Feasibility Study of Balloon-type Atmospheric Entry Probe for Titan

Paper number

IAC-11,A3,5,15,x11417

Author

Dr. Daisuke Akita, Tokyo Institute of Technology, Japan

Year

2011

Abstract

Balloons are attractive planetary exploration systems in that they can achieve both larger area observations than those achieved by rovers and higher resolution surface observations than those achieved by orbiters. Balloons can also provide wind distribution data by simply tracking the flight trajectory. In particular, balloons are appropriate for explorations of planets or moons that have a dense atmosphere, for example, Venus or Titan. However, some difficult operations, namely, multistage parachute deployments/separations, heat shield jettison, and balloon deployment/inflation, need to be performed during the atmospheric entry for planetary balloons. 

	Therefore, the author considers a planetary balloon system that is inflated in orbit around the planets or moons before the atmospheric entry. The balloon is inflated using He gas stored in the orbiter and then is separated from the orbiter. The inflated balloon is decelerated by the aerodynamic drag and then floats at a balanced altitude without the need for performing the abovementioned difficult operations during the atmospheric entry. The balloon system has the following advantages. (1) The abovementioned difficult operations are not required to be performed during the atmospheric entry. (2) Because the inflated balloon has a low ballistic coefficient, the balloon can deorbit by utilizing the aerodynamic drag rather than by using a rocket motor or a strong spring system. (3) The peak aerodynamic heating during the atmospheric entry will reduce owing to the low ballistic coefficient of the balloon-type entry probe.

	In this study, the feasibility of a balloon-type atmospheric entry probe for Titan is investigated by performing trajectory calculations for various balloon diameters and payload masses. The balloon is assumed to have a spherical shape. Therefore, the aerodynamic characteristics of the balloon do not depend on its attitude and are easy to estimate. The feasibility study focuses on (1) the tensile strength of the balloon material against the internal pressure, (2) the heat resistance of the balloon material against the aerodynamic heating, (3) the structural strength of the balloon against the dynamic pressure and the inertial force generated because of the deceleration of the balloon, and (4) the flight characteristics required for the stable floating of the balloon at a designed altitude. The results show that relatively small balloons can meet the abovementioned four minimum requirements. Although a single small balloon cannot carry a heavy payload, many small balloons can be used for simple distributed observations.

Abstract document

IAC-11,A3,5,15,x11417.brief.pdf

Manuscript document

IAC-11,A3,5,15,x11417.pdf (🔒 authorized access only).

To get the manuscript, please contact IAF Secretariat.