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At least 271 records · Page 15

Design of a compliant wheel for a miniature rover to be used on Mars

The Jet Propulsion Laboratory has identified the need for a compliant wheel for a miniature martian rover vehicle. This wheel must meet requirements of minimum mass, linear radial deflection, and reliability in cryogenic conditions over a five year lifespan. Additionally, axial and tangential deflections must be no more than 10 percent of the radial value. The team designed a wheel by use of finite element and dimensionless parameter analysis. Due to the complex geometry of the wheel, a finite element model describing its behavior was constructed to investigate different wheel configurations. Axial and tangential deflections were greatly reduced but did not meet design criteria. A composite material was selected for its high strength, toughness, fatigue resistance, and damping characteristics. The team chose a Kevlar fiber filled thermoplastic composite. This report is divided into four primary sections. First, the introduction section gives background information, defines the task, and discusses the scope and limitations of the project. Second, the alternative designs section introduces alternative design solutions, addresses advantages and disadvantages of each, and identifies the parameters used to determine the best design. Third, the design solution section introduces the methods used to evaluate the alternates, and gives a description of the design process used. Finally, the conclusion and recommendations section evaluates the wheel design, and offers recommendations pertaining to improvement of the design solution.

Carroll, Mark↗

Development of a miniature mass analyzer and associated instrumentation for improved capabilities in the analysis of low energy plasmas from a rocket or satellite platform

The University of Texas at Dallas (UTD) Center for Space Sciences (CSS) has designed, developed, and fabricated three miniature mass spectrometers and their associated instrumentation in fulfillment of a NASA contract. The ion mass spectrometer analyzers furnished under this contract were modeled after a unit developed during a previous NASA grant. Three assemblies are described: (1) the magnetic sector; (2) the ion detector; and (3) the amplifier and power supply.

Hoffman, John H.↗

Miniature modular microwave end-to-end receiver

An end-to-end microwave receiver system contained in a single miniature hybrid package mounted on a single heatsink is presented. It includes an input end connected to a microwave receiver antenna and an output end which produces a digital count proportional to the amplitude of a signal of a selected microwave frequency band received at the antenna and corresponding to one of the water vapor absorption lines near frequencies of 20 GHz or 30 GHz. The hybrid package is on the order of several centimeters in length and a few centimeters in height and width. The package includes an L-shaped carrier having a base surface, a vertical wall extending up from the base surface and forming a corner therewith, and connection pins extending through the vertical wall. Modular blocks rest on the base surface against the vertical wall and support microwave monolithic integrated circuits on top surfaces thereof connected to the external connection pins. The modular blocks lie end-to-end on the base surface so as to be modularly removable by sliding along the base surface beneath the external connection pins away from the vertical wall.

Sukamto, Lin M.↗

Cold-tip off-state conduction loss of miniature Stirling cycle cryocoolers

For redundant miniature Stirling-cycle cryocoolers in space applications, the off-state heat conduction down the coldfinger of one cooler is a parasitic heat load on the other coolers. At JPL, a heat flow transducer specifically designed to measure this load has been developed, and measurements have been performed on the coldfinger of a British Aerospace 80 K Stirling cooler with the tip temperature ranging between 40 and 170 K. Measurements have also been made using a transient warmup technique, where the warmup rates of the coldtip under various applied heat loads are used to determine the static conduction load. There is a difference between the results of these two methods, and these differences are discussed with regard to the applicability of the transient warmup method to a nonoperating coldfinger.

Kotsubo, V.↗

Miniature Reversal Electron-Attachment Detector

Miniature reversal electron-attachment detector (miniREAD) enables direct injection of air or vapor at atmospheric pressure from monitored area into mass-spectrometric instrument to detect explosives, narcotics, or other substances, vapors of which suspected of being present in low concentrations. In comparison with older reversal electron-attachment detector, miniREAD simpler in design; more rugged; and easier to build, repair, and maintain. In addition, probably more sensitive.

