Feasibility Assessment of Nonstop Mars Sample Return System

Abstract

Feasibility assessment of a Mars Aeroflyby Sample Collection (MASC) system for JAXA’s future Martian exploration has been conducted. In the mission scenario, the vehicle enters the Martian atmosphere, collects the Martian dust and atmosphere during the atmospheric flight, exits the Martian atmosphere, and is inserted into a parking orbit from which the return system is departed for the earth. To design aeroshell appropriate for this mission, a parametric study of aeroshells having large ballistic coefficient and moderate lift-to-drag ratio is made. Finally, a baseline design of the aeroshell in sphere-cone form is selected for the MASC system. In order to validate the aerodynamic coefficients, hypersonic wind tunnel tests and CFD analysis are conducted. I. Introduction Mars Exploration with Landers and Orbiters (MELOS) mission has come under review in Japan Aerospace Exploration Agency (JAXA) together with a lot of planetary scientific groups all over Japan. Mars orbiters for aeronomy and meteorology, 2-4 Mars landers for geoscience, and sample return systems are currently proposed, so that the next Mars exploration is expected to be a conglomerate mission, enjoying enhanced launch capability of the H-IIB rocket. In the early study of the mission design, the orbiters and the landers are transported altogether to Mars and inserted into an extended elliptic orbit, after which the orbiters are separated and maneuvered to their respective final orbits while the landers are ejected and flown into the Mars atmosphere. A A Mars sample return mission, in which a lander touches down the Mars ground, collects samples, lifts off, and returns to the earth, requires a huge exploration system since a large amount of propellant for orbital maneuver and lift-off is necessary. Instead, a nonstop Mars sample return mission using the aerocapture technologies has been considered. A schematic illustration of the orbital design in this “Mars Aeroflyby Sample Collection” is shown in Fig.1. It is known that micro-scale sand particles, or dust, are widespread in the Martian atmosphere up to the altitude of 35-40 km above the ground. If the spacecraft is made to flyby at these altitudes without touch-down, and to be inserted into the parking orbit by the aerocapture technique for the purpose of realizing an accurate interplanetary orbital maneuver to earth, the mission feasibility is expected to be considerably increased. According to Fujita’s analysis, 6 in order to reach altitudes below 40 km and an elliptic orbit with 150 x 3,000 km altitude from the primary elliptic orbit, the ballistic coefficient of the entry system should be greater than 700 kg/m 2 . In addition, in order to realize a broad aerocapture corridor, appropriate modulation of the L/D between -0.3 and 0.3 during the atmospheric flight is required. Therefore, in this study, parametric study is performed in order to propose the aeroshell shape to satisfy the desirable lift-to-drag ratio and ballistic coefficient. Next, wind tunnel tests and CFD calculation are carried out for the validation of the candidate aeroshell shape.