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Daniel Guggenheim School of Aerospace Engineering

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Now showing 1 - 10 of 35
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Flyby Trajectory Analysis and Thermal Simulation of a Venus Atmospheric Probe

2017-12-01 , Selvaratnam, Roshan

Cupid’s Arrow is a proposed interplanetary Venus mission aimed at sampling the noble gases in its atmosphere. These inert elements can provide an insight into the history of the planet’s formation and provide a reference for comparison with the Earth. The mission is comprised of a mothership and an atmospheric sample collection probe. This study is focused on the latter which will be deployed into Venus’ atmosphere and descend to an altitude of 120 km. The thermal environment of the Venusian exosphere is the primary driver of the probe design both in terms of its structure and material composition. The mission architecture being considered for this study takes advantage of a gravity assist flyby trajectory. The probe will be dropped off as a secondary payload en route to the spacecraft’s primary destination. The entry conditions at Venus and the trajectory of the probe relative to the mothership were determined using 2-body orbital mechanics. Using planar equations of motion, the probe’s entry into Venus’ atmosphere was simulated to predict the thermal environment that it would encounter. Initial results show a peak heat rate of approximately 220.3297 W/cm2 , a peak deceleration of 2.7654 Earth g’s and a total heat load of 15535 J/cm2 . The results of the thermal environment model and relative trajectory analysis were used to validate the baseline communications and TPS design. In addition to Venus, this mission concept could be used to explore other planetary atmospheres, especially those frequented by interplanetary flybys.

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Real-Time Hardware-in-the-Loop Hand-Off from a Finder Scope to a Larger Telescope

2017-11 , Aguilar-Marsillach, Daniel , Virani, Shahzad , Holzinger, Marcus J.

Electro-optical sensors play an increasingly important role in the SSA domain for tracking satellites and debris objects. Such sensors provide data that complement other methods, like radar based sensing, by providing a higher angular resolution, and thus improving the estimation of an object’s orbit, attitude and physical properties. The acquisition of such data is invaluable for obtaining more accurate collision risk assessments and formulating improved debris mitigation efforts. The Georgia Tech - Space Object Research Telescope aims to improve detection and tracking for agile Raven-class telescopes with narrow fields of view and high angular resolutions. A secondary imaging system was used to correct the Georgia Tech - Space Object Research Telescope’s pointing errors for tracking objects at high angular rates using a closed-loop controller. This paper will focus on the development and results of a real-time hardware-in-the-loop hand-off from a finder scope to a larger telescope.

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Advancing Supersonic Retropropulsion Using Mars-Relevant Flight Data: An Overview

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.

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State Machine Fault Protection for Autonomous Proximity Operations

2017-09 , Schulte, Peter Z. , Spencer, David A.

The capability to recover gracefully from hardware or software faults is critical for many aerospace applications. This is particularly true for missions involving proximity operations, where multiple vehicles are operating at close range. Previous proximity operations missions have experienced faults that resulted in a failure to meet mission objectives. Fault protection systems are used to detect, identify the location of, and recover from faults. Typically, aerospace systems use a rule-based paradigm for fault protection, where telemetry values are monitored against logical statements such as static upper and lower limits. The model-based paradigm allows more complex decision logic to be used. The state machine approach for model-based fault protection has been explored by industry but has not yet been widely adopted for aerospace applications. This study focuses on fault protection for the Guidance, Navigation, and Control vehicle subsystem, which is essential for any aerospace vehicle and has many complex and interrelated hardware and software components. Two separate case studies have been analyzed through this work, one for atmospheric flight and one for space flight. The first case involves detecting hardware faults on an unmanned aerial vehicle used for aerial surveying and mapping and is addressed in a previous paper. The second case is the focus of this paper and involves automated proximity operations during approach and capture of the orbiting sample canister for a Mars Sample Return mission. For each case study, high-level failure modes are identified and linked to individual root cause events via fault tree analysis. The results of the fault tree analyses are developed into a generic and modular state machine fault protection architecture. This architecture will apply to a wide variety of aerospace applications and contains components that can be rearranged, added, or removed easily. The architecture facilitates export of the state machine logic to flight software via autocoding or other methods.

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Solar Activity Investigation (SAI): A 6U CubeSat Mission Concept

2017-12 , Murphy, Neil , Jefferies, Stuart , Fleck, Bernhard , Berrilli, Francesco , Velli, Marco , Lightsey, E. Glenn , Gizon, Laurent , Braun, Doug

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Feasibility of Supersonic Retropropulsion Based on Assessment of Mars-Relevant Flight Data

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.

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A Passively Stable Pyramid Sail for the Deorbit of Small Satellite Constellations

2017-09 , Long, Alexandra C. , Spencer, David A.

