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End date: 2013 × Start date: 2011 × search.filters.applied.f.isSeriesOfPublicationTitle: Master of Science in Aerospace Engineering × search.filters.applied.f.resourcesubtype: Masters Project ×

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Now showing 1 - 10 of 22
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Investigation of Drag Modulated Supersonic Inflatable Aerodynamic Decelerators for Use on Sounding Rocket Payloads

2013-12-13 , Miller, Matthew J.

This paper presents an assessment of use of a supersonic inflatable aerodynamic decelerator for drag modulation of a sounding rocket payload bus structure as part of a high-altitude sample return mission. The scientific goal of this mission is to capture mesospheric dust and particulate matter located 45 km to 85 km in altitude. This mission is also to demonstrate technology that is capable of precise landings by combining a decelerator system comprised of inflatable aerodynamic decelerator to reach within 10 km with a guided parafoil system. Three decelerator configurations, the tension cone, attached isotensoid, and the trailing isotensoid, were examined on the metrics of decelerator mass, aerodynamic performance, and vehicle integration. The attached isotensoid was found to be the most mass efficient option, while the trailing isotensoid was determined to be preferable from an overall system level perspective. The decelerators’ precision landing capability through the use of drag modulation was also evaluated. Downrange error was reduced by 21% by drag modulation as compared to an 8.5 m supersonic disk-gap-band parachute. When coupled with a guided parafoil, drag modulation provides a 95% confidence level in landing within the 10 km parafoil capability region, and a 76% confidence level of landing within 5 km of the target.

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Aerodynamic Stability and Performance of Next-Generation Parachutes for Mars Descent

2013-07-18 , Gonyea, Keir

The aerodynamic stability and performance characteristics of next-generation supersonic parachutes were determined through wind tunnel testing. Canopy configurations included the disk-gap-band (DGB), ringsail, and ringsail-variant designs referred to as the disksail and starsail. Stereo photogrammetric processing was performed during testing, which was then used to estimate the static and dynamic moment coefficient curves as a function of total angle of attack. The dynamic components of the angle of attack and sideslip angle were shown to be significant, heavily influencing the resulting total angle of attack profile and moment coefficients. Uncertainty in the apparent mass of the canopies resulted in uncertainty in the moment coefficient magnitudes. From the stability curves, the peak moment, trim total angle of attack, and pitch stiffness at the trim angle could be determined. Parachute stability was assessed in the context of drag load and geometric porosity. An inverse relationship between the drag load and the stability of the canopies was generally seen. The DGB canopies tended to be more stable while the ringsail and disksail canopies had more drag. Similar stability properties as the DGB with slightly higher drag loads were obtained by increasing the geometric porosity distribution around the crown of the disksail canopies.

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Prox-1 Guidance, Navigation & Control Formulation and Algorithms

2013-05-01 , Zappulla, Richard, II

Beginning with the manned Gemini missions, proximity operations and rendezvous between two (2) spacecraft have significantly evolved from human-in-the-loop to ground-in-the-loop to more autonomous vehicles, such as the Japanese ETS-VII and the Russian Progress vehicles. Prior to the proposal for the Prox-1 mission, numerous other missions—such as XSS-10, XSS-11, DART, and Orbital Express—have demonstrated varying levels of autonomy. Unlike previous missions, the Prox-1 mission will utilize a completely autonomous GN&C system driven by an on-board GPS receiver, an uncooled infrared microbolometer, a three-axis magnetometer, an inertial measurement unit (IMU), and sun sensors. The GN&C algorithms and strategies discussed in this paper are designed around robust formulations that are shown to guarantee asymptotic stability and aid in mitigating risk involved with passive, autonomous proximity operations

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Structural Design, Analysis, and Test of the Prox-1 Spacecraft

2012-12-01 , Willingham, Allison L.

