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question: what will happen if orbit refuelling goes wrong? Won't it destroy everything in orbit?

JumpCrisscross 4mo ago
> what will happen if orbit refuelling goes wrong? Won't it destroy everything in orbit? No. What is the mechanism through which you suspected this could happen?
- bragr 4mo ago
  Kessler syndrome presumably?
  - hgoel 4mo ago
    Keeping the orbits low enough, and/or intentionally going suborbital after docking/before starting the fuel transfer, will make the chances of that being possible very low. It's also worth considering that they have demonstrated cryo propellant pumping between two tanks within a ship, so, AFAIK, transfer between two ships is more about testing the docking systems, than it is about the pumps. They could probably rig the system to first pump some inert gas to verify the quality of the docking, then try to pump propellants.
  - margalabargala 4mo ago
    ...caused by what?
    - deleted 4mo ago
      [deleted]
    - hilsdev 4mo ago
      Colliding tanks full of oxidizer and fuel?
      - margalabargala 4mo ago
        No, for the same reason that the explosion won't destroy the earth either.
bediger4000 4mo ago
Liquid handling in microgravity has always been weird. Big gas bubbles in the fluid, surface tension effects causing liquid to float in balls in the ullage, stuff like that. Turbopumps break if they ingest a larger bubble. There could be some odd failure modes I would think. Failure to pump the liquid, broken pumps, who really knows? My guess would be that a failure mode would be a big spill, a failure to pump, only partially refilling, or broken turbopumps before an explosion.
- idiotsecant 4mo ago
  Seems like you could use peristaltic pumps
  - pants2 4mo ago
    That would take ages!
    - idiotsecant 4mo ago
      Why?
- pmontra 4mo ago
  A probably very naive question: why not pistons?
  - labcomputer 4mo ago
    Because there’s a much, much simpler and easier way: 1. Connect the two ships 2. Connect the liquid valves from both cryo tanks together. 3. Spin the ships about the short axis 4. Open the vent valve for the cryo tank to receive liquid. 5. Lock closed the vent valve for the cryo tank to supple liquid. Steps 2, 4 and 5 are how you normally transfer cryo fluids between dewars on earth. You just to create pseudo gravity / acceleration in the body frame of the ships to make it work in space.
  - bediger4000 4mo ago
Lerc 4mo ago
Presumably the effect of any explosion would decrease proportional to the volume as it expands. Is there much volume in space?
- librasteve 4mo ago
  the clue is in the name
tristanj 4mo ago
All Starship test launches are suborbital so if anything goes wrong, the ship and debris fall back to Earth. Even if it was put in orbit, debris are not an issue because orbital decay at Low Earth Orbit (LEO) is significant. A satellite orbiting below 250km will fall back to earth within a few hours, and at 400km within a year. LEO below 500-600km has enough atmospheric drag to be self-cleaning. Orbital debris are more significant issue at higher orbits 800km and above.

> what will happen if orbit refuelling goes wrong? Won't it destroy everything in orbit? No. What is the mechanism through which you suspected this could happen?

bragr 4mo ago
Kessler syndrome presumably?
- hgoel 4mo ago
  Keeping the orbits low enough, and/or intentionally going suborbital after docking/before starting the fuel transfer, will make the chances of that being possible very low. It's also worth considering that they have demonstrated cryo propellant pumping between two tanks within a ship, so, AFAIK, transfer between two ships is more about testing the docking systems, than it is about the pumps. They could probably rig the system to first pump some inert gas to verify the quality of the docking, then try to pump propellants.
- margalabargala 4mo ago
  ...caused by what?
  - deleted 4mo ago
    [deleted]
  - hilsdev 4mo ago
    Colliding tanks full of oxidizer and fuel?
    - margalabargala 4mo ago
      No, for the same reason that the explosion won't destroy the earth either.

bediger4000 4mo ago

Liquid handling in microgravity has always been weird. Big gas bubbles in the fluid, surface tension effects causing liquid to float in balls in the ullage, stuff like that. Turbopumps break if they ingest a larger bubble. There could be some odd failure modes I would think. Failure to pump the liquid, broken pumps, who really knows? My guess would be that a failure mode would be a big spill, a failure to pump, only partially refilling, or broken turbopumps before an explosion.

idiotsecant 4mo ago
Seems like you could use peristaltic pumps
- pants2 4mo ago
  That would take ages!
  - idiotsecant 4mo ago
    Why?
pmontra 4mo ago
A probably very naive question: why not pistons?
- labcomputer 4mo ago
  Because there’s a much, much simpler and easier way: 1. Connect the two ships 2. Connect the liquid valves from both cryo tanks together. 3. Spin the ships about the short axis 4. Open the vent valve for the cryo tank to receive liquid. 5. Lock closed the vent valve for the cryo tank to supple liquid. Steps 2, 4 and 5 are how you normally transfer cryo fluids between dewars on earth. You just to create pseudo gravity / acceleration in the body frame of the ships to make it work in space.
- bediger4000 4mo ago

Lerc 4mo ago

Presumably the effect of any explosion would decrease proportional to the volume as it expands. Is there much volume in space?

librasteve 4mo ago
the clue is in the name

tristanj 4mo ago

All Starship test launches are suborbital so if anything goes wrong, the ship and debris fall back to Earth. Even if it was put in orbit, debris are not an issue because orbital decay at Low Earth Orbit (LEO) is significant. A satellite orbiting below 250km will fall back to earth within a few hours, and at 400km within a year. LEO below 500-600km has enough atmospheric drag to be self-cleaning. Orbital debris are more significant issue at higher orbits 800km and above.