Chutjian, Ara↗

Miniature Convection Cooled Plug-type Heat Flux Gauges

Tests and analysis of a new miniature plug-type heat flux gauge configuration are described. This gauge can simultaneously measure heat flux on two opposed active surfaces when heat flux levels are equal to or greater than about 0.2 MW/m(sup 2). The performance of this dual active surface gauge was investigated over a wide transient and steady heat flux and temperature range. The tests were performed by radiatively heating the front surface with an argon arc lamp while the back surface was convection cooled with air. Accuracy is about +20 percent. The gauge is responsive to fast heat flux transients and is designed to withstand the high temperature (1300 K), high pressure (15 MPa), erosive and corrosive environments in modern engines. This gauge can be used to measure heat flux on the surfaces of internally cooled apparatus such as turbine blades and combustors used in jet propulsion systems and on the surfaces of hypersonic vehicles. Heat flux measurement accuracy is not compromised when design considerations call for various size gauges to be fabricated into alloys of various shapes and properties. Significant gauge temperature reductions (120 K), which can lead to potential gauge durability improvement, were obtained when the gauges were air-cooled by forced convection.

Liebert, Curt H.↗

Miniature linear-to-rotary motion actuator

A miniature hydraulic actuation system capable of converting linear actuator motion to control surface rotary motion has been designed for application to active controls on dynamic wind tunnel models. Due to space constraints and the torque requirements of an oscillating control surface at frequencies up to 50 Hertz, a new actuation system was developed to meet research objectives. This new actuation system was designed and developed to overcome the output torque limitations and fluid loss/sealing difficulties associated with an existing vane type actuator. Static control surface deflections and dynamic control surface oscillations through a given angle are provided by the actuation system. The actuator design has been incorporated into a transonic flutter model with an active trailing edge flap and two active spoilers. The model is scheduled for testing in the LaRC 16 Foot Transonic Dynamics Tunnel during Summer 1993. This paper will discuss the actuation system, its design, development difficulties, test results, and application to aerospace vehicles.

Sorokach, Michael R., Jr.↗

Evolution of miniature detectors and focal plane arrays for infrared sensors

Sensors that are sensitive in the infrared spectral region have been under continuous development since the WW2 era. A quest for the military advantage of 'seeing in the dark' has pushed thermal imaging technology toward high spatial and temporal resolution for night vision equipment, fire control, search track, and seeker 'homing' guidance sensing devices. Similarly, scientific applications have pushed spectral resolution for chemical analysis, remote sensing of earth resources, and astronomical exploration applications. As a result of these developments, focal plane arrays (FPA) are now available with sufficient sensitivity for both high spatial and narrow bandwidth spectral resolution imaging over large fields of view. Such devices combined with emerging opto-electronic developments in integrated FPA data processing techniques can yield miniature sensors capable of imaging reflected sunlight in the near IR and emitted thermal energy in the Mid-wave (MWIR) and longwave (LWIR) IR spectral regions. Robotic space sensors equipped with advanced versions of these FPA's will provide high resolution 'pictures' of their surroundings, perform remote analysis of solid, liquid, and gas matter, or selectively look for 'signatures' of specific objects. Evolutionary trends and projections of future low power micro detector FPA developments for day/night operation or use in adverse viewing conditions are presented in the following test.

Watts, Louis A.↗

Miniature wide field-of-view star trackers for spacecraft attitude sensing and navigation

Introducing a family of miniature, wide field-of-view star trackers for low cost, high performance spacecraft attitude determination and navigation applications. These devices, derivative of the WFOV Star Tracker Camera developed cooperatively by OCA Applied Optics and the Lawrence Livermore National Laboratory for the Brilliant Pebbles program, offer a suite of options addressing a wide range of spacecraft attitude measurement and control requirements. These sensors employ much wider fields than are customary (ranging between 20 and 60 degrees) to assure enough bright stars for quick and accurate attitude determinations without long integration intervals. The key benefit of this approach are light weight, low power, reduced data processing loads and high information carrier rates for wide ACS bandwidths. Devices described range from the proven OCA/LLNL WFOV Star Tracker Camera (a low-cost, space-qualified star-field imager utilizing the spacecraft's own computer and centroiding and position-finding), to a new autonomous subsystem design featuring dual-redundant cameras and completely self-contained star-field data processing with output quaternion solutions accurate to 100 micro-rad, 3 sigma, for stand-alone applications.

