Phase Four's Second Generation RF Thruster, Maxwell Block 2, firing in one of the company's vacuum chambers.

Propulsion startup Phase Four has signed a memorandum of understanding with satellite refueling startup Orbit Fab aimed at preparing future Phase Four Maxwell engines for on-orbit refueling.

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Debra Werner is a correspondent for SpaceNews based in San Francisco. Debra earned a bachelor’s degree in communications from the University of California, Berkeley, and a master’s degree in Journalism from Northwestern University. She is a recipient...