Vary that thrust: longer hot-fire of Throttleable Liquid Propulsion Demonstrator

A new variable-thrust rocket engine demonstrator acing its second run of tests in Poland, November 2024.

The Throttleable Liquid Propulsion Demonstrator (TLPD) is a Łukasiewicz Research Network – Institute of Aviation rocket engine demonstrator that will be ideal for use as part of upper stages on small rockets and could be used on spacecraft, kick-stages or exploration missions. The engine can vary its thrust down to 10% and up to 110% of its ideal operating conditions, making it a good candidate for use on landing on other planets. It is restartable and runs on non-toxic easily-storable propellants.

The second phase of the test campaign had the engine firing up and running at varying thrusts for up to a minute at a time. A new combustion chamber – made with additive manufacturing techniques – added water-cooling to allow longer tests while also varying the thrust. It is one thing to keep a rocket engine running at different levels of power, but an extra difficulty to throttle between the different levels.

During the throttling the engine runs in so-called transient phases that are by definition dynamic and thus hard to predict or control. The complete engine design worked perfectly with very stable combustion for all engine operating points tested over the 14 hot-fire runs.

The project is part of ESA’s Future Launchers Preparatory Programme (FLPP) with prime contractor ‘Łukasiewicz Research Network – Institute of Aviation’ (Lukasiewicz-ILOT) based in Poland and partners Astronika and Jakusz SpaceTech. A Łukasiewicz spin-off company, Thaliana Space, will join the project in this second phase, working with potential customers to integrate their needs into the engine design.