[HN Gopher] NASA: Capillary Cup
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NASA: Capillary Cup
Author : ColinWright
Score : 141 points
Date : 2023-10-12 11:18 UTC (9 hours ago)
(HTM) web link (www.rit.edu)
(TXT) w3m dump (www.rit.edu)
| zackkatz wrote:
| The article doesn't address the question of how the cup truly
| works. It relies on capillary action but, based on the article,
| I'm not sure how.
|
| https://en.m.wikipedia.org/wiki/Capillary_action
| mallomarmeasle wrote:
| They say in the article that capillary action draws the coffee
| along the narrow edge. This is aided by surface tension, just
| like how water is drawn into a capillary tube.
| keepamovin wrote:
| How gorgeous! It's hilarious how yonic it appears when looking
| down upon the brim.
|
| I think it works because the narrowing channel has increasing
| surface area to volume ratio, as you proceed toward the spout,
| so the capillary forces pull along a gradient toward the spout,
| gently tugging the liquid toward it.
|
| The bowl of the cup is lightly pinched around the brim to
| provide a kind of barrier to prevent the globule of zero-g
| liquid from just floatin' away! Hahaha :)
| sandworm101 wrote:
| Fluid flows/sticks more easily along the sharp seam than the
| rounded corners. So there is always a little bit close to that
| sharp focus point near your lips. You slurp/sip from that sharp
| point, drawing more fluid along the seam.
|
| But, for exactly the same reasons, this thing is probably a
| pain to clean. Sharp corners and cleaning don't mix. That
| narrow seam will likely become caked in the dried residue of a
| hundred previous drinks. Even in an earth dishwasher, soap scum
| would be difficult to rinse out. I suspect these are not used
| many times.
| vanderZwan wrote:
| > _That narrow seam will likely become caked in the dried
| residue of a hundred previous drinks_
|
| On the other hand, without gravity there is convection, which
| means those corners probably don't dry out as quickly. If I'm
| right about that then rinsing left-over residue out with
| plain water is easier if you don't wait too long.
| ywnico wrote:
| Corners are actually super effective at moving liquid using
| surface tension (assuming the contact angle is such that the
| surface is concave). The key is that at the front of the
| liquid, where it's very thin in the corner, the surface has a
| small radius of curvature => low pressure. If there's a lot of
| fluid filling up a corner, the radius of curvature is large =>
| high pressure. So fluid naturally flows into the corner. This
| is used a lot in space applications, e.g., for propellant
| management devices [1].
|
| The first analysis of the effect I know of is a paper by Concus
| and Finn (1969) [2], who realized that fluid can be carried
| arbitrarily high in a triangular groove, even against gravity,
| and proposed that trees may use this mechanism to carry water
| to their highest reaches. (The catch is that the fluid front
| becomes thinner and thinner as it gets higher. And it starts
| breaking down when it gets so thin that the continuum limit no
| longer applies).
|
| If you like math, I'd highly recommend checking out Mark
| Weislogel's research [3] which deals with the dynamics of
| viscous flow in triangular grooves.
|
| Shameless plug: chapter 4 of my Ph.D. thesis [4] gives an
| introduction to the subject.
|
| [1] http://www.pmdtechnology.com/PMD%20Physics.html
|
| [2] https://doi.org/10.1073/pnas.63.2.292
|
| [3] https://scholar.google.com/citations?user=rNOJ49QAAAAJ
|
| [4]
| https://theses.hal.science/view/index/identifiant/tel-040155...
| gomox wrote:
| Here's a video of the cup in action:
| https://twitter.com/ISS_Research/status/1631385518796849152
|
| Apparently the thinning spout shape sucks up the glob of liquid
| into it by way of capillary action, with the dual benefit of
| making the glob stay inside the cup despite it being open, while
| also making it available for slurping at the edge.
|
| Very cool.
| clarkdale wrote:
| This would make a great gift for a space lover!
| wmanley wrote:
| It looks like it would be a great space lover.
| pierat wrote:
| To be fair, the lip of the object looks like a vagina. There's
| probably a reason they look functionally the same.
|
| (note: im referring to the physics of said 2 objects and how they
| keep liquids in. this isnt some bad sexual joke in jest.)
| itronitron wrote:
| They could call it the Cuppa-lingus
| queuebert wrote:
| The lip looks like labia -- the vagina is on the inside. But
| this being a nerd website, I can see how you wouldn't know ...
