Sierra Space Successfully Tests New 5,500 lbf Hypergolic Rocket Engine Capable of Continuous Throttling

Sierra Space Successfully Tests New 5,500 lbf Hypergolic Rocket Engine Capable of Continuous Throttling

New engine technology provides a high performance and deep throttling propulsion system for demanding in-space applications

LOUISVILLE, Colo. – Nov. 9, 2023  Sierra Space, a leading pureplay commercial space company building the first end-to-end business and technology platform in space, announced today that it successfully tested a new 5,500 lbf. hypergolic rocket engine that promises to become a groundbreaking addition to its engine portfolio.

Employing pure hydrazine fuel and MON3 oxidizer in a staged combustion cycle, the new engine delivers a vacuum specific impulse of over 339 seconds, making it very efficient for a storable engine. In addition, the engine is designed for continuous throttling from 5,500 lbf of thrust at 100% power down to 900 lbf at 17% power, allowing for precise control and maneuverability.

“This high-performance, re-usable bipropellant engine represents a major leap in space propulsion technology, setting new standards for efficiency, reusability and versatility,” said Tom Vice, CEO for Sierra Space. “This engine is tailored for in-space applications where reusability, storability, throttling and vehicle weight-saving are paramount, making it an excellent choice for landers, upper stages, transit vehicles and extended-duration missions.”

The use of hydrazine as the fuel provides commonality for spacecraft using hydrazine monopropellant thrusters for attitude control and maneuvering, thus simplifying overall propulsion system architecture.

The engine employs a highly innovative preburner – along with unique thrust chamber cooling – to provide high combustion efficiency and stability across the throttle range. Designed and developed by Agile Space Industries, the preburner underwent multiple hot-fire demonstrations in a standalone configuration prior to integration with the rest of the engine.

“In a timeline of 19 weeks, Agile was able to design, manufacture, test, iterate and deliver a reliable preburner,” said Agile Space Industries CEO Chris Pearson. “The timeline was extremely fast, especially given that this is the first time that we have been able to find, in the public record, that a high-flow hydrazine-rich preburner has been developed and used in an engine.  The initial prototype demonstrated stable operation across a 6:1 throttle range with high combustion efficiency.”

Following preburner development, the new VRM5500-H engine was tested at the US Army DEVCOM stand at Redstone Arsenal in Huntsville, Alabama. The engine exhibited efficient, stable combustion at all throttle points, with a minimum throttle Isp exceeding 339 seconds.

The teams at Sierra Space and Agile Space Industries executed the design, development and testing of the prototype engine in just over nine months by employing rapid design-to-test cycles and heavy use of advanced additive manufacturing techniques to minimize fabrication time. The thrust chamber and preburner are fully 3D printed on common metallic printers, demonstrating Sierra Space’s commitment to pushing the boundaries of design and manufacturing technologies in the aerospace industry.


About Sierra Space
Sierra Space is a leading, pureplay commercial space company at the forefront of innovation and the commercialization of space in the Orbital Age®, building an end-to-end business and technology platform in space to benefit life on Earth. With more than 30 years and 500 missions of space flight heritage, the company is enabling the future of space transportation with Dream Chaser®, the world’s only commercial spaceplane, and is bringing LIFE® (Large Integrated Flexible Environment) to low-Earth orbit with its modular, three-story commercial habitation and science platform. Both Dream Chaser and LIFE are central components to Orbital Reef, a mixed-use business park in LEO being developed by principal partners Sierra Space and Blue Origin, which is expected to be operational by the end of the decade. Sierra Space also builds and delivers a host of systems and subsystems across solar power, mechanics and motion control, environmental control, life support, propulsion and thermal control, offering myriad space-as-a-service solutions for the new space economy.


About Agile Space Industries

Agile Space Industries is an in-space propulsion solution provider, specializing in hypergolic chemical systems. Agile has industry leading expertise in the design of chemical-propulsion rocket thrusters. Rapid prototyping, development, qualification and delivery is catalyzed by in-house additive manufacturing and engine test capability. The company employs more than 65 people between facilities in Durango, Colorado, and Mount Pleasant, PA, that specialize in component, system development, test and additive manufacturing. Agile is working with numerous primes as well as the US Government on various spacecraft and launch vehicle propulsion projects.





Alex Walker, Sierra Space

(303) 803-2297 |


Juleah Kaliski, Agile Space Industries

(530) 351-2179 |

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