https://techcrunch.com/2023/04/24/ursa-major-to-provide-engines-for-the-upper-stage-of-astras-new-rocket/ > Astra’s new Rocket 4 launch vehicle will use Ursa Major’s Hadley liquid engine to power its upper stage, the two companies announced Monday. > Astra has been tight-lipped about the new upper stage engine that would power its new Rocket 4, with CEO Chris Kemp only telling investors last year that the rocket’s substantially increased payload capacity was thanks in part to engine upgrades. Outsourcing the engine helps clarify how Astra was able to so quickly pivot its plans for Rocket 4, including doubling the launch vehicle’s payload capacity from 300 kilograms to 600 kilograms.