Organizational Unit:

Space Systems Design Laboratory (SSDL)

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https://hdl.handle.net/1853/70747

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Daniel Guggenheim School of Aerospace Engineering

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https://finding-aids.library.gatech.edu/agents/corporate_entities/1138

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Publication Search Results

Now showing 1 - 10 of 131

Methodology for Optimal Design of a Conformal Ablative Heatshield

(Georgia Institute of Technology, 2018-06) Sidor, Adam T. ; Braun, Robert D. ; Kennedy, Graeme J.

Conformal ablators are low density composite materials comprised of a flexible fibrous substrate and polymer matrix. Recent advancements have improved the efficiency of conformal ablator fabrication through vacuum infusion processing where resin is directly injected into a fiber substrate enclosed in a matched mold. This mold filling process can be numerically simulated to inform mold and process design. An automated methodology pairing a mold filling simulation with an approach for tiling a heatshield geometry leads to designs optimized for manufacturing. Material property estimation generalizes the approach to a range of constituent materials, enabling rapid conceptual evaluation of a conformal ablative heatshield. This work improves on the state of the art which relies on heuristic methods tailored to a particular material and aeroshell geometry. Results for a 4.5 meter, 70 degree sphere-cone aeroshell demonstrate the power of an integrated approach.
Mars Molniya Orbit Atmospheric Resource Mining

(Georgia Institute of Technology, 2017-09) Mueller, Robert P. ; Braun, Robert D. ; Sforzo, Brandon ; Sibille, Laurent ; Gonyea, Keir C. ; Ali, Hisham

Landing on Mars is extremely difficult [1] and is considered one of NASA’s biggest technical challenges on the journey to Mars. Science magazine [2] reported the following about the NASA Mars Science Lab (MSL) Mission: “Not only will NASA have to slow the most massive load ever delivered to another planet's surface from hypervelocity bullet speeds to a dead stop, all in the usual "7 minutes of terror." But NASA is also attempting to deliver Curiosity to the surface of Mars more precisely than any mission before, within a 20-kilometer-long ellipse some 240 million kilometers from Earth. Both feats are essential to NASA's long-term goals at Mars: returning samples of Martian rock and sending humans to the Red Planet.” As a result of the thin Mars atmosphere, this challenge is exacerbated as the payload mass is increased. This NASA Innovative Advanced Concepts (NIAC) project has studied one of the top challenges for landing large payloads and humans on Mars by using advanced atmospheric In-Situ Resource Utilization (ISRU) methods that have never been tried or studied before. The proposed Mars Molniya Orbit Atmospheric Resource Mining concept mission architecture changes the paradigm of Mars landings for a wide range of vehicle classes to make the Earth-Mars round-trip travel robust, affordable, and ultimately routine for cargo and crew, therefore enabling the expansion of human civilization to Mars.
Vacuum Infusion Process Development for Conformal Ablative Thermal Protection System Materials

(Georgia Institute of Technology, 2017-09) Sidor, Adam T. ; Braun, Robert D. ; Beck, Robin A. ; Stackpoole, Margaret M.

Conformal ablators are low density composite materials comprised of a flexible fibrous substrate and polymer matrix. These materials are fabricated to near net shape by placing the substrate in a rigid, matched mold and infusing with liquid resin in an open, vacuum{ assisted immersion process. This process, originally developed for older rigid substrate ablators such as PICA, wastes a substantial amount of resin. In this work, a vacuum infusion process - a type of liquid composite molding where resin is directly injected into a closed mold under vacuum - is advanced for conformal ablators. The process reduces waste over the state-of-the-art technique and may eliminate the need for an atmosphere-controlled oven. Small, at samples of Conformal Phenolic Impregnated Carbon Ablator are infused using the new approach and subjected to a range of curing configurations and conditions. Resulting materials are inspected for quality and compared to material produced using the standard process. Density, resin mass fraction and char yield are measured. Lessons learned inform subsequent plans for process scale up.
Feasibility of Supersonic Retropropulsion Based on Assessment of Mars-Relevant Flight Data

(Georgia Institute of Technology, 2017-09) Sforzo, Brandon A. ; Braun, Robert D.

