Electron beam welding requires a vacuum.[1] So that's a promising technique for space welding.
Until recently, the whole object had to be in vacuum.
A recent breakthrough is a welding head which creates a local vacuum around the welding area, rather than putting the whole object into a vacuum chamber. This allows automated welding of big, thick objects, all the way up to nuclear reactor pressure vessels.
Not recently. Atmospheric EB has been around for a long time. Leybold started in the 60's and by the 70's a few companies had machines. Band saw blade welding is one of the big users of atmospheric EB.
The big problem with ATM EB is that the beam diffuses in the air rapidly so you have a few usable cm from the aperture to the work piece. The machines work by using a standard EB column with a turbo or diffusion pumped gun chamber firing down a baffled tube, each baffle having a small hole for the beam to pass and the space between the baffles is pumped by large vacuum pumps. PTR had a picture of such a machine and you can see a big umbilical of vacuum hoses snaking from the head to a battery of large Stokes piston vacuum pumps. Each baffle successively reduces the atmosphere leaking in until the isolation valve can be opened and the head can maintain enough vacuum to prevent flash over arcing.
A lot of that big stuff you see like pressure vessel welding uses reduced atmosphere welding where a small space is sealed as best as possible so the pressure can be reduced below 1 pascal (1E-2 Torr.) Then a standard pumped welding head can be used.
The more recent development was the plasma arc window stuff Brookhaven national labs did with Joining Tech (knew someone who worked for them when that project was active) though I know of no manufacturer using it.
This is a good example of a space-based research initiative that might find significant applications on Earth.
I think the key reason that space-based research tends to be so technologically fruitful is that it imposes a discipline on the science done, through the constraints that space imposes on meeting ambitious mission objectives.
Space initiatives also provide a justification for doing the kind of blue skies research that might otherwise find difficulty finding funding.
> I think the key reason that space-based research tends to be so technologically fruitful is that it imposes a discipline on the science done, through the constraints that space imposes on meeting ambitious mission objectives.
The enormous budget and the elite scientific and engineering talent also may help. On Earth, those resources don't usually go toward finding a new way to weld things.
The most recent Planet Money podcast talks about how the latest microchip innovation was proposed by a nuclear weapons researcher and cost the us government roughly 300-400 million but the engineering research to make a practical ultraviolet etching machine cost ASML nine billion and twenty years of development, they said if they knew it would take that long they might never have attempted it but they are now the sole maker of such devices which seems to have made the investment worthwhile.
It’s a bit weird that NASA are doing the research.
In the next century dozens of corporations bigger than most countries of Earth will be up in space mining millions of tons of gold and other rare materials, tax free anywhere.
It seems they will see the greatest benefit from this research, but they don’t want to pay for it?
I mean I would also choose to just get free stuff. But why are we giving it away?
1. Doing research is exactly the purpose of NASA.
2. I'm highly sceptical of the idea that space mining will be an economically profitable activity in the near future and even more sceptical of the idea that nation states on Earth won't find a way to tax it.
> I'm highly sceptical of the idea that space mining will be an economically profitable activity in the near future and even more sceptical of the idea that nation states on Earth won't find a way to tax it.
The US has carefully preserved the interests of private space minining companies in international agreements about space.
Look up the U.S. Commercial Space Launch Competitiveness Act of 2015, and the Artemis Accords as a start. Generally it's referred to as 'extraction', if you are searching. Here's a very good resource: [0]
The US delined to sign the Moon Agreement of 1984, at least in part because it designated the Moon (or some part) as the "common heritage of all mankind". The US objected because they said it contradicted free market principles. "Opponents of the Moon Treaty also expressed concerns that one of the goals of the agreement's proposed regulatory regime would be equitable sharing of benefits from lunar resources, as they worried this approach could disadvantage private sector initiatives."
It's probably not super realistic to mine resources in space and send the raw material down the gravity well but it's hard to imagine any space-based manufacturing without mining. Whether our species will ever attempt such a thing is.. who knows? But hauling heavy loads to and from Earth makes very little sense.
> It's probably not super realistic to mine resources in space and send the raw material down the gravity well
I wonder about it: Gravity pulling through zero drag (before the atmosphere) sounds like cheap transportation of just about any mass. We have lots of experience aiming the landing site of deorbiting objects.
