Tensegrity Heat Shield for Atmospheric Entry Through Celestial Bodies

2016 ◽  
Author(s):  
Shaurya Deep Chopra ◽  
Mircea Teodorescu ◽  
Steven Lessard ◽  
Adrian Agogino ◽  
Vytas SunSpiral
Keyword(s):  
Celestial Body ◽  
Flexible Structures ◽  
Vital Role ◽  
Heat Shield ◽  
Space Vehicles ◽  
Tensegrity Structures ◽  
Drag Forces ◽  
Rigid Rods ◽  
Heat Shields ◽  
Celestial Bodies

Heat shields play a vital role in protecting space vehicles during the atmosphere reentry. Therefore, they are essential for space vehicles, and better designed heat shields will vastly improve the ability both of robots and humans to explore extraterrestrial destinations. The main goal of the current paper is to investigate the feasibility of designing, building and deploying a tensegrity-based heat shield, which would withstand the atmospheric reentry of a low gravity and dense atmosphere celestial body (such as Titan), where the reentry accelerations and therefore, drag forces, will be lower than in the case of a high gravity planet (e.g., Earth or Mars). The paper is a preliminary study, which investigates the parameters that would be helpful in designing tensegrity-based heat shields. We explore the dynamics of entry and how the atmospheric forces interact with the heat shield. Tensegrity structures consist of tension elements used in conjunction with rigid rods which are actuated by changing the lengths of the tension elements. The advantage of the proposed approach versus the traditional one (rigid heat shields) is that tensegrity structures are flexible structures able to adapt the shape to obtain an optimal reentry configuration. The proposed heat shield will be able to fold in a small space during transport (e.g., to the target celestial body), unfold when the target is reached and provide additional mobility for an optimal reentry pattern. However, to achieve a deployable configuration, the tensegrity structure must withstand significant dynamics and thermal loads. We will use NASA Tensegrity Robotics Toolkit (NTRT) to simulate the structural designs of the heat shield as well as for designing the controllers.

Tensegrity Structures in the Design of Flexible Structures for Offshore Aquaculture

2007 ◽  
Author(s):  
O̸sten Jensen ◽  
Anders Sunde Wroldsen ◽  
Pa˚l Furset Lader ◽  
Arne Fredheim ◽  
Mats Heide ◽  
...  
Keyword(s):  
Flexible Structures ◽  
Weather Conditions ◽  
High Energy ◽  
Open Ocean ◽  
Element Analysis ◽  
Tensegrity Structures ◽  
Stiffness Properties ◽  
Offshore Aquaculture ◽  
And Performance ◽  
Open Ocean Aquaculture

Aquaculture is the fastest growing food producing sector in the world. Considerable interest exists in developing open ocean aquaculture in response to a shortage of suitable, sheltered inshore locations. The harsh weather conditions experienced offshore lead to a focus on new structure concepts, remote monitoring and a higher degree of automation in order to keep the cost of structures and operations within an economically viable range. This paper proposes tensegrity structures in the design of flexible structures for offshore aquaculture. The finite element analysis program ABAQUS™ has been used to investigate stiffness properties and performance of tensegrity structures when subjected to various forced deformations and hydrodynamic load conditions. The suggested concept, the tensegrity beam, shows promising stiffness properties in tension, compression and bending, which are relevant for development of open ocean aquaculture construction for high energy environments. When designing a tensegrity beam, both pre-stress and spring stiffness should be considered to ensure the desired structural properties. A large strength to mass ratio and promising properties with respect to control of geometry, stiffness and vibration could make tensegrity an enabling technology for future developments.