Mccarty, William↗

Development of a miniature actuator/controller system

Development of new products is often hampered or prevented by the cost and resource commitments required by a traditional engineering approach. Schaeffer Magnetics, Inc. identified the potential need for a miniature incremental actuator with an integrated controller but did not want the development to be subject to the obstacles inherent in the traditional approach. In response a new approach - the Pathfinder Engineering Program (PEP) - was developed to streamline new product generation and improve product quality. The actuator/controller system resulting from implementation of this new procedure is an exceptionally compact and self-contained device with many applications.

Stanley, Scott P.↗

Miniature laser ignited bellows motor

A miniature optically ignited actuation device has been demonstrated using a laser diode as an ignition source. This pyrotechnic driven motor provides between 4 and 6 lbs of linear force across a 0.090 inch diameter surface. The physical envelope of the device is 1/2 inch long and 1/8 inch diameter. This unique application of optical energy can be used as a mechanical link in optical arming systems or other applications where low shock actuation is desired and space is limited. An analysis was performed to determine pyrotechnic materials suitable to actuate a bellows device constructed of aluminum or stainless steel. The aluminum bellows was chosen for further development and several candidate pyrotechnics were evaluated. The velocity profile and delivered force were quantified using an non-intrusive optical motion sensor.

Renfro, Steven L.↗

Dual-Active-Surface Miniature Plug-Type Heat-Flux Gauges

Improved miniature plug-type heat-flux gauges developed for determining fluxes of heat through surfaces on both sides of heat-transfer walls. Walls are those of heat exchangers, engine housings, furnaces, chemical reactors, or any of variety of other structures in which fluxes of heat important quantities one seeks to measure.

Liebert, Curt H.↗

A Magnetically Suspended Wheel for a Miniature Gyro Made Using Planar Fabrication Technologies

The technical feasibility of a magnetically suspended rotating wheel for miniature gyro applications was investigated under a NASA SBIR contract. A concept for a configuration for a system of compact, lightweight magnetic actuators capable of generating the necessary suspension forces and fabrication using millimachining planar fabrication technologies was developed. Both capacitive and electromagnetic position sensing concepts were developed for implementing a closed loop control system for supporting the wheel. A finite difference technique, implemented in a spreadsheet environment, for analyzing the force characteristics of the actuator was used and the results verified with Finite Element Analysis.

Dauwalter, Charles R.↗

Power Electronics for a Miniaturized Arcjet

A 0.3 kW Power Processing Unit (PPU) was designed, tested on resistive loads, and then integrated with a miniaturized arcjet. The main goal of the design was to minimize size and mass while maintaining reasonable efficiency. In order to obtain the desired reductions in mass, simple topologies and control methods were considered. The PPU design incorporates a 50 kHz, current-mode-control, pulse-width-modulated (PWM), push-pull topology. An input voltage of 28 +/- 4V was chosen for compatibility with typical unregulated low voltage busses anticipated for smallsats. An efficiency of 0.90 under nominal operating conditions was obtained. The component mass of the PPU was 0.475 kg and could be improved by optimization of the output filter design. The estimated mass for a flight PPU based on this design is less than a kilogram.

