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Why isn’t it possible for a bunch of rockets with a little propellant left already in space to join forces with a rocket (rendezvous with it) to propel it furth

• sigmoid10 4y ago
  You'd need extra docking mechanisms, which would add a lot of complexity and negatively impact payload performance. By launching 2 rockets you're also doubling the launch cost. With today's prices, it's much more reasonable to design staged rockets and compact payloads than it is to use several rockets so that one of them may fly further. SpaceX aims to overcome this with starship, which is designed to be be refilled in orbit, but we have yet to see if and how it works.
• ChuckMcM 4y ago
  This is SpaceX's plan for Starship (and one of the reasons I think it will take longer than expected[1]). ULA posited an orbital tanker for cryogenic fuels[2] which was most notable for having an internal combustion engine that ran off the fuel it would hold to keep the fuel chilled. [1] If NASA were to plan a mission that needed on orbit refueling they would not even start building a spacecraft until they had tested out all of the elements of on orbit refueling before hand. SpaceX is "assuming" they can make it work and proceeding with Starship. To date NASA has awarded some contracts (https://spaceflightnow.com/2020/10/16/nasa-selects-companies-to-demonstrate-in-space-refueling-and-propellant-depot-tech/ https://spaceflightnow.com/2020/10/16/nasa-selects-companies...) [2] https://sciences.ucf.edu/class/wp-content/uploads/sites/23/2017/04/ULA-UCF.pdf https://sciences.ucf.edu/class/wp-content/uploads/sites/23/2...