adolph
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.
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> s0rce
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.
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> > duskwuff
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.)
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> > > s0rce
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.
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> > > > shmeeed
"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.
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> pjc50
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.
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> > adolph
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.
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shmeeed
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.
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> wingmanjd
This is the first time hearing the term "kilobucks". I
love it (and am stealing it for future conversations).
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> > liotier
In French project management parlance, we use k€
all the time.
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> > > msk-lywenn
I guess the french equivalent of kilobucks
would be briques (bricks)
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> > > > Ectiseethe
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.
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> > > > > pafje
See also the classic french movie:
https://fr.wikipedia.org/wiki/Pour_cen
t_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
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> > > > stymaar
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)
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> > > > > hashar
I still use « briques », typically
« 10 briques » instead of « 100 k
». I think there is some poetry in
sticking to the old obsolete term.
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> > > > partyficial
because of the metric system?
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> > > mapleoin
How do you pronounce that? Kilo-euro or
K-euro?
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> > > > Ectiseethe
Whenever I hear it, it is pronounced
"keuro" (k-uh-RO). And "meuro" (m-uh-RO)
for millions that are Mega-euros (M€).
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> > > > > liotier
kha-euh-ro - including the "euh"
impronounceable by non-French.
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> > goodmythical
I wish megabucks and gigabucks had the same
ring...
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> > > HPsquared
Megabucks is a common word but not often used
as a unit
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RobotToaster
> 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?
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> mannykannot
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.
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> > lugoues
I thought they just dumped it overboard but maybe
there are some ethical cruises... maybe.
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> > > idlewords
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.
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> > > > euroderf
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.)
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> > > mannykannot
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.
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s0rce
Siloxanes contaminate everything. We routinely see them on
various surfaces when doing X-ray photoelectron
spectroscopy.
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> isoprophlex
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.
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> > mrob
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.
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> > > s0rce
That's not always siloxanes, just atmospheric
hydrocarbons.
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> > cubefox
I bet some of these modern environmental
contaminants is causing the increasing age cohort
cancer rates.
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> > > awakeasleep
Look up the biocompatibility and safety
profiles of siloxanes
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> > > > cubefox
Yeah probably one of the others.
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> ericd
Apparently we also put polydimethylsiloxane in deep
frying oil. Wonder what that does to our innards.
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> > > ericd
Yeah, that's why it's included.
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golem14
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/
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ben_w
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.
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sprinkly-dust
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.
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> tedd4u
Project Hail Mary has a devilish contamination
subplot.
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RobotToaster
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.
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> idlewords
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-ac
b2-42e9c45...
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> > LeifCarrotson
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.
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> > > bobmcnamara
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.
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> > > MisterTea
> 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.
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> > RetroTechie
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)
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> s0rce
I don't see why not either, just get "organic"/plant
or mineral based cosmetics, deodorants and hair
products.
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> > Centigonal
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/
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ggm
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.
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> mananaysiempre
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.
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> > ggm
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.
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krunck
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?
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voidUpdate
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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