Phase Four
Phase Four develops and manufactures Hall Effect Thrusters and related electric propulsion systems for small satellites, selling directly to U.S. government national security programs and commercial space operators via B2B contracts.
- Company typePrivate
- Founded2015
- HeadquartersEl Segundo, United States
- Headcount11–50
- GTM typeB2B
- OfferingHardware or Manufacturing
What Phase Four does
Phase Four is an aerospace company, founded in 2015 and headquartered in El Segundo, California, that develops and manufactures electric propulsion systems for small satellites. Its core product is the Hall Effect Thruster (HET), a type of in-space electric propulsion that enables efficient maneuvering, orbit raising, and station-keeping for small-satellite platforms. The company is actively extending its product roadmap beyond the current HET family to new propulsion technologies, funded in part by recent capital injections.
The company sells directly to two primary customer segments: U.S. government agencies (national security space applications) and commercial space operators (satellite and in-space propulsion missions). Revenue is generated through hardware sales under B2B contracts, with pricing conducted on a quote basis rather than via published price lists. Distribution is direct and sales-led, with engagement via government procurement vehicles and direct relationships with commercial space primes and satellite integrators. Headcount is small (11-50), consistent with an early-production-stage hardware vendor scaling manufacturing rather than a volume manufacturer.
Capital structure is venture-backed and private. The company has raised cumulatively on the order of $35M+ across multiple rounds, most notably a $26M Series B led by New Science Ventures in 2021 and recent Series C activity including a $6.25M tranche from Leonid Capital Partners in March 2024 and a first close led by Artemis Group Capital in January 2025 covering nearly 60% of the round target. In April 2026, Phase Four was one of four firms selected by DARPA for the LASSO cislunar small-satellite orbiter concept-study program, alongside Benchmark Space Systems, Quantum Space, and Revolution Space, signaling an expansion of its addressable mission set from low-Earth-orbit small-sat propulsion into cislunar national-security missions.
Phase Four firmographics
Firmographics- Name
- Phase Four
- Website
- https://phasefour.io
- Company type
- Private
- Founded year
- 2015
- Operating status
- Operating
- Headcount range
- 11–50 employees
- Short description
- Phase Four develops and manufactures Hall Effect Thrusters and related electric propulsion systems for small satellites, selling directly to U.S. government national security programs and commercial space operators via B2B contracts.
- Ownership category
- akta.pro rank
Phase Four industry classification
Industry- Product category
- Space Propulsion Systems
- NAICS
- Guided Missile and Space Vehicle Propulsion Unit and Propulsion Unit Parts Manufacturing (336415), Guided Missile and Space Vehicle Manufacturing (336414), Other Guided Missile and Space Vehicle Parts and Auxiliary Equipment Manufacturing (336419)
- SIC
- Guided Missiles & Space Vehicles & Parts (3760), Engines & Turbines (3510)
- akta.pro primary industry
- Spacecraft Propulsion (In-Space) & Thrusters (IMABACAE)
- akta.pro secondary industries
- Spacecraft & Satellites (Civil/Commercial) (IMABACAB), Military Space Systems (Defense Spacecraft) (IMABACAC)
Keywords
Where Phase Four is headquartered
LocationHeadquarters
- HQ city
- El Segundo
- HQ country
- United States
- HQ region
- North America
Markets served
Phase Four business model
Business model- GTM type
- B2B
- Offering type
- Hardware or Manufacturing
- Cost components
- Technology or R&D, Supply Chain, Operations, Personnel, Marketing or Sales
Revenue model
- Propulsion Systems Sales: Sale of advanced propulsion systems including Hall Effect Thrusters to government and commercial space customers
- Government and Commercial Contracts: Contract-based revenue from U.S. government national security applications and commercial space exploration missions
Go-to-market motion2 records
Distribution channels2 records
Phase Four product offering
Product offeringCore offering
Phase Four designs, manufactures, and sells Hall Effect Thruster (HET) electric propulsion systems for small satellites. The thrusters provide in-space propulsion — including orbit-raising, station-keeping, and de-orbit — for both commercial satellite operators and U.S. government customers. The company's current focus is on scaling production of its HET product line and developing next-generation propulsion technologies for cislunar and national-security missions.
Product overview
Phase Four is an aerospace company developing advanced propulsion systems for space applications. The company's product portfolio centers on Hall Effect Thrusters, a type of electric propulsion technology, along with other advanced propulsion systems. The offerings are designed to serve both commercial and government space missions, addressing the expanding demand for in-space propulsion capabilities.
Differentiator
Problem solved
Functional benefit
Products and services
- Hall Effect Thrusters Electric propulsion thrusters based on the Hall Effect, providing in-space propulsion (orbit-raising, station-keeping, and de-orbit) for small satellites serving commercial and government space missions.
- Advanced Propulsion Systems Next-generation propulsion systems being developed by Phase Four to expand beyond the core Hall Effect Thruster line, targeting new in-space propulsion applications for space exploration and national security.