Several commercial organizations are developing plans to launch thousands of small satellites into Low Earth Orbit at altitudes ranging from 1,000-1,350 km, with the goal of providing global internet service. There is a clear need to deorbit these satellites at the end of their operational lifetime, in order to preserve the utility of high- value orbit regimes. Without a system to accelerate deorbit, the 150 kg-class satellites would take over 100 years to reenter the atmosphere. A standardized, bolt-on system is being developed to address the deorbit problem for microsatellites. The Passively Stable Pyramid Sail ([PS]2) is a thin-membrane drag sail with the geometry selected to establish aerodynamic stability. The system is capable of deorbiting small satellites from the planned constellation orbit altitudes within 25 years regardless of the operability of the host satellite. A design requirement of the drag device is that it will aerodynamically trim to a maximum drag attitude in the upper atmosphere, in order to accelerate the deorbit timeline. A stability analysis was conducted to evaluate possible geometries, and it was determined that the drag sail should have a square pyramid shape with an apex half-angle of 75°. For a 150 kg satellite at an altitude of 1,100 km, the system is designed to have a base area of 125 m2, which requires 8 meter long booms. The mass and stowed volume of the device are designed to be consistent with the 6U CubeSat standard. A 1/10 scale prototype of the [PS]2 system was selected for launch through the United Launch Alliance STEM CubeSat program. The mission, called the Aerodynamic Deorbit Experiment, will demonstrate the [PS]2 design from a 1U CubeSat platform. The system will have four 0.8 m long composite booms, and four triangular sail quadrants made of transparent CP1 material. This paper will provide an overview of the [PS]2 system, describe the design of the deployment system, and discuss the results of prototype testing.

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Judicial Evidential Reasoning for Decision Support Applied to Orbit Insertion Failure

2017-11 , Jaunzemis, Andris D. , Minotra, Dev , Holzinger, Marcus J. , Feigh, Karen M. , Chan, Moses W. , Shenoy, Prakash P.

Realistic decision-making often occurs with insufficient time to gather all possible evidence before a decision must be rendered, requiring an efficient process for prioritizing between potential action sequences. This work aims to develop a decision support system for tasking sensor networks to gather evidence to resolve hypotheses in the face of ambiguous, incomplete, and uncertain evidence. Studies have shown that decision-makers demonstrate several biases in decisions involving probability judgement, so decision-makers must be confident that the evidence-based hypothesis resolution is strong and impartial before declaring an anomaly or reacting to a conjunction analysis. Providing decision-makers with the ability to estimate uncertainty and ambiguity in knowledge has been shown to augment effectiveness. The proposed framework, judicial evidential reasoning (JER), frames decision-maker questions as rigorously testable hypotheses and employs an alternating-agent minimax optimization on belief in the null proposition. This approach values impartiality in addition to time efficiency: an ideal action sequence gathers evidence to quickly resolve hypotheses while guarding against bias. JER applies the Dempster-Shafer theory of belief functions to model knowledge about hypotheses and quantify ambiguity, and adversarial optimization techniques are used to make many-hypothesis resolution computationally tractable. This work includes derivation and application of the JER formulation to a GTO insertion maneuver anomaly scenario.

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Empirical Dynamic Data Driven Detection Tracking Using Detectionless and Traditional FiSSt Methods

2017-09 , Virani, Shahzad , Murphy, Timothy S. , Holzinger, Marcus J. , Jones, Brandon A.

Autonomous search and recovery of resident space object (RSO) tracks is crucial for decision makers in SSA. This paper leverages dynamic data driven approaches to improve methodologies used in real-time detection and tracking of RSOs with a low signal-to-noise ratio (SNR). Detected RSOs are assigned to be tracked using one of two simultaneously operating algorithms. The Gaussian Mixture Proability Hypothesis Density (GM-PHD) filter tracks all RSOs above a certain SNR threshold, while a Detectionless Multi-Bernoulli filter (D-MB) detects and tracks low SNR objects. The D-MB filter uses matched filtering for likelihood computation which is highly non-Gaussian for dim objects. Hence, the D-MB filter is particle based which leads to higher computational complexity. The primary idea proposed in this paper is to balance the computational efficiency of GM-PHD and high sensitivity of the D-MB likelihood computation by dynamically switching tracks between the two filters based on the SNR of the target; allowing for real-time detection and tracking. These algorithms are implemented and tested on real data of objects in the geostationary (GEO) belt using a wide field-of-view camera (18.2 degrees). A star tracking mount is used to inertially stare at the GEO belt and data are collected for 2 hours corresponding to RSOs being observed in 48.2 degrees of the GEO belt.

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Mars Molniya Orbit Atmospheric Resource Mining

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.

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