information technology and software
A Method For Developing And Maintaining Evolving Systems With Software Product Lines
The idea of a software product line has been developed that views software products that are substantially similar, or which have substantially similar content, as being different products in a line of products that the organization develops. For example, flight software for different missions can be viewed as a line of products that fulfills this purpose, with many of the products having similarities, or in extreme cases being very similar with a few specializations. This method expands this view further and sees an evolving system, one that will likely run for a long period of time, and which must have corrections, enhancements and changes made to it over a period of time, as essentially exhibiting a product line. More specifically, different versions or releases of the system are viewed as different 'products' that are substantially similar. This method opens a new field of developing a complex system that is likely to involve many interacting components for development as a product line, which can be developed with state-of-the-art software engineering techniques.
mechanical and fluid systems
Lateral Kevlar Suspension Device (LKSD)
This device has the ability to maintain consistent tension by taking advantage of the Kevlars high strength and low thermal conductivity properties. In addition to Kevlar, the unit is equipped with three spring-loaded tension assemblies should the band slacken during the cooling process, the spring force directs the pulley in an outward direction taking up any slack and maintaining the tension and stiffness of the system. This provides stability and good thermal isolation to the load attached while reducing parasitic heating.
Measuring Optical Null Lens Aberrations
This innovation uses image-based wavefront sensing or phase retrieval which uses light traveling through the optical system in generally the same way that it will in its as-used configuration. It estimates the wavefront of the optical system using images collected on a light detector (which can be the same detector used by the optical system in its intended use). This method uses several images taken through the null optic under test, with some aspect of the test setup being systematically varied from one image to the next. Usually this variation involves somewhat out-of-focus images that are taken systematically with different amounts of defocus. The light for each diversity-defocus image passes through the optical test setup and the null lens. The resulting irradiance of the transmitted beam is measured by a light detector and this image is saved on a computer where algorithms determine an estimate of the null lens's wavefront aberrations.
electrical and electronics
Sampling and Control Circuit Board
For fast platform dynamics, it is necessary to sample the IMU at quick intervals in order to fulfill the Nyquist sampling theorem requirements. This can be difficult in cases where low size, weight, and power are required, since a primary processor may already be saturated running the navigation algorithm or other system functions. Glenn's novel circuit board was designed to handle the sampling process (involving frequent interrupt requests) in parallel, while delivering the resulting data to a buffered communication port for inclusion in the navigation algorithm on an as-available basis. The circuit operates using a universal serial bus (USB) or Bluetooth interface. A control command is sent to the circuit from a separate processor or computer that instructs the circuit how to sample data. Then, a one-pulse-per-second signal from a GPS receiver or other reliable time source is sent to trigger the circuit to perform automatic data collection from the IMU sensor. This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities.
mechanical and fluid systems
Compact Vibration Damper
Structural vibrations frequently need to be damped to prevent damage to a structure. To accomplish this, a standard linear damper or elastomeric-suspended masses are used. The problem associated with a linear damper is the space required for its construction. For example, if the damper's piston is capable of three inches of movement in either direction, the connecting shaft and cylinder each need to be six inches long. Assuming infinitesimally thin walls, connections, and piston head, the linear damper is at least 12 inches long to achieve +/-3 inches of movement. Typical components require 18+ inches of linear space. Further, tuning this type of damper typically involves fluid changes, which can be tedious and messy. Masses suspended by elastomeric connections enable even less range of motion than linear dampers. The NASA invention is for a compact and easily tunable structural vibration damper. The damper includes a rigid base with a slider mass for linear movement. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A rack-and-pinion gear coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement. To achieve +/- 3 inches of movement, this design requires slightly more than six inches of space.
information technology and software
Inductive Monitoring System
The Inductive Monitoring System (IMS) software provides a method of building an efficient system health monitoring software module by examining data covering the range of nominal system behavior in advance and using parameters derived from that data for the monitoring task. This software module also has the capability to adapt to the specific system being monitored by augmenting its monitoring database with initially suspect system parameter sets encountered during monitoring operations, which are later verified as nominal. While the system is offline, IMS learns nominal system behavior from archived system data sets collected from the monitored system or from accurate simulations of the system. This training phase automatically builds a model of nominal operations, and stores it in a knowledge base. The basic data structure of the IMS software algorithm is a vector of parameter values. Each vector is an ordered list of parameters collected from the monitored system by a data acquisition process. IMS then processes select data sets by formatting the data into a predefined vector format and building a knowledge base containing clusters of related value ranges for the vector parameters. In real time, IMS then monitors and displays information on the degree of deviation from nominal performance. The values collected from the monitored system for a given vector are compared to the clusters in the knowledge base. If all the values fall into or near the parameter ranges defined by one of these clusters, it is assumed to be nominal data since it matches previously observed nominal behavior. The IMS knowledge base can also be used for offline analysis of archived data.
