Welding and outer space are the two things in life that always fascinated me. So undoubtedly the question has crossed my mind a few times: Can astronauts do welding jobs in the vacuum of empty space? It’s a fascinating topic to think about, and the answers to this space-related welding question will surprise you.
Space is the final frontier, it’s where science fiction meets reality. Humans have only taken their first baby steps into the vast encompassing cosmos, but have already achieved things beyond our wildest imagination:
- We have walked on the moon (suck it, conspiracy theorists);
- We have ‘space’-walked in outer-freakin-space!;
- We have built a permanent space station orbiting the earth;
- We have sent probes outside the solar system;
- We have sent probes to other worlds, Mars being the most prominent.
On our journeys, humans discovered many interesting things. Like the laws of physics working completely different in the vacuum of space than they do here on the earth. Yup, conditions in space are tough. You can’t survive there. But can you weld there? Kind of.
Can You Weld In The Vacuum Of Space?
Yes, welding in the vacuum of outer space is possible, but it is not similar to welding techniques we use on earth. Regular heat welding will not work in a space vacuum, since there is no oxidation layer. Humans in space use a technique known as ‘cold welding‘. This type of fusion welding is only possible in a vacuum.
Explaining cold welding means you should forget everything you know about regular welding. It’s not even close to the same thing, because the fundamental conditions under which it is done differ so much. Here’s my humble attempt to explain it in layman’s terms:
- In a vacuum, individual flat surfaces of two similar metals will naturally stick together;
- No fusion or heating is required in the process of cold welding;
- There is no liquid/molten phase required for the weld to permanently stick;
- In the absence of oxidation, dirt, debris and other contaminants, the atoms have no way of knowing they don’t belong together. Therefore, they stick and keep sticking together.
- All that is required for cold welding is two pieces being linked with some amount of force.
I understand if you’re still confused right now. I was, too. The guys over at the Veratasium YouTube channel always do an impressive job at explaining complicated subjects like these. They do a better job than me, in fact. Just check out their video and learn everything there is to know about space welding:
The Challenges Of Welding In Outer Space
Currently, the most common weld tool in space is the “variable power handheld laser torch“, a device that allows astronauts to do emergency repairs on the outside of the International Space Station (ISS). It is designed for both welding and brazing, making it a highly versatile tool with some very useful characteristics:
- Accuracy: The laser-guided torch easily indicates where the weld will end up. It’s easy to make an error in dangerous environments like outer space. Think underwater welding, but a 100 times worse.
- Maneuverability: Inside a space suit, moving around is hard. So making the tool move for you takes out a lot of the legwork and speeds up the welding job considerably.
- Ease of use: Astronauts train for a large range of tasks and are not fulltime hardcore welders. Making the tools easier to use will not only reduce the chance of complications.
There has been only one real experimental attempt throughout the history of space exploration into the practical use of welding. In 1969, cosmonaut Kozabov (together with his colleague Shonin) from the former Soviet Union attempted three different types of weld techniques in the vacuum of space on the Soyuz 6 mission, which were electron beam welding, low-pressure plasma arc welding, and consumable electrode welding. It worked, almost too good.
In the process, Kozabov *almost* accidentally caused a catastrophe. He managed to almost rupture the entire life capsule, risking full depressurization of the spacecraft. Would he have messed up, the death of the two cosmonauts would have been horrible. Hurled into space without spacesuits, their blood would have started boiling immediately, the skin will freeze, and all air would be removed from the lungs. In 30 agonizing seconds, their bodies would have inflated like a balloon. And eventually, death.
Obviously, the challenges of space welding are and continue to be huge:
- The environment is extremely hostile;
- The margin for error is tiny, even when maximum caution is used;
- Regular welding techniques will not be relevant in a vacuum;
- The range of tools is limited and using as little time as possible is essential;
- Securing welding power sources during a spacewalk is extremely difficult.
Metal Behavior In Outer Space
All of the weirdness surrounding welding in space boils down to one thing: How metals behave in a (near-)vacuum. As mentioned, the stuff gets pretty sticky towards similar metals, without much effort at all. Let’s find out what causes this weird behavior, because it’s actually something pretty amazing!
Why Does Metal Weld Together In Space?
Metal welds together in the vacuum of space, due to the fundamental structure of metals. Metals all contain positively charged ions (+), as well as freely moving negative electrons (-). On earth, the surface layers of metal react with the oxygen in the air to create a protective oxide layer around the metal. In a vacuum (such as space) this protective layer cannot be formed.
With a little bit of force or impact, metals of the same kind will fuse together. The electrons (-) from one piece of metal will automatically bond with electrons (-) from the other metal object. Atoms will not ‘know’ if they are part of metallic object A, or metallic object B. Thus they decide they are one big family instead.
What Happens If Two Pieces Of Metal Touch In Space?
It’s not true that two pieces of metal that touch in space randomly stick together and never let go. Most metal surfaces are irregular, containing space dust, or get battered by endless solar radiation. A metallic space object like the ISS is therefore not in danger of ‘sticky space junk’ that will permanently fuse.
The YouTube video at the top of this article also goes further into this topic. The ‘cold fusion’ of metals is actually a pretty interesting behavior, which can be exploited here on earth. It benefits nanotechnologies, among other things. The vacuum of space does deliver pretty cool ideas! But if it’s a vacuum, does that mean that rust cannot form either? I researched it for you guys, answers below.
Does Metal Corrode In Space?
It might surprise you that over time, some types of metals do corrode in (orbital) space. Even as high up as the ISS, oxidation occurs and metals will wear down. Outside of the solar system, such corrosion cannot occur, as there are no oxygen atoms available to corrode metals with.
In the absence of oxidation and moisture, rust cannot form. Corrosion will require these two elements for the chemical reaction to happen. So while human spaceflight does indeed experience corrosion in their spacecrafts and stations, metals in interstellar space would not experience such rust.
Spacing Out About Welding
Hopefully, the newly gained information in this article has helped you understand the challenges we face when it comes to using and fixing metal objects in space. The whole cold welding thing might space you out a bit at first. But once you start to wrap your head around it, you will actually start to see some interesting applications for it.
I’ve actually answered some other mind-blowing welding questions before. If you’re interested to learn about this stuff, I highly recommend you to check out my article on plasma cutter heat titled: “Is a plasma cutter hitter than the sun?“. I’ve also made a comparison between the heat of the plasma cutter and the temperature of the earth’s core. Super fun stuff. If all of this got you excited about welding, you can find a good overview of the best welding gear on this page. Thanks for reading along, and as always, weld on!