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NASA Investigates Laser-Beam Welding in a Vacuum for In-Space Manufacturing
- throwaway4220 2y agowas welding ever tried on station?
- basementcat 2y agoCold welds have taken place in space. https://en.m.wikipedia.org/wiki/Cold_welding https://en.m.wikipedia.org/wiki/Cold_welding
- mlindner 2y agoCold welding, despite the name, is not welding.
- ziddoap 2y agoI 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.
- Zondartul 2y agoCold 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.
- ziddoap 2y ago>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).
- grogenaut 2y agomy 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.
- namibj 2y agoNo, 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.
- sfink 2y agoI 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?
- yetihehe 2y ago> 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.
- pjc50 2y agoUltrasonic stir welding is already a thing: https://technology.nasa.gov/patent/TOP8-95 https://technology.nasa.gov/patent/TOP8-95
- namibj 2y agoUltrasonic welding is done commercial for cable harnesses to butt weld copper.
- userbinator 2y agoSurfaces 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 https://en.wikipedia.org/wiki/Gauge_block#Wringing
- deleted 2y ago[deleted]
- basementcat 2y agoPerhaps a more direct link https://www.nasa.gov/centers-and-facilities/marshall/nasa-to-transform-in-space-manufacturing-with-laser-beam-welding-collaboration/ https://www.nasa.gov/centers-and-facilities/marshall/nasa-to...
- trebligdivad 2y agoThanks! (Although, it is nice to see a good old /. link - pretty rare to see that on HN!)
- kristianp 2y agoWhat'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.
- ETH_start 2y agoSpace has a vacuum which reduces heat convection. My understanding is that laser welding would apply less heat to the area around the weld point.
- sandworm101 2y agoThe 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.
- yetihehe 2y agoWelding 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.
- namibj 2y agoNo, the needed arc can be metal vapor producing and using more thermionic electron emission than plasma current based. Current is also self-lensing.
- bloggie 2y agoFiber 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.
- ETH_start 2y agoThis 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.
- itronitron 2y agoThe applications on Earth are already realized: https://en.wikipedia.org/wiki/Laser_beam_welding#Equipment https://en.wikipedia.org/wiki/Laser_beam_welding#Equipment https://rickyswelding.com/best-laser-welding-machine/ https://rickyswelding.com/best-laser-welding-machine/
- ETH_start 2y agoOh, that's excellent
- mmooss 2y ago> 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.
- fmbb 2y agoIt’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?
- jaimex2 2y agoI take it they plan on chartering more Boeing launches then.
- ianschmitz 2y agoLaser welding has been around for a long time and is getting more common as of recent. Example: https://youtu.be/YTCnv1RV-Ns https://youtu.be/YTCnv1RV-Ns
- grogenaut 2y agoI was really interested in it but I'm very worried about my remaining eye.
- dreamcompiler 2y agoWelding 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.
- grogenaut 2y agoNot 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.
- bloggie 2y agoLaser 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.
- pengaru 2y ago> 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...
- jcgrillo 2y agoWhile 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.
- Animats 2y agoElectron 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 https://www.youtube.com/watch?v=GMSD5izdUyY
- MisterTea 2y agoNot 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.
- Havoc 2y agoI wonder if space vacuum would work similarly to welding techniques that require inert gas
- jcgrillo 2y agoHeat 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.
- amelius 2y agoWait, 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?
- Hasz 2y agoIf 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.
- MisterTea 2y agoSure 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.
- Ridius 2y agoThis is known as 'Cold Welding' https://en.wikipedia.org/wiki/Cold_welding https://en.wikipedia.org/wiki/Cold_welding
- MisterTea 2y agoVacuum 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.