A simulation platform for small solar system bodies' gravity using the Einstein-Elevator

Small solar system bodies (SSSBs), which, in this study, are defined primarily as asteroids and comets, are becoming increasingly important as more data have become available for their study. Their significance is also highlighted by missions such as NASA's "Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer" (OSIRIS-REx), or ESA's Rosetta. However, the study of the characteristics and behavior of these objects on Earth is a challenge, as the simulation of their environmental conditions is difficult. We present in this paper an approach to enable the gravity simulation of SSSBs, such as comets or asteroids, in a drop tower facility on Earth, which is being addressed as part of the AKUS ("Activity of Comets under Partial Gravity") project. This especially concerns gravity levels between 10-2 and 10-4g, where the duration of the adjusted acceleration ranges from 2.5 to 3.2 s. In order to simulate the conditions of SSSB as accurately as possible, an acceleration system based on servo motors and spindle axes has been developed. The accelerations are transferred from the motors to the spindle axes containing a comet-like sample. The current dimensions of the total load (including sample, sample holder, data- and communication box) are 315 × 160 × 331 mm3 (w × d × h), with a total weight of ∼15 kg. These are together placed inside a vacuum chamber providing a vacuum quality of 10-6 mbar. The whole setup is installed inside the Einstein-Elevator. Our results show that, with the current setup, we are able to generate conditions from 10-2g down to 10-3g. The maximum deviations under these conditions are ±5 · 10-4g. At 10-2g, the duration of the experiment is at least 2.5 s limited by the travel distance of the used spindle axes, whereas at 10-4g, a minimum duration of 3.5 s is planned. Moreover, the experiments can be conducted under vacuum conditions of 10-6 mbar. The results in this paper serve as a proof of concept for the generation and control of adjustable gravity levels for future SSSB experiments.