Gas Composition Sensing Using Carbon Nanotube Arrays
An array of carbon nanotubes (CNTs) in a substrate is connected to a variable-pulse voltage source. The CNT tips are spaced appropriately from the second electrode maintained at a constant voltage. A sequence of voltage pulses is applied and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of the current-voltage characteristics. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas. The CNTs in the gas sensor have a sharp (low radius of curvature) tip; they are preferably multiwall carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs), to generate high-strength electrical fields adjacent to the current collecting plate, such as a gold plated silicon wafer or a stainless steel plate for breakdown of the gas components with lower voltage application and generation of high current. The sensor system can provide a high-sensitivity, low-power-consumption tool that is very specific for identification of one or more gas components. The sensors can be multiplexed to measure current from multiple CNT arrays for simultaneous detection of several gas components.
mechanical and fluid systems
Feedthrough for Severe Environments and Temperatures
Space and ground launch support related hardware often operate under extreme pressure, temperature, and corrosive conditions. When dealing with this type of equipment, it is frequently necessary to run wiring, tubes, or fibers through a barrier separating one process from another with one or both operating in extreme environments. Feedthroughs used to route the wiring, tubes, or fibers through these barriers must meet stringent sealing and leak tightness requirements. This affordable NASA feedthrough meets or exceeds all sealing and leak requirements utilizing easy-to-assemble commercial-off-the-shelf hardware with no special tooling. The feedthrough is a fully reconfigurable design; however, it can also be produced as a permanent device. Thermal cycling and helium mass spectrometer leak testing under extreme conditions of full cryogenic temperatures and high vacuum have proven the sealing capability of this feedthrough with or without potting (epoxy fill) on the ends. Packing material disks used in the construction of the device can be replaced as needed for rebuilding a given feedthrough for another job or a different set of feeds if potting is not used for the original feedthrough build. (Potting on one or both sides of the sleeve provides double or triple leak sealing protection). Variable Compression Ratio (VCR) connectors were adapted for the pressure seal on the feedthrough; however, any commercial connector can be similarly adapted. The design can easily be scaled up to larger (2" diameter) and even very large (12" or more) sizes.
Strobing to Mitigate Vibration for Display Legibility
The dominant frequency of the vibration that requires mitigation can be known in advance, measured in real time, or predicted with simulation algorithms. That frequency (or a lower frequency multiplier) is then used to drive the strobing rate of the illumination source. For example, if the vibration frequency is 20 Hz, one could employ a strobe rate of 1, 2, 4, 5, 10, or 20 Hz, depending on which rate the operator finds the least intrusive. The strobed illumination source can be internal or external to the display. Perceptual psychologists have long understood that strobed illumination can freeze moving objects in the visual field. This effect can be used for artistic effect or for technical applications. The present innovation is instead applicable for environments in which the human observer rather than just the viewed object undergoes vibration. Such environments include space, air, land, and sea vehicles, or on foot (e.g., walking or running on the ground or treadmills). The technology itself can be integrated into handheld and fixed display panels, head-mounted displays, and cabin illumination for viewing printed materials.
An Additive Manufacturing Method for Sub-Micro Scale Three Dimensional Structures
The newly developed technology capitalizes on existing stereolithography techniques to fabricate a polymeric scaffold of the desired three dimensional structure employing a photosensitive polymer material. After the scaffold is complete nickel can be deposited onto the structure using a catalyst and a low temperature CVD process, at which point the polymer structure can be dissolved away leaving a nickel shell. Using the resulting nickel shell as yet another scaffold the desired material can be deposited using the appropriate CVD process since the melting point of nickel is 1455 oC. If necessary the nickel can then be preferentially etched away.