HE Prox-1 spacecraft is Georgia Institute of Technology’s entry into the 7th University Nanosatellite Program Competition, a two year cycle competition for the AFRL where university teams consisting of both graduate and undergraduate students design, build, and test a 50 kg nanosatellite for a team-specified mission. Judging is based on various presentations to the AFRL review teams, importance of the mission to AFRL objectives, and development of a sound nanosatellite system among other criteria [5]. Prox-1 is a nanosatellite which will demonstrate the use of low-thrust propulsion for automated safe trajectory control during proximity operations. Passive, image based observations will be used for the navigation and closed loop attitude control of Prox-1 relative to a deployed CubeSat. Prox-1’s objectives include: Rendezvous and proximity operations with a target CubeSat, automated relative navigation and trajectory control, closed-loop attitude control based upon automated image processing, and relative orbit determination using image-based angle and range estimates, validated by the Mission Operations System [4]. The student’s particular research involved design, build, and test of the structural components of the Prox-1 satellite. This paper will describe what design information was based on previous Prox-1 structure iterations, what design modifications were made to improve the structure’s capabilities and meet requirements, what analysis and testing was performed to validate those requirements, and what was needed to integrate with the subsystem components. When referring to different plate orientations in this document, the Prox-1 body coordinate frame is used. This is centered at the middle of the Lightband interface ring on the bottom plate, and in the same plane as the Launch Vehicle Interface. In the final structure configuration, the X-axis is pointing toward the Ppod deployment direction and cameras, the positive Y-axis is in the direction opposite of the thruster, and the Z-axis is pointing from the LVI plate toward the top plate [2]. All figures depicting the spacecraft will have this body coordinate frame pictured

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Supersonic Propulsive Divert Maneuvers for Future Robotic and Human Mars Missions

2013-12-13 , Mandalia, Amit B.

Future robotic and human missions to Mars require improved landed precision and increased payload mass. Two architectures that seek to meet these requirements using supersonic propulsive diverts are proposed in this paper: one utilizing a high-altitude propulsive divert and another with thrust vectoring during supersonic retropropulsion. Low ballistic coefficient entry vehicles decelerate high in the thin Mars atmosphere and may be used to deliver higher-mass payloads to the surface. A high-altitude supersonic propulsive divert maneuver is proposed as a means of precision landing for low ballistic coefficient entry vehicles that decelerate to supersonic speeds at altitudes of 20-60 km. This divert maneuver compares favorably to traditional precision landing architectures with up to 100% improvement in range capability while saving over 30% in propellant mass. Architectures which utilize hypersonic vehicles with ballistic coefficients of 10 kg/m2 were found to land within 500 m of a target with this maneuver alone. This high-altitude divert range capability is sensitive to altitude and flight-path angle variations at maneuver initiation and relatively insensitive to velocity at initiation. Propellant mass fraction is relatively invariant to the initial conditions and correlates directly with the divert distance. Supersonic retropropulsion has also been proposed as a means to deliver higher-mass payloads to the surface, and thrust vectoring during supersonic retropropulsion can save a substantial amount of fuel in a precision landing scenario. Propellant mass savings greater than 30% are possible if thrust vectoring is unconstrained during the supersonic phase of flight. Propellant mass fraction is found to be sensitive to the divert direction and also the altitude and flight-path angle, favoring low altitudes and shallow flight-path angles.

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Photogrammetry Analysis of a Hypersonic Inflatable Aerodynamic Decelerator Structural Test Article

2013-07-11 , Li, Lin

Analysis was performed on photogrammetry data of a 6m Hypersonic Inflatable Aerodynamic Decelerator (HIAD), an inflatable stacked torus used to aid in atmospheric entry, to understand its structural dynamics. Photogrammetry data was obtained during wind tunnel testing under various loading conditions. Test parameters included the freestream dynamic pressure, yaw angle and internal inflation pressure. In addition, two HIAD configurations were analyzed, the basic stacked torus (Baseline configuration) and a second configuration adding a torus near the shoulder to aid in rigidity (Tri-Tori configuration). The analysis includes estimating the deflection of the HIAD under loading as well as calculating the standard deviation relative to the mean deflection and the frequency content of the dynamic response. Under load, the deflection angle for each configuration ranged from 1° to 3° (1σ). Analysis of the results indicates that the Tri-Tori configuration did not demonstrate significant benefit over the Baseline. The photogrammetry data showed that the oscillatory motion increased with higher dynamic pressure but was insensitive to yaw angle. In addition, the analysis showed that the standard deviation of the HIAD shape with respect to the average deflection increased while moving radially outwards. However, the standard deviation values calculated from different camera pairs were inconsistent and did not produce the same standard deviations especially at the interface region. The frequency analysis showed that each radial member behaved similarly to a rigid oscillator, having the same frequency content of motion along each radial direction and increased amplitude when moving radially outward. Both the frequency and shape standard deviation analyses showed that the motion of the HIAD was piecewise continuous in the azimuthal direction. These discontinuities likely arose when stitching together the images from different camera pairs. The photogrammetry data is a valuable dataset providing insight into the static and dynamic response of the HIAD under loading. However, inconsistencies in the camera imaging and stitching need to be resolved and higher temporal resolution will improve the fidelity of analysis

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Evaluation of Deployable Aerosurface Systems for Mars Entry

2012-12-14 , Cruz-Ayoroa, Juan G.

