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Okay, I'm researching for a scene in my science fiction story. A character is in a spacecraft and needing to open a locked hatchway. It's locked electronically by an unknown code. All methods of forcing it open are failing, and there's limited time. So...I was thinking it might be plausible for the character to use an arc welder to just burn away the lock (holding the stick away from the metal so that it's essentially a torch). But then...I'm not sure if a spacecraft would keep an arc welder onboard. I've heard of arc welding experiments done in space before, but is that considered dangerous/antiquated?

Note: The spacecraft is a step above modern...it's futuristic, but I'd just like to stay a little grounded in reality. Any expert ideas are appreciated!

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    $\begingroup$ I think they'd probably use something more like this: technology.nasa.gov/patent/MFS-TOPS-5 $\endgroup$ – Morris The Cat Oct 11 at 13:41
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    $\begingroup$ It might be faster to use liquid nitrogen to break the lock, as it makes things brittle on contact. $\endgroup$ – cybernard Oct 12 at 0:26
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    $\begingroup$ Liquid nitrogen only makes plastics and non-austenitic metals brittle on contact. The lock is designed for cold of space so it going to austenitic. $\endgroup$ – user2617804 Oct 12 at 8:06
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    $\begingroup$ What is the purpose of this spacecraft- if it is to go to new or uncontrolled places then it can carry a lot more than it needs to handle any situation that meets at the other end (no hand waving needed)? $\endgroup$ – user2617804 Oct 12 at 8:32
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    $\begingroup$ From what materials will your spacecraft be made? 'Metal' is kind of broad. $\endgroup$ – Mast Oct 12 at 11:42
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Seems like Mast may have already alluded to it but I doubt modern spacecraft contain much weldable metal. I would be surprised if there is much or any steel left on spacecraft and I'm sure most of the aluminum is being replaced with carbon fiber if it hasn't already. I can't imagine there would be much use for a welder.

Additionally you have described a stick welder (which is a form of arc welding, but so are almost all forms of welding) which is probably the least likely form of welder you would find on a spacecraft. Stick welders have a really hard time welding thin materials and an even harder time welding aluminum. They also make extremely dirty welds and discharge a lot of shielding gasses. I think unless your world has some sort of propulsion system that makes weight a non-factor it would be extremely unlikely your ship would contain any steel or cast iron thick enough to be welded by a stick welder.

The ship would almost certainly want a TIG welder which can weld metal virtually as thin as metal can be and is perfect for welding aluminum. That being said most TIG machines are actually combo machines that can also stick weld, but I would think an organization making advanced spacecraft would be able to create a bespoke dedicated machine with the absolute bare minimum in order to save weight.

The issue: Stick welders can be used as a rudimentary cutting implement, but TIG and MIG welders can't really be used for that. (or not easily anyway) Additionally, in order to cut with a stick welder you need a welding rod that is oversized for the metal you are cutting, this would mean the ship just so happened to be carrying welding rods that it didn't really have a use for.

My suggestion: A sawzall or sawzall-like saw. A good demolition blade on a sawzall will cut through just about any material I expect you would find on a space craft like butter, and they are useful enough for so many tasks that it wouldn't be completely unreasonable to include one in a mission.

Additionally, depending on what the door's purpose is it probably wouldn't be unreasonable for it to not be very strong. If it just separates one part of the ship from another it probably wouldn't need to be that strong and therefore it may just be a door frame with a thin aluminum skin on it to save weight. You would be able to cut through a door like that with a steak knife.

