Sierra Space Successfully Completes VR35K-A Upper Stage Engine Test Campaign, Secures $16 Million AFRL Contract
Sierra Space, a leading commercial space company and defense technology prime, has successfully completed the test campaign for its fully integrated VR35K-A upper stage engine. This achievement marks a significant milestone in the company’s ongoing efforts to develop cutting-edge propulsion systems that support national security, exploration, and commercialization. Conducted under contract with the Air Force Research Laboratory’s (AFRL) Rocket Propulsion Division at Edwards Air Force Base in California, the test campaign validates Sierra Space’s continued advancement in next-generation propulsion technology.
This successful test campaign comes on the heels of another major development for Sierra Space. The company has secured a $16 million firm-fixed-price contract from AFRL to continue its upper stage engine maturation efforts. This award follows a previous $22 million contract granted in July 2023 by the Air Force Test Center at Edwards Air Force Base, further demonstrating the government’s confidence in Sierra Space’s innovative propulsion solutions.
Advancing Propulsion Technology with the VR35K-A Engine
The VR35K-A is a high-performance, liquid oxygen (LOX)/liquid hydrogen (LH2) upper stage engine designed to provide superior efficiency and reliability. Employing a fuel-rich staged combustion cycle, an innovative turbopump architecture, and a VORTEX® combustion chamber, the VR35K-A produces 35,000 lbf of thrust while outperforming existing propulsion systems on the market. The VORTEX® technology, patented by Sierra Space, enables efficient and stable combustion while ensuring active cooling of the combustion chamber, resulting in enhanced performance, reliability, and operational cost savings.
According to Dan Polis, Vice President of Engineering Solutions and Propulsion Systems at Sierra Space, “Our powerful new upper stage engine, the VR35K-A, represents a groundbreaking advancement in propulsion technology. By leveraging Sierra Space’s patented VORTEX engine design, we have achieved unprecedented efficiency, reliability, and affordability. This revolutionary engine delivers high performance, reduces complexity, and significantly lowers costs, allowing our customers and partners to transport up to 30% more payload mass to orbit. This engine is a testament to our company’s commitment to pushing the boundaries of space commercialization with scalable, cutting-edge solutions.”
Key Features and Capabilities of the VR35K-A Engine
The VR35K-A engine boasts several advanced features that distinguish it from traditional upper-stage engines:
- Simplified Operation: A single-shaft turbopump assembly enhances streamlined functionality, including start-up and shutdown procedures.
- Mechanically-Coupled Mixture Ratio Control: Ensures a precise balance between fuel and oxidizer for optimal combustion.
- Additive Manufacturing: Reduces production costs and lead times for complex engine components, making manufacturing more efficient and cost-effective.
The rigorous test campaign, completed in 2024 at Sierra Space’s Badger Propulsion Test Facility in North Freedom, Wisconsin, achieved all key objectives. The engine demonstrated stable and efficient thrust chamber operation, robust turbomachinery performance, precise mixture ratio control, and throttle capability while achieving high overall efficiency.
Strategic Partnership with Florida Turbine Technologies
Sierra Space has partnered with Florida Turbine Technologies, a subsidiary of Kratos Defense & Security Solutions, Inc., to develop and test the turbomachinery used in the VR35K-A engine. The engine’s single-shaft main turbopump assembly ensures simplified and reliable operation, while its mechanically-coupled mixture ratio control further enhances efficiency. Prior to full engine integration, Sierra Space conducted a comprehensive standalone turbomachinery test campaign to validate the system’s operating points and predicted performance.
Stacey Rock, President of Kratos’ Turbine Technologies Division, emphasized the importance of collaboration in advancing propulsion technology: “Kratos is a leader in propulsion technology, dedicated to the rapid development, demonstration, and deployment of innovative solutions. Our philosophy is to collaborate with industry leaders who share our mission of delivering cutting-edge technologies and capabilities to market quickly and cost-effectively. This partnership with Sierra Space has been highly successful and represents a cornerstone of our long-term strategic initiatives.”
The Future of National Security Space Launch (NSSL) Missions
Sierra Space’s VR35K-A engine plays a critical role in supporting larger payload deliveries to Low Earth Orbit (LEO) and beyond. As the demand for reliable and cost-effective space transportation grows, this engine will serve as a key solution for commercial and government customers. The recent AFRL contract reinforces the significance of this technology in future National Security Space Launch (NSSL) missions, ensuring that the United States maintains its leadership in space access and propulsion capabilities.
In addition to its role in upper-stage propulsion, Sierra Space is applying its VORTEX® combustion chamber technology to other propulsion systems, including in-space thrusters for orbital maneuvering and extraterrestrial landers. The company’s Dream Chaser® spacecraft, a reusable spaceplane designed for cargo and crew transportation, utilizes VORTEX technology in its reaction control system thrusters to enhance maneuverability and efficiency.
Pathway to Full Qualification and Commercial Deployment
Sierra Space continues to make significant progress toward full qualification and commercial deployment of the VR35K-A engine. In 2023, the company successfully completed engine component testing, paving the way for the full engine hot fire test campaign. With the recent test campaign now complete, the next phase will involve further maturation of the upper stage engine technology, leading into an extensive qualification phase.
The company’s roadmap includes additional engine refinements, system-level validation, and integration into future commercial and government space missions. This strategic approach ensures that Sierra Space remains at the forefront of propulsion innovation, providing scalable and efficient solutions for the evolving space industry.
About Sierra Space
Sierra Space is a leading commercial space company that is redefining space transportation, orbital infrastructure, and advanced propulsion systems in the new Orbital Age®. With over 30 years of experience and more than 500 successful spaceflight missions, the company is dedicated to building a comprehensive business and technology platform in space to benefit life on Earth.
Key areas of focus include:
- Space Transportation: Sierra Space is revolutionizing space travel with the Dream Chaser® spaceplane, designed to transport cargo and crew to the International Space Station (ISS) and other destinations.
- Space Destinations: The company is pioneering the future of space habitats with inflatable and expandable space station technology, creating a new paradigm for long-duration missions and commercial space operations.
- Orbital Services: Sierra Space provides a wide range of space-as-a-service solutions for commercial, Department of Defense (DoD), and national security customers, supporting satellite constellations and other critical missions.
- Advanced Propulsion Systems: Through innovations like the VR35K-A engine and VORTEX combustion technology, Sierra Space is advancing the state-of-the-art in propulsion for launch vehicles, in-space transportation, and extraterrestrial exploration.
By leveraging commercial business models, Sierra Space is driving cost efficiencies, expanding production capacity, and delivering scalable solutions to meet the demands of the new space economy.
For more information about Sierra Space and its revolutionary propulsion systems, visit www.sierraspace.com.