A question about something I heard today ...

[bobdude11]

 My local morning DJs do a did you know segment and today they stated (no source given that I recall), that when in space, if you touch two pieces of metal together, they will permanently fuse together.

 I am looking this up (I will post any findings shortly), but I was curious if anyone that has worked in the aerospace industry/space program/etc. could:

1. Tell me that this is true (for some strange reason I want it to be because it is just so COOL!)?

2. If true, can you detail some of the science behind it?

When I first heard it, I thought "Ok. if this is true, why and how does this happen?" - I had some thoughts, but I am looking into it (just got home from work and have not dug in yet - wanted to post on here for a quick and dirty answer from people in the know!)

 If I need to research it myself, just slap my hand and tell me ...  - I will post again in a few with what I find - first stop: NASA ...

[bobdude11]

 Ok, what I found so far is that it is caled Cold Welding and has to do with the lack of an oxidation layer ....

Two sites I found:

A. http://blog.koldcast.tv/2010/koldcast-news/15-strange-things-about-outer-space/

"7. Cold Welding

In space, pressing two uncoated pieces of metal will eventually fuse them together. The Earth’s atmosphere coats metallic surfaces with a layer of oxidized material, but in the vacuum of space, that layer barely exists. NASA used to be hyper-sensitive to cold welding, so the metal used in many spaceships is coated to prevent the reaction. But it takes more than a brief bump for two metals to fuse in space, and in the 1960s the phenomenon of instant, accidental cold welding was dispelled as a myth."



B. http://www.coolsciencefacts.com/2006/metal.html

Not sure te first one is entirely on the up and up, but the second one at least tries to explain the science ... I'll keep looking - fascinating stuff ...

[ka9q]

I've heard of that happening, but it's the vacuum that does it. You don't have to be in space.

I also know that special lubricants have to be used in space because many of the common ones have vapor pressures that are not insignificant.

[ka9q]

The second article states that metals form a protective oxide layer in air that keeps them from cold-welding. Only some metals form these hard oxides; aluminum is the best known example but titanium and zirconium do as well. So does the chromium component of stainless steel. But while iron oxidizes, the layer doesn't protect the metal; it falls off as rust. Some metals like copper and silver oxidize only slowly and/or in certain environments, and especially precious metals like gold and platinum don't oxidize at all under normal conditions. But they still don't cold-weld in an atmosphere, so it can't be the protective oxide layer that does it. I think the air molecules themselves get in the way.

[Glom]

If this is the case, does it have any manufacturing applications.

[bobdude11]

 Thank you all for clarifying. It seems counter-intuititve, but then thought that it would be better to investigate.
Part of that investigation is this forum. There are people on here that can really help to educate me.
 
 I am still finding some interesting stuff (see my next post). Suffice to say, when I start reading about this and other things related to space, I feel as though I have just begun my science educaton. I am a learned person, but this field has so many new things I am staggered by it.

[bobdude11]

If this is the case, does it have any manufacturing applications.

 Excellent question ... when I Googled it I found some things that used the term Cold Welding, most seemed decidedly Terran bound.

One thing that showed up was this document from 1950:
http://www.ieeeghn.org/wiki/images/e/ed/Dubilier_-_Fortune,_September_1950,_Cold_Welding.pdf
(NOTE: it was a direct link from this search (fourth item down for me - experience may vary, not valid with any other offers): On Google, search criteria was: industrial applications for cold welding (link to original search was just too big) , I didn't pull it from a wikipedia page - I try to find other sources first)

I also found this interesting:
http://www.assemblymag.com/articles/84188-the-cold-welding-process-is-being-used-for-more-and-more-high-volume-applications

The last one is from 2002 - so it does appear that there are industrial applications for Cold Welding.

[ka9q]

Suffice to say, when I start reading about this and other things related to space, I feel as though I have just begun my science educaton.

Space has always been an excellent place to teach science, especially physics. Without an atmosphere and in free fall physics becomes very "pure"; you can easily demonstrate many basic principles without interference from friction. Look on Youtube and elsewhere for videos by Don Petit and Richard Garriott. Both are American astronauts who have flown to the ISS (Garriott bought his own way on a Soyuz). Both did a marvelous series of educational videos while they were there.

My favorite Garriott clip shows floating magnets aligning themselves with the (changing) direction of the earth's magnetic field. For decades, we (AMSAT) have used this technique for passive stabilization of small satellites but having never been to space myself I hadn't actually seen it. It's amazingly effective.

My favorite Petit clip shows conservation of angular momentum by various objects, some rigid (a camera lens, a book) and some fluid and able to dissipate energy (a partly filled water bottle). The latter demonstration shows very clearly why the Apollo astronauts had such trouble maintaining a passive thermal control roll.

As the saying goes, a picture is worth a thousand words. I'd add that a video clip is probably worth a million.

[bobdude11]

Suffice to say, when I start reading about this and other things related to space, I feel as though I have just begun my science educaton.

Space has always been an excellent place to teach science, especially physics. Without an atmosphere and in free fall physics becomes very "pure"; you can easily demonstrate many basic principles without interference from friction. Look on Youtube and elsewhere for videos by Don Petit and Richard Garriott. Both are American astronauts who have flown to the ISS (Garriott bought his own way on a Soyuz). Both did a marvelous series of educational videos while they were there.

My favorite Garriott clip shows floating magnets aligning themselves with the (changing) direction of the earth's magnetic field. For decades, we (AMSAT) have used this technique for passive stabilization of small satellites but having never been to space myself I hadn't actually seen it. It's amazingly effective.

My favorite Petit clip shows conservation of angular momentum by various objects, some rigid (a camera lens, a book) and some fluid and able to dissipate energy (a partly filled water bottle). The latter demonstration shows very clearly why the Apollo astronauts had such trouble maintaining a passive thermal control roll.

As the saying goes, a picture is worth a thousand words. I'd add that a video clip is probably worth a million.

 I will certainly check those out.

[Glom]

Did just that.  It is so obvious yet never thought about it.  Should have done a timelapse showing the magnet rotating over the course of an orbit.  I understand that it would be hard to get it to stand still though for 90 minutes.

Nice of him to answer questions for kids in Scotland.

[bobdude11]

Did just that.  It is so obvious yet never thought about it.  Should have done a timelapse showing the magnet rotating over the course of an orbit.  I understand that it would be hard to get it to stand still though for 90 minutes.

Nice of him to answer questions for kids in Scotland.

Indeed!