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    $\begingroup$ Bear in mind that modern spacecraft still use a lot of minimally-modified 70s parts because engineering spacecraft is capital-H Hard and if you know a soyuz capsule works, and you're able to use one, why would you use anything else? They are starting to move away from that though. All that said, though, I don't know how much steel was on early spacecraft anyway. They definitely have to be mostly aluminum just for the weight. $\endgroup$ – Hearth Oct 13 at 20:45
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    $\begingroup$ I think a saw would generate particles that would be really bad in zero gravity, seems an unlikely piece of equipment to me. $\endgroup$ – msouth Oct 13 at 21:32
  • $\begingroup$ Could you improvise a plasma cutter from a TIG welder and a source of compressed air? $\endgroup$ – Robin Bennett Oct 14 at 12:38
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    $\begingroup$ @RobinBennett: You can cut with a TIG torch but since the tip is very thin you wont be able to cut anything with significant thickness. You'll also do damage to the tip although in this scenario that seems not very significant. $\endgroup$ – Jesse_b Oct 14 at 12:44
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    $\begingroup$ @msouth: That is a fair point I hadn't considered. This isn't really a productive counter "argument" but I can't imagine the particles from sawing would be any more significant than the particles from welding. Stick welding is especially dirty as it will leave a lot of dust from the unburnt flux. However any form of bad welding will throw off a ton of small metal "bb's" some stick to your work piece but some are just thrown off. Trying to cut metal with a welder is essentially bad welding so it will throw off a ton of metal pieces of various sizes. $\endgroup$ – Jesse_b Oct 14 at 12:59
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The equipment will depend on the mission. In particular, the length of the mission, the size of the crew, the total weight of the ship, and very strongly on the exact nature of what they are going to be doing.

Imagine a mission that is intended to be almost entirely observational. Go out to Jupiter, for example, and carefully look around. No landing on anything. No obtaining physical samples. The equipment for this is likely to be oriented towards keeping electronics and optics working. So they would have lots of equipment for that. Such a mission might be quite limited in mass. They might consider that, if they needed a huge industrial arc welder, they are probably already dead. Because they might think the only thing they could want to weld would be the ship's hull.

Turn it up a notch to landing on one or more of the Jovian moons and collect samples. Now you have physical equipment that may need to be patched up. Or adjusted due to last-second changes in schedule and plans. Oh, we can't possibly use this equipment module because the chemicals we have detected, from orbit, would utterly prevent its operation on this moon. So having it in the lander is a complete waste. Let's get it out of there fast so we can complete the mission. An arc welder might be the required tool. Or not, I'm not any kind of mechanic. But a lander could easily have a minor accident like bending a landing strut or scraping something. Or some equipment gets caught in a small little shift of rock. In the hands of a skilled tech an arc welder can do lots of cool things.

Turn it up yet another notch. It's a colonization mission. In this case, you would have many hard to predict tasks. Fix this, patch that, build the other. I once watched my uncle deal with a nut that had been "painted on" to a bolt. He got his arc welder and just sort of flicked it over the paint. The paint was gone and both the nut and bolt were fine. Not even warm.

So basically, the longer the mission, the more hands-on and heavy equipment oriented the mission, the more likely you will need an arc welder.

On the other hand, the more likely you will need any given chunk of equipment also. So the bigger the mission, the more likely you will be bringing various manufacturing equipment. It may not be very far in the future that an arc welder might be produced in a 3-D printer. There are 3-D printers now that will print in a variety of materials, which can then be cured using heat or microwaves etc., to achieve a variety of densities and hardness. It shouldn't be that big a deal to print most of the parts of an arc welder, then add the wires from non-specific supplies of wire. Possibly a few metal parts might need to be fashioned using other tools. And there you are, one arc welder. Overall, depending on the weight and room requirements on the ship, it might be preferable to take the data to run a 3-D printer, and tanks of printer material, than to try to take every possible tool you might need.

Indeed, on certain types of mission, you might be able to obtain the raw materials to make "3-D printer ink" rather than transport it. Maybe you only transport stuff you are not confident you can obtain locally. On the moon, for example, there is not much hydrogen available. So maybe you must transport tanks of hydrogen, possibly as water. Then you count on getting nearly everything else you need once you get there.

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    $\begingroup$ Nice notes about matching equipment to a mission. $\endgroup$ – Paul TIKI Oct 11 at 14:09
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    $\begingroup$ I like the portion about 3D printing tools as you need them. That sounds like something very useful for colony related spaceships $\endgroup$ – Enthus3d Oct 12 at 1:27
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    $\begingroup$ A modern switchmode welding power supply is a lot less massive than something using a traditional heavy iron mains-frequency transformer. $\endgroup$ – Chris Stratton Oct 13 at 21:27
  • $\begingroup$ It's a lovely answer. $\endgroup$ – Fattie Oct 14 at 12:28
  • $\begingroup$ My mind was blown trying to imagine a nut that was "painted on", but then I realised what you meant :P $\endgroup$ – Mirror318 Oct 14 at 14:19
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The cosmonauts of the Soyuz 6 mission (1969), Georgi Shonin and Valeri Kubasov, actually did test arc welding in space.