How much would the ship cost - can we do it without an engine or fuel, with a little boost in the right direction from an orbital base? What would be needed for the cargo to survive reentry and 'landing' - for exampple, a heat shield? After landing, how much would recovery and transportation of the cargo cost? You don't want to be retrieving it from under 3,000 m of water.
That is an interesting question. Doing it without losing the load seems challenging but could work if you're basically pummeling an area with raw ore then subsequently mining and refining it? I wonder what the atmospheric consequences would be?
> It seems they will see the greatest benefit from this research, but they don’t want to pay for it?
The US government also did the research on fracking (i.e., for natural gas extraction), as far as I know.
Back in the late 1950s when NASA was born, the US felt that if the Soviet Union obtained a significant advantage in space technology, it could be an existential threat. The government therefore invested directly in research.
The US still invests in research in nuclear energy and other things. Congress is just now passing laws that will allow the government to recover expenses for private commercial use of its space launch facilities (it's a bit more complex than that, and I don't recall the details).
Maybe it would make sense for anyone commercializing it to pay royalties, at least if they start earning serious revenue.
Private companies face a free rider problem in funding publicly available research, in that it's generally better to conserve one's capital and wait for someone else to pay for the research.
And corporations, as a whole, are no where near as large as governments.. government has grown precipitously relative to the private sector over the last 80 years. It's just that that spending growth has been concentrated mostly in social programs rather goods and services that face the free rider problem:
Increased supply will cause prices to fall, meaning the rate of profit will not be too extreme, especially how much easier sending stuff to space is getting
I cant wait, too many rare earths are dominated by BRICS countries
Rare-earth metals are far too plentiful and cheap on Earth to make it profitable to mine them in space and then ship them back to Earth.
Gold and platinum group metals are the only natural resources that could potentially be mined in space and then shipped back to Earth for sale at a profit. Maybe what we could see is such metals seeing their price come down as the supply increases from extraterrestrial sources, and and as a consequence of the resultant increase in abundance of these metals, new applications being found for them, which in turn would increase the productivity of the global economy.
Gold and platinum group metals have a lot of industrial uses that cannot currently be exploited due to their extreme scarcity and expense.
Vacuum Laser welding is very much a thing already. Years back the old president wanted my team to build one from an old Wentgate e-beam chamber. Shipper destroyed the chamber in transit and my boss got into a silly fight with the vendor and shipper which killed the project. We then got a quote from EVO Beam who builds electron beam welders and other e-beam machines who does dual process, laser and EB in the same machine. Wound up buying another EB machine instead.
The challenge of welding in a vacuum is the molten weld pool emits metal weld vapor which impinges on surfaces in a linear trajectory from the pool. Think PVD, physical vapor deposition. So your beam delivery optics get a nice coating of whatever you are welding. I had some fun ideas for mitigating this in our design but never put it to test.
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.
> 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.
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.
> 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.
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
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.
Wait, if you are in a vacuum and thus there is no oxidation layer, can't you just press two (identical) metals together and they will be joined because the electrons don't know which of the two objects they're in?
If you get your two surfaces very very close, sure. The problem is most non-ground metal is going to have a surface finish that is too rough for this to work.
You could squeeze things together, but this depends on part geometry.
Sure but the surfaces have to be perfectly flat to where you measure the roughness in angstroms. Not something you can perform by hand or with mechanical polishing.
Welding aluminum in Earth's atmosphere is difficult because aluminum oxide forms on the surface and it has a higher melting point than the aluminum inside. So to weld aluminum you need to keep oxygen away from the weld, usually by flooding the weld with argon or some other inert gas.
In a vacuum this problem wouldn't exist and aluminum should be no more difficult to weld than steel.
Not a metalurgist, but agree the oxide problem would go away. However I think you'd have a worse problem with heat. Aluminum in my limited experience gets really hot and soupy when welded, so that you have to go quite fast in many cases. Without an atmosphere to sync some of the heat, you might have very interesting thermal issues. You'd definitely need much bigger heat syncs. However depends likely on the scale of welding that's happening. Definitely will be interesting.
Laser welding has quite different challenges from electrical welding as the heat-affected zone is so much smaller, much less energy is delivered to the metal to perform the weld. I'd like to read more about the research in the article to see what they've done to address this or if it was even an issue for them! It probably depends on the thickness and orientation of the metal and fixturing.
