Compliant mechanisms in lunar surface exploration: design and technology considerations for dust mitigation

The experience gained from Apollo lunar exploration and multiple robotic lunar missions has underscored the considerable challenges posed by the lunar environment for hardware operations. These challenges encompass a wide range of issues, including thermal extremes during the lunar day and night cycle, vacuum conditions limiting the choice of suitable materials (including lubricants), harsh radiation exposure, micro-meteorite impacts, and the prevalent issue of lunar dust and regolith. Lunar regolith, the surface material covering the Moon, consists of particles of varying dimensions, ranging from fine lunar dust with grain sizes measured in micrometres to larger pebbles and rock fragments. Lunar dust, in particular, has proven to be an exceptionally formidable obstacle for lunar exploration. The array of challenges it presents includes obstructed vision for both astronauts and cameras, potential inhalation and irritation of the respiratory system, loss of traction, false instrument readings, thermal control complexities, dust coating and contamination, abrasion, seal failures, and the vexing problem of clogged mechanisms. The primary focus of the work presented here lies in the realm of mechanism design, specifically targeting the pressing issue of mechanism clogging induced by the lunar dust. The solution proposed in this work can be characterised as implicit dust mitigation. It focuses on a deliberate design choice that employs compliant mechanisms to eliminate the most dust-sensitive components within mechanisms, namely, inter-element gaps. Unlike traditional mechanisms that rely on rigid-body joints, such as hinges and sliders, compliant mechanisms leverage elastic deformation to achieve motion. Consequently, they are free of the inter-element gaps susceptible to dust accumulation, which can lead to increased friction and eventual jamming. By replacing traditional tribological contacts with compliant hinges and flexures that facilitate motion through flexible deformation, this approach yields mechanisms that are inherently resistant to dust-induced jamming. However, the design of compliant mechanisms presents its own set of challenges. In this work, a range of design methodologies were explored, encompassing analytical and topology optimisation-based approaches. Additionally, various polymers suitable for additive manufacturing were examined in the context of their compatibility with the compliant mechanism design. The intricate relationship between material properties and design methodologies is discussed within this work, providing useful insight into the potential problems of various methodology and material choices. The culmination of these efforts resulted in the design, manufacturing, and testing of multiple compliant grippers. Early prototypes were tested to refine the methodology, test procedures, and ultimately design more sophisticated compliant grippers that aimed to emulate the functionality of the Apollo geological tool known as Tongs. The final design approach proposed here comprises a two-step process involving topology optimisation followed by an analytical re-design step. The latter is tailored towards reducing stress levels in the flexures and enhancing large-scale deformations. These advances were followed by a series of tests enhanced with the use of Digital Image Correlation tools, enabling the visualisation of deformation fields within the grippers. Finally, an additional set of tests was conducted using the lunar regolith simulant EAC-1A to validate the dust-resilient behaviour of the mechanisms and demonstrate their effectiveness in the lunar environment. This research not only contributes to addressing the specific challenges of lunar dust but also advances the broader understanding of compliant mechanisms, their design methodologies, and their applicability in lunar exploration

Topology Optimization of Compliant Mechanisms as a Design Method to Improve Hardware Performance in Lunar Dust Environment

The experience from the Apollo missions showed that Lunar regolith particles are exceptionally sharp, electrostatically charged, adhesive, and pose a significant risk to mission hardware by entering gaps between the elements of mechanisms and can cause damage especially where rigid body relative displacements occur. The present work presents an alternative approach for the design of hardware that will operate on the Lunar surface. The authors propose the use of compliant mechanisms to produce monolithic mechanisms that are intrinsically resilient to Lunar dust. To support the design of compliant mechanisms topology-optimisation based design methods are here proposed. Topology optimization focuses on optimizing material distribution for a given design space and boundary conditions with the goal of maximizing the performance of the design. Achieving topologically optimized compliant mechanisms, so far, has proven to be challenging, especially when compared to static structures, and the use of commercial software does not automatically translate in ease of use. In this work, several MATLAB routines that can support topology optimisation of compliant mechanisms are explored. The advantages and disadvantages of each routine are highlighted and their application to a compliant force inverter is presented

