Spacecraft Life Extension System
It seems that with our capture tool and docking technology as developed for ESS, we might create the first business case in on-orbit-servicing. Telecommunication satellites typically cost at least $250 million and are designed for an average on-orbit life-time of 10-15 years. Once their on-board propellant load is depleted, the satellites are boosted into a disposal orbit and decommissioned, even though their revenue-generating communications relay payloads continue to function.
The OLEV (Orbitl Life Extension Vehicle) will significantly prolong the operating lifetimes of valuable telecommunication satellites.
OLEV will operate as an orbital tugboat, supplying the propulsion, navigation and guidance to keep a telecommunications satellite in its proper orbital slot for many additional years. Another application of the OLEV could be the rescue of a spacecraft that has been placed in a wrong orbit by its launch vehicle, or which has stranded in an incorrect orbital location during positioning manoeuvres. The system is designed to easily mate with all current and future telecommunications satellites. It will link up using our proprietary docking device (the modified ESS capture tool, see Fig. below) that connects to the telecommunication satellite's apogee kick motor, as we have proposed within the ESS technology study. Meanwhile we have made a lot of effort to redesign the capture tool towards increasing its fail-safe behaviour, e.g., by using additional redundant sensors. |
Apogee kick motors are used by nearly every telecommunications satellite for orbital boost, and they provide a strong, easy accessible interface point for the OLEV. A corresponding license contract has already been signed, and it seems that even the model based vision and the tele-presence concepts developed in our lab will be applied in this worldwide first on-orbit-servicing project.
For tracking and capturing the satellite, a complex model is currently being developed in our lab. It includes all effects of orbital disturbances in GEO as well as the dynamic coupling between the satellite and the solar generators, taking in account the excitation of the thrusters and a possible collision during the docking phase. A simulation tool for visualization of the docking dynamics, with a human operator in the loop, is also under development.
DLR-RM contributions to the OLEV system are:
- Capture Tool, including locking mechanism, sensors and control software
- Tele-manipulation software to guide the Capture Tool which is mounted to the OLEV into the apogee-motor of the target satellite
- Ground Control System and capture strategies
- Hardware-in-the-loop simulations (HIL) of the final approach and docking phases at EPOS (European Proximity Operations Simulator)
The Video (right side) shows the final approach and docking phase (by courtesy of Dutch Space): Mediaplayer (900kB) Realplayer (300kB).