The kickass aluminum welding process doesn't melt aluminum at all. It's called friction stir welding. Invented in the UK in the 1990s, it involves moving a rotating tool through the aluminum. The rotation softens and mixes the solid metal, refining the grain structure and blending the two pieces together. It's what SpaceX uses to weld the tanks on the Falcon 9.
While you're correct about the oxide issue, there are welding processes which mitigate this. In particular, using alternating current instead of direct current causes a "cleaning" effect which knocks the oxide off of the weld area. Laser welding does a similar thing.
If you're welding aluminum with DC stick, DC TIG, or just an oxy-acetylene torch you can get good results by grinding the weld area with a flapper disk and brushing immediately before welding with a stainless wire brush that has never touched anything but aluminum. For DC TIG and oxy-acetylene I've used flux coated welding rods as filler material with some luck.
Also, you always need to keep oxygen away from weld, no matter what process or material you're welding. At welding temperatures metals will burn in the presence of oxygen. We do this by using shielding gasses, flux which burns and displaces the oxygen, using a slightly fuel-rich (or "reducing") flame, physically displacing all the oxygen (forge welding) etc.
Correct about keeping oxygen away regardless of material. Aluminum is just much less forgiving than steel in this regard. I use the DC TIG process even for steel because it makes cleaner welds than sticks do. (TIG is also slower than stick, so it's less good for high-volume welding.) I've never tried flux-coated rods with aluminum because they seemed like a gimmick to me, but maybe I'll do an experiment.
Welding with current typically requires electrric arc. That typically requires some gas at high enough pressure. Welding in space would mean you need a lot of gas, which has to be shipped from earth and it's pretty hard to keep enough pressure near weld when you're in vacuum. Lasers have the smallest heat affected zone of all welding, so you need to get rid of smaller amount of heat after welding, pretty usable when you don't have atmosphere around you to cool your welds.
The current is the problem. Between the current flowing through the metal, and the resulting electromagnetic emissions, arc welding on an ungrounded spacecraft will no doubt cause all sorts of headaches. A laser does not require passing current through the object.
Fiber lasers can be quite efficient and the weld process itself is very efficient as less energy is delivered to the metal to perform the weld. Good beam control ensures a minimum of metal is melted to perform the weld and also doesn't get too hot to vaporize and sputter. I don't know about overall efficiency but laser welding continues to displace electrical welding due to a much higher level of process variable control.
I know nothing about welding, what is the distinction?
I clicked on that Wiki link and it said cold welding is "welding process", and the hyperlink to the regular welding page includes solid-state welding, which mentions cold welding.
Cold welding is unintentional, spontaneous joining of two metal parts in vacuum. You don't want that to happen, especially if the parts are meant to move.
Normal welding is intentional application of heat to partially melt two parts at the seam, so that they "mix" in semi-liquid state and become one part when they solidify. Welding may or may not use a third material (solder) to aid the process.
>Cold welding is unintentional, spontaneous joining of two metal parts in vacuum.
Is the only distinction the intention, though?
Because I saw some examples of industrial applications of cold welding, so I'm still not quite getting why cold welding isn't considered welding (I have been googling since my original comment, but not finding anyone making this same distinction).
my understanding, welding is where the metals mix and bond directly. Solder is where they flow and fill the gaps completely, but they're not mixing. According to the webs welding is where both metals melt and mix. Soldering is where only the solder melts. I think you can imagine that if you flow a solder completely between two piece of metal then there'd be no air and it'd basically a really good cold weld. Imagine sticking two pieces of wood together with peanut butter. The PB doesn't actually chemically bond to the wood nor does it merge with the wood.
Cold welding in my understanding is where the metals are very very flat against each other and held togehter by that. like when you have 2 sheets of paper against each other and try to pull them apart without sliding them off of each other or grabbing corners.
In a good weld you actually make 2 (or 3) pieces of metal into one.
No, you don't need to melt the metal to mix; it's just almost always easier to do it that way.
As soon as you cause conditions under which grain boundaries wander, you get welding if the two pieces happen to touch at an atomic/molecular level.
Note explosion welding: you use a shockwave to hold the pieces together while aggressively dislocating grain boundaries. The result is a (very good) weld. Many glues involve welding behavior, especially if they are used without waiting minutes to hours for the bond to harden before loading it.
