Space Vehicles Commons^™

Multiphysics Transport In Porous Thermal Protection Systems: Experimental Characterization Of Gas Permeability And Radiative Properties, Yejajul Hakim

Theses and Dissertations--Mechanical and Aerospace Engineering

Porous thermal protection systems (TPS) used in hypersonic vehicles exhibit coupled gas and radiative transport across multiple regimes and length scales. Accurate performance prediction requires reliable characterization of permeability, slip-flow behavior, and radiative transport properties, particularly for low-permeability and charred materials where existing data are limited. This dissertation presents experimental methods for characterizing multiphysics transport in porous TPS materials. A modular flow system was developed to measure permeability and slip behavior in both virgin and charred materials under relevant environments. A transient pressure decay method enables accurate permeability estimation in low-permeability regimes and provides insight into effective pore structure. Results …

Kentucky Re-Entry Universal Payload System (Krups): Second Atmospheric Re-Entry Flight, Kirsten F. Ford

Theses and Dissertations--Mechanical and Aerospace Engineering

Kentucky Re-entry Universal Payload System (KRUPS) is a small-scale re-entry capsule developed at the University of Kentucky. The KRUPS project began in 2013 with the aspiration of providing an affordable and repeatable method of collecting data on the re-entry environment. Numerically-based methods used to model re-entry require experimental data to validate their predictions. However, re-entry data is not easily obtained. Flight tests of re-entry vehicles require extensive time and resources, including a substantial financial burden. Alternatively, ground testing is not able to accurately and completely replicate the complex re-entry environment. Thus, there is a need for an inexpensive and accessible …

Investigation Of Subsurface Thermal Radiation Phenomena In Fibrous Thermal Protection Systems, Colby L. Gore

Theses and Dissertations--Science, Technology, Engineering, and Mathematics (STEM) Education

Atmospheric re-entry induces intense thermal stress upon vehicles through a high-enthalpy boundary layer that encompasses the craft. To protect these vehicles, numerous insulative methods, known as thermal protection systems (TPS), are deployed to protect the craft during re-entry. The TPS materials insulate the craft from intense thermal transmission that would terminate a mission. In hypersonic environments, vast temperature gradients exist, enforcing the exponential effect of thermal radiation. However, TPS materials are commonly low-density fibrous materials that allow for the potential to be penetrated by thermal radiation. A series of arc-jet tests was completed to replicate enhanced radiative conditions in a …

Electronics Design For Krepe Atmospheric Entry Capsule Avionics, Matt Ruffner

Theses and Dissertations--Electrical and Computer Engineering

This research documents the design, testing, and implementation of sensing, control, and communications subsystems for small atmospheric entry capsules. Atmospheric entry capsules pose a unique electronics design challenge given mission requirements, environmental constraints, and inherent risk involved in space based missions. Previous work on small satellites developed the CubeSat platform as a means of ensuring reliability after university-led small satellite missions experienced failures. The publication of the CubeSat platform allowed researchers to focus on the payload science utilizing a standardized form-factor and reusable electronics. Environmental and operational constraints of CubeSats and atmospheric entry capsules overlap and best-practices associated with building …

A Decoupled Engineering Methodology For Accurate Prediction Of Ablative Surface Boundary Conditions In Thermal Protection Systems, Justin Cooper

Theses and Dissertations--Mechanical and Aerospace Engineering

The main objective of the present work is to demonstrate a method for prediction of aerothermal environments in the engineering design of hypersonic vehicles as an alternative to the current heritage method. Flat plate and stagnation point boundary layer theory require multiple assumptions to establish the current engineering paradigm. Chief among these assumptions is the similarity between mass and heat transfer. Origins of these assumptions are demonstrated and their relationship to conservative engineering design is analyzed, as well as conditions where they possibly break down. An alternative approach for assessing aerothermal environments from the fluid domain is presented, which permits …

Kentucky Re-Entry Universal Payload System (Krups): Hypersonic Re-Entry Flight, John Daniel Schmidt

