Berthing and Docking
QinetiQ Space is the prime contractor for the development of the International Berthing and Docking Mechanism (IBDM), the European androgynous low impact docking mechanism that is capable of docking and berthing large and small spacecraft.
The IBDM is designed according to the International Docking System Standard (IDSS) and is hence compatible with the future ISS International Docking Adapter (IDA) on the US side of the International Space Station (ISS).
The IBDM is fully redundant, features a safe mode that can work even in case of vehicle power failure and has been successfully tested on the NASA/JSC Six-Degree-of-Freedom Dynamic Test System (SDTS) for a range of vehicles between 5 and 25 tons.
The IBDM is the baselined Docking mechanism on Sierra Nevada’s Dreamchaser.
The IBDM provides both docking and berthing capability. The docking mechanism comprises a Soft Capture Mechanism (SCS), and a structural mating system called the Hard Capture System (HCS). The IBDM avionics runs in hot redundancy.
Soft Capture System
The SCS utilises active control using 6 servo-actuated legs, which are coordinated to control the SCS ring in its 6 degrees of freedom. The leg forces are measured to modify the compliance of the SCS ring to facilitate alignment of the active platform during capture. A large range of vehicle mass properties can be handled. Mechanical latches achieve soft capture.
Hard Capture System
The HCS uses structural hook mechanisms to close the sealed mated interface. QinetiQ Space has developed several generations of latches and hooks to come to the final hook design.
The key feature of IBDM is that it is a fully computer controlled mechanism having the following SAFE advantages:
- Smooth: it provides a capability for low impact docking in order to reduce or eliminate the need for impact energy to achieve spacecraft interface alignment and capture. A low impact mechanism greatly reduces the contact forces during mating and as a result alleviates the large loads that the structure is required to withstand.
- Autonomous: the IBDM comprises autonomous fast switch-over from primary to redundant lane in case of a failure.
- Flexible: a large range of vehicle mass properties can be handled, as the SCS uses configurable active control, making it possible to be used for a wide variety of applications ranging from explorations to resupply missions.
- Effective: a very high capture success rate (> 98%), enabled by an agile force-sensing controlled capture mode.
- SAFE: the IBDM comprises a backup or safe mode in which the Steward platform behaves like an electro-magnetic damper. This mode is used if two failures have occurred in the IBDM avionics – or on command by the hosting vehicle – or in case no electrical power is applied to the IBDM, and hence provides a safe situation for both the vehicle and the ISS, even during the docking phase.
The QinetiQ Space capabilities in the system lead and in the development of complex mechanisms is strongly funded on 30 years of experience in the development of all breeds of space projects involving mechanisms, associated control electronics and software and complete validation and verification of the system.
Some examples are:
- Mechanisms in scientific instruments for microgravity research on the ISS
- Mechanisms in fluid research facilities for the Photon capsule
- Clampband based mechanism for small satellite ejection systems
- Astronaut tensioning system mechanism for the ISS treadmill