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search.filters.applied.f.advisor: Braun, Robert D. × End date: 2006 × Start date: 2006 × search.filters.applied.f.isOrgUnitOfPublicationTitle: Daniel Guggenheim School of Aerospace Engineering × search.filters.applied.f.isOrgUnitOfPublicationTitle: Space Systems Design Laboratory (SSDL) × search.filters.applied.f.isSeriesOfPublicationTitle: Master's Projects ×

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Now showing 1 - 4 of 4
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Optimal trajectories for soft landing on asteroids

2006-12-15 , Lantoine, Gregory

Robotic exploration of asteroids has been identified by NASA as a major long-term goal. Central to many asteroid missions is a precise soft landing to enable surface exploration or exploitation. This paper describes a technique for computing optimal autonomous controlled trajectories for soft landing in an irregular gravity field of a rotating asteroid. We will first discuss the complexity of the forces that act on the spacecraft during a landing and how we can model them. Then, we will present the numerical method used to solve the optimal control problem, and typical results are shown on case studies at asteroids Vesta and Golevka. In each example, we will identify the best mission design scenarios, as well as some operational difficulties. Finally, we will investigate sensitivity to parameter uncertainties and the implementation of a real-time feedback controller to increase landing accuracy.

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Entry System Design of the Mars Gravity Biosatellite

2006-04-19 , Francis, Scott

The Mars Gravity Biosatellite will be launched to low Earth orbit and will study the effects of partial gravity on mammalian physiology. The entry vehicle will return 15 live mice to the Earth’s surface from low Earth orbit, landing in the Woomera Prohibited Area in central South Australia. This study establishes a baseline for the entry, descent, and landing system through the comparison of various concepts. The Discoverer capsule from the military’s Corona program of the 1950’s and 60’s is chosen over other concepts as the baseline aeroshell after an analysis of static stability and payload requirements for this mission. A nominal trajectory is developed based on science requirements, the safety of the mice, and payload recovery requirements. A sensitivity study is performed on the entry trajectory to determine the effects various parameters have on the nominal entry and a Monte Carlo dispersion analysis is used to establish a 3-σ landing ellipse, which fits within the boundaries of the Woomera Prohibited Area. A discussion of potential de-orbit propulsive devices is given in relation to the required de-orbit ∆V. A 16 m parachute is chosen as the baseline due to the resulting 4.8 m/s ground impact velocity and a crushable aluminum foam is chosen as a means to attenuate the shock of ground impact.

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An Evaluation of Ballute Entry Systems for Lunar Return Missions

2006-05-07 , Clark, Ian G.

A study was undertaken to assess the advantages and feasibility of using ballutes for Earth entry at lunar return velocities. Using analysis methods suitable for conceptual design, multiple entry strategies were investigated. Entries that jettison the ballute after achieving orbit were shown to reduce heating rates to within reusable thermal protection system limits and deceleration was mitigated to approximately four g’s when a moderate amount of lift was applied post-jettison. Ballute size drivers were demonstrated to be the thermal limitations and areal densities of the ballute material. Performance requirements for both of those metrics were generated over a range of total ballute system masses.

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Mars Entry, Descent and Landing Parametric Trades

2006-05-01 , Wells, Grant

The purpose of this investigation is to begin forming a dataset to be the basis of a Mars entry, descent and landing mission design handbook for planetary probes. The premise of the project is that Mars entry, descent and landing can be parameterized with five variables: (1) entry mass, (2) entry velocity, (3) entry flight path angle, (4) vehicle aeroshell diameter, and (5) vertical lift-to-drag ratio. For combinations of these input parameters, the following trajectory information will be determined: peak deceleration, peak heat rate, heat load, and the altitude at which Mach 2 is reached (for parachute deployment).

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