Theses and Dissertations--Mechanical and Aerospace Engineering

The Kentucky Re-entry Universal Payload System (KRUPS) is a small capsule designed as a technology testbed for re-entry experiments. For its first incarnation, KRUPS has been designed to test Thermal Protection Systems (TPS) and instruments in re-entry flights. Because of the unique environment a vehicle undergoes during re-entry, there is a high-demand for experimental data from re-entry experiments. KRUPS has been developed at the University of Kentucky (UK) over the past seven years to meet this demand. After completing sub-orbital campaigns, the first KRUPS hypersonic re-entry mission was attempted. The mission involved building three 11-inch diameter capsules each outfitted with …

The Kentucky Re-Entry Universal Payload System (Krups): Orbital Flight, James Tyler Nichols

Theses and Dissertations--Mechanical and Aerospace Engineering

Due to the uniqueness of atmospheric entry environments, ground facilities cannot accurately replicate re-entry conditions. Consequently, scientists primarily rely on numerical models to predict these conditions and inform Thermal Protection System (TPS) designs. These models often lack flight validation, which is necessary for increasing their fidelity. Thus, there is a substantial need to obtain such data to advance modeling capabilities.

The Kentucky Re-entry Universal Payload System (KRUPS) is an adaptable test-bed for scientific experimentation with initial application to TPS. This vehicle was designed at the University of Kentucky to serve as an inexpensive means of obtaining validation data to enhance …

Structural Optimization Of Space Transit Vehicle Concept, Hercules, James Philip Rogers

Theses and Dissertations--Mechanical and Aerospace Engineering

STRUCTURAL OPTIMIZATION OF SPACE TRANSIT VEHICLE CONCEPT, HERCULES:

A COMPARATIVE STUDY OF STRUCTURAL OPTIONS

Hercules is a vehicle concept developed by NASA Langley's Vehicle Analysis Branch to satisfy the need for sustainable transit between Earth, the moon, and Mars. Hercules features unprecedented abort capabilities and mission flexibility to aid in NASA's Mars campaign. By utilizing modern software to perform structural analysis and optimization for a large selection of stiffened panel concepts, beam concepts, and materials trends in the structural optimization emerge. These trends will be invaluable for the design of future spacecraft needed to fulfill similar roles.

The structural optimization …

Development Of Universal Solver For High Enthalpy Flows Through Ablative Materials, Umran Duzel

Theses and Dissertations--Mechanical and Aerospace Engineering

Atmospheric entry occurs at very high speeds which produces high temperature around the vehicle. Entry vehicles are thus equipped with Thermal Protection Systems which are usually made of ablative materials. This dissertation presents a new solver that models the atmospheric entry environment and the thermal protection systems. In this approach, both the external flow and the porous heat shield are solved using the same computational domain. The new solver uses the Volume Averaged Navier-Stokes Equations adapted for hypersonic non-equilibrium flow, and is thus valid for both domains. The code is verified using analytical problems, set of benchmarks and also a …

Single-Degree-Of-Freedom Experiments Demonstrating Electromagnetic Formation Flying For Small Satellite Swarms Using Piecewise-Sinusoidal Controls, Ajin Sunny

Theses and Dissertations--Mechanical and Aerospace Engineering

This thesis presents a decentralized electromagnetic formation flying (EMFF) control method using frequency-multiplexed sinusoidal control signals. We demonstrate the EMFF control approach in open-loop and closed-loop control experiments using a single-degree-of-freedom testbed with an electromagnetic actuation system (EAS). The EAS sense the relative position and velocity between satellites and implement a frequency-multiplexed sinusoidal control signal. We use a laser-rangefinder device to capture the relative position and an ARM-based microcontroller to implement the closed-loop control algorithm. We custom-design and build the EAS that implements the formation control in one dimension. The experimental results in this thesis demonstrate the feasibility of the …

Verification And Validation Studies For The Kats Aerothermodynamics And Material Response Solver, Olivia Schroeder

Theses and Dissertations--Mechanical and Aerospace Engineering

Modeling the atmospheric entry of spacecraft is challenging because of the large number of physical phenomena that occur during the process. In order to study thermal protection systems, engineers rely on high fidelity solvers to provide accurate predictions of both the thermochemical environment surrounding the heat shield, and its material response. Therefore, it is necessary to guarantee that the numerical models are correctly implemented and thoroughly validated. In recent years, a high-fidelity modeling tool has been developed at the University of Kentucky for the purpose of studying atmospheric entry. The objective of this work is to verify and validate this …