Companies that use Phase Four
Customer profileSegments2 records
Ideal customer profiles2 records
Phase Four technology and API
TechnologyTechnology focussed Yes
API detail
- Has API
- No
- API docs
- API detail
Core technology
AI maturity
App detail
Feature1 record
Phase Four partnerships and signals
Strategic signalScale indicators2 records
Recent moves4 records
Expansion highlights4 records
Phase Four competitors and assessment
Company assessmentDirect peers
- Busek Space Propulsion & Systems: Busek is a U.S. specialist in electric and chemical propulsion for spacecraft, including Hall Effect Thrusters. It is one of the closest direct competitors to Phase Four in the smallsat EP category, supplying both commercial and government customers.
- Accion Systems: Accion develops non-pressurized electric propulsion (TILE) for small satellites. It is a direct venture-backed EP competitor targeting the same smallsat customer base as Phase Four.
- ThrustMe: ThrustMe is a French startup focused on iodine and electric propulsion for small satellites. It is a direct technology peer competing for commercial and institutional EP contracts.
- Morpheus Space: Morpheus Space provides nano-satellite electric propulsion systems for commercial constellations. It competes with Phase Four in the same smallsat EP niche and shares a similar venture-backed, hardware-sales model.
- Sitael Aerospace: Sitael is an Italian space company developing Hall Effect Thrusters and other electric propulsion systems. It is a direct EP peer serving European institutional and commercial satellite programs.
Broad incumbents
- Aerojet Rocketdyne (L3Harris): Aerojet Rocketdyne, now part of L3Harris, is a legacy prime for space propulsion across chemical, electric, and solid rocket systems. It competes with Phase Four on government propulsion contracts and sets the incumbent benchmark for flight heritage.
- Apollo Fusion (Astra): Apollo Fusion, acquired by Astra, developed Hall Effect Thrusters for satellite propulsion. It is a direct technology competitor that has been absorbed into a larger launch-and-services platform.
- Rocket Lab: Rocket Lab has expanded beyond launch into space systems including the SolAero acquisition and broader spacecraft components. It competes with Phase Four for satellite propulsion dollars as a vertically integrated platform.
- Safran Aircraft Engines (Space Propulsion): Safran, via its space propulsion activities (formerly Snecma/Safran Space), is a major EP supplier for European and institutional programs. It is a broad incumbent competing for the same government prime contracts Phase Four targets.
Emerging players
- Momentus Space: Momentus offers in-space transportation services using its Vigoride plasma propulsion platform. It overlaps with Phase Four's in-space mobility value proposition but at the service/platform level rather than pure hardware sales.
Market position
Strengths5 records
Weaknesses5 records
Competitive moat3 records
Key risks6 records
Key highlights6 records
Customer concentration
Phase Four social profiles
Digital presencePhase Four financial estimates
Financial estimateRevenue estimate
Valuation estimate
Phase Four leadership team
Management profileNumber of profiles
Profiles3 records
Phase Four funding detail
Funding detailFunding overview
Funding rounds8 records
Investors12 records
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Phase Four M&A and investment
M&A and investmentM&A
Investments
M&A and investment is available on the Subscription and Enterprise plan.Contact sales →
Frequently asked questions about Phase Four
What does Phase Four do?
Phase Four designs, manufactures, and sells Hall Effect Thruster (HET) electric propulsion systems for small satellites. The thrusters provide in-space propulsion — including orbit-raising, station-keeping, and de-orbit — for both commercial satellite operators and U.S. government customers. The company's current focus is on scaling production of its HET product line and developing next-generation propulsion technologies for cislunar and national-security missions.
Is Phase Four a public or private company?
Phase Four is a private company. It is classified as venture growth investor backed and is currently operating.
When was Phase Four founded?
Phase Four was founded in 2015. It employs 11 to 50 people.
Where is Phase Four based?
Phase Four is headquartered in El Segundo, United States, in the North America region.
How does Phase Four make money?
Two revenue lines are on record. Propulsion Systems Sales are the primary driver. The others are government and Commercial Contracts.
Who are Phase Four's main competitors?
Direct peers on record are Busek Space Propulsion & Systems, Accion Systems, ThrustMe, Morpheus Space and Sitael Aerospace. Broad incumbents are Aerojet Rocketdyne (L3Harris), Apollo Fusion (Astra), Rocket Lab and Safran Aircraft Engines (Space Propulsion). Momentus Space is listed as an emerging player.
Does Phase Four have an API?
No public API is recorded for Phase Four.
What industry is Phase Four in?
Phase Four's product category is Space Propulsion Systems. Its primary akta.pro industry code is IMABACAE, Spacecraft Propulsion (In-Space) & Thrusters, with a secondary code of IMABACAB, Spacecraft & Satellites (Civil/Commercial). Its NAICS code is 336415 and its SIC code is 3760.