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OPERATOR · OPERATOR PROFILE · DATA AS OF 2026-06-10

Phase Four

Acquired Acquired HQ: El Segundo, California Founded 2015

El Segundo RF/Hall thruster startup (Maxwell line, multi-mode ASCENT/hydrazine technology) that ran out of runway in 2025: Apex acquired its Hall-effect thruster technology and personnel (Sept 2025) and Quantum Space acquired the remaining propulsion assets. Retained for historical award attribution and as an M&A comp; not an active operator.

48.0
ARI Composite
Moderate Risk
#34 of 56
Peer Rank
Manufacturing cohort
Total Launches
No flights tracked
Estimated valuation
Not disclosed

FINANCIAL HEALTH

48.0
ARI composite · Moderate Risk
Peer rank#34 of 56
Peer groupManufacturing
Data coverage38%

SECTOR POSITION

Rank within sector#34 of 56
Tracked peers56

REGISTRY DATA

Legal namePhase Four, Inc.
OwnershipAcquired
HeadquartersEl Segundo, California
CountryUS
Founded2015
AliasesPhase Four, Phase Four Inc, Maxwell engine
Key programsMaxwell RF thruster line (historical), Multi-mode ASCENT/hydrazine propulsion (historical)
Gov customersAFRL (historical)
IPO statusWound down 2025; assets to Apex (thruster tech) and Quantum Space (propulsion assets)

Source: space_company_registry.json · Operator homepage → · SpaceNews documents the Sept 2025 asset dispositions to Quantum Space and (10 days earlier) Apex.

METHODOLOGY

Launch history and subsystem outcomes aggregate from AstraVeris's launch_events table with Wilson 95% lower bounds on success rates. ARI scores come from the 11-factor composite (/finance/methodology/). Constellation counts derive from the live CelesTrak/GCAT object catalog. Gov contracts from USAspending.gov awards; private deals from deduplicated pipeline deal extraction. Absence of a row means "not tracked" — we never fabricate. See /methodology/ for the full data model and /data-licensing/ for licensing terms.

Not investment advice. For insurance underwriting, verify against primary-source filings and operator investigation reports.