Flight data provided by SpaceX for flights was analyzed to demonstrate the applicability of telemetry during SRP to Mars relevant conditions. This information was provided under the framework of a public-private partnership with NASA, executed as a Space Act Agreement. Analysis focused on the entry burn portion of the trajectory. Flight conditions were provided to confirm SRP occurred during an applicable range of mach numbers and dynamic pressures to match Mars SRP initiation conditions. Vehicle trajectory and attitude history were provided for the SRP segment as well as onboard sensors for temperature, pressure, heat flux, and strains to compare between missions. Furthermore, NASA airborne assets provided thermal imagery of the first stage during SRP to provide comparison to onboard data. Plume tracking analysis was compared to dynamic data from sensors with little correlation. Analysis of these onboard sensor data and examination of the details for several missions, the performance of the Falcon 9 vehicle during SRP appeared to be well behaved for these flights. This study illustrates that SRP methodology implemented for the Falcon 9 first stage entry does not adversely affect the vehicle and shows promise for future implementation.
Advancing Supersonic Retropropulsion Using Mars-Relevant Flight Data: An Overview

(Georgia Institute of Technology, 2017-09) Braun, Robert D. ; Sforzo, Brandon A. ; Campbell, Charles H.

Advanced robotic and human missions to Mars require landed masses well in excess of current capabilities. One approach to safely land these large payloads on the Martian surface is to extend the propulsive capability currently required during subsonic descent to supersonic initiation velocities. However, until recently, no rocket engine had ever been fired into an opposing supersonic freestream. In September 2013, SpaceX performed the first supersonic retropropulsion (SRP) maneuver to decelerate the entry of the first stage of their Falcon 9 rocket. Since that flight, SpaceX has continued to perform SRP for the reentry of their vehicle first stage, having completed multiple SRP events in Mars-relevant conditions in July 2017. In FY 2014, NASA and SpaceX formed a three-year public-private partnership centered upon SRP data analysis. These activities focused on flight reconstruction, CFD analysis, a visual and infrared imagery campaign, and Mars EDL design analysis. This paper provides an overview of these activities undertaken to advance the technology readiness of Mars SRP.
Guidance Trades for High Ballistic Coefficient Mars Lander Trajectories

(Georgia Institute of Technology, 2017-02) Anderson, Tyler R. ; Braun, Robert D.

Large ballistic coefficient entry vehicles are required to achieve more ambitious exploration goals at Mars. These trajectories exhibit several characteristics that make successful landings difficult including low altitude deceleration and inability to decelerate under parachute. One promising mission architecture involving propulsive supersonic descent and landing is proposed as a candidate for future high ballistic-coefficient vehicles. This paper will investigate guidance options for precision landing using hypersonic bank-angle steering and thrust vector controlled propulsive descent. First, a numerical predictor-corrector guidance algorithm is applied to examine the benefits and trade-offs of range targeting during the hypersonic regime. This is compared against the state-of-the-art Apollo Final Phase guidance algorithm. Next, a modification is included to increase guidance performance. Finally, a propulsive divert algorithm is assessed for its impact on landing accuracy and propellant usage.
Characterization of Guidance Algorithm Performance for Drag Modulation-Based Aerocapture

(Georgia Institute of Technology, 2017-02) Werner, Michael S. ; Braun, Robert D.

Discrete-event drag modulation systems are an attractive option for flight control during aerocapture. These systems require precise timing of the drag modulation events to ensure accurate final orbit delivery. Two different guidance schemes for discrete-event drag-modulated aerocapture are evaluated: a heuristic deceleration profile curve-fit method and a higher-fidelity numeric predictor-corrector algorithm. The accuracy and computational performance of these algorithms is examined in a series of Monte-Carlo simulations of aerocapture missions at Earth, Mars, and Titan. Results indicate that while the deceleration curve-fit method requires minimal amounts of computation time, additional modifications must be made to ensure its robustness to day-of-flight uncertainties. At both low and medium guidance rates, the numeric predictor-corrector algorithm is able to effectively guide drag modulation events in the face of uncertainty.
Development of an Earth Smallsat Flight Test to Demonstrate Viability of Mars Aerocapture

(Georgia Institute of Technology, 2017-01) Werner, Michael S. ; Woollard, Bryce A. ; Tadanki, Anirudh ; Pujari, S. R. ; Braun, Robert D. ; Lock, Robert E. ; Nelessen, Adam P. ; Woolley, Ryan C.

