Rolls-Royce plc last Friday said it has made an additional investment in Reaction Engines as part of a wider funding round in the United Kingdom-based advanced technology aircraft and rocket engine designer and developer, and has also partnered with the small company to develop high-speed aircraft propulsion systems.

Terms of the latest funding round and investment by Rolls-Royce, also based in the U.K., were not disclosed.

Rolls-Royce, Britain’s BAE Systems

, and Boeing’s [BA] HorizonX ventures arm were all part of a $37.3 million funding round for Reaction Engines in 2018. BAE in 2015 invested around $40 million in Reaction Engines for a 20 percent stake in the company.

The past two years Rolls-Royce and Reaction Engines have been working under a U.K. Ministry of Defence contract on design studies, research, development, and experimentation related to high-Mach advanced propulsion systems.

“We have been working closely with Reaction engines for the past two years, including exploring the potential of high-Mach systems for defense applications, and I am delighted that we are able to strengthen that relationship,” Mark Thompson, director of Global Strategy & Business Development for Rolls-Royce, said in a statement. “This partnership follows our recent announcements with Boom Supersonic and Virgin Galactic. Reaction Engines’ thermal management skills, added to our suite of existing technologies and capabilities, will further assist us as we explore opportunities in supersonic and hypersonic aviation. Building on our many decades of innovation, we will also explore the use of Reaction Engines’ technology within our aerospace gas turbines and its potential application in future hybrid-electric propulsion systems, as we look to make flying ever more efficient and sustainable.”

Reaction Engines, which also has a site in Denver, said the new partnership with Rolls-Royce is a step toward its commercializing plans with market ready applications. The company has more than 200 employees.

Reaction Engines touts its precooler technology for heat management at “extremely low weight and at a compact size.” The technology is a key part of its Synergetic Air-Breathing Rocket Engine, which is refers to as SABRE, that is being designed for air-breathing thrust from a runway to speeds exceeding Mach 5 in the atmosphere, and for next-generation space access vehicles.

Reaction Engines says that components and technologies of SABRE have been successfully tested and demonstrated and that a successful ground-based high-temperature test of the precooler took place in 2019.