Startup · United States
Phase Four
HQ HawthorneFounded 201511-50 employees
Phase Four developed radio-frequency electric and multimode spacecraft propulsion. Quantum Space acquired its multimode propulsion assets and Southern California test facility in September 2025; other propulsion technology went to Apex.
Funding1 round · $26.0M
- Equity raised
- $26.0M
- Latest
- $26.0MSeries B · Jun 11, 2021
| Announced | Stage | Amount | Valuation | Lead investors | Other investors | Confidence |
|---|---|---|---|---|---|---|
| Jun 11, 2021 | Series B | $26.0M | — | — | — | Reported |
- Series B$26.0MJun 11, 2021
Raised counts equity rounds; debt, secondary sales and grants are totaled separately. Amounts in other currencies are converted at the announcement month's average rate. A ~ marks an estimated or converted amount.
Systems1
Newest unveiled first. Open a system for its milestone timeline, components and sources.
People2
- J. P. Sheehan
Co-founder
- Simon Halpern
Co-founder
Company Metrics
Employee-profile counts reflect LinkedIn profiles associated with the company, not verified headcount. One observation establishes a baseline; it does not establish growth.
Sources4
Systems1
- 1
SpaceNews · Sep 22, 2025 · Supports Organization, System
“The company announced Sept. 22 it acquired Phase Four’s multi-mode propulsion technology and its integration and test facility in Southern California.”
Funding1
- 2
VC News Daily · Supports Funding round, Organization
“Phase Four has closed a Series B investment round of $26 million led by New Science Ventures. >> Click here for more funding data on Phase F”
People1
- 3DatabasePhase Four | Crunchbase
Crunchbase · Supports Role
“founders: [{'id': 'j-p-sheehan', 'type': 'person', 'value': 'J. P. Sheehan'}, {'id': 'simon-halpern', 'type': 'person', 'value': 'Simon Halpern'}]”
Other1
- 4DatabaseLinkedIn company profile
LinkedIn · Supports Organization · description, Organization · employee range, Organization · founded year, Organization · hq city, Organization · ownership, Organization · website, Organization metric · employees in linkedin, Organization metric · followers
“about: Based in Hawthorne, California, Phase Four is enabling the exponential growth of satellite constellations by solving the satellite’s costliest problem, the propulsion system. By eliminating the most common failure points in legacy technologies – electrodes, high-voltage electronics, and complex fabrication – Phase Four has built a system that offers reliable high performance with baked-in manufacturability. Our systems provide Hall Effect Thruster performance at a fraction of the price and delivery timeline, with nearly double the lifespan. Check out our open positions at at www.phasefour.io/careers if you have interest in joining our mission.”
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