OT: Zero-Gee Soldering

Interesting!

I can't figure why he's doing what he is doing. Hmm, smoke does not go up.

greg

What is up at zero-gee?

Did you read the article? They explain that they're testing it to make sure they can do repairs on a future Mars mission.

In zeroG, smoke goes towards the return vent. It's critical to keep air moving in space, or you end up asphyxiating in a cloud of CO2 around your head.

I scanned the artilcle. I usually appy heat to the joint myself. greg

Soldering? It's as easy as pulling the faulty module and subbing in your only spare AE-35 Antenna Orientation Unit.

I saw it in a documentary.

Tim.

But the AE-35 was not faulty, it was the PIC based computer that got it wrong

martin

Was that a Y2K bug?

On Thu, 23 Feb 2006 19:42:12 GMT, snipped-for-privacy@pitt.edu (GregS) Gave us:

It was a phenomena they discovered. Have you not ever seen the water blob experiments?

Anyway... the smoke is going in many directions. It was in earth orbit.

On Thu, 23 Feb 2006 20:46:23 GMT, snipped-for-privacy@pitt.edu (GregS) Gave us:

Too much information...

Y2k1 bug, although in every previous fault, it was due to human factors.

Ken

It looks to me like there's a ventilation fan or some sort, with the airflow from the astronaut's left to his right (our right to left).

Cheers! Rich

I've observed *SIMILAR* behavior while soldering here on good ol' terra firma in full-gee conditions - Not as... "dramatic", shall we say - The bead of rosin generally just kind of rotates around the bottom of the ball of hot solder, but it's clearly visible and totally unmistakable.

Having it start "doing laps" in zero gee isn't a real big surprise - What *IS* a surprise is that it stayed on the solder-glob, rather than flinging off to land who-knows-where. I wouldn't have expected the surface tension (Assuming that's the mechanism...) to be strong enough to keep it racing around the glob, rather than having the centrifical force pitch it across the cabin. Perhaps that would become an issue if it were heated even more/longer, so that the rosin bead picked up even more speed? (As in "hitting escape velocity")

Or perhaps it's some sort of "micro-gravity" effect - The rosin bead is effectively a satellite (in *VERY* close orbit) around the solder-glob?

Don Bruder wrote in news:43fe50b6$0$95962$ snipped-for-privacy@news.sonic.net:

I believe that surface tension and lack of escape speed is the answer.

Also, no gravity, no convection. Heat and smoke go the way of the air conditioning vents.

cheers

buck

I'm sorry Dave. I can't do that.

I was thinking that the Coriolis force might get the blob spinning. But the dynamics of this system appear to be the reverse of the classic 'bathtub drain funnel' case. There, the conservation of momentum cause the water to increase its velocity as their distance from the axis of rotation decreases. Here, the blob should slow down as its mass moves radially away from the solder blob.

I'm wondering if the vaporization of the flux has some asymmetry between the leading edge and trailing edge of the solder-flux interface that would cause more vapors to be emitted from the trailing edge. Sort of like a little rocket engine.

As the flux blob rolls along, the leading edge would be somewhat cooler. As it comes into contact with the solder, it begins to absorb heat. The trailing blob edge would be hotter and have a higher vapor pressure than the leading edge.

I'd bet on the being *EXACTLY* the mechanism.

Why would the leading edge be cooler, though?

One idea: The rosin blob acts as a (more or less) solid - Think a BB that's stuck to a marble somehow, yet free to roll in any direction. The trailing edge lifts off the solder blob, makes the trip "up and over the top" as it rolls along, and by the time it hits the "front", where it's about to come into contact with the blob again, it has cooled.

Make any sense, or do ya think I'm barking up the wrong tree completely?

Because it has rotated away from the solder blob for a moment.

Exactly. The flux blob rolls along the solder blob much the same way as a tire rolls along the road. The effects of surface tension will modify this somewhat. In fact, the surface tension on the cooler side of the flux (the side approaching the solder) may provide some attractive force pulling the flux blob in that direction harder than the hot side of the blob.

martin