Uncertainty Quantification of Thermocouple Air Temperature Measurement in Highly Radiative Environment: Application to Turbofan Engine Compartment

2016 ◽  
Author(s):  
Y. Sommerer ◽  
V. Drouin ◽  
X. Nicolas ◽  
B. Trouette
Keyword(s):  
Heat Flux ◽  
Temperature Measurement ◽  
Air Temperature ◽  
Data Bank ◽  
Heat Shield ◽  
Engine Compartment ◽  
Heat Shields ◽  
Air Speed ◽  
Thermocouple Temperature ◽  
The Impact

This paper focuses on thermocouple air temperature measurement uncertainty due to the radiative fluxes present in the engine compartment where engine case skin temperature can exceed 900 K. To really measure air temperature, the convective heat flux in the thermocouple bead must be predominant. This is why heat shields are used in order to reduce the radiative heat flux on the bead. However, in engine compartment, the heat shield orientation must be optimized since numerous hot walls surround the thermocouple. In order to evaluate the impact of badly oriented heat shields and to provide a data bank for numerical simulation validations, a heated wind tunnel has been used. It has been shown that the uncertainty on the thermocouple temperature can reach dozens of degrees depending on the air speed and the heat shield orientation. Furthermore a specific 3D thermocouple model has been build and validated by comparison with the lab measurements. Then this thermocouple 3D model has been integrated in the whole engine compartment aero-thermal model in order to quantify the uncertainty of the thermocouple air temperature measurement in the real engine environment.

scholarly journals Study of Manufacturing Process of Holes in Aeroengine Heat Shield

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Anyuan Jiao ◽  
Weijun Liu
Keyword(s):  
Cutting Temperature ◽  
Dimensional Accuracy ◽  
Aircraft Engine ◽  
Heat Shield ◽  
Drilling Process ◽  
High Plasticity ◽  
Processing Efficiency ◽  
Technical Parameters ◽  
Nickel Based Superalloy ◽  
Heat Shields

The nickel-based superalloy GH3128 with high plasticity, high long-lasting creep strength, good resistance to oxidation and stamping, and good welding performance is widely used in aircraft engine heat shields. The many holes that need to be machined on the heat shield are not only small in diameter but also dense, and GH3128 as a typical hard-to-process material has the problems of large cutting force, high cutting temperature, and serious hardening. Therefore, poor dimensional accuracy and residual burrs have become the main factors that limit the processing efficiency and processing quality. So, a novel combination of manufacturing processes was proposed. Firstly, laser cutting technology was used to process the base hole in a GH3128 plate, followed by reaming, and finally, using a magnetic abrasive finishing effector to remove burrs formed during the first two steps. The whole drilling process of the heat shields fully meets the requirements of the technical parameters. This study provides new reference for manufacturing the holes of a heat shield and other similar porous parts.

scholarly journals Characterization of Spatter and Sublimation in Alloy 718 during Electron Beam Melting

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 5953
Author(s):  
Ahmad Raza ◽  
Eduard Hryha
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Elevated Temperatures ◽  
Ion Beam ◽  
High Vacuum ◽  
Alloying Elements ◽  
Heat Shield ◽  
Alloy 718 ◽  
Feedstock Powder ◽  
Heat Shields

Due to elevated temperatures and high vacuum levels in electron beam melting (EBM), spatter formation and accumulation in the feedstock powder, and sublimation of alloying elements from the base feedstock powder can affect the feedstock powder’s reusability and change the alloy composition of fabricated parts. This study focused on the experimental and thermodynamic analysis of spatter particles generated in EBM, and analyzed sublimating alloying elements from Alloy 718 during EBM. Heat shields obtained after processing Alloy 718 in an Arcam A2X plus machine were analyzed to evaluate the spatters and metal condensate. Comprehensive morphological, microstructural, and chemical analyses were performed using scanning electron microscopy (SEM), focused ion beam (FIB), and energy dispersive spectroscopy (EDS). The morphological analysis showed that the area coverage of heat shields by spatter increased from top (<1%) to bottom (>25%), indicating that the spatter particles had projectile trajectories. Similarly, the metal condensate had a higher thickness of ~50 μm toward the bottom of the heat shield, indicating more significant condensation of metal vapors at the bottom. Microstructural analysis of spatters highlighted that the surfaces of spatter particles sampled from the heat shields were also covered with condensate, and the thickness of the deposited condensate depended on the time of landing of spatter particles on the heat shield during the build. The chemical analysis showed that the spatter particles had 17-fold higher oxygen content than virgin powder used in the build. Analysis of the metalized layer indicated that it was formed by oxidized metal condensate and was significantly enriched with Cr due to its higher vapor pressure under EBM conditions.