During the test, Kubasov almost burned through the hull of the Soyuz 6’s living compartment, a mistake that would have hurled the pair into space without spacesuits to face the final 30 seconds of their lives. Fortunately, the hull remained intact, but with a warning about the harshness and complexity of welding in space. (James A. Wilkey "Welding in Space", American Welding Society, 22 July 2015)

The answer is yes: the Russians have tested it and it works.

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  • $\begingroup$ Wow, chilling close call. Do you have any idea what the astronauts did to dispose of the tiny beads of molten metal that fall off as you weld??? Since they wouldn't fall to the ground...seems like that would be a problem, as @Starfish Prime pointed out. I mean, I know they had a system...just have no idea what it was... $\endgroup$ – cal Oct 12 at 3:19
  • $\begingroup$ @cal: No idea... $\endgroup$ – AlexP Oct 12 at 5:06
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    $\begingroup$ My God, there's an article "welding in space". Wow! $\endgroup$ – Fattie Oct 14 at 12:29
  • $\begingroup$ The 1st 5 paragraphlets of that article are (probably :-) ) rubbish. The rest maybe not. There has been much said about vacuum decompression survival and few accounts read like that one. The 2001 movie would have ended part way through if this was true (which doesn't prove anything :-) ). "Open the pod bay door HAL". ' I'm sorry, I can't do that Dave.' :-) [[ move each letter of HAL one place down the alphabet and what do you get ? :-) ]] $\endgroup$ – Russell McMahon Oct 14 at 12:50
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Arc welding in an atmosphere on a spacecraft sounds undesirable. You're generating some really unpleasant fumes and potentially releasing reasonable volumes of shielding gasses (bad news in confined spaces, also inconvenient if your atmosphere reprocessing life support can't keep up) and some potentially quite dangerous sparks and small metal fragments (conductive dust in microgravity is going to play havoc with electrical and electronic systems that aren't thoroughly sealed).

If you're not in an atmosphere, you should be using something more intrinsically awesome that takes advantage of the environment, such as electron beam welding, but that doesn't necessarily help in your specific situation.

As the author, you are of course free to handwave some arc welding devices. Have a look at the ones in Aliens, for example... general purpose compact utility tools, perhaps more justifiable than a proper welding rig.

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    $\begingroup$ If you’re not in an atmosphere why not take along a few sheets of sandpaper and use contact welding instead. Wait... Sandpaper is nowhere near as unfathomably awesome as an electron cannon. Gotcha. $\endgroup$ – Joe Bloggs Oct 12 at 21:08
  • $\begingroup$ TIG welding would solve the sparking issue, though not the shielding gas one. $\endgroup$ – Skyler Oct 14 at 14:15
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One of the problems with arc welding is you need to generate an actual arc. In atmosphere, this isn't a problem because the electricity is arcing through the gasses to complete the circuit.

In a vacuum, like outside of a spaceship, this is going to be a problem. No gas to arc across, no arc. No way to complete the circuit. So this depends on which side of the door your character is on and what he has to hand. Break down the problems one at a time.

You could simply handwave an arc welder aboard as emergency equipment. That's the easy out. Justification could be that gas-based welding (I imagine) would be way more dangerous aboard a spacecraft. While current based welding systems do not share the same dangers, they have their own set of problems.

If you don't want to give a narrative excuse for having a welding rig on board, you could have your character MacGuyver it. A welder isn't really all that complex from an electrical standpoint. I don't have an electrical background but I found this paper on what it takes. I have a welder that can run off the same circuit as our clothes dryer so I imagine the ship will be able to supply an adequate amount of power. So your guy breaks down some non-survival-based equipment like a microwave oven, adds the extra stuff he needs and he builds a welding rig.