For example, "contact cement" (polychloroprene glue) works by precipitating a polychloroprene layer from a solvent into the surface pores of both to-be-bonded parts, letting all the solvent dry, and then forcing such prepared surfaces together to cause intimate interaction of the polymer chains on the surfaces to weld into a single layer of polychloroprene that's solvent-soaked into both it's sides (which wouldn't be possible unless the materials are extremely porous).
However, solids are very bad at wetting surfaces, so you will have a hard time getting the needed atomic contact.
Welding isn't really applicable to composites like wood or paper.
> Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material.[1][2] Heat is generated by friction between the rotating tool and the workpiece material, which leads to a softened region near the FSW tool. While the tool is traversed along the joint line, it mechanically intermixes the two pieces of metal, and forges the hot and softened metal by the mechanical pressure, which is applied by the tool, much like joining clay, or dough.
Normal welding needs heat to melt the metals. Cold welding happens without heat. Two metal parts will cold-weld on any smooth, touching faces if the air molecules that keep the two separated disappear.
Sure, I mean I read both the wikipedia pages so I've understood that. And I'm not trying to be obtuse here, honestly, but that still doesn't really help me understand why "cold welding, despite the name, _is not welding_".
Your description, and wiki's, both sound like it is welding.
And after spending an embarrassing amount of time last night going down a welding rabbit hole, I have not seen anyone else claim that "cold welding is not welding". I'm pretty sure it is.
Cold welding is basically galling like you get with stainless on stainless under high pressure. Uniformity and consistency is hard to achieve so besides accidentally sticking things that shouldn't be stuck and the lightest duty applications the usefulness is limited.
I wonder if cold welding could be useful in space, though. Make the two surfaces totally flat, clean them in vacuum, and then press them together to weld them.
Ok, "clean them in vacuum" is kind of a "now draw the rest of the owl" type of thing. But I wonder what's possible when you don't have an atmosphere to mess up the surface. Could you scrape off the oxide layer of aluminum, for example, and get it smooth enough to cold weld without worrying about it re-oxidizing because there's no air?
This is the hard part. They need to be flat to less than atom size over whole area, at least several square centimeters. We can't do that yet economically. If they are not so flat, your weld will be pretty weak.
BUT if you could make them flat enough and then wiggle them ultrasonically so that those almost flat surfaces rub the rest of bumps, that would probably not require a lot of heat and energy to make a pretty good connection.
In order to make a surface properly flat you need to have the cleave surface line up with crystal boundaries, but crystals are randomly oriented in three dimensions meaning the surface can't be truly flat.
And that's even assuming the solid you're working with is crystalline of the sort that can do this. Many materials are alloys meaning that cold welding would be further difficult.
Perhaps a more direct link https://www.nasa.gov/centers-and-facilities/marshall/nasa-to...
Thanks! (Although, it is nice to see a good old /. link - pretty rare to see that on HN!)
Electron beam welding requires a vacuum.[1] So that's a promising technique for space welding.
Until recently, the whole object had to be in vacuum. A recent breakthrough is a welding head which creates a local vacuum around the welding area, rather than putting the whole object into a vacuum chamber. This allows automated welding of big, thick objects, all the way up to nuclear reactor pressure vessels.
[1] https://www.youtube.com/watch?v=GMSD5izdUyY
Not recently. Atmospheric EB has been around for a long time. Leybold started in the 60's and by the 70's a few companies had machines. Band saw blade welding is one of the big users of atmospheric EB.
The big problem with ATM EB is that the beam diffuses in the air rapidly so you have a few usable cm from the aperture to the work piece. The machines work by using a standard EB column with a turbo or diffusion pumped gun chamber firing down a baffled tube, each baffle having a small hole for the beam to pass and the space between the baffles is pumped by large vacuum pumps. PTR had a picture of such a machine and you can see a big umbilical of vacuum hoses snaking from the head to a battery of large Stokes piston vacuum pumps. Each baffle successively reduces the atmosphere leaking in until the isolation valve can be opened and the head can maintain enough vacuum to prevent flash over arcing.
A lot of that big stuff you see like pressure vessel welding uses reduced atmosphere welding where a small space is sealed as best as possible so the pressure can be reduced below 1 pascal (1E-2 Torr.) Then a standard pumped welding head can be used.
