Periodic Reporting for period 3 - E.T.PACK (Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit)
Período documentado: 2021-11-01 hasta 2022-11-30
The potential impact for society is supported by a fundamental characteristic of LWTs: they are reversible devices that convert orbital energy into electrical energy and vice versa without using any consumable. Such a property is key for several space applications. For instance, a LWT in generator mode can be used for deorbiting spacecraft at the end of life, thus contributing to solve the space debris problem that is one of the most important space challenges for the next decades. LWTs in thruster mode can provide indefinite station keeping, which is of particular importance for satellites orbiting at very low orbit and the International Space Station that requires about 10 tons of propellant per year. The opening of new horizons for science and technology is also envisaged because LWTs can be used as scientific instruments and in missions to planets with magnetospheres as Jupiter.
Novel Vlasov-Poisson solvers to study tape-like LWTs have been developed. A database with characteristic (I-V) curves has been computed and made public. UC3M tether flight simulator BETsMA v2.0 has been updated with electrical and dynamic models. Algorithms to make optimal mission design with different types of tethers and in active and passive modes were developed. A novel software was developed to simulate tether deployment. An intensive simulation campaign to determine the performance and the requirements of LWTs was carried out using BETsMAv2.0 and FLEX. A code for the simulation of the attitude dynamics during the deployment phase was also developed and used extensively to find the requirements of the avionics.
Direct synthesis of the low work function material C12A7:e- as powder, printable pastes with C12A7:e- powder and brazeable metal fillers were prepared. The printing and firing of the functional paste on a metal substrate for contacting C12A7:e- as low work function material on a tether tape and generating the LWT were done. An intensive testing campaign of the LWT coating regarding electron emission, optical, mechanical, and thermal properties as well as under space condition was carried out. Additionally, the coating of an insulated tether segment was investigated, as well as the joint of different tether segments. A 50cm long LWT demonstrator was manufactured and its industrial production assessed.
After performing a detailed design of the deployment mechanism (DM) focussed on the future IOD of the deorbit device, the mechanical parts of the DM were manufactured, including the cold gas assembly manifolds.
Gears and motors were procured and assembled in the DM. The manufactured prototype underwent key functional tests at SENER and then it was tested at UNIPD and assembled with the Cold Gas System. The manufacturing of the DM prototype is complete of the mechanical parts, motors, motor drivers, on-board computer, and Cold Gas system.
The heaterless hollow cathode electron emitter (HCE), which is the baseline emitter for the IOD mission, and the expellant system were further optimized to meet the requirements for current emission, voltage operation (about 20 to 30 V EMF provided by tether), power consumption, lifetime, mass flow and ignition cycles. An extensive test campaign was carried out to demonstrate the fullfillment of the requirement. The electronics of the HCE was developed at a breadborad level. Different prototypes of the PETE Device were manufactured and tested.
A complete Engineering model of the DK, including the tether, the deployment mechanism, the cold gas system, the Electron Emitter elements, the control board, the attitude control and the remaining avionics elements, has been design, manufactured, integrated and extensively tested. It is a 12U and 24 kg device that can host a 500m long bare tether. The verification activity concluded that the DK has reached TRL4 at system level. TRL6 has been reached by avionics, structure and tether, whereas TRL4 was reached for the cold gas system and the hollow cathode electronics.