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Title:Assessment of hypersonic separation dynamics for drag modulation entry systems at Mars
Author(s):McClary, Michelle
Advisor(s):Putnam, Zachary R
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Discrete-Event Drag Modulation
Drag Modulation Separation Dynamics
Drag Modulation Recontact Analysis
Abstract:This thesis presents an analysis of the hypersonic separation dynamics for a drag modulation entry system, consisting of a planetary entry vehicle and deployable drag area, that performs a jettison event during planetary entry or aerocapture. The entry vehicle is modeled as a blunted spherecone and the deployable drag area is modeled as a conical frustum. Hypersonic aerodynamic coefficients are obtained with Newtonian Aerodynamics. The first portion of the thesis identifies separation times for a range of vehicle parameters and flight conditions which includes vehicle size, drag area size, and jettison velocity. For a given entry trajectory, a minimum separation time is found for a jettison velocity that corresponds to maximum dynamic pressure. Results show that entry vehicles with a larger initial ballistic coefficient will require less time to achieve a separation distance of one drag area aft radius in addition to a smaller range of separation times over possible jettison conditions. The second portion of this work determines if recontact occurs between the two bodies after jettison and explores the affect of applying an impulse to the drag area at jettison to improve jettison performance. Emphasis is placed on determining what flight conditions lead to a recontact-free jettison event and, for jettison events that are not successful, how large of an impulse must be applied to prevent recontact. Results indicate recontact is most likely to occur at jettison conditions with low dynamic pressures and an impulse is required when jettison occurs with large angle of attack and angle of attack rates in conjunction with small differences in ballistic coefficient between the entry vehicle and drag area. Sensitivity analysis is performed to determine which conditions are most important to the success of the jettison event. Results show that the difference in ballistic coefficient between entry vehicle and drag area is the most influential parameter in determining the recontact-free jettison envelope. This envelope can be manipulated through moving the drag area center of gravity off of the axis of symmetry. Overall, results indicate a successful jettison, with no recontact, is possible and likely for typical blunt body spherecone entry trajectories and attitude dynamics. Minimizing the chance of recontact for entry trajectories can be achieved through a jettison event closer to maximum dynamic pressure which will also reduce the time to separate.
Issue Date:2020-07-21
Type:Thesis
URI:http://hdl.handle.net/2142/108498
Rights Information:Copyright 2020 Michelle McClary and Dr. Zachary Putnam
Date Available in IDEALS:2020-10-07
Date Deposited:2020-08


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