Using an adaptive nozzle to improve rocket engine performances
Creators: name:  J. SENON 
name:   S. ALLARDET 
name:   J. SIMON 
name:   P. PEMPIE 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: SPACE
ADVANCED TECHNOLOGIES
REUSABILITY

description: One of the best known problems in the design of liquid rocket engines is the adaptation of the nozzle to a given mission - i.e. to a given altitude range. Indeed, the efficiency of an engine is optimal when the pressure of the ejected gases corresponds to the ambient pressure. However, when a rocket engine is used, it is most often a question of moving from sea level to an orbit in space. Consequently, the ambient pressure varies widely, whereas the ejection pressure of a rocket engine is fixed by the size of its nozzle. This is one of the main reasons why space launch vehicle designers use multiple stages, and therefore multiple engines with different nozzle sizes. Of course several solutions have been studied, among them the aerospike nozzle is probably the most famous. However, these still have drawbacks that prevent their implementation on a launcher scale. We propose here the use of an adaptive divergent device, i.e. a divergent capable of varying its cross-section and therefore its outlet pressure. Where an aerospike type nozzle becomes complicated to cool and generates a gain in mass, the proposed device does not change the design method of a bell nozzle rocket engine. Another comparison can be made with the Vinci upper stage engine developed by Arianegroup, which has a nozzle extension. Although in this case the nozzle extension is to save space, one could imagine the engine operating in two modes, retracted or extended. However, this would only allow optimal operation at two altitudes. Our adaptive nozzle is a truncated cone-shaped ring composed of a set of prismatic tiles extending the divergent nozzle. The translation of these tiles via an adapted deployment system allows the length of the divergent nozzle and therefore its outlet section to be varied step by step. This will allow the engine to have a defined range of operating altitude as required. This now patented innovation is currently being implemented within the CNES PERSEUS student project on a MINERVA engine using the LOX/CH4 propellant combination. Called Mini Viserion, this rocket engine with a nominal thrust of 5kN is entirely designed by the IPSA student association Innovative Propulsion Laboratory (IPL) teams. This project involves the design of a pintle-type injection system and a regenerative cycle combustion chamber. But it also involves the design of a thrust recovery device allowing TVC and of course the adaptive divergent nozzle with its deployment system. The medium-term objective is to prepare and carry out the first tests on a test bench during 2022. At stake are the functional validation of this innovation and the production of a new rocket engine for the student PERSEUS project. To conclude, we have quickly defined the problem to which this project is trying to respond today. The need is clearly defined and the idea is now to test an innovative solution on a rocket engine in order to characterise its working. At the end, this innovation could equip most of the existing rocket engines.