SPACE INDEX COMPANIES INSIGHTS SECTORS PRODUCTS NEWS BLOG ANSWERS RESEARCH ABOUT FOR COMPANIES BUILD / 2026.06.04
Phase Four logo Phase Four Developed electrodeless radio-frequency and multi-mode electric propulsion systems for satellites vs Portal Space Systems Manufactures solar-thermal-propelled spacecraft buses for high-delta-v, multi-orbit maneuverability and tactically responsive space operations Portal Space Systems logo
HEAD-TO-HEAD1 shared sector
Phase Four Portal Space Systems
Founded 2015 2021
Headquarters Hawthorne, California Bothell, Washington
Type private private
Status closed operating
Employees 5 22
Total funding $35.8M $20M
Latest round Series C Seed
Sectors Space Propulsion, Satellite Components & Subsystems Space Transportation & Logistics, Satellite Manufacturing, Space Propulsion
Products listed 4 3
Federal contracts
Launches
Leaders listed Steve Kiser, M. Umair Siddiqui, Simon Halpern Jeff Thornburg, Ian Vorbach, Prashaanth Ravindran
News mentions 0 0
SHARED SECTORS
FREQUENTLY ASKED

How do Phase Four and Portal Space Systems compare?

Both companies work in Space Propulsion. Phase Four was founded in 2015 and Portal Space Systems in 2021.

Which is larger, Phase Four or Portal Space Systems?

Portal Space Systems reports the larger workforce, with 22 employees versus 5.

Numbers refresh on every render against the live Space Index database. Federal contract data from USAspending.gov; launches from LaunchLibrary2.