Gunter H. Just

In-orbit servicing (IOS) is rapidly emerging as a transformative solution to enhance the longevity, sustainability, and cost-effectiveness of space assets, and the need for high levels of onboard guidance, navigation \& control (GNC) autonomy is the main focus of current research in the field. To meet these demands, artificial intelligence (AI) is increasingly being integrated into spacecraft GNC systems. In particular, Reinforcement Learning (RL) has gained traction for its capacity to learn control policies through interaction with the environment, without requiring full knowledge of system dynamics. The work focuses on the hardware-in-the-loop (HIL) verification of a deep reinforcement learning agent for trajectory optimization, trained for autonomous proximity operations targeting an uncooperative object and focusing on its 3D reconstruction and mapping, coupled with a model predictive controller to track the generated guidance and enforce compliance with the constraints. The testing campaign is conducted at the Orbital Robotics Lab of the European Space Agency, using the REACSA floating platform with a camera mounted on-board for image acquisition and a mockup representative of a GEO-satellite, in the ORBIT flat floor facility, setup to recreate the space environment with a sunlamp functioning as light source.This work demonstrates the feasibility and value of hardware-in-the-loop testing for AI-driven spacecraft guidance systems to bridge the gap between simulation and flight. This approach is a key step toward safe, autonomous proximity operations in future in-orbit servicing missions.

This paper investigates the penetration performance of soil‐burrowing probes with different tip designs during shallow‐depth penetration in various media, including terrestrial soils (Hostun sand) and well‐characterized planetary soil simulants (LHS‐1 Lunar regolith simulant and MGS‐1 Martian regolith simulant). The analysis evaluates performance based on the pressure required to successfully penetrate the soil, comparing a conical tip design (i.e., the traditional tip design of penetrometers) with a plant root‐inspired design. For each soil type, three different levels of soil compaction were considered to verify how initial soil porosity affects penetration performance. The study involves both experimental and numerical analyses. Experimentally, penetration tests were conducted in chambers filled with Hostun sand, LHS‐1, and MGS‐1. Numerically, a three‐dimensional Discrete Element Model was developed to simulate probe penetration in soil packings with geomechanical properties of Hostun sand, LHS‐1, and MGS‐1, respectively. In accordance with the experimental findings, the modeling results show significant advantages of the plant root‐inspired tip design over the conical tip. Indeed, the plant root‐inspired design encountered lower soil resistance pressure during penetration across all soil types and compaction levels: the arithmetic mean values of the pressure reductions associated with the use of the bioinspired tip design resulted 25.5% experimentally and 25.4% numerically compared with the non‐bioinspired tip.

This paper presents the concept of a radiofrequency (RF) sensor designed to estimate the mass of the regolith acquired by a sampling device or excavator in planetary environments. The sensor utilizes a microstrip line with an open end as the sensing element, with the mass estimation based on measurements of the phase of the reflection coefficient (S11 of the scattering matrix) for the line immersed in the regolith. The Rotary Clamshell Excavator (RCE) was employed for the experimental evaluation of the sensor’s performance. The RCE successfully passed an environmental test campaign, demonstrating its suitability for future lunar missions. The test results indicate that the RF sensor can estimate the mass of the acquired regolith with reasonable accuracy, approximately 15%, making it a viable solution for rough mass estimation in sampling devices and excavators.

Establishing a permanent human presence on the Moon or Mars requires a secure supply of oxygen for life support and refueling. The electrolysis of water has attracted significant attention in this regard as water-ice may exist on both the Moon and Mars. However, to date there has been no study examining how the lower gravitational fields on the Moon and Mars might affect gas-evolving electrolysis when compared to terrestrial conditions. Herein we provide experimental data on the effects of gravitational fields on water electrolysis from 0.166 g (lunar gravity) to 8 g (eight times the Earth’s gravity) and show that electrolytic oxygen production is reduced by around 11% under lunar gravity with our system compared to operation at 1 g. Moreover, our results indicate that electrolytic data collected using less resource-intensive ground-based experiments at elevated gravity (>1 g) may be extrapolated to gravitational levels below 1 g.

Future sustained human presence on the Moon will require us to make use of lunar resources. This in‐situ resource utilisation (ISRU) process will require suitable feedstock (i.e., lunar regolith) that has been both acquired and prepared (or beneficiated) to set standards. Acquisition of pre‐processed regolith, is an often overlooked engineering challenge in the demanding and low‐gravity environment of the lunar surface. Currently, regolith excavation and size separation are often developed independently of each other. Here, we present the Lunar Excavation and Size Separation System (LES³), which is an engineered one‐system solution to combine the acquisition of lunar regolith as well as separate it into two distinct size fractions, and therefore, can assist to define the quality of the feedstock material for ISRU processes. Intended for use with a lightweight (40–60 kg) lunar rover (LUnar Volatiles Mobile Instrumentation‐X; LUVMI‐X) currently under development, the mechanism utilises vibrations to reduce excavation forces and facilitate size separation. Low excavation forces are crucial for lunar excavators to be deployable on lightweight robotic platforms as limited traction forces are available. The rationale behind the mechanism is explained, its capabilities in the support of science and ISRU are showcased, and results from several laboratory test campaigns, including tests of gravitational dry sieving of different regolith simulants, are presented. The LES³ can excavate up to 100 g in a single charge while maintaining excavation forces of less than 8 N and having a mass of less than 2 kg. Finally, areas of improvement for a second iteration of the design are presented and explained. The LES³ proof of concept shows that combining of regolith excavation and size‐separation in a single mechanism is feasible.