LOUISVILLE, Colorado – February 12, 2025 –Sierra Space, Inc., a leading commercial aerospace and defense technology company building a platform in space to benefit life on Earth® , today announced the successful completion of the test campaign for its fully integrated VR35K-A upper stage engine, commissioned by the Rocket Propulsion Division of the Air Force Research Laboratory (AFRL), Edwards, Air Force Base, Calif. This marks a significant step forward in Sierra Space’s development of advanced propulsion systems.
Additionally, the company has been awarded a $16 million firm-fixed-price contract by AFRL to continue development of upper-stage engines to fulfill future National Security Space Launch (NSSL) missions. This is a follow-up toa contract worth more than $22 million awarded to Sierra Space in July 2023 by the Air Force Test Center at Edwards Air Force Base in California.
The VR35K-A is a high-performance liquid oxygen (LOX)/liquid hydrogen (LH2) engine that utilizes a fuel-rich staged combustion cycle, innovative turbopump architecture, and a VORTEX® combustor to produce 35,000 lbf of thrust with higher performance than any engine currently on the market. Sierra Space’s patented VORTEX technology enables efficient and stable combustion while providing active cooling to the combustor, delivering high performance and reliability.
Other key features of the VR35K-A include: Simplified Operation: A single-shaft turbopump design for streamlined functionality, including startup and shutdown. Mechanically linked ratio control: ensures precise balance between fuel and oxidizer. Additive manufacturing: reducing production costs and lead times for complex components.
“Our powerful new upper stage engine, the VR35K-A, represents a breakthrough advancement in propulsion technology, leveraging Sierra Space’s patented VORTEX engine design to achieve unprecedented efficiency, reliability and affordability,” said Dan Polis, Vice President of Engineering Solutions and Propulsion Systems at Sierra Space. “We are delivering high performance, reduced complexity and significant cost savings with this revolutionary new product, allowing our customers and partners to deliver up to 30% more payload mass to space. This engine is a testament to our company’s commitment to pushing the boundaries of space commercialization with advanced, scalable solutions.”
“Kratos is a leader in propulsion technology, committed to the rapid development, demonstration and deployment of innovative solutions,” said Stacey Rock, President of Kratos’ Turbine Technologies Division. “Our philosophy is to collaborate with industry leaders who share our mission to bring advanced technologies and capabilities to market quickly and cost-effectively. This partnership with Sierra Space has proven to be very successful and is a cornerstone of our long-term strategic initiatives.”
Sierra Space’s VR35K-A engine will address a critical industry need in supporting larger payload deliveries to low Earth orbit and beyond. Sierra Space is also applying its VORTEX combustion chamber technology to engines and thrusters to support in-space propulsion for spacecraft maneuvering in orbit and extraterrestrial landers. For example, Sierra Space’s Dream Chaser ® spacecraft uses VORTEX in its reaction control system thrusters.
In 2023, Sierra Space announced that the VR35K-A had completed engine component testing, allowing the company to move on to a full engine hot fire test campaign. Sierra Space will then continue to develop its higher-stage engine technology as it moves into a more extensive qualification phase.
About Sierra Space
Sierra Space is a leading commercial space company at the forefront of innovation and commercialization of space in the Orbital Age®, building an end-to-end business and technology platform in space to benefit life on Earth. With over 30 years and 500 missions of space heritage, the company is reinventing both space transportation with Dream Hunter®, the world’s only commercial spacecraft, and the future of space destinations with the company’s inflatable and expandable space station technology. Using commercial business models, the company also provides orbital services to commercial, DoD, and national security organizations, and is expanding manufacturing capacity to meet the needs of constellation programs. Additionally, Sierra Space builds a broad range of systems and subsystems in the areas of solar energy, mechanical and motion control, environmental control, life support, propulsion, and thermal control, and offers numerous space-as-a-service solutions for the new space economy.
Source: Sierra Space
