The raise, which Ellis described as "war chest doubled," was led by Fidelity and comes eight months after Relativity brought in $500 million in a round led by Tiger Global. The $650 million in equity added BlackRock, Centricus, Coatue and Soroban Capital as new Relativity investors, with a host of existing investors – including Fidelity, Tiger, Baillie Gifford, K5 Global, Tribe Capital, XN, Brad Buss, Mark Cuban, Jared Leto and Spencer Rascoff – building on prior stakes.

Relativity has now raised $1.34 billion in capital since its founding in 2015, with its valuation climbing to $4.2 billion from $2.3 billion in November. Its headcount has grown to 400 people, with Ellis saying the company plans to "add several more hundred this year."

"We've signed up to create a lot of value, certainly remaining the second most highly valued space company in the world," Ellis said, as SpaceX commands an industry-leading $74 billion valuation.