One of the challenges presented by the exploration of Mars is the entry, descent and landing (EDL) of payloads to the surface. Current robotic missions to Mars are reaching the limist of existing Viking heritage EDL technologies. A number of EDL technology improvements can be made to extend the capabilities beyond the current landed mass limits, including increasing the entry vehicle hypersonic drag and lift capability. Technologies being currently studied include inflatable aerodynamic decelerators, which are designed to increase vehicle drag. Many of these concepts center on axisymmetric designs, which provide high drag but relatively low lift and are most easily integrated to blunt entry vehicles. However, due to packaging density and launch vehicle fairing constraints, it is likely that future missions will require the use of slender bodies. This study investigates three deployable concepts designed to provide better integration into a slender vehicle while augmenting its performance by increasing its hypersonic drag. The deployable aerosurfaces are applied to a 5 meter diameter slender vehicle for a robotic mission at Mars with entry masses ranging from 10 to 60t. A multidisciplinary design optimization framework is used to estimate the landed mass capability of each system. Results show that the deployable concepts can significantly improve payload mass capability by reducing the terminal propulsion propellant required. Initial feasibility studies show that the concepts are hypersonically statically stable and comply with mechanical and thermal material capabilities

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Flexible Thermal Protection System Physics-Based Modeling for Temperature Profile Predictions

2013-12-03 , Rossman, Grant A.

Candidate material testing was performed on various Flexible Thermal Protection Systems (FTPS) layup configurations in an arc-jet ground test facility. A physics-based thermal model was created to predict the thermal-material response of each FTPS layup under arc-jet induced thermal loading. Initial thermal model temperature predictions of embedded thermocouples for FTPS test articles showed an unsatisfactory correlation to arc jet test data. The Levenberg-Marquardt (LM) inverse parameter estimation technique was implemented to reduce discrepancies between thermal model temperature predictions and experimental thermocouple temperature measurements by iteratively modifying FTPS thermal parameters within the model, such as thermal conductivity and specific heat. A formal parameter estimation methodology, previously applied for ablative TPS, is applied to this FTPS problem to improve understanding estimation behavior and LM error minimization. Nominal, uncertainty, sensitivity, and inverse analysis are performed on scaled thermal inputs to provide insight on solution uniqueness and stability. This error minimization technique is demonstrated on a previously flown FTPS layup configuration consisting of two outer fabric layers, two insulation layers, and one gas barrier layer. Results show that the LM method is a viable technique for inverse parameter estimation of FTPS thermal modeling problems.

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A Method to Characterize Parachute System Instability Modes

2013-06-05 , Bernatovich, Michael , Clark, Ian

A simplified, yet robust, parachute system stability analysis is performed using a 5-DOF (altitude, pitch, & yaw) descent trajectory simulation. Several trade studies are performed to determine what types of initial conditions and wind perturbations can result in pitching (i.e. planar) or coning instability modes. Building on these results, several vehicle design sensitivities are performed to roughly describe the trend in stability with canopy trailing distance, canopy diameter, & payload mass. As a complement to these sensitivities and trade studies, an early Mars EDL research drop test is analyzed as a case study. During this drop test, the system experienced uncharacteristically large pitch oscillations primarily driven by canopy vortex shedding. Data from this drop test will be used to determine the trajectory & vehicle design space within which this behavior could be expected.

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Implementation of a Mesomechanical Material Model for IAD Fabrics within LS-DYNA

2012-12-14 , Hill, Jeremy

The implementation and evaluation of a high fidelity material model for dry fabrics is the main objective of this paper. Inflatable Aerodynamic Decelerators (IADs) and other air inflated structures quite often utilize woven fabrics due to their lightweight and high loading carrying capabilities. Design optimization of these inflated structures relies on a detailed understanding of the woven fabric mechanics. Woven fabrics are composite orthotropic materials that respond differently under load from traditional solid mechanics. While low fidelity fabric materials usually assume a continuous medium, a higher fidelity model needs to account for the reorientation of yarns and weave geometry. An existing mesomechanical material model within the LS-DYNAÒ commercial non-linear finite element software package is utilized. In this paper, experimental stress-strain data for Kevlar 129 samples are validated against numerical simulations of models with matching geometry and loading conditions.

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