Tech Briefs

GPS Satellite Geometry Analysis Tool (GPSGEM)

The purpose of the GPS Satellite Geometry Analysis Tool (GPSGEM) is to evaluate GPS satellite geometry for a given Earth-fixed location or for a provided trajectory. The tool will generate a listing of all satellites in view, the best satellite combination defined by the most optimum Geometric Dilution of Precision (GDOP), the GDOP profile expected if all satellites are available, and the worst-case GDOP profile when one or two satellites are removed from the available constellation. The tool will provide the navigation controller with insight into the expected performance of the GPS constellation, and allow an assessment of the implications to onboard navigation performance for the ascent, orbit, abort, and entry phases of flight.

Posted in: Briefs, Communications, Finite element analysis, Global positioning systems, Global positioning systems (GPS), Spacecraft guidance, Entry, descent, and landing, Satellites

Propellant Distributor for a Thruster

Innovators at NASA's Glenn Research Center have developed several new technological innovations to improve the capability of Hall-effect thrusters, which are used primarily on Earth-orbiting satellites and can also be used for deep-space robotic vehicles. Hall thrusters are susceptible to discharge channel erosion from high-energy ion impingement, which can reduce operational thruster lifetimes. Glenn researchers have developed several approaches to mitigate this problem. One is a magnetic circuit design that minimizes discharge chamber ion impingement. Another successful improvement developed by Glenn is a means of replacing eroded discharge channel material via a channel wall replacement mechanism. A third innovation is a propellant distributor that provides both a high degree of flow uniformity, and shielding from back-sputtered contamination and other potential contaminants. All of these advances work toward increasing the operational lifetime and efficiency of Hall thrusters.

Posted in: Briefs, Propulsion, Propellants, Performance upgrades, Engine efficiency, Satellites

Nanotubular Toughening Inclusions

This technology is used for making stable resin dispersions and composite plastic films, and for standard polymer melt processing.

NASA's Langley Research Center has developed an extensive technology portfolio on novel methods for effective dispersion of carbon nanotubes (CNTs) in polymers. The technology portfolio extends from making stable dispersions of CNTs in polymer resins to processes for making composite CNT/polymer films and articles. The technologies apply to a range of polymer types, enable low or high CNT loadings as needed, and can be used with a variety of standard polymer processing methods, including melt processing. Currently, the technology is being used commercially for electrically conductive polymer films for components in electronic printers and copiers.

Posted in: Briefs, Materials, Fabrication, Composite materials, Nanomaterials, Polymers

Floating Ultrasonic Transducer Inspection System and Method for Nondestructive Evaluation

The design allows a probe to easily move over surfaces being inspected without using a liquid couplant.

NASA's Langley Research Center has developed a Floating Ultrasonic System for improved nondestructive testing. Most ultrasonic scanners require an external liquid coupling agent (e.g., water, gel, oil) to make a good contact between the probe and the surface being scanned; however, some surfaces are sensitive to moisture and/or contamination created by these agents. NASA created the Floating Ultrasonic System to address this issue. NASA's technology is based on a momentary touching scheme where a vibrating probe comes in contact with the structure for fractions of a second while performing measurements, giving the probe the appearance of floating across a surface. The design allows for the easy movement of the probe over surfaces being inspected without the use of a liquid couplant between the probe and the surface. Initial test results have also shown NASA's system to have performance comparable to that of liquid-couplant-based ultrasonic scanners.

Posted in: Briefs, Sensors, Vibration, Inspections, Non-destructive tests, Test equipment and instrumentation

Development of Sodium Lidar for Spaceborne Missions

The metal layers at mesospheric altitudes are excellent tracers of neutral atmosphere dynamics, and have been used since the 1960s to study the chemistry and dynamics of the mesosphere. Ablation from meteors is believed to be the chief source of metals such as Na, Mg, K, Fe, and Ca in the middle atmosphere. Due to its relative abundance, large backscatter cross-section, and visible atomic transition, sodium (Na) has been used extensively for lidar studies of the mesosphere.

