Search Results (4)

The growing amount of space debris in geocentricorbit poses a significant threat to the future of space operations. To mitigate this problem, current international guidelines state that a satellite should be able to deorbit or insert into a graveyard orbit within 25 years from the end of its operational life. In this context, drag-enhancing devices such as drag sails are currently an active field of research and development because of their ability to make a spacecraft decay from low Earth orbit without the need for any on-board propellant. Drag sails, conceptually similar to solar sails, are thin membranes deployed by a spacecraft at the end of its operational life to increase the area-to-mass ratio and, consequently, atmospheric drag. To be effectively exploited, a drag sail should maximize the surface area exposed to atmospheric particle flow. However, this would require a fully functional three-axis stabilization system, which may either be unavailable or non-functional on an orbiting satellite after years of space operations. To simplify the deorbiting phase, in this paper we propose to use a spin-deployed and spin-stabilized drag sail, which represents a reasonable compromise between simplicity of implementation and deorbiting performance in terms of total decay time. In fact, a spinning drag sail could take advantage of centrifugal force to unfold and of gyroscopic stiffness to maintain an inertially fixed axis of rotation. Numerical simulations accounting for the main perturbation effects quantify the effectiveness of the proposed device compared with an optimal configuration (i.e., a three-axis stabilized drag sail) and a tumbling drag sail. Full article

Collisions of space debris and micrometeorites with spacecraft represent an existential hazard for human activities in near-Earth orbits. Currently, guidelines, policies, and best practices are encouraged to help mitigate further propagation of this space debris field from redundant spacecraft and satellites. However, the existing space debris field is an environment that still poses a great threat and requires the design of contingency and fail-safe systems for new spacecraft. In this context, both the monitoring and tracking of space debris impact paths, along with knowledge of spacecraft design features that can withstand such impacts, are essential. Regarding the latter, terrestrial test facilities allow for replicating of space debris collisions in a safe and controlled laboratory environment. In particular, light-gas guns allow launching impactors at speeds in the high-velocity and hypervelocity ranges. The data acquired from these tests can be employed to validate in-orbit observations and structural simulations and to verify spacecraft components’ survivability. Typically, projectiles are launched and protected using a sabot system. This assembly, known as a launch package, is fired towards a sabot-stopping system. The sabot separates from the rest of the launch package, to avoid target contamination, and allows the projectile to travel towards the target through an opening in the assembly. The response and survivability of the sabot-stopping system, along with the transmission of the forces to the light-gas gun structure and prevention of target contamination, is an important design feature of these test apparatuses. In the framework of the development of Malta’s first high-velocity impact facility, particular attention was dedicated to this topic: in this paper, the description of a novel sabot-stopping system is provided. The system described in this research is mechanically decoupled from the interaction with the impact chamber and the light-gas gun pump tube; this solution avoids damage in case of failures and allows easier operations during the pre- and post-test phases. Full article

The presence of a number of space debris in low Earth orbits poses a serious threat for current spacecraft operations and future space missions. To mitigate this critical problem, international guidelines suggest that an artificial satellite should decay (or be transferred to a graveyard orbit) within a time interval of 25 years after the end of its operative life. To that end, in recent years deorbiting technologies are acquiring an increasing importance both in terms of academic research and industrial efforts. In this context, the plasma brake concept may represent a promising and fascinating innovation. The plasma brake is a propellantless device, whose working principle consists of generating an electrostatic Coulomb drag between the planet’s ionosphere ions and a charged tether deployed from a satellite in a low Earth orbit. This paper discusses an analytical method to approximate the deorbiting trajectory of a small satellite equipped with a plasma brake device. In particular, the proposed approach allows the deorbiting time to be estimated through an analytical equation as a function of the design characteristics of the plasma brake and of the satellite initial orbital elements. Full article

The growth of orbital space debris is both a consequence of and a potential hindrance to space activities. The risks posed by space debris propagation in the most used orbital regions highlight the need to adequately address the challenges posed to the sustainability in outer space. The preservation of the access to and usability of outer space in the long-term requires that action is taken which has to be the result of both mitigation and remediation measures for existing and future space missions. As the enforcement of such technical measures will depend on adequate regulation, they need to be approached also from a legal perspective. The deficiencies in law for space debris remediation mechanisms originate from the fact that although technical concepts have been developed, the legal framework for space activities does not impose any legal obligations for debris removal and on-orbit servicing. Nevertheless, an overview of the relevant legal framework shows that there is a legal basis for the protection of the outer space environment which can, as has already been the case with space debris mitigation guidelines, be substantiated in more concrete terms by the formulation of voluntary, non-binding instruments and included in national legislation. Full article