L'Affaire Siloxane | Hacker News Reader

L'Affaire Siloxane

mceglowski.substack.com

299 pointsidlewords55 comments

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.

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.

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 lubricant supplier silently changed the formula of their sewing machine oil. (Or maybe even that one of the suppliers to the lubricant company changed something - it's turtles all the way down.)

Yes, you would also audit the quality system for your suppliers to confirm they are sufficiently controlling for upstream changes. In theory you can have all your ducks in a row.

"In theory" is doing a lot of heavy lifting there. ;)

Depending on the product and quantity, you can factor your purchase price level times 2-10 for every level of sub- and sub-sub-supplier you want to have audited to your "wacky spec" - which may even still sound kinda reasonable, until you realize your attack surface is basically fractal to the n-th degree. The amount of process steps and auxiliaries used in manufacturing is absolutely staggering.

Edit: I need to add this depends a lot on the sector. There's useful certificates for a lot of industries, if you choose to believe them.

The "curious task" full reference from Hayek:

“The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.”

Intended as a warning against command economies and centralized structures more generally, because the information-processing requirements are much larger than one might expect. But of course there are few things more central-planning than a space programme.

In this case a broader reading is an exhortation to guard against intellectual hubris. Through its various trials NASA seems like a good organization for learning from error and not accepting easy answers (except when they have to terrible results), and in this siloxane story I'm glad to see evidence of institutional curiosity that I could not have drempt up.

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.

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

I wish megabucks and gigabucks had the same ring...

Megabucks is a common word but not often used as a unit

In French project management parlance, we use k€ all the time.

I guess the french equivalent of kilobucks would be briques (bricks)

Historically, a "brique" used to be a million of anciens Francs (old Francs), then converted to 10 000 nouveaux Francs (new Francs) in 1960.

Since the switch to euro, I think the most commonly accepted value of one "brique" is (unofficially) 10 000 €, but the uncertainty makes it basically useless.

See also the classic french movie: https://fr.wikipedia.org/wiki/Pour_cent_briques,_t%27as_plus......

I can't recall I've heard "brique" used since the switch to € but it might just be my local bubble

If you were born before WWII, yes.

(The only person I know that still used «briques» in these decades were my grand parents born in the 1920th)

I still use « briques », typically « 10 briques » instead of « 100 k ». I think there is some poetry in sticking to the old obsolete term.

because of the metric system?

How do you pronounce that? Kilo-euro or K-euro?

Whenever I hear it, it is pronounced "keuro" (k-uh-RO). And "meuro" (m-uh-RO) for millions that are Mega-euros (M€).

kha-euh-ro - including the "euh" impronounceable by non-French.

> 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?

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.

I thought they just dumped it overboard but maybe there are some ethical cruises... maybe.

It's fine to dump sewage overboard if you're far enough from shore. Cruise ships treat it to some extent, but ultimately it all becomes fish food.

In the same way that every breath you take contains at least one atom-or-molecule of Caesar's last breath, every sip you take contains at least one atom-or-molecule of every cruise ship waste jettison. (Assuming sufficient worldwide diffusion time.)

It seems that in most ports they are required to hold and treat it (and, perhaps to a lesser extent, in inshore waters.) Fouling the places they take their customers to is ultimately bad for business.

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

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.

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.

That's not always siloxanes, just atmospheric hydrocarbons.

I bet some of these modern environmental contaminants is causing the increasing age cohort cancer rates.

Look up the biocompatibility and safety profiles of siloxanes

Yeah probably one of the others.

Apparently we also put polydimethylsiloxane in deep frying oil. Wonder what that does to our innards.

For antifoaming?

Yeah, that's why it's included.

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 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.

Project Hail Mary has a devilish contamination subplot.

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.

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.

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

It's really, really complicated. Even "organic" or "all natural" products often contain synthetic contaminants as a result of manufacturing, packaging, or shipping processes. Unless NASA were to set up separate factories and supply chains for manufacturing all known sources of siloxane contamination (either on their own or in partnership with manufacturers), it would be very difficult to actually get a siloxane-free product with any kind of certainty or consistency.

An example with a different contaminant: We can't seem to keep carcinogenic plasticizers out of our RXBars and our baby formula[1]. Those products are already way more regulated than something like wet wipes, and the companies that make them have a strong interest in keeping them free of contamination.

[1] https://www.plasticlist.org/

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...

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.

> Why wasn't the result to simply ban siloxane-containing cosmetics and wipes?

I would assume there is an approval process in place and alternatives have to go through this process before they can be sent up. It might take months or years for approval.

You can't just replace stuff in a sealed environment - if the new stuff is better in one way it might be worse than others. Gotta do the qualification work - remember they're drinking piss up there.

Got it. Time to introduce a "certified siloxane free" programme for the space station building & supply industry.

Just joking here, but reading between the lines it might not be such a bad idea? (if doable)

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.

I’d say that has been true since we started using spectrometers (of all kinds). Those things are preposterously sensitive and pretty damn routine. Nowadays of course there are also other, more narrowly scoped detection methods as well, such as PCR.

PCR/amplification is black magic. I'm also amazed by "no the DNA will be too old" keeps turning out not to be entirely true: People getting out of jail from re-testing evidence 20+ years later, Hominid DNA statements being made from archaic bones..

Animal population studies used to be (in my understanding) largely observational. Now, people can do scat tests and identify individuals.

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?

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

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