WHAT IS ON-ORBIT SERVICING?

The term ‘On-Orbit Servicing’ (OOS) defines a series of activities performed in space comprising inspection, repairing, refueling, refurbishment and update of existing orbital vehicles. Unmanned OOS is perceived as a very efficient and cost-effetive way to extend the operational life of satellites orbiting the Earth.

 

JOINING OPERATIONS IN SPACE

In-space rendezvous and joining of two bodies was one of the first technological challenges that space engineers dealt with; since the first active docking of two spacecraft during Gemini XIII mission under the command of Neil Armstrong (1966), active joining of two or more bodies radically changed and evolved in different concepts of operations. Usually, the approaching spacecraft is denominated chaser, and the approached body is referred as target.

The main joining operations can be classified depending on mission target attributes:

  1. if the target is passive (e.g.: uncooperative spacecraft, space junk or small bodies) the chaser shall approach and capture it, usually without the presence of joining interfaces or other useful grasping element; another common issue of this operation is the possible target tumbling motion;
  2. in case of cooperative bodies there is an ulterior classification:
  • berthing (assisted joining): the process needs the help of a grapple interface (such as ISS robotic arms) to bring one spacecraft and mate it to the other module;
  • docking (active mating): the joining processof two separate free flying spacecraft through active proximity manoeuvres.

 

DOCKING

Docking mechanisms can be classified as gender-mate and androgynous. Gender-mate interfaces has unique design and spacecraft of the same gender cannot be joined, while androgynous mechanisms have identical interfaces, and spacecraft can dock with every satellite with the same port.

ARCADE &

ARCADE-R2

The student experiment ARCADE, developed in the framework of the REXUS/BEXUS programme, is a technology demonstrator of docking and rendezvous technologies. ARCADE tested a gender-mate docking mechanism based on the ESA Automatic Transfer Vehicle interface.

More on ARCADE

TETHERED

SOFT DOCKING

An innovative tethered docking system is in development, aiming to realize a simple soft docking probe guided by magnetic interactions. Its working principle was assessed by FELDs experiment,  in the framework of ESA Drop Your Thesis! programme; further studies on tether dynamics are performed by STAR experiment.

More on Tethered Docking

More on FELDs

More on STAR

SEMIANDROGYNOUS

MULTIFUNCTIONAL

 INTERFACES

Researches focused on the development of (1) a semiandrogynous interface, combining gender-mate simple mechanisms with the androgyny concept, and (2) a multifunctional port. Prototypes have been realized to perform laboratory tests; the most complex geometries were 3D printed, reducing cost and manufacturing times

More on the SEMIANDROGYNOUS MECHANISM (SAM)

More on the MULTIFUNCTIONAL INTERFACE (MUSA)

 

CAPTURE

Almost all the existing Earth-orbiting satellites were not conceived to support On Orbit Servicing; thus, they are not provided with any device – optical markers, handles – that will help their location and grasping. Such satellites are defined as non cooperative objects. Space debris can also be ascribed to this category.
Our research group is developing a new capture technology, based on Electro-Adhesion, allowing to grasp non cooperative objects

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    SPACE ROBOTICS

    Robotics is a subject of key importance in space systems and allows a huge number of operations in different mission scenarios. Robotic systems are used for exploration (e.g. planetary rovers), for capture/berthing of space objects or for servicing of orbital vehicles (e.g. assembly of ISS modules). For this reason the interest on space robotics is growing and a lot of research is performed in order to find new solutions and applications.
    SSG takes part to this research field in two different ways: first, by designing innovative actuators that provide considerable improvements with respect to traditional devices and, second, by developing laboratory applications for the simulation of the relative dynamics between satellites in close approach. The first activity aims at the modelling, design and testing of sctuators based on smart materials and, in particular, Dielectric Elastomers (DE). The use of such innovative materials allows to obtain improved perfomances

    DIELECTRIC ELASTOMERS ACTUATORS

    Dielectric Elastomers have the capability to show large deformations under high voltage loads; actuators based on those materials do not suffer wear nor fatigue issues, and show highly damped vibrations, thus requiring no maintenance and transferring low disturbance to the surrounding structures. In particular, they could be used for space mechanisms applications such as adaptive structures and robotic manipulators.

    ROBOTIC SIMULATOR

    The increasing number of human objects in space has laid the foundation of a novel class of orbital missions for servicing and maintenance. The main goal of this research is the development, building and testing of a robotic manipulator for the simulation of orbital maneuvers, with particular attention to Active Debris Removal and on-orbit servicing.

     

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