47,709 research outputs found
Study of hybrid air vehicles stability using computational fluid dynamics
This paper uses Computational Fluid Dynamics to predict aerodynamic damping of airships or
hybrid air vehicles. This class of aircraft is characterised by large lifting bodies combining buoyancy
and circulatory lift. Damping is investigated via forced oscillations of the vehicle in pitch and yaw. The
employed method is verified using data for lighter than air vehicles. The use of fins and stabilisers was
found to be beneficial. The rear part of the body was dominated by separated flow that containedmore
frequencies than the forcing frequency imposed on the body. The final design is seen to be dynamically
stable across a range of conditions for small pitch angles
Shock shapes and pressure distributions for large angle pointed cones in helium at Mach numbers of 8 and 20
Shock shape and surface pressure measurements on hypersonic pointed cones in heliu
IMPMOT user's manual
This user's manual describes the input and output variables as well as the job control language necessary to utilize the IMP-H apogee motor firing program, IMPMOT. The IMPMOT program can be executed as either a stand-alone program or as a member of the flight dynamics system. This program is used to determine the time and attitude at which to fire the IMP-H apogee boost motor. The IMPMOT program is written in FORTRAN 4 for use on the IBM 360 series computer
Computational fluid dynamics challenges for hybrid air vehicle applications
This paper begins by comparing turbulence models for the prediction of hybrid air vehicle (HAV) flows. A 6 : 1 prolate spheroid is employed for validation of the computational fluid dynamics (CFD) method. An analysis of turbulent quantities is presented and the Shear Stress Transport (SST) k-ω model is compared against a k-ω Explicit Algebraic Stress model (EASM) within the unsteady Reynolds-Averaged Navier-Stokes (RANS) framework. Further comparisons involve Scale Adaptative Simulation models and a local transition transport model. The results show that the flow around the vehicle at low pitch angles is sensitive to transition effects. At high pitch angles, the vortices generated on the suction side provide substantial lift augmentation and are better resolved by EASMs. The validated CFD method is employed for the flow around a shape similar to the Airlander aircraft of Hybrid Air Vehicles Ltd. The sensitivity of the transition location to the Reynolds number is demonstrated and the role of each vehicle£s component is analyzed. It was found that the ¦ns contributed the most to increase the lift and drag
Fabrication and Electrical Characterization of Fully CMOS Si Single Electron Devices
We present electrical data of silicon single electron devices fabricated with
CMOS techniques and protocols. The easily tuned devices show clean Coulomb
diamonds at T = 30 mK and charge offset drift of 0.01 e over eight days. In
addition, the devices exhibit robust transistor characteristics including
uniformity within about 0.5 V in the threshold voltage, gate resistances
greater than 10 G{\Omega}, and immunity to dielectric breakdown in electric
fields as high as 4 MV/cm. These results highlight the benefits in device
performance of a fully CMOS process for single electron device fabrication.Comment: 7 pages, 7 figure
Portable, high intensity isotopic neutron source provides increased experimental accuracy
Small portable, high intensity isotopic neutron source combines twelve curium-americium beryllium sources. This high intensity of neutrons, with a flux which slowly decreases at a known rate, provides for increased experimental accuracy
Catalytic surface effects on space thermal protection system during Earth entry of flights STS-2 through STS-5
An on going orbiter experiment catalytic surface effects experiment being conducted on the Space Shuttle is discussed. The catalytic surface effects experiment was peformed on four of the five flights of Columbia. Temperature time histories and distributions along the midfuselage and wing of the orbiter were used to determine the surface catalytic efficiency of the baseline high temperature reusable surface insulation. Correlation parameters are shown that allow the comparison of all flight data with predictions from the design and surface emittance decreased as a result of contaminants during the five flights of the Space Shuttle
Performance of an ablator for Space Shuttle inorbit repair in an arc-plasma airstream
An ablator patch material performed well in an arc plasma environment simulating nominal Earth entry conditions for the Space Shuttle. Ablation tests using vacuum molded cones provided data to optimize the formulation of a two part polymer system for application under space conditions. The blunt cones were made using a Teflon mold and a state of the art caulking gun. Char stability of formulations with various amounts of catalyst and diluent were investigated. The char was found to be unstable in formulations with low amounts of catalyst and high amounts of diluent. The best polymer system determined by these tests was evaluated using a half tile patch in a multiple High Temperature Reusable surface Insulation tile model. It was demonstrated that this ablator could be applied in a space environment using a state of the art caulking gun, would maintain the outer mold line of the thermal protection system during entry, and would keep the bond line temperature at the aluminum tile interface below the design limit
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