Pinero, Luis R.↗

Miniature Comet Ice and Dust Experiment (Mini-CIDEX)

This document reports the extent of the progress attained by Lockheed Martin Astronautics (LMA) in the development of equipment designed for the miniature Comet Ice and Dust EXperiment (mini-CIDEX) on NASA contract No. NAS2-14042 from the Ames Research Center (ARC). This report is in two parts. The first part summarizes progress in chronological order. The contents of the first part have been extracted from the monthly reports submitted by LMA to ARC over the duration of the program. The second part is a summary of the designs that were extracted from the mini-CIDEX contract designs and implemented into mission studies performed under different funding but in parallel to the mini- CIDEX contract time period. These second part activities were not performed under contract No. NAS2-14042; however, they are included in this report to show how it was intended that the mini-CIDEX be used on actual mission spacecraft.

Hayden, Jeffrey L.↗

Design and Performance of a Miniature Lidar Wind Profiler (MLWP)

The directional velocity of the wind is one of the most critical components for understanding meteorological and other dynamic atmospheric processes. Altitude-resolved wind velocity measurements, also known as wind profiles or soundings, are especially necessary for providing data for meteorological forecasting and overall global circulation models (GCM's). Wind profiler data are also critical in identifying possible dangerous weather conditions for aviation. Furthermore, a system has yet to be developed for wind profiling from the surface of Mars which could also meet the stringent requirements on size, weight, and power of such a mission. Obviously, a novel wind profiling approach based on small and efficient technology is required to meet these needs. A lidar system based on small and highly efficient semiconductor lasers is now feasible due to recent developments in the laser and detector technologies. The recent development of high detection efficiency (50%), silicon-based photon-counting detectors when combined with high laser pulse repetition rates and long receiver integration times has allowed these transmitter energies to be reduced to the order of microjoules per pulse. Aerosol lidar systems using this technique have been demonstrated for both Q-switched, diode-pumped solid-state laser transmitters (lambda = 523 nm) and semiconductor diode lasers (lambda = 830 nm); however, a wind profiling lidar based on this technique has yet to be developed. We will present an investigation of a semiconductor-laser-based lidar system which uses the "edge-filter" direct detection technique to infer Doppler frequency shifts of signals backscattered from aerosols in the planetary boundary layer (PBL). Our investigation will incorporate a novel semiconductor laser design which mitigates the deleterious effects of frequency chirp in pulsed diode lasers, a problem which has limited their use in such systems in the past. Our miniature lidar could be used on a future Mars lander and perhaps find its own niche in terrestrial applications due to its potential low cost an small size.

Cornwell, Donald M., Jr.↗

Construction of a Chemical Sensor/Instrumentation Package Using Fiber Optic and Miniaturization Technology

The objective of this research was to construct a chemical sensor/instrumentation package that was smaller in weight and volume than conventional instrumentation. This reduction in weight and volume is needed to assist in further reducing the cost of launching payloads into space. To accomplish this, fiber optic sensors, miniaturized spectrometers, and wireless modems were employed. The system was evaluated using iodine as a calibration analyte.

Newton, R. L.↗

Miniature Quadrupole Mass Spectrometer Array

JPL is funded by Code U to develop a Miniature QMSA for an EVA flight test. The initial intent was to fly an experiment internal to the astronaut suit during a shuttle EVA. Following discussions with JSC the suit application was abandoned in favor of other more urgent needs. The JSC EVA office was particularly interested in hydrazine detection on the astronaut suit. While discussing and exploring the implementation of such an experiment, managers at JSC suggested combining the interests of two JSC groups. The Life Support and Thermal Systems Branch, Crew and Thermal Systems Division has a need for an ammonia detection instrument, while the EVA office has a need for hydrazine detection. The two groups were pursuing separate single-purpose solutions. Instead, the JPL QMSA offers a single instrument solution via a portable instrument to be used by an astronaut on an EVA. Such an instrument would serve both the ammonia leak detection and the hydrazine contamination needs. The need for the QMSA was defined as urgent and targeted for a January 1999 flight. While the original JPL task (as funded by Code U) was for an experiment flight with JPL delivery in October 1998, this task was for a qualified flight instrument with a planned JPL delivery in August 1998. This schedule was very demanding and dictated a fast-tract implementation.

Karmon, D.↗