The more recent development was the plasma arc window stuff Brookhaven national labs did with Joining Tech (knew someone who worked for them when that project was active) though I know of no manufacturer using it.
This is a good example of a space-based research initiative that might find significant applications on Earth.
I think the key reason that space-based research tends to be so technologically fruitful is that it imposes a discipline on the science done, through the constraints that space imposes on meeting ambitious mission objectives.
Space initiatives also provide a justification for doing the kind of blue skies research that might otherwise find difficulty finding funding.
The applications on Earth are already realized:
https://en.wikipedia.org/wiki/Laser_beam_welding#Equipment
https://rickyswelding.com/best-laser-welding-machine/
Oh, that's excellent
> I think the key reason that space-based research tends to be so technologically fruitful is that it imposes a discipline on the science done, through the constraints that space imposes on meeting ambitious mission objectives.
The enormous budget and the elite scientific and engineering talent also may help. On Earth, those resources don't usually go toward finding a new way to weld things.
The most recent Planet Money podcast talks about how the latest microchip innovation was proposed by a nuclear weapons researcher and cost the us government roughly 300-400 million but the engineering research to make a practical ultraviolet etching machine cost ASML nine billion and twenty years of development, they said if they knew it would take that long they might never have attempted it but they are now the sole maker of such devices which seems to have made the investment worthwhile.
It’s a bit weird that NASA are doing the research.
In the next century dozens of corporations bigger than most countries of Earth will be up in space mining millions of tons of gold and other rare materials, tax free anywhere.
It seems they will see the greatest benefit from this research, but they don’t want to pay for it?
I mean I would also choose to just get free stuff. But why are we giving it away?
1. Doing research is exactly the purpose of NASA. 2. I'm highly sceptical of the idea that space mining will be an economically profitable activity in the near future and even more sceptical of the idea that nation states on Earth won't find a way to tax it.
> I'm highly sceptical of the idea that space mining will be an economically profitable activity in the near future and even more sceptical of the idea that nation states on Earth won't find a way to tax it.
The US has carefully preserved the interests of private space minining companies in international agreements about space.
Look up the U.S. Commercial Space Launch Competitiveness Act of 2015, and the Artemis Accords as a start. Generally it's referred to as 'extraction', if you are searching. Here's a very good resource: [0]
The US delined to sign the Moon Agreement of 1984, at least in part because it designated the Moon (or some part) as the "common heritage of all mankind". The US objected because they said it contradicted free market principles. "Opponents of the Moon Treaty also expressed concerns that one of the goals of the agreement's proposed regulatory regime would be equitable sharing of benefits from lunar resources, as they worried this approach could disadvantage private sector initiatives."
[0] https://www.csis.org/analysis/salmon-swimming-upstream-chart...
It's probably not super realistic to mine resources in space and send the raw material down the gravity well but it's hard to imagine any space-based manufacturing without mining. Whether our species will ever attempt such a thing is.. who knows? But hauling heavy loads to and from Earth makes very little sense.
> It's probably not super realistic to mine resources in space and send the raw material down the gravity well
I wonder about it: Gravity pulling through zero drag (before the atmosphere) sounds like cheap transportation of just about any mass. We have lots of experience aiming the landing site of deorbiting objects.
How much would the ship cost - can we do it without an engine or fuel, with a little boost in the right direction from an orbital base? What would be needed for the cargo to survive reentry and 'landing' - for exampple, a heat shield? After landing, how much would recovery and transportation of the cargo cost? You don't want to be retrieving it from under 3,000 m of water.
That is an interesting question. Doing it without losing the load seems challenging but could work if you're basically pummeling an area with raw ore then subsequently mining and refining it? I wonder what the atmospheric consequences would be?
Also, the ore may be affected by the heat. It's enough to incinerate many things falling from space.
> It seems they will see the greatest benefit from this research, but they don’t want to pay for it?
The US government also did the research on fracking (i.e., for natural gas extraction), as far as I know.
Back in the late 1950s when NASA was born, the US felt that if the Soviet Union obtained a significant advantage in space technology, it could be an existential threat. The government therefore invested directly in research.
The US still invests in research in nuclear energy and other things. Congress is just now passing laws that will allow the government to recover expenses for private commercial use of its space launch facilities (it's a bit more complex than that, and I don't recall the details).
