Project Objective

This work directly identifies the feasibility of staged combustion detonation engines.

Project Description

Overall, the long-term goal is to evaluate the use of staged combustion with detonation-based engines. Staged combustion is high efficiency but could potentially rob the rotating detonation rocket engine (RDRE) of all its potential performance gains due to deflagrative losses. As combustion products enter the chamber at higher and higher temperatures, they may simply burn rather than detonation. This work showed that this was not the case and maintained detonative performance at relatively high pressures and injection temperatures. The long-term goal is to push the limits of detonation performance with the extremes of staged combustion and demonstrate superior performance to the state-of-the-art liquid rocket engines.

Project Results and Conclusions

Rotating detonation rocket engines (RDREs) hold the promise of increased performance and reduced thrust chamber assembly length and weight. The consumption of propellants by a detonation wave moving at 1-2 km/s increases combustor power density by an order of magnitude when compared to today’s devices. In particular, the gaseous oxygen (Gox)/kerosene system has delivered some attractive performance in preliminary testing, but additional exploration is required to assess performance and operability changes for usage in staged combustion applications. It is essential to gain understanding of the sensitivity of the detonative performance to injection system design and oxygen-rich preburner operation. While preburner temperatures are generally set by turbine material limits in today’s staged combustion engines, the kinetics of detonative combustion can dictate a lower temperature to maximize performance. Purdue University has been working in this field since 2019 when a highly successful test campaign was conducted using a preburner feeding warm oxygen to an RDRE combustor using transverse jet injection of RP2 kerosene fuel. Results from this test campaign were highly encouraging as rotating detonations were observed in the vast majority of the 45 tests conducted. In addition to high performance and operability, dramatic soot reduction was noted in some operating conditions. These encouraging results are prompting additional efforts using additively manufactured, water-cooled chambers in order to assess impacts of injector designs, preburner operation, and cooling loads.

The prime objective of this work is to assess the performance and operability of an additively manufactured RDRE chamber using Gox and RP-2 propellants. In 2022 Center Innovation Fund (CIF) efforts, a 1000-lbf class water cooled combustor was designed and manufactured and is currently under testing evaluation. Preburner Gox temperature is a prime design variable in terms of operability as it appears there is a balance between combustion kinetics and performance/operability based on earlier efforts in the 2019 campaign. This work directly addresses the STMD capability gap for novel and innovative engine cycle studies and RDRE advancement. The mission pull is directly tied to the agency’s need for high performance storable lander propulsion systems in support of HLS and SLS. It is a transformative technology also with broad applicability to other engine systems and scales.