Investigation of usage of different methane fuel qualities for rocket engines with respect to the pyrolysis stability

Background

Around the world, several organizations are researching and developing rocket engines using liquid methane and oxygen as propellants. This propellant combination, sometimes called “methalox”, has gained interest over the last years due to its favorable specific gravity, storage temperature, and thermal stability, which allow for the design of efficient and compact launch vehicles. Moreover, methane can be obtained from various sources, including biogas and natural gas, but it can also be synthesized from water and hydrogen using the Sabatier process. This makes methane an interesting fuel for missions to e.g. Mars, where these components are locally available.

As part of the European effort to develop methane-based rocket engines, KTH’s division of Heat and Power Technology (HPT) and industrial partner GKN Aerospace formed the MERiT project. In this research project, we are investigating the characteristics of methane when used as a coolant in additively manufactured cooling channels for rocket nozzles. One of the main aspects under investigation is the thermo-catalytic decomposition of methane in such channels. This so-called pyrolysis results in the deposition of solid carbon on the cooling channel walls, which act as a thermal insulator. This deposition therefore leads to higher wall temperatures and reduced engine lifetime. The pyrolysis of methane depends, amongst others, on the flow properties, temperature, pressure and residence time, but also on the catalytic properties of the channel wall material and the purity of the fuel. These aspects are currently the focus of the investigation at HPT and an experimental setup, called the MERiT Small Pyrolysis Setup (SPS) has been developed with which the effects of these variables can be studied.

Thesis objectives

The aim of the thesis project is to design and implement an experimental campaign on the Small Pyrolysis Setup (SPS), with the objective of mapping the pyrolysis effect for the test samples (of rocket nozzle’ cooling channels) for different qualities/purities of methane fuel. The project work will also include a feasibility study on the economic effect of using lower grade methane fuel for rocket engines.

Specific objectives

• To perform a literature review on the methane fuel qualities used in rocket engines and current trends.

• To familiarize with the SPS and previous developments and the gas mixing station, gas analysis instrumentation and gas chromatograph.

• To prepare an experimental plan for material testing with the goal of reaching the pyrolysis inception conditions for different methane fuel qualities.

• To run experiments, collect and interpret data, and report this information.

• To perform a feasibility study on the economic effect of usage of lower grade methane for space launch.

• To work together with researchers at HPT to validate the measurement system for the operating conditions found in real rocket nozzle cooling channels.

Main deliverables

• Final thesis report and presentation of the project

• Material measurement results

Duration

The project should start in Jan-Feb 2025, with a duration of up to 6 months.

Location

KTH, Department of Energy Technology

Main Supervisors

Examiner