Implicit lunar dust mitigation technology: compliant mechanisms

The finest fraction of the lunar regolith, namely the lunar dust, poses a challenge for hardware design and lunar operations. The Apollo missions experienced equipment malfunctions and failures due to dust interactions with hardware. In this work we focus on the problems related to the clogging of rigid body mechanisms. We explain the causes of the problem and propose a solution consisting of replacing traditional mechanisms with compliant mechanisms. There are multiple methods for synthesizing compliant mechanisms, but two approaches are most commonly used: analytical design and topology optimization. In this paper using a compliant gripper as an example, the suitability of these methods to design compliant mechanisms used in extra-vehicular activities is investigated. In doing so, the feasibility of using complaint mechanisms in the lunar equipment as part of dust mitigation strategies for surface projects is also demonstrated

Innovative Mars Global International Exploration (IMaGInE) mission

This paper presents the conceptual design of the IMaGInE (Innovative Mars Global International Exploration) Mission whose mission objectives are to deliver a crew of four astronauts to the surface of Deimos and a robotic exploration mission to Phobos for approx-imately 343 days during the years 2031 and 2032, perform surface excursions, technology demonstrations, and In Situ Resource Utilization (ISRU) of the Martian moons as well as site reconnaissance for future human exploration of Mars. This is the winning mission design of the 2016 Revolutionary Aerospace Systems Concepts-Academic Linkage (RASC-AL) competition, awarded with the "Best in Theme," "Best Overall," and "Pio-neering Exceptional Achievement Concept Honor (PEACH)" prizes. This competition was sponsored by NIA and NASA

Implicit lunar dust mitigation technology: Compliant mechanisms

The finest fraction of the lunar regolith, namely the lunar dust, poses a challenge for hardware design and lunar operations. The Apollo missions experienced equipment malfunctions and failures due to dust interactions with hardware. In this work we focus on the problems related to the clogging of rigid body mechanisms. We explain the causes of the problem and propose a solution consisting of replacing traditional mechanisms with compliant mechanisms. There are multiple methods for synthesizing compliant mechanisms, but two approaches are most commonly used: analytical design and topology optimization. In this paper using a compliant gripper as an example, the suitability of these methods to design compliant mechanisms used in extra-vehicular activities is investigated. In doing so, the feasibility of using complaint mechanisms in the lunar equipment as part of dust mitigation strategies for surface projects is also demonstrated

Compliant Mechanisms for Dust Mitigation in Lunar Hardware Development: Technology and Material Considerations

No abstract available

Advanced Oxidation Protein Products and Carbonylated Proteins Levels in Endovascular and Open Repair of an Abdominal Aortic Aneurysm: The Effect of Pre-, Intra-, and Postoperative Treatment

Background. In recent years, a rapid increase in studies focusing on the role of oxidative stress in the pathogenesis of an abdominal aortic aneurysm (AAA) has been observed. Oxidative modifications of proteins are infrequently evaluated in reference to AAA. Objectives. The intensity of oxidative protein modifications, presented as advanced oxidation protein products (AOPP) and carbonylated proteins (C=O), in AAA patients qualified for surgery was estimated. The effect of surgical techniques and intraoperative and postoperative treatment on AOPP and C=O levels was evaluated. Patients. The EVAR group, consisting of 30 patients, was classified for endovascular aneurysm repair, whereas 28 patients were classified for conventional open repair (OR). Methods. AOPP and C=O were measured using a colorimetric assay kit. Results. A significantly lower AOPP level obtained 2-4 days after EVAR surgery in comparison with the value found before surgery was noted. In the case of OR postoperative treatment, a tendency of AOPP level to increase was observed. The tendency of C=O to decrease after surgery in the EVAR group was indicated. However, the C=O level tended to increase after OR surgery and reached a significantly higher value 5-7 days after surgery compared with the value obtained before surgery. Conclusions. Based on our results, it may be concluded that AAA as well as surgical technique contribute to the formation of AOPP and C=O. The analysis of changes in AOPP and C=O values obtained after surgery revealed a significant effect of a patient’s condition before surgery as well as the choice of surgery technique on the values of the studied parameters revealed during postoperative treatment

