Preliminary Design of a Small Hydrogen Peroxide Cooled Thrust Chamber for Additive Manufacturing

Abstract

As a part of a Future Launcher Preparatory Programme contract issued by the European Space Agency, the aerospace startup company Dawn Aerospace is developing an integral, additive manufactured (AM), liquid rocket engine. This 2.5 kN class engine is propelled by the storable propellants 90% hydrogen peroxide and kerosene and used in the application of a (sub)orbital spaceplane. In this study, a preliminary design for the thrust chamber of the AM engine is proposed, which is realized from the superalloy Inconel 718. To avoid the chamber wall from melting under the extreme thermal loads which originate from the ongoing combustion reaction, both regenerative cooling and film cooling with hydrogen peroxide are considered. The proposed designs are based on a custom-developed 2-D numerical analysis code, which considers non-linear steady-state heat transfer and linear elastic structural deformation. The results of this code are validated against hot-fire tests of both regenerative cooled and film cooled thrust chambers, propelled by 90% hydrogen peroxide and kerosene. Moreover, an immersion screening test campaign is conducted to validate the chemical compatibility of AM Inconel 718 with 90% hydrogen peroxide. This thesis compares the proposed AM chamber designs to the current bimetallic chamber design that is already developed and hot-fired by Dawn Aerospace. The bimetallic design comprises a coated copper-alloy liner and relies mostly on non-AM production techniques. The coating is introduced to improve the chemical compatibility with hydrogen peroxide. Simulations show that the total available delta-v of the spaceplane is reduced from 3.46 km/s to 3.38 km/s when the bimetallic design is replaced by an AM Inconel 718 design, relying on regenerative cooling and film cooling. On the contrary, the AM design may offer a thrust chamber dry mass reduction of more than 75%, whereas the total number of sealing interfaces can be reduced by more than 50%. In addition, the inspection-heavy coating, which is plated onto the copper alloy liner of the current bimetallic engine design, can be removed in the AM design.