Sensibility study for different nozzle configuration on the heat load and aerodynamic behaviour for the THEMIS demonstrator
Creators: name:  M. LANTELME 
name:   A. BOURGOING 
name:   C. BERTORELLO 
name:   P. TRAN 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: SPACE
REUSABILITY
REUSABLE LAUNCH VEHICLE

description: This papers focus is on the aerodynamic and aerothermal loads that a reusable launch vehicle (RLV) faces during different phases of their flight trajectory. The analysis is performed on a working design of the THEMIS demonstrator developed at Ariane Group SAS under an ESA contract. THEMIS (Technologies for a Methane Innovative Stage) is planned to be a real scale demonstrator that is part of ESAs future launcher preparatory program and which will use the PROMETHEUS (Precursor Reusable Oxygen METhane cost Effective propUlsion System) engine currently being developed. It is designed as a vertical take-off vertical landing configuration (VTVL) and therefore relies on retropropulsion for deceleration and its maneuvers to reach its designated landing site. PROMETEUS investigates the possibility of a reusable 100-tons class LOx-LCH4 engine. The knowledge gained during CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations) and THEMIS will provide the information and experience required to determine the future of European operational launchers. Within this paper, we will investigate different configurations of the three nozzles foreseen to be used for the THEMIS demonstrator. Several parameters are varied to study the influence on the heat flux distribution and the overall aerodynamic behaviour and stability of the launcher. The reference configuration foresees a linear alignment of the three nozzles and includes landing legs. The sensitivity study presented in this paper is focused to the rocket engines aft-bay arrangement. The changes studied are the distance between the nozzles, the extreme gimballing positions of the two nozzles on both side of the central one, and the longitudinal emergence of the three nozzles. The shape of the nozzles remains unchanged. In order to execute this sensibility analysis, this paper presents results of CFD calculations, which are performed for those different geometries at a fixed flight point chosen to ensure significant aerothermal loads. All CFD calculations are performed for the controlled descent flight of the reusable THEMIS demonstrator in moments when the nozzles are not ignited. The paper describes the consequences of the different configurations and tends to provide a determination of the best overall configuration minimizing the aerothermal loads. In order to determine this, trade-offs must be performed between the effects on different zones of the launcher (launchers landing legs, base of the launcher; internal/external walls of the nozzles) and the investigated physical properties. Impacts of these changes of shape are also addressed on the aerodynamic behaviour of the vehicle through the analysis of global aerodynamic coefficients (lift, drag) and the static stability of the vehicles (positions of centre of pressure). Furthermore, the phenomena occurring in the flow field and its impacts on the pressure and heat flux distribution are investigated: This includes analysing differences occurring for the different configurations in the recirculation zone within the non-ignited nozzles or between the nozzles, the shock positions and possible shock-boundary layer interactions. The hereafter presented results were investigated within a collaborative effort between Ariane Group SAS in Les Mureaux centre and ONERA Toulouse. This research is performed within the ASCenSIon project (Advancing Space Access Capabilities - Reusability and Multiple Satellite Injection) project funded by the European Commission (Horizon 2020).