scholarly journals Reference frame and map projection for irregular shaped celestial bodies

2020 ◽  
Vol 2 ◽  
pp. 1-2
Author(s):  
Krisztián Kerkovits ◽  
Tünde Takáts
Keyword(s):  
Celestial Body ◽  
Reference Frame ◽  
Reference Frames ◽  
Surfaces Of Revolution ◽  
Map Projection ◽  
Map Projections ◽  
Ellipsoid Of Revolution ◽  
Celestial Bodies ◽  
Best Fitting ◽  
Comet 67P

Abstract. Recent advancements of technology resulted in greater knowledge of the Solar System and the need for mapping small celestial bodies significantly increased. However, creating a good map of such small objects is a big challenge for the cartographer: they are usually irregular shaped, the usual reference frames like the ellipsoid of revolution is inappropriate for their approximation.A method is presented to develop best-fitting irregular surfaces of revolution that can approximate any irregular celestial body. (Fig. 1.) Then a simple equal-area map projection is calculated to map this reference frame onto a plane. The shape of the resulting map in this projection resembles the shape of the original celestial body.The usefulness of the method is demonstrated on the example of the comet 67P/Churyumov-Gerasimenko. This comet has a highly irregular shape, which is hard to map. Previously used map projections for this comet include the simple cylindrical, which greatly distorts the surface and cannot depict the depressions of the object. Other maps used the combination of two triaxial ellipsoids as the reference frame, and the gained mapping had low distortion but at the expense of showing the tiny surface divided into 11 maps in different complicated map projections (Nyrtsov et. al., 2018). On the other hand, our mapping displays the comet in one single map with moderate distortion and the shape of the map frame suggests the original shape of the celestial body (Fig. 2. and 3.).

Experimental Studies and Numerical Modeling of Copper Nets in Marine Environment

2011 ◽  
Author(s):  
Igor Tsukrov ◽  
Andrew Drach ◽  
Judson DeCew ◽  
M. Robinson Swift ◽  
Barbaros Celikkol ◽  
...  
Keyword(s):  
Marine Environment ◽  
Copper Alloy ◽  
Flexible Structures ◽  
Experimental Studies ◽  
Finite Element Program ◽  
Drag Forces ◽  
Waves And Currents ◽  
Element Program ◽  
Marine Applications ◽  
Increased Strength

Copper alloy netting is increasingly used for offshore aquaculture, harbor protection and other marine applications. Its advantageous characteristics include high resistance to biofouling and increased strength compared to polymer nets. However, the hydrodynamic properties of copper nets are not well studied. In this paper, the results of experimental studies of drag forces on copper alloy net panels are reported. Based on these studies, empirical values for drag coefficients are proposed for various types of copper nets, and compared to the corresponding data for polymer netting. It is shown that copper nets exhibit significantly lower resistance to the current flow which corresponds to lower values of drag coefficient. Coefficients obtained from the experiments are incorporated into the finite element program Aqua-FE, developed at the University of New Hampshire for analysis of flexible structures subjected to waves and currents in marine environment. The results of the numerical simulations for a small volume fish cage, subjected to two different sets of environmental conditions, are analyzed to compare how introduction of copper netting instead of traditional nylon nets affects the dynamic response of the system.

scholarly journals Once more on the origin of Semetic and Greek star names: an astromonic-etymological approach updated

2005 ◽  
Vol 09 (01) ◽  
pp. 3-43
Author(s):  
Gennadij Kurtik ◽  
Alexander Militarev
Keyword(s):  
Celestial Body ◽  
The Other ◽  
Historical Background ◽  
Semitic Languages ◽  
Greek Culture ◽  
Celestial Bodies ◽  
Greek World ◽  
Modern Astronomy

