Phase Four, Founded in 2015 and headquartered in Hawthorne, California, is at the forefront of developing advanced in-space propulsion systems. The company's mission is to provide versatile electric propulsion solutions for a variety of satellites, fuels, and mission types, ensuring constellation operators have the broadest set of options to perform their missions. Phase Four's focus areas include satellite services, propulsion systems, and other developments aimed at revolutionizing satellite mobility. Notable partnerships include collaborations with Redwire and the Air Force Research Laboratory (AFRL), underscoring their commitment to innovation and excellence in the aerospace industry.

Technology & Innovation

Phase Four's technological advancements are reshaping the landscape of satellite propulsion. Their flagship product, the Valkyrie Thruster, is based on the NASA-licensed “H71M” Hall-effect Thruster (HET). This system offers best-in-class performance in thrust, efficiency, and total impulse, and is specifically designed for operations ranging from Low Earth Orbit (LEO) to Cis-Lunar environments. Developed in partnership with Redwire, the Valkyrie Thruster can be delivered ten months after an order is placed. 

In addition to the Valkyrie, Phase Four is actively engaged in research and development through its PlasmaWorks initiative. This program focuses on advancing RF plasma propulsion, exploring new propellants, and developing applications of plasma propulsion in space. Notably, Phase Four is pioneering the development of an electrodeless iodine plasma thruster in the United States, a project supported by a Phase 2 Small Business Innovation Research grant funded by AFWERX. The use of iodine as a propellant offers several advantages, including lower cost, higher storage density, and improved supply chain robustness compared to traditional propellants like xenon and krypton. 

Products & Services

Phase Four's product portfolio is designed to meet the diverse needs of satellite operators and researchers. The Valkyrie Thruster stands out with its modern design, offering a thrust range of 20-34 mN, specific impulse between 1200-1300 seconds (using xenon), and a system mass of 13 kg. Its compatibility with both xenon and krypton propellants provides flexibility for various mission requirements.

Beyond hardware, Phase Four offers comprehensive services to support satellite missions. These services include environmental testing (such as pressure and leak testing), propellant logistics (ordering, receiving, and storing EP propellants), fill operations for EP systems, and delivery of fully fueled systems to launch sites. This end-to-end support ensures that clients receive reliable and efficient propulsion solutions designed to their specific needs.

Recent Developments & Achievements

Phase Four has achieved significant milestones in recent times. In January 2025, the company announced the first close of its Series C funding round, securing nearly 60% of the target raise. This round was led by Artemis Group Capital, an investment firm helmed by former NASA Administrator Jim Bridenstine, highlighting strong investor confidence in Phase Four's innovative propulsion solutions. 

Additionally, in October 2024, Phase Four announced the planned commercialization of their monopropellant multimode capability. This development aims to provide satellites with better maneuverability and operability in space at an affordable cost, further solidifying Phase Four's position as a leader in next-generation electric propulsion solutions. 

Future Prospects & Industry Impact

Phase Four is composed to play a pivotal role in shaping the future of the space and satellite industry. Their ongoing research into advanced propellants like iodine and the development of multimode propulsion systems are set to offer more efficient and cost-effective solutions for satellite mobility. By addressing the critical challenges of in-space propulsion, Phase Four is enabling the exponential growth of satellite constellations and contributing to the advancement of space exploration technologies.

Phase Four's commitment to innovation and excellence in in-space propulsion systems positions them as a key player in the aerospace industry. Their cutting-edge technologies and comprehensive services are transforming the way satellites operate and maneuver in space.

Click here to learn more about Phase Four's In-Space Propulsion Systems and Technologies