If your guy has to go outside the ship he might need some sort of medium that will stick to a surface and allow electricity to arc through. I think the gel depicted in the show "Firefly" would be an imaginative way to start

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    $\begingroup$ ++ for McGyvered arc welder! Improvised equipment is great for stories. Not an answer to the ? but I recall reading about bike thieves who broke locks using pressurized gas, which gets extremely cold. Once cold the locks are brittle and break with a strike. Pressurized gas tanks might be more common on a spacecraft than an arc welder. If you use oxygen, remind your wingman to put out his stogie first. $\endgroup$ – Willk Oct 11 at 22:41
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    $\begingroup$ Real spaceships wouldn't likely use arc welders because they're tricky in space (not impossible though, from what I can tell). They'd have newer technologies that work better, like laser welders. weldingschool.com/blog/welding/history-of-welding-in-space So I'd think a better option than hand-waving an arc welder on board would be not hand-waving a proper welder. Probably harder to MacGyver though. $\endgroup$ – MichaelS Oct 12 at 7:12
  • $\begingroup$ Arc welding actually works fine in space, High voltage will actually generate a field emission by vaporizing microscopic portions of the electrodes. This does however quickly eat through electrodes. $\endgroup$ – John Oct 13 at 2:25
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In a large space habitats (say, 50+ people), arc welding (esp. argon or co2 - using varieties) will be probably quite common. Argon and co2 are not toxic, can be recycled out of the atmosphere (that's how we get argon on earth and any space habitat is expected to recycle co2 anyway). These welding methods (TIG/MIG/MAG) are applicable to iron and aluminium alloys and probably a lot more, generally don't depend on gravity and produce little to no byproducts in gaseous or dust form.

A lot of modern welding inverters come with an plasma-cutting option that use compressed air (the air is released back to the atmosphere with an ozone scent, but otherwise unchanged).

MMA welding (stick welding) is probably not really useful in space setup.

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In a post modern spacecraft as you specify, I'd imagine having an arc welder similar to those found in many home workshops around the world today is quite unlikely.

However, depending on the mission profile having some form of equipment to weld a patch onto the hull or repair equipment is definitely plausible, though I'd guess it would be more likely a gasless MIG or TIG welder for improved weld quality and versatility. Both of which could be fairly quickly modified to melt something metallic and exposed.

Which brings me on to the next point, all you need to bodge together an arc welder is a current source and the right electrodes. I've personally done a bit of very basic welding with a 24V truck battery, jumper cables and a spare weld rod that was rolling around the bottom of the boat, it wasn't pretty but it held. Depending on the lock, if it's anything like the form of a padlock running current through the shackle until it glows then hit it with a hammer and you're in.

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  • $\begingroup$ Note "Gasless MIG" doesn't exist, MIG stands for metal inert gas. I think what you are referring to is MAG or flux core welding which is a welding process that uses a wire feed welder with the flux gasses located in the core of the wire. These machines are actually mostly a gimmick and have almost no use in the real world. They are sold to be cheap MIG knock offs and I really doubt they would be used in any actual application. $\endgroup$ – Jesse_b Oct 14 at 12:00
  • $\begingroup$ @Jesse_b The small consumer welders are a bit feeble and only work well in limited situations. However FCAW welding is VERY popular and functional in a number of market segments, shipbuilding is a big one. kobelco.co.jp/english/ktr/pdf/ktr_26/049-054.pdf $\endgroup$ – KalleMP Oct 14 at 12:12
  • $\begingroup$ @KalleMP: I believe it. I've always heard it's useful outdoors in high wind situations but flux core wire can be used in a MIG machine and I would be surprised if any commercial application of it wasn't. To my knowledge the only people buying wire feed machines without a gas hookup are home gamers that think they found an amazing deal on a MIG machine from harbor freight. $\endgroup$ – Jesse_b Oct 14 at 12:34
  • $\begingroup$ Also I have to contest the statement: "Flux-cored wires occupy more than 30% of the total amount of arc welding materials consumed domestically." They are certainly the most popular home gamer machines in modern times because you can buy one for as cheap as $150 (significantly less than a real machine) and are often falsely advertised as "gasless MIG" so they are a very attractive purchase for people trying to get into hobby welding, but that doesn't translate to commercial applications. $\endgroup$ – Jesse_b Oct 14 at 12:40
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Any rational spaceship will have a manual override behind a locked cover on every door or hatch, that cover lock can be picked in a few minutes by young MacGyver, TheLocksmitingLawyer or smashed in moments by detective Spooner.

The only door with no easy override would be the brig. This will require additional plot manipulation.

To do the welding will require a gouging rod and an un-fused connection to a power bus. A gouging rod is typically a copper plated carbon rod by the copper is a convenience to allow holding from the end. Any carbon rod from some experiment, or some carbon fibre / nano-tube reinforced material could serve the same purpose, perhaps an artificial limb component made for this purpose.

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