A Stellar Drop Campaign for Team SILOE

SILOE, an acronym for 'Surface Investigation in Low Gravity Environment', is a project that aims to examine the influence of gravity on surface dynamics. To this end, the project seeks to estimate the bearing capacity of different granular materials that can be found on planetary surfaces or asteroids in Lunar and Martian gravity conditions and vacuum environments. The experimental setup, conceived by five students of ISAE-SUPAERO (Toulouse, France), entailed the release of a spherical projectile onto a variety of materials, including quartz sand and a lunar regolith simulant, within a vacuum chamber. The design and construction of the vacuum chamber constituted the most challenging aspect of the project, as it required the creation of a hermetically sealed environment that precluded the entry of air following the disconnection of the vacuum pump. This was imperative for the maintenance of a vacuum condition throughout the experiment.

The experiment was selected in January 2024 to be part of the ESA Academy Experiments Programme. The experiment, with the configuration previously detailed, was subjected to testing in the GraviTower, utilising the Mars and Moon gravity modes at the Drop Towers facility (Bremen, Germany) in early December.

The drop campaign at ZARM, Bremen, lasted two weeks, with the first week dedicated to the preparation of the experiment, outgassing of the different materials and additional functional tests. By the end of the first week, the experiment had been mounted in ZARM's capsule, and the coding of the release mechanism had been integrated into ZARM's software. This was done to ensure that the projectile would be released at the correct moment in the capsule's trajectory, i.e. at the correct gravity level. During the second week, all drop tests in Lunar and Martian gravity were performed. In the case of Martian gravity, the experimenters were also granted the opportunity to utilise a newly developed mode of the GraviTower. 

Following a series of 65 drops in a low-gravity environment, the team extracted their experiment from the capsule and returned to their university. There, they will proceed to analyse the data, which includes video analysis of each drop, and prepare scientific publications.