Heat Shield Mass Minimization for an Aerocapture Mission to Neptune

Abstract

This paper discusses the sizing of the heat shield of a lifting-body spacecraft, protected by a rigid aeroshell, to minimize its mass for a future aerocapture mission to Neptune. Reducing the heat shield mass is a primary requirement for the mission design because the high expected heat loads can raise the value of its mass fraction to levels that would be unacceptable for the successful execution of the mission. The heat shield is divided into several regions, each of which is characterized by different levels of the entering heat flux. Its mass is minimized by identifying the most suitable materials to be used in the different zones and by determining their minimum thicknesses. To accomplish these tasks, a mapping is established a priori based on a common case treated in the literature. The analysis demonstrates that to minimize the mass for this vehicle, it is necessary to adopt a heat shield composed of different ablative materials that vary depending on the area to be protected. The front part of the spacecraft, near the stagnation point, should be protected exclusively by carbon phenolic, a high-density material, using substantial thicknesses, whereas thinner, lower-density ablative materials should be used to protect the ventral and dorsal regions. The frontal area alone constitutes approximately half of the entire mass of the heat shield while covering less than 10% the total surface.

Coupled versus uncoupled optimal solutions for thermal and dynamic problems in spacecraft atmospheric flight

“…To obtain answers to the research questions described in the introduction, the objective of the study focuses on a more general optimization process. As mentioned, in recent studies (Mazzaracchio and Marchetti, 2012;Mazzaracchio, 2013aMazzaracchio, , 2013b, the author was interested in identifying the optimal combination of trajectories and related heat shield configurations, namely, the locations and thicknesses of the ablative and eventual reusable zone, for some classes of aeroassisted orbital maneuvers. These configurations maximized the payload mass transported by a given spacecraft.…”

“…Even this choice is related to the reduction of the computational load, with a consequent impact at the level of representativity. The optimization of the aeroassisted orbital maneuvers and of the heat shields of space vehicles has been addressed by the author (Mazzaracchio and Marchetti, 2010;Mazzaracchio and Marchetti, 2012;Mazzaracchio, 2013aMazzaracchio, , 2013b) using an original and highly representative model of the heat shields. In the 2010 and 2012 papers, the analysis was conducted by coupling the thermal and dynamic problems, whereas the study was performed with decoupling in the 2013 paper.…”

Feasibility and Performance Analysis of Neptune Aerocapture Using Heritage Blunt Body Aeroshells (Pre-print)

“…Aerocapture studies have historically used a mid lift-to-drag ( / ) vehicle with / of 0.6-0.8 to accommodate the large navigation and atmospheric uncertainties at Uranus and Neptune [15][16][17][18][19]. Aerocapture at Jupiter and Saturn is considered a long-term goal due to the extreme aerothermal conditions during the atmospheric pass.…”