The funding comes from Reid Hoffman from Greylock Partners. Reid Hoffman, also the co-Founder of LinkedIn, has joined Apollo Fusion's Board of Directors.

Apollo's mission is to help "enable the second space race" with a new satellite propulsion system that delivers 3 times more total impulse per kg (or per volume) than existing propulsion systems on the market.

This Series B investment brings the total amount raised to over $18 million for Apollo Fusion, which will use the funds to ramp up manufacturing to deliver to commercial and government customers in the US and Europe.

"We're seeing tremendous interest from big prime contractors and from fast-moving startups," says Mike Cassidy, CEO of Apollo Fusion. "The biggest customers have demanding requirements at the scale we're discussing, so with this investment we're expanding our testing and manufacturing capability to meet their needs."

The expansion includes a doubling of Apollo's lab space, increasing the manufacturing capacity to deliver hundreds of systems per year, and commissioning several new large thermal vacuum chambers to accelerate acceptance testing of hundreds of Apollo Constellation Engine (ACE) propulsion systems.

Reid Hoffman noted, "The new space race has the potential to create entirely new and extremely large global markets. I am excited about Apollo's rapid progress in this industry and about the outstanding track record of the Apollo management team."

Cassidy's previous role was in Google's moonshot factory, Google X, where he was Vice President and project leader for the high-flying telecommunications project Loon. He founded Apollo Fusion with Ben Longmier who was a professor of Aerospace Engineering at University of Michigan and who was the co-founder of an aerospace company which was acquired by Apple.

Longmier, who holds advanced degrees in Physics, Nuclear Engineering, and Plasma Physics, said, "Our team brought over 100 years of electric propulsion experience to this new, clean-sheet design. The result is seven major proprietary innovations that deliver performance up to 3x better than competitors."

About the Apollo Constellation Engine

ACE is a smaller, lighter, more efficient electric propulsion system. Unique features make ACE up to 3x smaller and lighter per impulse than any other flight system. With major innovations in the cathode, flow system, magnetic lensing, magnetic circuit, thermal radiation, and propellant, ACE offers revolutionary performance, verified by The Aerospace Corporation - a widely respected independent testing lab.

About Apollo Fusion

Apollo Fusion was founded by Mike Cassidy (serial entrepreneur of four successful startups and former Vice President at Google as leader of Project Loon) and Ben Longmier (former professor of Aerospace Engineering at the University of Michigan and founder of an aerospace company which was acquired by Apple). The Apollo Fusion team also includes domain experts in nuclear physics, plasma physics, and propellants, in addition to aerospace, electrical, mechanical, software, and nuclear engineering. The team has over 100 years worth of Hall thruster experience and is based in Silicon Valley.