82,927 research outputs found
Development of Innovative Heat Sinks for Power Electronics Cooling within the More Electrical Aircraft
Peer ReviewedPostprint (published version
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Microscale Freeform Integration by Directed Self Assembly
Most solid freeform fabrication (SFF) manufacturing processes assemble uniform
components such as powder particles or polymer chains to produce desired geometries. Their
capacity for producing highly functional parts (integrated actuation, sensing, and electronics)
will dramatically increase when multiple materials and functional subcomponents can be
automatically integrated. This paper addresses criteria for a system that integrates multiple
materials and components through computer-controlled self-assembly. It builds complex systems
from layers of self-assembled micro-components. The paper will address implementation
methods, present a concept demonstration, and consider its application to micro-thermoelectric
systems. This manufacturing process can be enhanced further through integration with mature
additive processes.Mechanical Engineerin
The Cosmic Infrared Background Experiment (CIBER): A Sounding Rocket Payload to Study the Near Infrared Extragalactic Background Light
The Cosmic Infrared Background Experiment (CIBER) is a suite of four instruments designed to study the near infrared (IR) background light from above the Earth's atmosphere. The instrument package comprises two imaging telescopes designed to characterize spatial anisotropy in the extragalactic IR background caused by cosmological structure during the epoch of reionization, a low resolution spectrometer to measure the absolute spectrum of the extragalactic IR background, and a narrow band spectrometer optimized to measure the absolute brightness of the Zodiacal light foreground. In this paper we describe the design and characterization of the CIBER payload. The detailed mechanical, cryogenic, and electrical design of the system are presented, including all system components common to the four instruments. We present the methods and equipment used to characterize the instruments before and after flight, and give a detailed description of CIBER's flight profile and configurations. CIBER is designed to be recoverable and has flown twice, with modifications to the payload having been informed by analysis of the first flight data. All four instruments performed to specifications during the second flight, and the scientific data from this flight are currently being analyzed
Visible and infrared linear detector arrays for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)
The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) instrument uses four separate focal plane assemblies consisting of line array detectors that are multiplexed to a common J-FET preamp using a FET switch multiplexing (MUX) technique. A 32-element silicon line array covers the spectral range from 0.41 to 0.70 microns. Three additional 64-element indium antimonide (InSb) line arrays cover the spectral range from 0.68 to 2.45 microns. The spectral sampling interval per detector element is nominally 9.8 nm, giving a total of 224 spectral channels. All focal planes operate at liquid nitrogen temperature and are housed in separate dewars. Electrical performance characteristics include a read noise of less than 1000 e(-) in all channels, response and dark nonuniformity of 5 percent peak to peak, and quantum efficiency of greater than 60 percent
The Mid-Infrared Instrument for the James Webb Space Telescope, VIII: The MIRI Focal Plane System
We describe the layout and unique features of the focal plane system for
MIRI. We begin with the detector array and its readout integrated circuit
(combining the amplifier unit cells and the multiplexer), the electronics, and
the steps by which the data collection is controlled and the output signals are
digitized and delivered to the JWST spacecraft electronics system. We then
discuss the operation of this MIRI data system, including detector readout
patterns, operation of subarrays, and data formats. Finally, we summarize the
performance of the system, including remaining anomalies that need to be
corrected in the data pipeline
Oxygen boost pump study
An oxygen boost pump is described which can be used to charge the high pressure oxygen tank in the extravehicular activity equipment from spacecraft supply. The only interface with the spacecraft is the +06 6.205 Pa supply line. The breadboard study results and oxygen tank survey are summarized and the results of the flight-type prototype design and analysis are presented
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Expanding Rapid Prototyping for Electronic Systems Integration of Arbitrary Form
An innovative method for rapid prototyping (RP) of electronic circuits with components
characteristic of typical electronics applications was demonstrated using an enhanced version of
a previously developed hybrid stereolithography (SL) and direct write (DW) system, where an
existing SL machine was integrated with a three-axis DW fluid dispensing system for combined
arbitrary form electronic systems manufacturing. This paper presents initial efforts at embedding
functional electronic circuits using the hybrid SL/DW system. A simple temperature-sensitive
circuit was selected, which oscillated an LED at a frequency proportional to the temperature
sensed by the thermistor. The circuit was designed to incorporate all the required electronic
components within a 2.5” x 2” x 0.5” SL part. Electrical interconnects between electronic
components were deposited on the SL part with a DW system using silver conductive ink lines.
Several inks were deposited, cured, and tested on a variety of SL resin substrates, and the E 1660
ink (Ercon Inc, Wareham, MA) was selected due to its measured lowest average resistivity on
the SL substrates. The finished circuit was compared with Printed Circuit Board (PCB)
technology for functionality. The electronic components used here include a low voltage battery,
LM 555 timer chip, resistors, a thermistor, capacitors, and Light Emitting Diodes (LEDs). This
circuit was selected because it (1) represented a simple circuit combining many typically used
electronic components and thus provided a useful demonstration for integrated electronic
systems manufacturing applicable to a wide variety of devices, and (2) provided an indication of
the parasitic resistances and capacitances introduced by the fabrication process due to its
sensitivity to manufacturing variation. The hybrid technology can help achieve significant size
reductions, enable systems integration in atypical forms, a natural resistance to reverse
engineering and possibly increase maximum operating temperatures of electronic circuits as
compared to the traditional PCB process. This research demonstrates the ability of the hybrid
SL/DW technology for fabricating combined electronic systems for unique electronics
applications in which arbitrary form is a requirement and traditional PCB technology cannot be
used.Mechanical Engineerin
Optical properties monitor: Experiment definition phase
The stability of materials used in the space environment will continue to be a limiting technology for space missions. The Optical Properties Monitor (OPM) Experiment provides a comprehensive space research program to study the effects of the space environment-both natural and induced-on optical, thermal and space power materials. The OPM Experiment was selected for definition under the NASA/OAST In-Space Technology Experiment Program. The results of the OPM Definition Phase are presented. The OPM Experiment will expose selected materials to the space environment and measure the effects with in-space optical measurements. In-space measurements include total hemispherical reflectance total integrated scatter and VUV reflectance/transmittance. The in-space measurements will be augmented with extensive pre- and post-flight sample measurements to determine other optical, mechanical, electrical, chemical or surface effects of space exposure. Environmental monitors will provide the amount and time history of the sample exposure to solar irradiation, atomic oxygen and molecular contamination
Planck pre-launch status: HFI ground calibration
Context. The Planck satellite was successfully launched on May 14th 2009. We have completed the pre-launch calibration measurements of the High Frequency Instrument (HFI) on board Planck and their processing.
Aims. We present the results of the pre-launch calibration of HFI in which we have multiple objectives. First, we determine instrumental parameters that cannot be measured in-flight and predict parameters that can. Second, we take the opportunity to operate and understand the instrument under a wide range of anticipated operating conditions. Finally, we estimate the performance of the instrument built.
Methods. We obtained our pre-launch calibration results by characterising the component and subsystems, then by calibrating the focal plane at IAS (Orsay) in the Saturne simulator, and later from the tests at the satellite level carried out in the CSL (Liège) cryogenic vacuum chamber. We developed models to estimate the instrument pre-launch parameters when no measurement could be performed.
Results. We reliably measure the Planck-HFI instrument characteristics and behaviour, and determine the flight nominal setting of all parameters. The expected in-flight performance exceeds the requirements and is close or superior to the goal specifications
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