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 Relativity Space Manufactures reusable medium-to-heavy-lift launch vehicles using large-scale metal 3D printing and autonomous robotics Relativity Space logo
HEAD-TO-HEAD1 shared sector
Phase Four Relativity Space
Founded 2015 2015
Headquarters Hawthorne, California Long Beach, California
Type private private
Status closed operating
Employees 5 1,285
Total funding $35.8M $1.4B
Latest round Series C Series F
Sectors Space Propulsion, Satellite Components & Subsystems Launch Services, Space Propulsion
Products listed 4 4
Federal contracts
Launches 3 (0%)
Leaders listed Steve Kiser, M. Umair Siddiqui, Simon Halpern Eric Schmidt, Maria Seferian, Kevin Wu
News mentions 0 0
SHARED SECTORS
FREQUENTLY ASKED

How do Phase Four and Relativity Space compare?

Both companies work in Space Propulsion. Phase Four was founded in 2015 and Relativity Space in 2015.

Which is larger, Phase Four or Relativity Space?

Relativity Space reports the larger workforce, with 1,285 employees versus 5.

Which has more launches, Phase Four or Relativity Space?

Relativity Space leads with 3 tracked launches (0% success rate).

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