Assessment of the problem:

Nowadays the only in space assembled structure is the International Space Station. It also allows the dock of the crew module through a very specific interface. Spacecrafts that want to dock it have to base their design on that specific interface, making it a very complex and elitist job.

Future more ambitious missions will require bigger and more complex spacecraft with the need of in orbit assembly to overcome launcher limits. More simple and reliable docking system will also open the door to in orbit refueling for interplanetary travel and satellite maintenance.

Solution description:

The project strictly addresses challenge needs by foreseeing components assembly and docking in space, as well as the approach and alignment design. The solution has been purposely made as simple as possible and as generally replicable as possible. An autonomous mechanism is considered to avoid using robotic arms and human control. Finally, the mechanism is also able to release the connected parts.

- Description of the mechanism: The proposed solution is composed by a male and female interface. The male hosts a pyramid trunk shape extrusion and a low power camera for led pattern recognition, while the female has a complementar hole with two non pyrotechnic hold down and release mechanisms to ensure the lock and unlock phase once the approaching object arrives at the target position. The lateral pin mechanism fits into a lateral hole in the male interface to fix the two components. The second one is placed at the base of the female cavity and allows the separation of the two components once released. Both of them are reusable thanks to an electro-actuated motor that recompresses the spring in the original position. Each module is equipped with a rad-hard microprocessor for image processing, LEDs controlling and the capability to interconnect with other SMI modules to share information.

- Visual approach method: The high precision approach, of paramount importance for spacecraft docking, is performed with an optical camera on the chaser object and a set of LEDs on the target object. By recognising the LED pattern, the docking system software is able to compute the relative attitude and position. Four brighter LEDs are used for initial approach (approximately from 250m to 50m), then a cross pattern of seven smaller LEDs is acquired for the final close approach.

Spacecraft manoeuvering will be performed by the on-board orbital and attitude control system.

Innovation of the solution:

- Standardization: The proposed design is aimed at standardizing the docking interface for as many applications as possible, making in orbit operation more and more accessible for a great number of space industries and enhancing competition and future development.

- Modularity capabilities: The system modularity increases the flexibility of the system. One or several systems can be fitted depending on the spacecraft dimension and use. For example one unit is used in case of a small satellite for servicing while four modules can be mounted on the structural ring of a space station module coordinating the LEDs pattern among the units.