Verification of the Technology Combination Analysis Tool (TCAT) for space logistics modeling in the Earth-Moon system
Creators: name:  S.W. PAEK 
name:   P. HUBER 
name:   F. BRANCATO 
name:   M. CHAVY-MACDONALD 
name:   J. KNEIB 
name:   R. CRISTOFOLETTI 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: SUSTAINABLE SPACE
LOGISTICS

description: The Technology Combination Analysis Tool (TCAT) is a Python-based space transportation modelling package with feasibility assessment applications in active debris removal (ADR), on-orbit servicing (OOS), and constellation deployment. Developed by the EPFL Space Center (eSpace), the TCAT was first used to evaluate the system architecture of multiple ADR satellites. Now that satellite constellations for Earth observation and telecommunications, including space internets, are being deployed at an unprecedented rate, decision-makers could benefit from the rapid-prototyping capability of TCAT in spacecraft sizing and constellation design with potential applications in space traffic management where strategic options for constellation-level OOS could be explored and evaluated promptly in support of future technology planning. Another use of the TCAT is architecting logistics scenarios in the Earth-Moon system, which is the topic of this paper. The problem size is then increased drastically in terms of both spatial and temporal scales relative to the aforementioned ADR and OOS examples near Earth, which would necessitate and testify the power of prototyping even further. This paper reports the recent progress at the EPFL Space Center (eSpace) in extending the capabilities of the TCAT towards Earth-Moon scenario modelling. Its main capabilities are currently the rapid sizing of spacecraft using high-thrust propulsion for active debris removal and lunar cargo delivery missions. To implement the desired capabilities into the TCAT, a modelling approach for low-thrust Earth-Moon trajectories was adopted from the literature. Also, a third-party astrodynamics software, called FreeFlyer, was used to simulate these trajectories and integrated into the framework. Several challenges had to be overcome during the implementation, most notably the suitable adaptation of the convergence algorithm used in TCAT. Finally, to test the implementation, two example missions were modeled, namely the European Space Agencys European Student Moon Orbiter (ESMO) mission and its Small Missions for Advanced Research in Technology-1 (SMART-1) mission. Physically relevant output values, such as the required propellant mass, have been compared to the test missions and deviations between 73% and 123% have been found. Several reasons for these large deviations have been investigated, of which issues with the force model are likely among the most impactful ones. Notwithstanding these deviations, the integration of TCAT and FreeFlyer should be regarded successful given the technical challenges of suitably adapting the convergence algorithm, whose procedures and results are detailed. The limitation of the TCAT tool is currently addressed in multiple ways, such as using it for ADR/OOS scenarios where the two-body approximation is sufficient, incorporating high-fidelity force models, etc. Another feature that can be integrated into the extended TCAT is a database containing specifications of ion thrusters and other electric propulsion systems. The modelling of electric propulsion systems (EPS) is much newer and harder compared to chemical propulsion and the need of an up-to-date and scalable system is of high importance. In addition to archiving the database of ion engines, their design parametrization has been carried out. The database system, in its standalone mode, is able to perform basic CRUD (Create, Read, Update and Delete) operations on a database as well as plot the measurable quantities on a graph. Integrating this electric propulsion database into the TCAT or other platforms is being envisioned where applicable.