Protolaunch Tackles European Deep Throttling Needs with Controller Development

Protolaunch Awarded Contract to Develop Engine Control Systems Targeting Deep Throttling Ranges for Bi-Propellant Liquid Rocket Engines

Westcott UK - 10/11/2025 – Protolaunch are thrilled to announce its selection by the European Space Agency for the design, development and verification of a multivariable control system for bi-propellant Liquid Rocket Engines (LREs). These systems will improve closed loop control of throttleable engines to enable precise and deep LRE throttling.

Addressing Europe’s Capability Gap

The success of next-generation space missions – specifically Reusable Launchers and advanced Landers required for autonomous planetary exploration – is dependent on High-Performance LREs. Currently, European LREs lack widespread capabilities that define this performance tier, notably: deep throttlability, multiple restart functionality, and extended operational life. 

Protolaunch has been awarded a contract to address this deep throttling challenge by developing a sophisticated multivariable, closed-loop controller. This system is designed to enable precise and deep throttling by dynamically monitoring key engine variables, including chamber pressure, mixture ratio, and overall engine health.

Collaborative Design and Cross-Engine Verification

To ensure the controller meets the future demands of the European space sector, Protolaunch will be proactively engaging with industry stakeholders to gain insights into engine control priorities.

The controller's cross-engine compatibility will also be rigorously verified using two distinct platforms:

·       Protolaunch’s own 500N Liquid Rocket Engine (Arctic-FOx).

·       Airborne Engineering Ltd’s 1500N Lambda Engine 

Verification testing will be executed across two dedicated sites: Protolaunchs’ In-House Propulsion Testing Facility (E-Site) and Airborne Engineering Ltd’s propulsion testing facility, both located at the Westcott Space Cluster in the UK. These campaigns are designed to verify the controller's ability to achieve precise and deep throttling.

Project Source

This 24-month project is carried out under a programme of, and funded by, the European Space Agency’s General Support Technology Programme (GSTP).

Building on Throttling Heritage

This project builds on Protolaunch’s existing throttling expertise – following the delivery of cavitating venturi valves for an autonomous planetary Lander application (see press release here).

Looking Ahead

Protolaunch remains dedicated to advancing its throttling technologies across the full spectrum of chemical propulsion, including cryogenic applications. We are actively seeking opportunities to leverage this unique throttling experience in future space exploration missions.

Get Involved: If you are engaged in developing a Reusable Launch Vehicle, Lander Vehicle, or another platform that requires advanced throttling applications and would like your specific priorities captured in the development of this engine controller, our Commercial Development Manager, Charlie Goodwin will welcome responses via email (charlie@protolaunch.co.uk).

Views expressed in this publications can in no way be taken to reflect the official opinion of the European Space Agency.

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