Phase Four
Phase Four is a leading provider of electric propulsion systems for small satellites, developing innovative radio-frequency thrusters that simplify spacecraft propulsion while reducing size, weight, and cost.
- Founded
- 2015
- Headquarters
- El Segundo, United States
- Ownership
- Private
- Last round
- Undisclosed round · $12.9M2025-01
Quick Facts
About Phase Four
Phase Four is a leading provider of electric propulsion systems for small satellites, developing innovative radio-frequency thrusters that simplify spacecraft propulsion while reducing size, weight, and cost. The Hawthorne, California company produces turn-key plasma propulsion systems for commercial and government customers.
In July 2024, Phase Four announced the Maxwell Block 3 plasma propulsion thruster, with orders open for Q1 2024 delivery from the company's new 25,000 square-foot manufacturing facility. Maxwell Block 3 offers significantly shorter lead times and lower prices compared to legacy plasma propulsion systems while exceeding Hall effect thruster performance.
In October 2024, Phase Four announced commercialization of monopropellant multi-mode capability, combining high-thrust chemical propulsion with efficient electric propulsion using a single propellant. The RF thruster uniquely supports chemical propellant integration, eliminating auxiliary xenon or krypton tanks required by other multi-mode systems. Ground demonstrations using ASCENT and hydrazine systems are planned with DoD and private partners by Q1 2025.
The hallmark of Phase Four's technology is flexible architecture utilizing traditional noble gases and alternative propellants including iodine, water, and air. The next-generation RF plasma thruster doubles peak specific impulse above 900 seconds compared to earlier blocks, doubling total impulse for fixed propellant tank sizes. Phase Four continues advancing versatile electric propulsion technology for the growing small satellite market.
Funding history
4 events| Date | Round | Amount | Investors | Source |
|---|---|---|---|---|
| 2025-01-06 | Undisclosed round | $12.9M | —Form D filed 2025-01-17 by PHASE FOUR, INC.: $12.9M sold of a $19.8M offering (first sale 2025-01-06). | sec.gov |
| 2021-06-10 | Undisclosed round | $5.5M | —Form D filed 2021-07-23 by PHASE FOUR, INC.: $5.5M sold of a $27.0M offering (first sale 2021-06-10). | sec.gov |
| 2020-01-15 | Undisclosed round | $3.6M | —Form D filed 2020-01-29 by PHASE FOUR, INC.: $3.6M sold of a $17.6M offering (first sale 2020-01-15). | sec.gov |
| 2015-12-11 | Undisclosed round | $1.1M | —Form D amendment filed 2016-01-05 by PHASE FOUR, INC.: $1.1M sold of a $1.1M offering (first sale 2015-12-11). | sec.gov |
Signals
- Verification
- Verified 2026-09-05
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Frequently asked about Phase Four
Quick answers to the questions readers most often search for.
- When was Phase Four founded?
- Phase Four was founded in 2015 in United States.
- Where is Phase Four headquartered?
- Phase Four is headquartered in El Segundo, United States.
- What does Phase Four do?
- Phase Four is a leading provider of electric propulsion systems for small satellites, developing innovative radio-frequency thrusters that simplify spacecraft propulsion while reducing size, weight, and cost. The Hawthorne, California company produces turn-key plasma propulsion systems for commercial and government cus…
- Is Phase Four a public or private company?
- Phase Four is a privately held company and is not listed on any stock exchange.
- What sector does Phase Four operate in?
- Phase Four works in propulsion.
Sources
The structured fields on this page (founding year, location, sector, status, listing) and the profile text are drawn from the sources below. How profiles are drafted and checked is described in our methodology.
- Official website (phasefour.io)
- SEC Form D · retrieved 2026-09-05
- SEC Form D · retrieved 2026-09-05
- SEC Form D · retrieved 2026-09-05
- SEC Form D · retrieved 2026-09-05
Data Accuracy Notice: Information about Phase Four is compiled from publicly available sources including company websites, press releases, regulatory filings, and industry reports. Data is reviewed periodically but may not reflect the most recent developments.