A smallsat mission concept is developed to demonstrate the feasibility of an aerocapture system at Earth. The proposed mission utilizes aerocapture to transfer from a GTO rideshare trajectory to a LEO. Single-event drag modulation is used as a simple means of achieving the control required during the maneuver. Numeric trajectory simulations and Monte Carlo uncertainty analyses are performed to show the robustness of the system to day-of-flight environments and uncertainties. Similar investigations are performed at Mars to show the relevance of the proposed mission concept to potential future applications. The spacecraft design consists of a 24.9 kg vehicle with an attached rigid drag skirt, and features commercially-available hardware to enable flight system construction at a university scale. Results indicate that the proposed design is capable of targeting the desired final orbit, surviving the aerothermodynamic and deceleration environments produced during aerocapture, and downlinking relevant data following the maneuver.
Thermogravimetric Analysis of Carbon Felt Insulation for Flexible Thermal Protection System Thermal Response Modeling

(Georgia Institute of Technology, 2017-01) Rossman, Grant ; Braun, Robert D.

A multi-layered, Flexible Thermal Protection System (FTPS) heatshield configuration layup has previously undergone ground-based testing in an arc-jet facility to simulate atmospheric entry heat exposure. An existing thermal response model has been developed at NASA to simulate heat transfer through an FTPS layup during an arc-jet experiment by predicting measured temperatures between layers. A carbon felt insulator, located in the middle of this FTPS layup, decomposes when exposed to high heating in an atmosphere that contains significant amounts of oxygen. The current module in the FTPS thermal response model that simulates insulator decomposition has not yet leveraged experimentally determined quantities. In an effort to achieve better temperature predictions in the thermal model, a Thermogravimetric Analysis (TGA) experimental campaign was performed on virgin samples of a carbon felt insulator to rigorously characterize decomposition by obtaining its activation energy. Experiments were performed in a zero-moisture air environment using Standard TGA and Modulated TGA methods with a TA Instruments Q5000IR apparatus to obtain estimates of activation energy. The mean activation energy for carbon felt was determined to be 131.56 kJ/mol and 121.16 kJ/mol for Standard and Modulated TGA methods, respectively. Limited TGA testing resources in the past have resulted in rough approximations FTPS insulator activation energy with little knowledge of uncertainty. This TGA experimental campaign also determined the corresponding activation energy uncertainty for carbon felt samples using a t-distribution. The activation energy standard deviation was determined to be 5.79 kJ/mol and 8.66 kJ/mol for Standard and Modulated TGA methods, respectively. The activation energy obtained from the Standard TGA method was inserted into the FTPS thermal response model to compare resulting temperature profile predictions with measured thermocouple temperature data recorded during ground-based arc-jet testing. Preliminary results show significant improvement in thermal response model temperature predictions using this experimentally-determined value for activation energy. This investigation shows promise for a newly developed decomposition module within the FTPS thermal response model based on rigorous experimentation and enables future probabilistic analysis to include activation energy as an uncertain parameter.
Design of a Novel Hypersonic Inflatable Aerodynamic Decelerator for Mars Entry, Descent, and Landing

(Georgia Institute of Technology, 2017-01) Skolnik, Nathaniel ; Kamezawa, Hiromasa ; Li, Lin ; Rossman, Grant A. ; Sforzo, Brandon ; Braun, Robert D.

Entry, descent, and landing (EDL) is especially challenging on Mars because the atmosphere is too thin to provide substantial deceleration, but thick enough to generate significant heating during the reentry phase. As a result, innovative ideas are required to enable future high-mass Mars landing missions. One such promising approach is to use an inflatable aerodynamic decelerator (IAD). Compared with traditional rigid aeroshells, IADs are made of lightweight, flexible materials that can be folded into a smaller volume in the rocket payload fairing and inflated prior to atmospheric entry. Such IADs are able to reduce the ballistic coefficient and peak heating, providing an opportunity to land at higher surface elevations on Mars. Currently, NASA Langley Research Center is investigating the development of Hypersonic Inflatable Aerodynamic Decelerators (HIADs) to enable future large robotic and human exploration missions. Much of the previous work performed on HIADs has focused on symmetric shapes that fly through the atmosphere with ballistic trajectories or trajectories with low lift-to-drag ratios accomplished via CGoffset. The present investigation assesses the technical feasibility of a novel HIAD concept that can vary lift-to-drag ratios between 0.2 and 0.5, is aerodynamically stable between 0.6 km/s and 6.5 km/s, is extensible to aeroshell diameters of 15 to 20 meters, and possesses an approximately smooth outer mold line to avoid localized heating.