Bio-inspired Micro-drills for Future Planetary Exploration

In a domain such as space technology, where robustness, mass, volume and power efficiency are key, biological organisms may provide inspiration for new systems with high performance. By using micro-technology processes, designers of space systems may take advantage of the millions of years over which miniaturised mechanisms in plants and animals have been optimised for survival. Space exploration often requires systems equipped with drills, and miniaturised drillers could enable a number of new space operations. Two natural digging systems have been studied as potential miniature space digging systems; the ovipositors of the female locust and of sirex noctilio, a species of woodwasp. Being insectoid systems, the mechanics of their design work on an inherently small scale, though they are also thought to be scalable. Results of preliminary studies, performed during collaboration between the Advanced Concepts Team of ESA, the University of Bath, the University of Surrey, D’appolonia and EADS-Astrium, are presented and discussed. Engineering solutions are proposed and analysed to assess the potential of new bio-inspired miniaturised digging systems for space applications. INTRODUCTION This paper presents and discusses the potential for innovative solutions and applications for bio-inspired, miniaturised drilling systems. A biomimetic study has been performed in order to find inspiration from nature in the design of novel mechanisms. In particular, two organic drills, which have been assessed in more detail, are presented and discussed. During a study carried out between the Advanced Concepts Team of ESA, the University of Bath, the University of Surrey, D’appolonia and EADS-Astrium, drilling mechanisms used by the woodwasp Sirex noctilio [29] and the female locusts, Schistocerca gregaria and Locusta migratoria [30] were identified being of particular interest for further development and were chosen as the subjects of more detailed preliminary studies [20, 21]. The following work describes digging mechanisms already developed for space applications and discusses the scope in potential for missions involving miniaturised drilling systems. The basic notions of biomimetics are presented and its relevance to the design of innovative systems is analysed. Two natural digging systems are described and engineered solutions based on these are proposed for future space missions. DRILLING IN SPACE Subsurface analysis is a growing requirement for space science missions for research in areas such as exobiology [10], study of the early solar system [8, 9], and the search for underground resources [10]. Some characteristics of underground material may be derived remotely, for instance using ground penetrating radar. Using this example, however, depth and resolution of data are limited by available power and the material under study [11, 13]. However, with direct contact the quality and amount of information able to be extracted may be increased sensibly. Impactor vehicles can be used in some cases to gain physical access to bodies’ interiors, hitting them at hypervelociy, but are not always a feasible or desirable option. Drilling mechanisms still have the potential to offer an optimal choice when seeking range and fidelity of data acquisition across a broad spectrum of scenarios, whether for sample return or in situ analysis. A BIO-INSPIRED APPROACH For thousands of years, humans have been inspired by nature. In the engineering of systems, efforts have been made in recent years to formalise this process, attempting to systematically distil ideas useful for engineered systems from biological analogues. In this way, biomimetics does not attempt to copy biological systems for the sake of it, nor to copy all of a system's characteristics directly. Rather, the key to successful biomimetic engineering is in finding biological systems that can in some way be useful in an engineering solution, then applying them at an optimal level of abstraction. When considering space systems, this is a salient point in the motivation of biomimetics, given that biological systems have evolved to survive in terrestrial environments very different to the vacuum of orbit or extraterrestrial surfaces. However many potential areas where biomimetic engineering could be of benefit in space have already been identified, with ever growing interest in the field [1-2]. Taking a high level view, there are abundant examples of biological systems that display characteristics that are desirable in space missions. These include robustness, adaptability, integration and autonomy all of which might be included in a biomimetically designed system. Particularly relevant to this paper, however, it is the abundance of high-performance miniaturized systems that can be found in nature. The thousands of insect species, for example represent a vast resource of ready-designed systems, optimized through millions of years of evolution, using far less mass and volume than most conventionally engineered systems. Advances in micro systems technology (MST) are enabling the conception of new solutions in space system design. The ability to use novel micro-fabrication techniques to produce devices with very small dimensions allows designers to consider the manufacture of new systems with a step change from conventional masses and volumes. Such drastic improvements may prove to be enabling for space missions, potentially allowing increases in mission capabilities or decreases in cost. Additionally, MST products give consistency in reproduction and provide opportunities for mass production. Applications involving large numbers of identical microsystems can be envisaged and have the potential to be realised at acceptable cost. Not only do these technologies allow reduction in scale, however, greater integration of different functions in a small device could lead to entirely new mission designs. For biomimetics, MST is an enabling technology, allowing the application of ready-made, biological, highly integrated miniaturized systems in an engineered design. REVIEW OF DRILLING SYSTEMS FOR SPACE APPLICATIONS The following table summarises a selection of drilling systems designed and launched for use in space. Table 1: A selection of drilling systems from past and ongoing space missions [14, 10] Instrument Mission Mass (kg) Approx. Volume cm Power (W) Luna 16/20 drills Luna 16,20 13.6 140 Luna 23/24 drill Luna 23,24 750000 Apollo drills Apollo 11-12, 14-17 13.4 25000 3000 Viking scoops Viking 1 2 11.3 49000 ~200 DS2 microdrill Deep Space 2 <0.05 <11 <10 Philae SD2 drill Rosetta 4.8 1100 230 Beagle-2 RCG MEX/B-2 0.35 180 6 Beagle-2 PLUTO MEX/B-2 0.34 (mole) 0.89 (total) 560 3 MER RAT MER – A/B 0.7 110 5-10