Feasibility of Electrified Propulsion for Ultra-Efficient Commercial Aircraft Final Report

MIT, Aurora Flight Sciences, and USC have collaborated to assess the feasibility of electric, hybridelectric, and turbo-electric propulsion for ultra-efficient commercial transportation. The work has drawn on the team expertise in disciplines related to aircraft design, propulsion-airframe integration, electric machines and systems, engineering system design, and optimization. A parametric trade space analysis has been carried out to assess vehicle performance across a range of transport missions and propulsion architectures to establish how electrified propulsion systems scale. An optimization approach to vehicle conceptual design modeling was taken to enable rapid multidisciplinary design space exploration and sensitivity analysis. The results of the analysis indicate vehicle aero-propulsive integration benefits enabled by electrification are required to offset the increased weight and loss associated with the electric system and achieve enhanced performance; the report describes the conceptual configurations than can offer such enhancements. The main contribution of the present work is the definition of electric vehicle design attributes for potential efficiency improvements at different scales. Based on these results, key areas for future research are identified, and extensions to the trade space analysis suitable for higher fidelity electrified commercial aircraft design and analysis have been developed

Self-aligned via and trench for metal contact in III-V semiconductor devices

A semiconductor processing method for the formation of self-aligned via and trench structures in III-V semiconductor devices (in particular, on InP platform) is presented, together with fabrication results. As a template for such self-aligned via and trench formations in a surrounding polymer layer on a semiconductor device, we make use of a sacrificial layer that consists of either a Si O2 dielectric hard mask layer deposited on the device layers or a sacrificial semiconductor layer grown on top of the device epitaxial layers (e.g., InP on an InGaAs etch stop), both laid down on the device layers before patterning the device geometry. During the semiconductor device etching, the sacrificial layer is kept as a part of the patterned structures and is, therefore, perfectly self-aligned. By selectively removing the sacrificial layer surrounded by the polymer that is etched back within the thickness of the sacrificial layer, an opening such as a via and a trench is formed perfectly self-aligned on the device top area in the place of the sacrificial layer. This process yields a pristine semiconductor surface for metal contacts and fully utilizes the contact area available on the device top, no matter how small the device area is. This approach thus provides as low an Ohmic contact resistance as possible upon filling the via and the trench with metal deposition. The additional use of a thin Si3 N4 protecting layer surrounding the device sidewalls improves the robustness of the process without any undesired impact on the device electrical passivation (or on the optical mode characteristics if the device also includes a waveguide). This method offers metal contacts scalable to the device size, being limited only by the feasible device size itself. This method is also applicable to the fabrication of other III-V based integrated devices. © 2006 American Vacuum Society

Electrically-reconfigurable integrated photonic switches

We report remotely electrically reconfigurable photonic switches that intimately integrate waveguide electroabsorption modulators with surface-normal photodiodes, avoiding conventional electronics. These switches exhibit full C-band wavelength conversion at 5 Gb/s and are remotely reconfigurable within tens of nanoseconds

Solar assisted heat pump system with volume solar collector. Technical report

The system uses the attic of the house with a large south facing window as the solar collector. An air-to-water heat pump uses the attic air as a heat source to heat a volume of storage water during the heating season. During the cooling season the attic is ventilated and the heat pump uses the attic air as a heat sink while cooling the storage water. The computer program was developed to include a heat exchanger in the attic which could by-pass the heat pump condenser cooling water, thus permitting direct heat exchange between the attic air and the storage water whenever a favorable temperature existed. The program also accounts for the effect of the incidence angle of insolation and the effect of the number of glass plates on the transmittance and absorptance of the collector and windows. Other refinements include: the use of a sophisticated nighttime setback thermostat, account of internal heat generation and infiltration loss. Among all of the parameter variations, the use of an attic heat exchanger resulted in the maximum savings in the heating/cooling energy consumption of the house. The use of double-glazed windows too, resulted in substantial energy savings. The total energy consumption was found to depend strongly on the infiltration rate. The program was also used to simulate the same system under weather conditions existing at several different geographic areas

Multifunctional integrated photonic switches for nanosecond packet-switched wavelength conversion

We report multifunctional integrated photonic switches that provide optical wavelength conversion across the C-band at 3.5 Gb/s that is electrically packet-switched within a reconfiguration time of <2.5ns. These switches also provide optical packet-switching in <300ps. © 2005 Optical Society of America

Multifunctional integrated photonic switches

Traditional optical-electronic-optical (o-e-o) conversion in today's optical networks requires cascading separately packaged electronic and optoelectronic chips and propagating high-speed electrical signals through and between these discrete modules. This increases the packaging and component costs, size, power consumption, and heat dissipation. As a remedy, we introduce a novel, chip-scale photonic switching architecture that operates by confining high-speed electrical signals in a compact optoelectronic chip and provides multiple network functions on such a single chip. This new technology features low optical and electrical power consumption, small installation space, high-speed operation, two-dimensional scalability, and remote electrical configurability. In this paper, we present both theoretical and experimental discussion of our monolithically integrated photonic switches that incorporate quantum-well waveguide modulators directly driven by on-chip surface-illuminated photodetectors. These switches can be conveniently arrayed two-dimensionally on a single chip to realize a number of network functions. Of those, we have experimentally demonstrated arbitrary wavelength conversion across 45 nm and dual-wavelength broadcasting over 20 nm, both spanning the telecommunication center band (1530-1565 nm) at switching speeds up to 2.5 Gb/s. Our theoretical calculations predict the capability of achieving optical switching at rates in excess of 10 Gb/s using milliwatt-level optical and electrical switching powers

Scalable wavelength-converting crossbar switches

We report scalable low-power wavelength-converting crossbar switches that monolithically integrate two-dimensional compact arrays of surface-normal photodiodes with quantum-well waveguide modulators. We demonstrate proof-of-concept, electrically reconfigurable 2 × 2 crossbars that perform unconstrained wavelength conversion across 35 nm in the C-band (1530-1565 nm), using only <4.3-mW absorbed input optical power, and with 10-dB extinction ratio at 1.25 Gb/s. Such wavelength-converting crossbars provide complete flexibility to selectively convert any of the input wavelengths to any of the output wavelengths at high data bit rates in telecommunication, with the input and output wavelengths being arbitrarily chosen within the C-band. © 2004 IEEE