Maybe it would make sense for anyone commercializing it to pay royalties, at least if they start earning serious revenue.
Private companies face a free rider problem in funding publicly available research, in that it's generally better to conserve one's capital and wait for someone else to pay for the research.
And corporations, as a whole, are no where near as large as governments.. government has grown precipitously relative to the private sector over the last 80 years. It's just that that spending growth has been concentrated mostly in social programs rather goods and services that face the free rider problem:
https://ourworldindata.org/grapher/social-spending-oecd-long...
Increased supply will cause prices to fall, meaning the rate of profit will not be too extreme, especially how much easier sending stuff to space is getting
I cant wait, too many rare earths are dominated by BRICS countries
Rare-earth metals are far too plentiful and cheap on Earth to make it profitable to mine them in space and then ship them back to Earth.
Gold and platinum group metals are the only natural resources that could potentially be mined in space and then shipped back to Earth for sale at a profit. Maybe what we could see is such metals seeing their price come down as the supply increases from extraterrestrial sources, and and as a consequence of the resultant increase in abundance of these metals, new applications being found for them, which in turn would increase the productivity of the global economy.
Gold and platinum group metals have a lot of industrial uses that cannot currently be exploited due to their extreme scarcity and expense.
[dead]
Vacuum Laser welding is very much a thing already. Years back the old president wanted my team to build one from an old Wentgate e-beam chamber. Shipper destroyed the chamber in transit and my boss got into a silly fight with the vendor and shipper which killed the project. We then got a quote from EVO Beam who builds electron beam welders and other e-beam machines who does dual process, laser and EB in the same machine. Wound up buying another EB machine instead.
The challenge of welding in a vacuum is the molten weld pool emits metal weld vapor which impinges on surfaces in a linear trajectory from the pool. Think PVD, physical vapor deposition. So your beam delivery optics get a nice coating of whatever you are welding. I had some fun ideas for mitigating this in our design but never put it to test.
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.
> 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.
> 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...
> 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.
> 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.
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
> No. You sound so certain, yet: 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.
Wait, if you are in a vacuum and thus there is no oxidation layer, can't you just press two (identical) metals together and they will be joined because the electrons don't know which of the two objects they're in?
If you get your two surfaces very very close, sure. The problem is most non-ground metal is going to have a surface finish that is too rough for this to work.
You could squeeze things together, but this depends on part geometry.
Sure but the surfaces have to be perfectly flat to where you measure the roughness in angstroms. Not something you can perform by hand or with mechanical polishing.
This is known as 'Cold Welding' https://en.wikipedia.org/wiki/Cold_welding
Welding aluminum in Earth's atmosphere is difficult because aluminum oxide forms on the surface and it has a higher melting point than the aluminum inside. So to weld aluminum you need to keep oxygen away from the weld, usually by flooding the weld with argon or some other inert gas.
In a vacuum this problem wouldn't exist and aluminum should be no more difficult to weld than steel.
Not a metalurgist, but agree the oxide problem would go away. However I think you'd have a worse problem with heat. Aluminum in my limited experience gets really hot and soupy when welded, so that you have to go quite fast in many cases. Without an atmosphere to sync some of the heat, you might have very interesting thermal issues. You'd definitely need much bigger heat syncs. However depends likely on the scale of welding that's happening. Definitely will be interesting.
Laser welding has quite different challenges from electrical welding as the heat-affected zone is so much smaller, much less energy is delivered to the metal to perform the weld. I'd like to read more about the research in the article to see what they've done to address this or if it was even an issue for them! It probably depends on the thickness and orientation of the metal and fixturing.
The kickass aluminum welding process doesn't melt aluminum at all. It's called friction stir welding. Invented in the UK in the 1990s, it involves moving a rotating tool through the aluminum. The rotation softens and mixes the solid metal, refining the grain structure and blending the two pieces together. It's what SpaceX uses to weld the tanks on the Falcon 9.
While you're correct about the oxide issue, there are welding processes which mitigate this. In particular, using alternating current instead of direct current causes a "cleaning" effect which knocks the oxide off of the weld area. Laser welding does a similar thing.
