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Daniel Guggenheim School of Aerospace Engineering

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search.filters.applied.f.advisor: Braun, Robert D. × End date: 2017 × Start date: 2017 × Item Type: Publication ×

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Use of the Mars atmosphere to improve the performance of supersonic retropropulsion

2017-05-23 , Gonyea, Keir C.

NASA has landed seven vehicles on the surface of Mars using parachutes for supersonic descent. These parachutes are unsuited to future high mass missions due to inflation, drag, and aerothermodynamic complications. Supersonic retropropulsion is a candidate technology to replace supersonic parachutes, but is hindered by its large associated propellant mass. Atmospheric-breathing propulsion systems may reduce this mass constraint by ingesting oxidizer from the surrounding atmosphere. However, the Martian atmosphere, which is composed of primarily carbon dioxide, necessitates that metal fuels be used in order to combust the available oxidizer. This thesis advances the state of the art of atmospheric-breathing supersonic retropropulsion (ABSRP) by providing the first exploration into the feasibility and potential performance of ABSRP as a technology solution for high-mass Mars missions. Specific advancements include the development of modeling methods and tools, the evaluation of conceptual ABSRP performance and sensitivities, and the formulation of vehicle concepts. Model development targeted components and subsystems most relevant to ABSRP in order to capture the necessary physics and provide a preliminary integrated vehicle simulation for future conceptual design efforts. Models were developed to assess metal – CO2 combustion performance and sensitivity to both the engine design and operating regime. These tools include an equilibrium combustion simulation to evaluate engine efficiency, a finite-rate kinetics simulation to investigate the time-dependent phenomena, and a particle burning simulation to assess diffusion effects. Case studies are presented for ABSRP relevant mixtures and conditions to predict propulsion performance of the ABSRP engine across a range of conditions and verify that reasonably sized combustion chambers can provide complete combustion of the propellant. Exploration of the performance results indicate that ABSRP systems have promising propulsive performance relative to comparative rocket systems and do not have unacceptable burning timescale constraints. The propulsion system results are used in an ABSRP vehicle model, which accounts for the variable engine performance across different flight regimes. This model is used to search the design space and determine the performance and sensitivity of multiple proposed ABSRP vehicle concepts relative to competing propulsive solutions. The investigation includes an assessment of feasible and unfeasible regions of the design space in addition to design trends for optimal configurations. Mass favorable vehicles of multiple architectures are compared to understand their relative performance. Vehicle architectures involving ABSRP are seen to have optimal mass performance, which demonstrates the potential applicability of atmospheric-breathing propulsion for Mars descent.

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Development of an Earth SmallSat Flight Test to Demonstrate Viability of Mars Aerocapture

2017-05-01 , Werner, Michael S.

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. Low- and high-fidelity guidance algorithm choices are considered. 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

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Trajectory Trade-space Design for Robotic Entry at Titan

2017-05-01 , Roelke, Evan

In recent years, scientific focus has emphasized other ocean worlds such as Europa, Enceladus, and Titan, due to their potential for harboring life. The only spacecraft ever to land on these moons was the Huygens Probe in 2005; however, this probe’s main purpose was to study the atmosphere and surface of Titan, with no real landing target. Future missions to other ocean worlds would likely require a science target and thus add several constraints to the mission such as arrival time, entry state, and aeroshell geometry, among others. Of the three ocean worlds previously mentioned, Titan is an optimal target for initial mission concepts for several reasons. The atmospheric composition, winds, and surface features are well studied by Cassini and the Huygens Probe. Additionally, of the aforementioned moons, Titan does not have a thick ice sheet to penetrate in order to sample the surface and/or liquid seas, enabling such mission to double as a stepping stone for missions to other ocean worlds. Finally, Titan exhibits a myriad of interesting planetary features that, if studied, could further the understanding of both Titan’s and the solar system’s geologic history. In this paper we analyze the trade-spaces of various important parameters involved in Entry, Descent, and Landing (EDL) as it pertains to robotic missions for Titan in order to provide a guideline for optimizing a mission’s system parameters while minimizing both system complexity and the landing footprint. It is found that the ideal geometry is a ballistic spherecone body entering from orbit to allow flexibility in the entry state vector. The aerothermodynamic environment is most affected by the entry velocity and the vehicle bluntness ratio, while the peak deceleration is most influenced by the entry velocity and entry flight path angle. In addition, multiple parachutes decrease the landing footprint, impact speed, and descent time compared to single parachute systems, at the expense of being more complex. Larger ballistic coefficients decrease the landing footprint and descent time while increasing the impact speed. Finally, it is discovered that the uncertainty in the entry altitude and flight path angle have the most impact on the final state vector.

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