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Heat rejection and work holding seem like two hard problems in space. On the lunar surface at least you have some gravity to help with the former, but your heat

Heat rejection and work holding seem like two hard problems in space. On the lunar surface at least you have some gravity to help with the former, but your heat affected zone is bound to be much larger because the only way heat leaves the part is radiation. Also, laser welders (at least terrestrial ones) have a copper tip that you drag across the part which keeps the laser a consistent distance away from the weld. This will also heat up in a vacuum, and naively seems like it probably won't work. When welding thin material on Earth we use copper backing plates to suck heat out of the weld area, that could work in space. In zero g it would be easy to lose them (and your clamps). All these things are surmountable I'm sure, would love to know more about how they plan to do it.

MisterTea 2y ago
> but your heat affected zone is bound to be much larger because the only way heat leaves the part is radiation. Which is the whole point of processes like laser and electron beam welding: minimum heat input to achieve the required penetration. Some parts can be held in your bare hand immediately after welding and they might be warm or hot to the touch. Sure there are parts that are glowing hot but those are usually big, deep welds. > Also, laser welders (at least terrestrial ones) have a copper tip that you drag across the part which keeps the laser a consistent distance away from the weld. You are thinking of a cutting head. Welding heads can completely omit a coaxial gas nozzle and use an air knife or nothing if the focal distance is long enough to prevent spatter from hitting the sacrificial cover glass in front of the focal lens. > When welding thin material on Earth we use copper backing plates to suck heat out of the weld area, that could work in space. There are methods of radiating heat into space which is likely what will be employed in the tooling and fixturing. Also, if the heat input in minimal and there is enough mass the part heat sinks itself. I work in an e-beam and laser welding shop and I have built laser welding workstations.
- jcgrillo 2y ago
  > Which is the whole point of processes like laser and electron beam welding: minimum heat input to achieve the required penetration. Surely we can agree, all things being equal, the heat affected zone will be larger absent conductive heat transfer? > You are thinking of a cutting head. No. You sound so certain, yet: https://www.millerwelds.com/equipment/welders/handheld-laser/optx-2kw-handheld-laser-welder-m90602#!/?product-options-title=optx-2kw-240v-complete-package-951000109 https://www.millerwelds.com/equipment/welders/handheld-laser... > There are methods of radiating heat into space Like what? I'm not familiar with this and the article doesn't go into any specifics. Would be interested to know what a radiative heat sink looks like.
  - MisterTea 2y ago
    > Surely we can agree, all things being equal, the heat affected zone will be larger absent conductive heat transfer? It depends on the parts and is figured out in engineering before we even have tooling made. This is the same situation in vacuum laser and EB here on earth. The minimal heat input allows the part to heat sink itself. If we need more heat sinking we use copper mass cut to shape but that is rarely needed. In production welding there might be dozens of hot, welded parts in the vacuum chamber to reduce the number of time consuming pump down cycles.
    - jcgrillo 2y ago
      I guess it all depends what the work is, I was imagining structural work, like the stuff you'd use hundreds of amps and 3/8" rods for on Earth. Also, I assumed the work would be done by people using hand tools rather than robots with fixtures and the like. But TBH I have no idea what the "moon base structural welder" job description actually looks like :p
  - MisterTea 2y ago
    > No. You sound so certain, yet: https://www.millerwelds.com/equipment/welders/handheld-laser https://www.millerwelds.com/equipment/welders/handheld-laser... Ugn, HN throttled my replies and lost the one I was writing. The nozzle is there for shield gas delivery. It also has a very short focal length making the focal point extremely distance sensitive so it has a wheel at the tip of the nozzle to keep the height constant. Since this is for welding in a vacuum you can omit the nozzle and even the wheel if you have a steady enough hand.

MisterTea 2y ago

> but your heat affected zone is bound to be much larger because the only way heat leaves the part is radiation. Which is the whole point of processes like laser and electron beam welding: minimum heat input to achieve the required penetration. Some parts can be held in your bare hand immediately after welding and they might be warm or hot to the touch. Sure there are parts that are glowing hot but those are usually big, deep welds. > Also, laser welders (at least terrestrial ones) have a copper tip that you drag across the part which keeps the laser a consistent distance away from the weld. You are thinking of a cutting head. Welding heads can completely omit a coaxial gas nozzle and use an air knife or nothing if the focal distance is long enough to prevent spatter from hitting the sacrificial cover glass in front of the focal lens. > When welding thin material on Earth we use copper backing plates to suck heat out of the weld area, that could work in space. There are methods of radiating heat into space which is likely what will be employed in the tooling and fixturing. Also, if the heat input in minimal and there is enough mass the part heat sinks itself. I work in an e-beam and laser welding shop and I have built laser welding workstations.

jcgrillo 2y ago
> Which is the whole point of processes like laser and electron beam welding: minimum heat input to achieve the required penetration. Surely we can agree, all things being equal, the heat affected zone will be larger absent conductive heat transfer? > You are thinking of a cutting head. No. You sound so certain, yet: https://www.millerwelds.com/equipment/welders/handheld-laser/optx-2kw-handheld-laser-welder-m90602#!/?product-options-title=optx-2kw-240v-complete-package-951000109 https://www.millerwelds.com/equipment/welders/handheld-laser... > There are methods of radiating heat into space Like what? I'm not familiar with this and the article doesn't go into any specifics. Would be interested to know what a radiative heat sink looks like.
- MisterTea 2y ago
  > Surely we can agree, all things being equal, the heat affected zone will be larger absent conductive heat transfer? It depends on the parts and is figured out in engineering before we even have tooling made. This is the same situation in vacuum laser and EB here on earth. The minimal heat input allows the part to heat sink itself. If we need more heat sinking we use copper mass cut to shape but that is rarely needed. In production welding there might be dozens of hot, welded parts in the vacuum chamber to reduce the number of time consuming pump down cycles.
  - jcgrillo 2y ago
    I guess it all depends what the work is, I was imagining structural work, like the stuff you'd use hundreds of amps and 3/8" rods for on Earth. Also, I assumed the work would be done by people using hand tools rather than robots with fixtures and the like. But TBH I have no idea what the "moon base structural welder" job description actually looks like :p
- MisterTea 2y ago
  > No. You sound so certain, yet: https://www.millerwelds.com/equipment/welders/handheld-laser https://www.millerwelds.com/equipment/welders/handheld-laser... Ugn, HN throttled my replies and lost the one I was writing. The nozzle is there for shield gas delivery. It also has a very short focal length making the focal point extremely distance sensitive so it has a wheel at the tip of the nozzle to keep the height constant. Since this is for welding in a vacuum you can omit the nozzle and even the wheel if you have a steady enough hand.