Comparisons Of Ablator Experimental Performance To Response Modeling And Effects Of Water Phase Transition In Porous Tps Materials, David L. Smith

Theses and Dissertations--Mechanical and Aerospace Engineering

The Mars Science Laboratory Entry Descent and Landing Instrumentation (MEDLI) project performed extensive arc jet tests for development, qualification, and calibration of instrumented heat shield plugs. These plugs each contained several thermocouples for recording near-surface and in-depth temperature response of the Phenolic Impregnated Carbon Ablator (PICA) heat shield. The arc jet test results are entered into a comprehensive database so that broad trends across the test series can be compared. One method of analysis is to compare with ablator material response calculations and solve the in-depth heat conduction equations. Using the near-surface thermocouple measurements as a boundary condition in numerical …

Small Satellite Noncommutative Rotation Sequence Attitude Control Using Piezoelectric Actuators, Joshua L. Evans

Theses and Dissertations--Electrical and Computer Engineering

Attitude control remains one of the top engineering challenges faced by small satellite mission planning and design. Conventional methods for attitude control include propulsion, reaction wheels, magnetic torque coils, and passive stabilization mechanisms, such as permanent magnets that align with planetary magnetic fields. Drawbacks of these conventional attitude control methods for small satellites include size, power consumption, dependence on external magnetic fields, and lack of full control authority. This research investigates an alternative, novel approach to attitude-control method for small satellites, utilizing the noncommutative property of rigid body rotation sequences. Piezoelectric bimorph actuators are used to induce sinusoidal small-amplitude satellite …

Numerical Investigation On Charring Ablator Geometric Effects: Study Of Stardust Sample Return Capsule Heat Shield, Haoyue Weng, Alexandre Martin

Mechanical Engineering Faculty Publications

Sample geometry is very influential in small charring ablative articles where 1D assumption might not be accurate. In heat shield design, 1D is often assumed since the nose radius is much larger than the thickness of charring. Whether the 1D assumption is valid for the heat shield is unknown. Therefore, the geometric effects of Stardust sample return capsule heat shield are numerically studied using a material response program. The developed computer program models material charring, conductive heat transfer, surface energy balance, pyrolysis gas transport and orthotropic material properties in 3D Cartesian coordinates. Simulation results show that the centerline temperatures predicted …

Numerical Study Of Spallation Phenomenon In An Arc-Jet Environment, Raghava Davuluri, Alexandre Martin

Mechanical Engineering Faculty Publications

The spallation phenomenon might affect the aerodynamic heating rates of re-entry vehicles. To investigate spallation effects, a code is developed to compute the dynamics of spalled particles. The code uses a finite-rate chemistry model to study the chemical interactions of the particles with the flow field. The spallation code is one-way coupled to a CFD solver that models the hypersonic flow field around an ablative sample. Spalled particles behavior is numerically studied for argon and air flow field. The chemistry model is compared with that of Park's model which complies with oxidation and sublimation and shows disagreement for nitridation.

A Design Pathfinder With Material Correlation Points For Inflatable Systems, Jared T. Fulcher

Theses and Dissertations--Mechanical and Aerospace Engineering

The incorporation of inflatable structures into aerospace systems can produce significant advantages in stowed volume to mechanical effectiveness and overall weight. Many applications of these ultra-lightweight systems are designed to precisely control internal or external surfaces, or both, to achieve desired performance. The modeling of these structures becomes complex due to the material nonlinearities inherent to the majority of construction materials used in inflatable structures. Furthermore, accurately modeling the response and behavior of the interfacing boundaries that are common to many inflatable systems will lead to better understanding of the entire class of structures. The research presented involved using nonlinear …

Multidimensional Modeling Of Pyrolysis Gas Transport Inside Orthotropic Charring Ablators, Haoyue Weng

