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Title:Optimal lift and drag modulation hypersonic control options for high ballistic coefficient entry vehicles at Mars
Author(s):Richardson, Nicklaus O.
Advisor(s):Putnam, Zachary R.
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Hypersonic control
entry, descent, and landing
optimal control
Abstract:Future Mars entry, descent, and landing (EDL) missions will require larger mass vehicles and payloads, especially if humans are to land on the surface. Current Mars EDL technology relies heavily on Viking-era supersonic parachutes that are approaching their landed mass limits; however, supersonic retropropulsion (SRP) is a promising replacement for parachutes. Minimizing the propellant mass fraction (PMF) for SRP would enable larger payload masses. Maximizing the terminal descent initiation (TDI) altitude is also an important parameter for parachute deployment systems. The ability of different control methods, lift-only, drag-only, and both lift-and-drag control, to separately maximize TDI altitude and minimize PMF was assessed and compared over a range of entry conditions. Results show optimal control profiles that were always bang-bang with similar profiles for both cost functions. The number of switches that was optimal at a given entry state had a strong, direct relationship to entry flight-path angle with at most two-switches for lift control and at most four switches for drag control. Drag-only control was found to be better than lift-only control at steep entry flight path angles while lift-and-drag control was better than either at shallow entry flight-path angles. Adding drag control to lift-only systems was found to reduce PMF by approximately 40% across ballistic coefficients of 300 kg/m2 to 600 kg/m2 and entry velocities between 5 to 7 km/s. The set of feasible TDI states of each control method was assessed by linking the set of reachable TDI states from the hypersonic flight phase to the set of controllable TDI states from the propulsive descent phase. Increased controllability of lift-and-drag control and larger ballistic coefficients for drag control increases the size of the intersection of these two sets.
Issue Date:2019-04-26
Rights Information:Copyright 2019 Nicklaus Richardson
Date Available in IDEALS:2019-08-23
Date Deposited:2019-05

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