If you're welding aluminum with DC stick, DC TIG, or just an oxy-acetylene torch you can get good results by grinding the weld area with a flapper disk and brushing immediately before welding with a stainless wire brush that has never touched anything but aluminum. For DC TIG and oxy-acetylene I've used flux coated welding rods as filler material with some luck.
Also, you always need to keep oxygen away from weld, no matter what process or material you're welding. At welding temperatures metals will burn in the presence of oxygen. We do this by using shielding gasses, flux which burns and displaces the oxygen, using a slightly fuel-rich (or "reducing") flame, physically displacing all the oxygen (forge welding) etc.
Correct about keeping oxygen away regardless of material. Aluminum is just much less forgiving than steel in this regard. I use the DC TIG process even for steel because it makes cleaner welds than sticks do. (TIG is also slower than stick, so it's less good for high-volume welding.) I've never tried flux-coated rods with aluminum because they seemed like a gimmick to me, but maybe I'll do an experiment.
>I've never tried flux-coated rods with aluminum because they seemed like a gimmick to me, but maybe I'll do an experiment.
They suck to use but they work. They're not really a production item. They're more for globbing something together in the field.
> They suck to use but they work
Yep, exactly. I welded a fitting onto a cast aluminum intake manifold using these things and an oxy-acetylene torch and it came out "good enough"
> In a vacuum this problem wouldn't exist and aluminum should be no more difficult to weld than steel.
Aluminum is a PITA for more reasons than its oxide layer...
Laser welding has been around for a long time and is getting more common as of recent.
Example: https://youtu.be/YTCnv1RV-Ns
I was really interested in it but I'm very worried about my remaining eye.
What's wrong with using an electric current to weld? Why use such an inefficient source of heat?
I feel lasers might have more safety problems too.
Welding with current typically requires electrric arc. That typically requires some gas at high enough pressure. Welding in space would mean you need a lot of gas, which has to be shipped from earth and it's pretty hard to keep enough pressure near weld when you're in vacuum. Lasers have the smallest heat affected zone of all welding, so you need to get rid of smaller amount of heat after welding, pretty usable when you don't have atmosphere around you to cool your welds.
No, the needed arc can be metal vapor producing and using more thermionic electron emission than plasma current based. Current is also self-lensing.
The current is the problem. Between the current flowing through the metal, and the resulting electromagnetic emissions, arc welding on an ungrounded spacecraft will no doubt cause all sorts of headaches. A laser does not require passing current through the object.
Fiber lasers can be quite efficient and the weld process itself is very efficient as less energy is delivered to the metal to perform the weld. Good beam control ensures a minimum of metal is melted to perform the weld and also doesn't get too hot to vaporize and sputter. I don't know about overall efficiency but laser welding continues to displace electrical welding due to a much higher level of process variable control.
Space has a vacuum which reduces heat convection. My understanding is that laser welding would apply less heat to the area around the weld point.
I wonder if space vacuum would work similarly to welding techniques that require inert gas
I take it they plan on chartering more Boeing launches then.
was welding ever tried on station?
Cold welds have taken place in space.
https://en.m.wikipedia.org/wiki/Cold_welding
Cold welding, despite the name, is not welding.
I know nothing about welding, what is the distinction?
I clicked on that Wiki link and it said cold welding is "welding process", and the hyperlink to the regular welding page includes solid-state welding, which mentions cold welding.
Cold welding is unintentional, spontaneous joining of two metal parts in vacuum. You don't want that to happen, especially if the parts are meant to move.
Normal welding is intentional application of heat to partially melt two parts at the seam, so that they "mix" in semi-liquid state and become one part when they solidify. Welding may or may not use a third material (solder) to aid the process.
>Cold welding is unintentional, spontaneous joining of two metal parts in vacuum.
Is the only distinction the intention, though?
Because I saw some examples of industrial applications of cold welding, so I'm still not quite getting why cold welding isn't considered welding (I have been googling since my original comment, but not finding anyone making this same distinction).
my understanding, welding is where the metals mix and bond directly. Solder is where they flow and fill the gaps completely, but they're not mixing. According to the webs welding is where both metals melt and mix. Soldering is where only the solder melts. I think you can imagine that if you flow a solder completely between two piece of metal then there'd be no air and it'd basically a really good cold weld. Imagine sticking two pieces of wood together with peanut butter. The PB doesn't actually chemically bond to the wood nor does it merge with the wood. Cold welding in my understanding is where the metals are very very flat against each other and held togehter by that. like when you have 2 sheets of paper against each other and try to pull them apart without sliding them off of each other or grabbing corners.
