L'Affaire Siloxane (mceglowski.substack.com)

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

> 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?

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.

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.

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.

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.

I feel the microplastics contamination story which turns out to be measuring nitrile gloves used preparing samples is in this space. We can now measure things down to levels that may exceed our ability to exclude them as contaminants, routinely.

There is an even more fantastic incident with Ritonavir (Norvir), where the manufacturer lost the ability to make a retroviral drug for an extended time.

Something like that during a covid like moment would suck donkey rocks.

https://pmc.ncbi.nlm.nih.gov/articles/PMC4479028/

I am mildly concerned about the "normalised deviance" of the siloxanes in the water. It's probably an acceptable amount and it's probably fine, but "eh, its only a bit worse than expected, what's the worst that could happen" is what lost 2 space shuttles

While this is all new to me, surprises like this are a big part of why I now think we should aim for the Moon first, and only consider Mars when the moon bases are nice and boring.

If there was any "we don't even know if this is an emergency" surprise interaction along these lines, a 3-day emergency resupply mission (or evacuation) is much, much easier than a 6-9 month trip when the planets align.

No mention was made of eliminating the siloxane use by astronauts: leave-in hair conditioner, deodorant, etc.

I wonder if they track PFAS/PFOS contamination also?