further inflow of oxidizer gas through the holes in the membrane ionizer. Optionally the ionizer could be maintained at a positive electric potential with respect to the cathode, in which case the resulting electric field would accelerate the ions toward the cathode. This work was done by Frank Hartley of Caltech for NASA’s Jet Propulsion Laboratory.

Posted in: Briefs, TSP, Physical Sciences, Fuel cells, Gases

Read More >>

Miniature Ion-Mobility Spectrometer

Advantages would include robustness, simplicity, and extreme miniaturization. The figure depicts a proposed miniature ion-mobility spectrometer that would be fabricated by micromachining. Unlike prior ion-mobility spectrometers, the proposed instrument would not be based on a time-of-flight principle and, consequently, would not have some of the disadvantageous characteristics of prior time-of-flight ion-mobility spectrometers. For example, one of these characteristics is the need for a bulky carrier-gas-feeding subsystem that includes a shutter gate to provide short pulses of gas in order to generate short pulses of ions. For another example, there is need for a complex device to generate pulses of ions from the pulses of gas and the device is capable of ionizing only a fraction of the incoming gas molecules; these characteristics preclude miniaturization. In contrast, the proposed instrument would not require a carrier-gas-feeding subsystem and would include a simple, highly compact device that would ionize all the molecules passing through it.

Posted in: Briefs, TSP, Physical Sciences, Downsizing, Microelectromechanical devices, Performance upgrades, Product development

Read More >>

Miniature Ion-Array Spectrometer

The mode of operation would differ from that described in the preceding article. The figure depicts a proposed miniature ion-mobility spectrometer that would share many features of design and operation of the instrument described in the immediately preceding article. The main differences between that instrument and this one would lie in the configuration and mode of operation of the filter and detector electrodes. A filter electrode and detector electrodes would be located along the sides of a drift tube downstream from the accelerator electrode. These electrodes would apply a combination of (1) a transverse AC electric field that would effect differential transverse dispersal of ions and (2) a transverse DC electric field that would drive the dispersed ions toward the detector electrodes at different distances along the drift tube. The electric current collected by each detector electrode would be a measure of the current, and thus of the abundance of the species of ions impinging on that electrode. The currents collected by all the detector electrodes could be measured simultaneously to obtain continuous readings of abundances of species. The downstream momentum of accelerated ions would be maintained through neutralization on the electrodes; the momentum of the resulting neutral atoms would serve to expel gases from spectrometer, without need for a pump.

Posted in: Briefs, TSP, Physical Sciences, Downsizing, Microelectromechanical devices, Performance upgrades, Product development

Read More >>

Rapid Development of Process Control Systems Using a Model-Based Approach

Developing an effective control system requires creation of an accurate, system-specific model. Developing a control system rapidly and cost effectively requires a disciplined approach that exposes design limitations early so they can be corrected before the costs and schedule go out of control. A trial-and-error development approach is utilized primarily when the control system is presumed to be simple or when there is insufficient time to conduct a full development cycle. This approach is characterized by a relatively small investment in up-front planning, followed by multiple iterations of build and test.

Posted in: Briefs, Physical Sciences, CAD, CAM, and CAE, Electronic control systems, Product development

Read More >>

Promoted-Combustion Chamber With Induction Heating Coil

Tests can be done at temperature and pressure combinations not previously attainable. An improved promoted-combustion system has been developed for studying the effects of elevated temperatures on the flammability of metals in pure oxygen. In prior promoted-combustion chambers, initial temperatures of metal specimens in experiments have been limited to the temperatures of gas supplies, usually near room temperature. Although limited elevated temperature promoted- combustion chambers have been developed using watercooled induction coils for preheating specimens, these designs have been limited to low-pressure operation due to the hollow induction coil. In contrast, the improved promoted-combustion chamber can sustain a pressure up to 10 kpsi (69 MPa) and, through utilization of a solid induction coil, is capable of preheating a metal specimen up to its melting point [potentially in excess of 2,000 °F (≈1,100 °C)]. Hence, the improved promoted-combustion chamber makes a greater range of physical conditions and material properties accessible for experimentation.

Posted in: Briefs, Physical Sciences, Metals, Oxygen, Combustion and combustion processes, Test procedures, Thermal testing

Read More >>

Thermal Spore Exposure Vessels

Thermal masses are minimized to enable rapid heating and cooling. Thermal spore exposure vessels (TSEVs) are laboratory containers designed for use in measuring rates of death or survival of microbial spores at elevated temperatures. A major consideration in the design of a TSEV is minimizing thermal mass in order to minimize heating and cooling times. This is necessary in order to minimize the number of microbes killed before and after exposure at the test temperature, so that the results of the test accurately reflect the effect of the test temperature.

Posted in: Briefs, TSP, Bio-Medical, Medical

Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.