The contribution is a new version of the paper "From Mesopotamia to Greece: to the Origin of Semitic and Greek Star Names" once written by a Sumerologist (L.Bobrova) and etymologist (A. Militarev), and recently revised, updated and corrected in most part by a historian of the Mesopotamian astronomy (G. Kurtik). The present paper analyzes Sumerian and Akkadian (Babylonian) names of 34 celestial bodies, and their equivalents in other Semitic languages (Arabic, Hebrew, Syrian Aramaic, and Ge`ez, or ancient Ethiopian) and in Greek and Latin. Its main goal is to demonstrate the importance of Sumerian and Babylonian celestial body names as a source of corresponding terms in other cultures, up to the conventional inventory of modern astronomy, and to reveal four strategies by which other cultures drew ideas for name-giving from the treasury of Mesopotamia's lexicon of celestial bodies. Whereas one of these strategies -- echoing, or full translation, of a Sumero-Akkadian term -- is axiomatic, the other three -- shift of meaning or interpretation of a Sumero-Akkadian term; lexical, or "material" borrowing; and, especially, folk etymology, or misinterpretation -- are understudied and practically unnoticed. The authors do not focus on such complicated matters as a historical background of Mesopotamian influence, direct or indirect, on Greek culture; a direction and routes of inter-borrowing between different speaking areas other than Akkadian and their contacts with the Greek world; a chronology of all kinds of cultural contacts and influences; probable connections between the early pre-Islamic Arabic and Babylonian traditions; or the problem of identification of Mesopotamian constellation and stars. However, the data presented may give a certain impulse to further investigation of these matters, while feasible etymologies and relations established between names can even throw some light upon debatable identification cases.

scholarly journals Impact of Heat Shield Thickness on Performance of Roll through Simulation

2019 ◽  
Vol 9 (2) ◽  
pp. 3105-3109
Keyword(s):  
Dissipation Rate ◽  
Heat Dissipation ◽  
Electrical Energy ◽  
Power Input ◽  
Surface Coatings ◽  
Heat Shield ◽  
Steady Temperature ◽  
Time Saving ◽  
Heat Shields ◽  
Stainless Steel 316

Rolls of the packing machine undertakes an imperative job in packing industries. So as to decrease the power input and reducingthe heat dissipation rate, there are numerous methodologies, for example, surface coatings, surface boronizing and with heat shields and so forth. This work is expected to reducethe power contribution to heaters by diminishing the heat dissemination rate utilizing heat shields with simulation of different thicknesses. There is a decrease of dissipation of heat by using Stainless steel 316 Ti (0.7 mm thickness) heat shields and there is a reduction of 13.9% in power input, 28% time saving and14% in heat dissipation rate is noticedwhencompared to standard rolls up to steady surface temperature where there is saving of 198W per hour in power after steady temperature. Hence an attempt is being made for improving results that are obtained from experiments by using simulation through ANSYS steady state thermal analysis. From the results it is inferred that as thickness of heat shield increases the input electrical energy for the heater goes on reducing and results shows that 0.7 mm thickness shield is 4.28% efficient than 0.8 mm heat shield. Further through simulation optimum thickness is was observed. But thickness is restricted to 1mm only because of machine specification complexity. Further the results of simulation for varying thickness are presented with contours of temperature distribution and heat flux.

Some Problems of Planetary Atmosphere Entry

1967 ◽  
Vol 71 (684) ◽  
pp. 813-820 ◽  
Author(s):  
H. Julian Allen
Keyword(s):  
Planetary Atmosphere ◽  
Additional Research ◽  
Heat Shield ◽  
Aerodynamic Heating ◽  
Space Vehicles

Summary:—Progress in understanding the atmosphere heating problems of space vehicles at hyperbolic entry speeds is reviewed. The various sources of aerodynamic heating are discussed along with the response of suitable heat shield materials to these inputs. It is shown that even for optimum shaped vehicles the problems are formidable at entry speeds greatly in excess of Earth parabolic speed. Much additional research, particularly of ablation materials, will be needed to effect satisfactory designs for such craft.

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