Sizing of an Entry, Descent, and Landing System for Human Mars Exploration

Abstract

masses on the order of 40 to 80 metric tons. 2 This will involve landing approximately two orders of magnitude more mass on the Martian surface in a single landing than has been achieved to date.Such a task is not to be taken lightly.Indeed, among the most difficult tasks in any mission to the Martian surface is Entry, Descent, and Landing (EDL).The EDL systems proposed in this paper are designed to be capable of landing human-class payloads on Mars.Restrictions placed on the vehicle (such as deceleration limits) make these systems suitable for crewed descent, although they could also be configured to deliver cargo.This study includes the examination of a number of possible descent scenarios, sequences, and trajectories in conjunction with the required hardware.Using an Apollo-like capsule (blunt body with sidewall angle of 32º) and assuming a conservative atmosphere as a baseline, this study performs two sweeps of vehicle mass and size for each scenario: one at an angle of attack of -21.7º (hypersonic liftto-drag ratio of 0.3) and one at an angle of attack of -40.8º (hypersonic lift-to-drag ratio of 0.5).This information is employed to size the EDL system with the objective of achieving the greatest landed mass for a given entry mass.Here, analysis focuses on sizing of the ablative thermal protection system, aeroshell, parachute system, propulsion system (including tanks and engine), reaction control system and other subsystems.The study is concluded by placing these findings in context of proposed human Mars architectures and the Vision for Space Exploration.While most estimates place the first human mission to Mars more than 25 years in the future, there is a serious need to begin work today.Knowledge gained now may be leveraged to guide robotic precursors, maximize the return from lunar testing, and improve current human Mars mission concepts. II. Overview of Martian Environment A. Atmosphere ModelThe atmospheric density on Mars varies significantly with season, dust content, position (latitude), and time of day.These parameters were randomly varied for 1000 cases using Mars-GRAM 2005 in order to create atmosphere profiles.Mars-GRAM is a widely used Mars atmospheric model which uses the MOLA (Mars Orbiter Laser Altimeter) reference altitude, measured from data collected on the Mars Global Surveyor spacecraft.Cumulative distribution functions of density were constructed for each altitude from -8 km to 152 km MOLA.The density at the 30% point for the 0 km cumulative distribution function was chosen.Using this 0 km 30% value, the atmosphere with the lowest 4 km density was baslined.This atmosphere satisfies hydrostatic equilibrium, resulting in a realistic and conservative atmosphere.The resulting density profile gives a MOLA 0 km density of 0.012439 kg/m³.Approximately 70% of the atmospheric density profiles simulated had a higher 0 km density.This baseline density profile is shown in Figure 1.