Theses and Dissertations--Mechanical and Aerospace Engineering

During hypersonic atmospheric entry, spacecraft are exposed to enormous aerodynamic heat. To prevent the payload from overheating, charring ablative materials are favored to be applied as the heat shield at the exposing surface of the vehicle. Accurate modeling not only prevents mission failures, but also helps reduce cost. Existing models were mostly limited to one-dimensional and discrepancies were shown against measured experiments and flight-data. To help improve the models and analyze the charring ablation problems, a multidimensional material response module is developed, based on a finite volume method framework. The developed computer program is verified through a series of test-cases, …

Volume Averaged Modeling Of The Oxidation Of Porous Carbon Fiber Material, Alexandre Martin

Mechanical Engineering Faculty Publications

Charring ablators remain the premium choice for space exploration missions that involve atmospheric re-entry. This type of ablative material is composed of a carbon matrix, usually made of fibers, which is then impregnated with a resin. During re-entry, the high heat flux produced by convective heating causes the material to chemically react. First, the resin pyrolyzes, and is vaporized into a gas that travels through the material, and is eventually ejected at the surface. Then, as the temperature rises, the surface of the porous matrix recess through ablative processes. For re-entry conditions typical of space exploration missions, this is mainly …

Modeling Of Chemical Nonequilibrium Effects In A Charring Ablator, Alexandre Martin

Mechanical Engineering Faculty Publications

Charring ablators remain the premium choice for space exploration missions that involve atmospheric re-entry. These type of ablative material are composed of a carbon matrix, usually made of fibers, which is then impregnated with a resin. During re-entry, the high heat flux produced by convective heating causes the material to chemically react. First, the resin pyrolyzes, and is vaporized into a gas that travels through the material, and is eventually ejected at the surface. Since the composition of the gas at the surface greatly affects the heat flux, and therefore the surface temperature, it is thus important to be able …

An Attitude Determination System With Mems Gyroscope Drift Compensation For Small Satellites, Maxwell Bezold

Theses and Dissertations--Electrical and Computer Engineering

This thesis presents the design of an attitude determination system for small satellites that automatically corrects for attitude drift. Existing attitude determination systems suffer from attitude drift due to the integration of noisy rate gyro sensors used to measure the change in attitude. This attitude drift leads to a gradual loss in attitude knowledge, as error between the estimated attitude and the actual attitude increases.

In this thesis a Kalman filter is used to complete sensor fusion which combines sensor observations with a projected attitude based on the dynamics of the satellite. The system proposed in this thesis also utilizes …

Visual Attitude Propagation For Small Satellites, Samir Ahmed Rawashdeh

Theses and Dissertations--Electrical and Computer Engineering

As electronics become smaller and more capable, it has become possible to conduct meaningful and sophisticated satellite missions in a small form factor. However, the capability of small satellites and the range of possible applications are limited by the capabilities of several technologies, including attitude determination and control systems. This dissertation evaluates the use of image-based visual attitude propagation as a compliment or alternative to other attitude determination technologies that are suitable for miniature satellites. The concept lies in using miniature cameras to track image features across frames and extracting the underlying rotation.

The problem of visual attitude propagation as …

Multi-Dimensional Modeling Of Charring Ablators, Haoyue Weng, Huaibao Zhang, Ovais U. Khan, Alexandre Martin

Mechanical Engineering Faculty Publications

Re-entry of a spacecraft occurs at the hypersonic regime where the flow field is extremely complex: high temperature gradients occurring in the shock-layer region ionize and dissociate the air. Even if a large portion of heat generated during this process is convected away in the surrounding air, a fraction of it is still transferred to the vehicle. Therefore, it is important to protect the vehicle with a suitable kind of shielding. Of the many techniques available today, use of ablative material is gaining popularity. The basic idea behind an ablating heat shield is that the energy incident on the spacecraft …

Numerical Modeling Of The Cn Spectral Emission Of The Stardust Re-Entry Vehicle, Alexandre Martin, Erin D. Farbar, Iain D. Boyd

Mechanical Engineering Faculty Publications

Re-entry vehicles designed for space exploration are usually equipped with thermal protection systems made of ablative material. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple ow chemistry models. In order to obtain better predictions, an appropriate gas ow chemistry model needs …