Sierra Space Tests New Hypergolic Rocket Engine with Continuous Throttling Capability

Sierra Space Tests New Hypergolic Rocket Engine with Continuous Throttling Capability

Sierra Space, one of the leading pureplay commercial space companies building the first end-to-end business and technology platform in space, announced 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 of 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 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.

Click here to learn more about Spacecraft Thrusters on SATNow.

Publisher: SatNow

GNSS Constellations - A list of all GNSS satellites by constellations


Satellite NameOrbit Date
BeiDou-3 G4Geostationary Orbit (GEO)17 May, 2023
BeiDou-3 G2Geostationary Orbit (GEO)09 Mar, 2020
Compass-IGSO7Inclined Geosynchronous Orbit (IGSO)09 Feb, 2020
BeiDou-3 M19Medium Earth Orbit (MEO)16 Dec, 2019
BeiDou-3 M20Medium Earth Orbit (MEO)16 Dec, 2019
BeiDou-3 M21Medium Earth Orbit (MEO)23 Nov, 2019
BeiDou-3 M22Medium Earth Orbit (MEO)23 Nov, 2019
BeiDou-3 I3Inclined Geosynchronous Orbit (IGSO)04 Nov, 2019
BeiDou-3 M23Medium Earth Orbit (MEO)22 Sep, 2019
BeiDou-3 M24Medium Earth Orbit (MEO)22 Sep, 2019


Satellite NameOrbit Date
GSAT0223MEO - Near-Circular05 Dec, 2021
GSAT0224MEO - Near-Circular05 Dec, 2021
GSAT0219MEO - Near-Circular25 Jul, 2018
GSAT0220MEO - Near-Circular25 Jul, 2018
GSAT0221MEO - Near-Circular25 Jul, 2018
GSAT0222MEO - Near-Circular25 Jul, 2018
GSAT0215MEO - Near-Circular12 Dec, 2017
GSAT0216MEO - Near-Circular12 Dec, 2017
GSAT0217MEO - Near-Circular12 Dec, 2017
GSAT0218MEO - Near-Circular12 Dec, 2017


Satellite NameOrbit Date
Kosmos 2569--07 Aug, 2023
Kosmos 2564--28 Nov, 2022
Kosmos 2559--10 Oct, 2022
Kosmos 2557--07 Jul, 2022
Kosmos 2547--25 Oct, 2020
Kosmos 2545--16 Mar, 2020
Kosmos 2544--11 Dec, 2019
Kosmos 2534--27 May, 2019
Kosmos 2529--03 Nov, 2018
Kosmos 2527--16 Jun, 2018


Satellite NameOrbit Date
Navstar 82Medium Earth Orbit19 Jan, 2023
Navstar 81Medium Earth Orbit17 Jun, 2021
Navstar 78Medium Earth Orbit22 Aug, 2019
Navstar 77Medium Earth Orbit23 Dec, 2018
Navstar 76Medium Earth Orbit05 Feb, 2016
Navstar 75Medium Earth Orbit31 Oct, 2015
Navstar 74Medium Earth Orbit15 Jul, 2015
Navstar 73Medium Earth Orbit25 Mar, 2015
Navstar 72Medium Earth Orbit29 Oct, 2014
Navstar 71Medium Earth Orbit02 Aug, 2014


Satellite NameOrbit Date
NVS-01Geostationary Orbit (GEO)29 May, 2023
IRNSS-1IInclined Geosynchronous Orbit (IGSO)12 Apr, 2018
IRNSS-1HSub Geosynchronous Transfer Orbit (Sub-GTO)31 Aug, 2017
IRNSS-1GGeostationary Orbit (GEO)28 Apr, 2016
IRNSS-1FGeostationary Orbit (GEO)10 Mar, 2016
IRNSS-1EGeosynchronous Orbit (IGSO)20 Jan, 2016
IRNSS-1DInclined Geosynchronous Orbit (IGSO)28 Mar, 2015
IRNSS-1CGeostationary Orbit (GEO)16 Oct, 2014
IRNSS-1BInclined Geosynchronous Orbit (IGSO)04 Apr, 2014
IRNSS-1AInclined Geosynchronous Orbit (IGSO)01 Jul, 2013