As part of my engineering portfolio this page present a talk given at ASTRA'2000 about the Windball concept. At this time I was working as research assistant at the Autonomous System Lab at EPFL.

This talk had two goals : proposing an innovative locomotion concept for martian exploration and promoting use of SMA actuation in space engineering.

Researchs to validate this concept including modelizations and wind tunnel tests were realized by Moritz von Heimendahl as part his undergraduate semester projects.

As far as I know this activity stopped after my departure of the lab.


Innovative Locomotion Concept for Long-Range Mission and Study of Martian Wind

T. Estier, R. Siegwart
EPFL (Swiss Federal Institute of Technology Lausanne)
DMT-ISR, 1015 Lausanne, Switzerland
E-mail :
phone : +41 21 693 38 85

Keywords : locomotion concept, planetary exploration, SMA actuators, Mars wind study

On Mars, wind, storms and dust devils are a frequent phenomena due to the instability of the atmosphere. This creates an aggressive environment, but offers also an important opportunity as a source of energy, even at the low Martian atmospheric pressure (during typical conditions, dynamic pressure at the maximum likely wind velocity of 30 m/sec would be 10 N/m2).

A wind propelled robotics system, which would not consume any other energy for its locomotion, could significantly increase the range and the length of exploration missions. In this case, the small amount of available solar energy could be used almost exclusively for payload operation and communication. The robot system has no long-term energy storage requirements, thus avoiding the problem of low-temperature energy storage. Another source of energy produced by the Martian environment is the large temperature variation between night and day (130° K to as high as 300° K, with a mean of 215° K) which can be used to directly activate Shape Memory Alloy (SMA) actuators.

The robotic system proposed in this paper is composed of a central payload connected to a spherical wire structure made up of SMA micro-actuators, enabling a complete morphological phase change based on ambient temperature. Its mission objective is the study of wind and storm effects near the surface by virtue of its trajectory. Simultaneously, the system provides long-term mobility for a few 100 grams payload, thereby offering the opportunity to explore the Martian surface on a very large scale.

Its operational cycle is composed of two distinct phases. During the night, at low temperature, the external structure is deployed around the payload and offers maximal resistance to the wind. This constitutes its motion configuration and the system is simply propelled by the wind. During the day, the high temperatures transition change the robot to a configuration that reduces drastically the wind effects and that brings the payload in contact with the ground. Under this configuration, the robot is stationary. It recharges its batteries using the solar panels covering the payload, performs atmospheric and ground measurements, is identified and localized by an orbiter and finally transmits the collected data to the orbiter.


Start online presentation or download it as pdf file. (4.2 MB!)

Table of contents


This conceptual study was followed by two reports (unpublished) produced by Moritz von Heimendahl as results of his semester projects (undergraduate research projects):