Speaker
Dr
Lorenzo Marconi
(Arescosmo S.p.A.)
Description
The concept of space tethers has great potential in space applications; for this reason they have been investigated as electrodynamics power generators or motors, momentum exchange and orbital stabilization assets or formation flying connection and pulling ropes. In the most recent years, in the context of ESA (European Space Agency) Clean Space Initiative and general interest in space debris removal missions, they have been included as one of the key technologies for capturing and de-orbiting large space target debris by pulling them. Tether as pulling capture system reveals two opposite aspect, a potential simplicity before the capture phase (simple mechanism, simple rendez-vous, versatile and cheaper) and a complexity after capture related the control and complex stack. Tether would act as a flexible link, elastic or rigid, between the chaser spacecraft and its capture system, consisting, for instance, in a harpoon or a net. Tether elasticity is an important element to take into account for the controllability of the stack. On one side, a high elasticity tether leads to a simpler control problem and a better shocks reduction. On the other hand it may include the presence of a potential resonance with sloshing and an increased risk of collision after the de-orbit burn.
In Elastic Tether Design and Dynamic Testing, the ESA TRP (Technology Research Program), Arescosmo, with its local partners *Aviospace* and *Gottifredi Maffioli*, are currently studying and developing both a rigid and a highly elastic tether. Main objectives of the TRP are two; first to increase the TRL of the tether for ADR (Active Debris Removal) missions to 5-6 through an extensive environmental and functional test campaign at both material and assembly levels. Second to deliver two full-size (100 meters long) rigid and elastic tethers as fully functional Engineering Model (EM) with associated datasheets tabulating nominal and extreme values for parameters providing also a clear view of the design parameters-performances dependencies for the future CE (Concurrent Engineering) assessments to be done at system and mission levels. The on-going TRP is related to the activities for the e.Deorbit mission, now in Phase B1, and it reflects the ESA implementation plan of technologies required for ADR missions.
The current paper describes the work that has been performed so far in the study. This includes design, material level characterization tests, and development tests at assembly level on scaled models of the tether system in various configurations (rigid, flexible, with and without thermal protection system). The relevant test results and the lessons learned that have guided the final design are discussed, including the various engineering challenges that were faced in designing the tether system. These challenges include thermal and chemical constraints resulting from the thruster plumes of the chaser spacecraft, physical performance of the elastic system under various load conditions, and manufacturing considerations such as the need for dedicated thermal treatments (vacuum stripping and heating treatment) of some of the materials used. The paper also describes the customized BoL and EoL tests designed to evaluate the performance of the tether systems before and after ageing in thermal-vacuum conditions. The test program exposed complex failure mechanisms where interfaces (braiding and seaming) were key points the required updates to the system design. In conclusion an overview of the planned activities until the final wrap-up will be presented.
Primary authors
Andrea Messidoro
(Arescosmos S.p.A)
Dr
Lorenzo Marconi
(Arescosmo S.p.A.)
