L'Affaire Siloxane

L'Affaire Siloxane(mceglowski.substack.com)

87 points by idlewords 1 day ago | 15 comments

shmeeed 2 hours ago |

Part of my job is to keep siloxanes out of a complex, multi-step, multi-sub-contracted manufacturing process. A supplier change that should have been a simple affair has cost us several kilobucks in analyses in the past months. I hate the stuff.

wingmanjd 1 minute ago | |

This is the first time hearing the term "kilobucks". I love it (and am stealing it for future conversations).

s0rce 2 hours ago |

Siloxanes contaminate everything. We routinely see them on various surfaces when doing X-ray photoelectron spectroscopy.

isoprophlex 2 hours ago | |

Indeed. "Grease peaks" we called them, they were always there in basically all NMR or MS spectra I took as an organic chemist. Like PFAS or microplastics, you just can't get rid of them.

mrob 5 minutes ago | | |

You can see this grease by the effect it has on water contact angle. If you have a smooth glass/metal/ceramic surface, cleaned by a highly effective method (e.g. an ultrasonic cleaner), water poured on it will slide off easily without forming beads ("water-break test"). But if you leave it out in ordinary air for some time, the water will form beads again even if you never touch it. Exact time varies depending on air quality, but probably within a few hours.

RobotToaster 2 hours ago |

I'm sceptical of the claim that they couldn't eliminate the majority of them from stuff that's shipped up to the ISS. Even if it meant making special space certified hair conditioner.

idlewords 1 hour ago | |

There's a nice paper on this, ICES-2018-123 "Dimethylsilanediol (DMSD) Source Assessment and Mitigation on ISS: Estimated Contributions from Personal Hygiene Products Containing Volatile Methyl Siloxanes (VMS)". The upshot is more than half of the siloxane burden on ISS comes from God knows where (packaging, plastics, machinery, you name it).

https://ttu-ir.tdl.org/items/ff1a240e-1fb1-4b04-acb2-42e9c45...

LeifCarrotson 1 hour ago | | |

From the paper:

> The main sources of VMS were determined to be antiperspirants ... skin lotions ... wipes ... and hair conditioner. Several siloxanes-free options are available for [these products]. These products are now being assessed for crew member use in future increments.

From the blog:

> At present the agency is testing a new filtration system to put in front of the heat exchangers, to try to protect them, and continuing to try to cut down on siloxanes at the source level. There are probably people at NASA now whose entire career has been built on siloxane control.

Why wasn't the result to simply ban siloxane-containing cosmetics and wipes? The cosmetics are up to the individual astronaut, which is a little crazy, but the wipes are provided by NASA, and they're still using siloxane-bearing wipes, which shortens the life of their water systems and costs crazy amounts of money.

s0rce 1 hour ago | |

I don't see why not either, just get "organic"/plant or mineral based cosmetics, deodorants and hair products.

RobotToaster 2 hours ago |

> while a further 7,000 kilograms of treated urine were sitting in orbital storage tanks, waiting to be processed.

Is that a record for the biggest piss bottle ever made?

mannykannot 13 minutes ago | |

A two meter cubed volume would be sufficient to hold that much. I would guess that cruise ships store more urine than that, though presumably not separated from everything else humans dump into toilets.

With the qualification 'in orbit', I imagine it is.

sprinkly-dust 2 hours ago |

I hope to see these seemingly mundane unknown unknowns raised in space travel centered hard science fiction. I think The Martian and Seveneves almost captured these but not quite.

tedd4u 31 minutes ago | |

Project Hail Mary has a devilish contamination subplot.

adolph 2 hours ago |

An interesting substory that is simultaneously reminiscent of the Fogbank story and how Hayek's "curious task" is much more broadly applicable:

  There is a good cautionary tale here from the Space Shuttle era. That vehicle 
  had heat resistant tiles that had to be attached to the aluminum belly of the 
  orbiter. A special cloth had been certified for wiping the aluminum clean 
  before applying the primer that securely bonded the tiles to the metal. After 
  years of uneventful use, tile engineers discovered that new replacement tiles 
  were no longer curing properly.
  
  A careful investigation revealed that the supplier of that special cloth had 
  changed the lubricant used in the machine that sews its hem. Minute amounts 
  of the lubricant were being deposited on the stitching, and enough of that 
  residue was getting on the aluminum skin to prevent the tile adhesive from 
  curing properly.

s0rce 1 hour ago | |

In medical device manufacturing you have systems in place that your vendors have to disclose changes to their manufacturing process that hopefully can catch stuff like this before people die. I can see how minute stuff gets easily passed off as not an important change.

duskwuff 50 minutes ago | | |

Especially if the real change is a couple levels separated from the problem. For instance, I can imagine a situation where the manufacturer of that "special cloth" didn't even change anything themselves, but their machine lubricant supplier silently changed their formula a bit. (Or maybe even that one of the suppliers to the lubricant company changed something - it's turtles all the way down.)

There is a good cautionary tale here from the Space Shuttle era. That vehicle had heat resistant tiles that had to be attached to the aluminum belly of the orbiter. A special cloth had been certified for wiping the aluminum clean before applying the primer that securely bonded the tiles to the metal. After years of uneventful use, tile engineers discovered that new replacement tiles were no longer curing properly. A careful investigation revealed that the supplier of that special cloth had changed the lubricant used in the machine that sews its hem. Minute amounts of the lubricant were being deposited on the stitching, and enough of that residue was getting on the aluminum skin to prevent the tile adhesive from curing properly.