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I was thinking about these drawings yesterday when I saw the mockup of a ring made from 32 Starship fuselages. Welded end to end, 32 pieces would net a 1/4 mil

I was thinking about these drawings yesterday when I saw the mockup of a ring made from 32 Starship fuselages. Welded end to end, 32 pieces would net a 1/4 mile diameter ring with a volume ~85x the ISS. Elon estimates that the refueling procedure necessary for interplanetary starship missions would require 8 fuel tanker starship launches, but this could be cut in half if the tankers were stripped of the elements needed for reentry and landing. I could see the economics working out to where it would make more sense to launch stripped down single use fuel tanker starships, and then sell the empty orbiting shells to someone interested in building in space. https://caseyhandmer.wordpress.com/2021/11/17/science-upside-for-starship/#:~:text=32%20segment%20ring%20station%20composed%20of%20dockable%20modified%20Starship%20barrels https://caseyhandmer.wordpress.com/2021/11/17/science-upside....

rtkwe 5y ago
The exterior structure is a fraction of what you need for a working station though. It is a limiting factor on size because traditionally the module needs to fit in a faring but doing that doesn't save much cost because you still have to haul up all the other equipment.
- ortusdux 5y ago
  Exactly. Many reusable starships flights would be needed to ferry up all the trappings of a working station, while returning reusable elements like the engines from the now mothballed fuel tanker ships. I just meant to point out that a stripped down starship would consist of 30+ tons of easily weldable steel pre-fabricated into a reinforced pressure vessel. Spacex's interplanetary goals would benefit from treating the tanker starships as expendable, and if someone was inclined to start building habitations similar to those depicted in the link, they could buy up the building-blocks for a song.
  - idlewords 5y ago
    Nothing is easily weldable in space, and empty hulls aren't habitrail elements that you can connect into something useful (unless a lot of design goes into it up front). Even if the hulls were free, the cost of creating such a space station would be prohibitive.
    - politician 5y ago
      Don’t metals spontaneously weld in vacuum?
      - rtkwe 5y ago
        It's not perfect and you wouldn't want to trust it for a habitat. It requires the surfaces to be pretty meticulously clean and it's not as strong as traditional welds.
      - ortusdux 5y ago
        Yes, under certain circumstances. Two pieces of identical metal, with no surface coatings or oxides, will directly bond if placed in intimate contact. Done properly, the weld would be as strong as the metal. As Feynman put it, the atoms have no way of knowing they are in different pieces. Similar results can be reliably recreated on earth. Ultrasonic welding rubs two pieces of metal together until the oxide breaks apart leaving pure metal to fuse. Explosive welding creates a plasma that strips off the oxide layer, and then propels the metals into each other. This method has the benefit of bonding dissimilar metals, and usually produces bonds that are as strong as the weakest metal.
      - wnkrshm 5y ago
        They also become brittle due to cosmic particles, if one e.g. wants to think about interstellar travel.
    - ortusdux 5y ago
      Nothing is easy in space, but 304L SS is easier to weld than 2219 Al or Ti, the main structural metals on the ISS. Welding in space has been well studied by both NASA and Roscosmos. Most testing was done in the 60s and 70s in preparation for possible repairs due to high-velocity impacts. More reciently, testing has been focused on 3d printing via additive welding. The main issue with welding in space is the lack of convection based cooling, which means the welds take longer to cool through conduction, which can result in a larger HAZ. Increasing the mass and heat capacity of the adjacent material greatly reduces this. The lack of an atmosphere and contaminants makes space a near ideal welding environment.

rtkwe 5y ago

The exterior structure is a fraction of what you need for a working station though. It is a limiting factor on size because traditionally the module needs to fit in a faring but doing that doesn't save much cost because you still have to haul up all the other equipment.

ortusdux 5y ago
Exactly. Many reusable starships flights would be needed to ferry up all the trappings of a working station, while returning reusable elements like the engines from the now mothballed fuel tanker ships. I just meant to point out that a stripped down starship would consist of 30+ tons of easily weldable steel pre-fabricated into a reinforced pressure vessel. Spacex's interplanetary goals would benefit from treating the tanker starships as expendable, and if someone was inclined to start building habitations similar to those depicted in the link, they could buy up the building-blocks for a song.
- idlewords 5y ago
  Nothing is easily weldable in space, and empty hulls aren't habitrail elements that you can connect into something useful (unless a lot of design goes into it up front). Even if the hulls were free, the cost of creating such a space station would be prohibitive.
  - politician 5y ago
    Don’t metals spontaneously weld in vacuum?
    - rtkwe 5y ago
      It's not perfect and you wouldn't want to trust it for a habitat. It requires the surfaces to be pretty meticulously clean and it's not as strong as traditional welds.
    - ortusdux 5y ago
      Yes, under certain circumstances. Two pieces of identical metal, with no surface coatings or oxides, will directly bond if placed in intimate contact. Done properly, the weld would be as strong as the metal. As Feynman put it, the atoms have no way of knowing they are in different pieces. Similar results can be reliably recreated on earth. Ultrasonic welding rubs two pieces of metal together until the oxide breaks apart leaving pure metal to fuse. Explosive welding creates a plasma that strips off the oxide layer, and then propels the metals into each other. This method has the benefit of bonding dissimilar metals, and usually produces bonds that are as strong as the weakest metal.
    - wnkrshm 5y ago
      They also become brittle due to cosmic particles, if one e.g. wants to think about interstellar travel.
  - ortusdux 5y ago
    Nothing is easy in space, but 304L SS is easier to weld than 2219 Al or Ti, the main structural metals on the ISS. Welding in space has been well studied by both NASA and Roscosmos. Most testing was done in the 60s and 70s in preparation for possible repairs due to high-velocity impacts. More reciently, testing has been focused on 3d printing via additive welding. The main issue with welding in space is the lack of convection based cooling, which means the welds take longer to cool through conduction, which can result in a larger HAZ. Increasing the mass and heat capacity of the adjacent material greatly reduces this. The lack of an atmosphere and contaminants makes space a near ideal welding environment.