Phase Four, Inc.
aka Phase Four
Phase Four, founded in 2015 and headquartered in Hawthorne, California, developed radiofrequency (RF) plasma electric propulsion systems and Hall effect thrusters for small satellites. The company's Maxwell RF thruster flew on SpaceX Transporter-1, and its Valkyrie Hall thruster was developed for Space Development Agency missions in partnership with Redwire. In September 2025, Quantum Space acquired Phase Four's multi-mode propulsion assets and integration/test facility.
Launches
Payloads in Orbit
Active Sats (reported)
Funding Raised
Products & Services
Maxwell RF Thruster
operationalCompact radiofrequency plasma thruster (approx. 6 kg) offering propellant-agnostic operation. Flew on SpaceX Transporter-1 in 2021.
Since 2021
Valkyrie Hall Effect Thruster
operationalHall effect thruster based on the NASA-designed H71M, developed with Redwire for government and commercial missions including Space Development Agency programs.
Since 2024
Maxwell Block III Multi-Mode System
operationalMonopropellant multi-mode propulsion system supporting ASCENT or hydrazine chemical propellants, enabling dual chemical/electric operation.
Since 2025
Key Challenges
No events recorded.