Posted in: Briefs, Photonics, Lidar, Weather and climate, Metals, Sodium, Test procedures

Additive-Manufactured, Very Lightweight, Diamond Turned Aspheric Mirror

Industrial-grade, lightweight mirrors used in military and aeronautics have tight specifications brought on by demanding performance parameters. For example, a mirror that is used in an orbiting telescope would have to be extremely lightweight, stiff, and be configured to operate in extreme temperatures. These parameters traditionally work against each other. A material that is stiff is typically heavy, and a mirror that is lightweight and machinable may greatly distort when exposed to extreme heat or cold. Furthermore, materials that fit some of these parameters may not be easily machined to create a mirror, an art that requires high-precision tooling.

Posted in: Briefs, Photonics, Mirrors, Additive manufacturing, Lightweight materials

Partially Transparent Circular Mask to Suppress Narrowband Laser Light

The evolved Laser Interferometry Space Antenna (eLISA) is the implementation of the original Laser Interferometry Space Antenna (LISA) concept that will be proposed for the European Space Agency's (ESA) L.3 Cosmic Visions opportunity. The eLISA observatory uses lasers to range between pairs of freely falling test masses in adjacent, widely separated spacecraft. The measurement is made continuously, requiring simultaneous transmission and reception of a 1064-nm laser beam through an optical telescope.

Posted in: Briefs, Photonics, Measurements, Antennas, Lasers, Spacecraft

Characterizing Richness of Previously Unmapped Terrain and Estimating Its Impact on Navigation Performance Using 3D Range Sensors in Flight

Landers to large planetary bodies such as Mars typically use a secondary reconnaissance spacecraft to generate high-fidelity 3D terrain maps that are subsequently used for landing site selection and creating onboard maps for terrain-relative navigation systems. This luxury does not exist with small primitive bodies such as comets and asteroids. For these bodies, the landing spacecraft has to perform the 3D mapping and, with possible help from ground control, choose a feasible landing site. To enable this operation, the spacecraft would need to carry a 3D ranging sensor system such as a LIDAR. With the spacecraft placed in extended mapping orbits, 3D range measurement data is then used to create a shape model of the object. Terrain-based navigation schemes that employ cameras could then be used to image, detect, match, and track features against the map database to provide a 6-degrees-of-freedom (DOF) navigation solution during descent. Camera-based systems, however, are not robust to lighting variations, and do not provide a direct 3D position/range feedback.

Posted in: Briefs, Photonics, Cartography, Terrain, Entry, descent, and landing, Spacecraft

Aircraft Configured for Flight in an Atmosphere Having Low Density

The autonomous airplane can be folded in a confined volume, transported, and deployed in terrestrial or extraterrestrial venues.

Posted in: Briefs, Aeronautics, Aerospace, Airframes, Aircraft instruments, Product development, Storage, Entry, descent, and landing

Electric Field Activated Shape Memory Polymer Composite

Applications include intelligent medical devices, smart armor, turbine blade stabilization, and aircraft wing stabilization.

NASA’s Langley Research Center has developed a novel shape memory polymer (SMP) made from composite materials for use in morphing structures. In response to an external stimulus such as a temperature change or an electric field, the thermosetting material changes shape, but then returns to its original form once conditions return to normal. Through a precise combination of monomers, conductive fillers, and elastic layers, the NASA polymer matrix can be triggered by two effects — Joule heating and dielectric loss — to increase the response. The new material remedies the limitations of other SMPs currently on the market; namely, the slow stimulant response times, the strength inconsistencies, and the use of toxic epoxies that may complicate manufacturing. NASA has developed prototypes and now seeks a partner to license the technology for commercial applications.

Posted in: Briefs, Materials, Electric power, Product development, Heat treatment, Composite materials, Polymers, Smart materials

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