In a good weld you actually make 2 (or 3) pieces of metal into one.
No, you don't need to melt the metal to mix; it's just almost always easier to do it that way. As soon as you cause conditions under which grain boundaries wander, you get welding if the two pieces happen to touch at an atomic/molecular level.
Note explosion welding: you use a shockwave to hold the pieces together while aggressively dislocating grain boundaries. The result is a (very good) weld. Many glues involve welding behavior, especially if they are used without waiting minutes to hours for the bond to harden before loading it. For example, "contact cement" (polychloroprene glue) works by precipitating a polychloroprene layer from a solvent into the surface pores of both to-be-bonded parts, letting all the solvent dry, and then forcing such prepared surfaces together to cause intimate interaction of the polymer chains on the surfaces to weld into a single layer of polychloroprene that's solvent-soaked into both it's sides (which wouldn't be possible unless the materials are extremely porous).
However, solids are very bad at wetting surfaces, so you will have a hard time getting the needed atomic contact.
Welding isn't really applicable to composites like wood or paper.
Is the grain boundaries wander and it touches on the atomic level is it not mixing?
And thanks for the additional details
> No, you don't need to melt the metal to mix; it's just almost always easier to do it that way.
Except for welding aluminum, where friction stir welding does exactly that to solid metal.
The point of the friction is to generate heat.
Yes, but not to the point of melting in this case.
https://en.wikipedia.org/wiki/Friction_stir_welding
> Friction stir welding (FSW) is a solid-state joining process that uses a non-consumable tool to join two facing workpieces without melting the workpiece material.[1][2] Heat is generated by friction between the rotating tool and the workpiece material, which leads to a softened region near the FSW tool. While the tool is traversed along the joint line, it mechanically intermixes the two pieces of metal, and forges the hot and softened metal by the mechanical pressure, which is applied by the tool, much like joining clay, or dough.
Normal welding needs heat to melt the metals. Cold welding happens without heat. Two metal parts will cold-weld on any smooth, touching faces if the air molecules that keep the two separated disappear.
Sure, I mean I read both the wikipedia pages so I've understood that. And I'm not trying to be obtuse here, honestly, but that still doesn't really help me understand why "cold welding, despite the name, _is not welding_".
Your description, and wiki's, both sound like it is welding.
And after spending an embarrassing amount of time last night going down a welding rabbit hole, I have not seen anyone else claim that "cold welding is not welding". I'm pretty sure it is.
Cold welding is basically galling like you get with stainless on stainless under high pressure. Uniformity and consistency is hard to achieve so besides accidentally sticking things that shouldn't be stuck and the lightest duty applications the usefulness is limited.
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I wonder if cold welding could be useful in space, though. Make the two surfaces totally flat, clean them in vacuum, and then press them together to weld them.
Ok, "clean them in vacuum" is kind of a "now draw the rest of the owl" type of thing. But I wonder what's possible when you don't have an atmosphere to mess up the surface. Could you scrape off the oxide layer of aluminum, for example, and get it smooth enough to cold weld without worrying about it re-oxidizing because there's no air?
> Make the two surfaces totally flat
This is the hard part. They need to be flat to less than atom size over whole area, at least several square centimeters. We can't do that yet economically. If they are not so flat, your weld will be pretty weak.
BUT if you could make them flat enough and then wiggle them ultrasonically so that those almost flat surfaces rub the rest of bumps, that would probably not require a lot of heat and energy to make a pretty good connection.
Surfaces that aren't that flat, already have an interesting weld-like behaviour, although they can still be separated relatively easily:
https://en.wikipedia.org/wiki/Gauge_block#Wringing
Ultrasonic stir welding is already a thing: https://technology.nasa.gov/patent/TOP8-95
Ultrasonic welding is done commercial for cable harnesses to butt weld copper.
In order to make a surface properly flat you need to have the cleave surface line up with crystal boundaries, but crystals are randomly oriented in three dimensions meaning the surface can't be truly flat.
And that's even assuming the solid you're working with is crystalline of the sort that can do this. Many materials are alloys meaning that cold welding would be further difficult.