Selected Atherosclerosis-Related Diseases May Differentially Affect the Relationship between Plasma Advanced Glycation End Products, Receptor sRAGE, and Uric Acid

Our study aimed to identify the relationship between advanced glycation end products (AGEs), soluble receptor for advanced glycation end products (sRAGE), the AGEs/sRAGE, and uric acid (UA) levels in selected atherosclerosis diseases, i.e., abdominal aortic aneurysms (AAA), aortoiliac occlusive disease (AIOD), and chronic kidney disease (CKD), resulting from apparent differences in oxidative stress intensity. Furthermore, we suggest that increased AGEs levels may stimulate an antioxidant defense system reflected by the UA level. The studied group size consisted of 70 AAA patients, 20 AIOD patients, 50 patients in the pre-dialyzed group (PRE), and 35 patients in the hemodialyzed group (HD). The enzyme-linked immunosorbent assay was used to measure AGEs and sRAGE levels. We found a significantly higher concentration of AGEs in CKD patients as compared to AAA and AIOD patients. Furthermore, the sRAGE level was higher in the CKD patients in comparison to AIOD and AAA patients. UA level was significantly higher in the PRE group compared to AAA patients. In conclusion, the diseases included in this study differ in the anti- and prooxidant defense system, which is reflected in the relations between the AGEs, the sRAGE, the AGEs/sRAGE ratio, as well as the UA levels

The Association of Serum Thrombomodulin with Endothelial Injuring Factors in Abdominal Aortic Aneurysm

Background. The aim of the present study was to evaluate the concentration of serum thrombomodulin (sTM) in the AAA patients and to examine its correlation with various factors which may potentially participate in the endothelial injury. Materials and Methods. Forty-one patients with AAA were involved and divided into subgroups based on different criteria. Concentration of sTM was measured using enzyme-linked-immunosorbent assay (ELISA). The results were compared with those obtained in 30 healthy age- and sex-matched volunteers. Results. The higher concentration of sTM was observed in AAA patients compared with those in controls volunteers [2.37 (1.97–2.82) ng/mL versus 3.93 (2.43–9.20) ng/mL, P < 0.001]. An elevated sTM associated significantly with increased triglycerides (TAG) [P = 0.022], cholesterol [P = 0.029], hsCRP [P = 0.031], and advanced glycation end products (AGEs) [P = 0.033]. Conclusions. The elevation of serum sTM level suggests that endothelial damage occurs in AAA pathogenesis. The correlations observed indicate that lipids abnormalities, inflammation, and oxidative stress may be involved in this destructive process

The Association of Serum Thrombomodulin with Endothelial Injuring Factors in Abdominal Aortic Aneurysm

Background. The aim of the present study was to evaluate the concentration of serum thrombomodulin (sTM) in the AAA patients and to examine its correlation with various factors which may potentially participate in the endothelial injury. Materials and Methods. Forty-one patients with AAA were involved and divided into subgroups based on different criteria. Concentration of sTM was measured using enzyme-linked-immunosorbent assay (ELISA). The results were compared with those obtained in 30 healthy age- and sex-matched volunteers. Results. The higher concentration of sTM was observed in AAA patients compared with those in controls volunteers [2.37 (1.97–2.82) ng/mL versus 3.93 (2.43–9.20) ng/mL, P < 0.001]. An elevated sTM associated significantly with increased triglycerides (TAG) [P = 0.022], cholesterol [P = 0.029], hsCRP [P = 0.031], and advanced glycation end products (AGEs) [P = 0.033]. Conclusions. The elevation of serum sTM level suggests that endothelial damage occurs in AAA pathogenesis. The correlations observed indicate that lipids abnormalities, inflammation, and oxidative stress may be involved in this destructive process