| ;-)
| pierat wrote:
| that was a pre-coffee post. thats my only defense :/
| make3 wrote:
| this sounds like a joke of bad taste but I've seen a video of
| someone drinking from the cup in zero G and it looked so much
| like a vagina, even more with the added liquid for some reason,
| that the video looked like a parody skit
| helpfulContrib wrote:
| Stupid question: Is the math of the design of cup based on the
| math of the water? In other words, are the actual curves and
| angles of things derived from the surface tension properties of
| water in space?
|
| So, if one wanted to make a capillary cup for custard, it'd be
| different dimensions? Would love to see a parametric version of
| this (OpenSCAD?) somehow that can be generated for different
| liquids ...
| rtkwe wrote:
| It would need to be different for custard or it just may not
| work properly past a certain viscosity point where the
| resistance to flow in the matter overcomes the forces pulling
| it into the corner. Or it might just flow slowly enough it's
| not functional but still forms the same shapes eventually not
| sure. Zero-G fluid dynamics are difficult to work with
| intuitively.
| ywnico wrote:
| To expand on your point a bit, it depends on the type of
| fluid. Newtonian fluids [1] (a good approximation for water
| and many other "normal" fluids) will be pulled into the
| groove regardless of how viscous they are. E.g., the cup
| would probably work for treacle (syrup). Custard is non-
| Newtonian; more specifically, it's probably a Bingham fluid
| [2], meaning it acts like a solid until enough shear stress
| is applied, and then it acts like a liquid. The problem here
| is that even if there's enough shear stress for the custard
| far from the walls to move, the custard deep in the corner
| will likely remain a solid. So the corner capillary effect
| won't work.
|
| [1] https://en.wikipedia.org/wiki/Newtonian_fluid
|
| [2] https://en.wikipedia.org/wiki/Bingham_plastic
| DrThunder wrote:
| I'm more interested in the astronaut wearing the Starfleet Deep
| Space Nine uniform.
| NoGravitas wrote:
| That is Italian astronaut Samantha Cristoforetti. She is known
| for installing the first microgravity espresso machine, and
| brewing the first cup of espresso in space (which depended on
| the cup shown in the article). The Star Trek uniform references
| Captain Janeway's love of coffee and willingness to go to
| extreme measures to ensure its availability.
| DrThunder wrote:
| Niiiice. I forgot they had the same style uniform in Voyager
| too.
| moffkalast wrote:
| "There's coffee in that nebula"
| rtkwe wrote:
| There's some neat video of Don Pettit who did the work on the
| prototype version made out of what looks like plastic sheets and
| Kapton tape. He's very happy to go on shows and talk about it so
| there's lots of video of him explaining the principals. This [0]
| is the original NASA recording of him explaining it.
|
| [0] https://www.youtube.com/watch?app=desktop&v=pct3JhVFSLo
|
| [1] https://www.youtube.com/watch?v=ugQIivUuuXk
| vidanay wrote:
| He is the most "uncomfortable" NASA astronaut I have ever seen.
| He seems to really not want to be on camera whereas every other
| one I've ever seen is fine with it.
| rtkwe wrote:
| I'm not sure that might just be how he speaks, he seems to do
| a fair amount of non-mandatory PR engagements if he really
| didn't like doing them. I read his mood as more "excited
| energy" from an unpolished public speaker rather than
| distinctly unhappy to be performing, he came up from the
| scientist track rather than the pilot/military track for
| astronauts which can also explain it somewhat maybe.
| wyldfire wrote:
| > "We take gravity for granted," Pettit said. "Generally, we are
| unaware of the weight of our hands, or how easily we pour coffee
| into a cup. We don't stop to think, 'Will the coffee rise up and
| pour out?' or 'Can we pour the coffee?' We just do it. Gravity
| handles this for us by applying force to the coffee, pulling
| downward."
|
| Donald Pettit is tugut mang fo wa Earther. Oye, Beltalowda!
| Maxion wrote:
| Oye, we all share da inyalowda space together, sasa ke?
| qrush wrote:
| I rarely feel some RIT pride but for some reason, seeing this
| domain on HN sparks it. If you spent many a winter traversing
| windy long walks and tunnels in Rochester like I did - hoping you
| are doing well.
| c0unt wrote:
| I opened the link in the middle of class at RIT and got so
| confused why I was seeing the RIT domain. Nice to see it on
| here!
| floren wrote:
| Still fighting science with wood, buddy.
| deelowe wrote:
| This is a neat engineering achievement, but is it practical?
| What's the benefit of pouring the liquid out of a bag into this
| versus drinking out of the bag directly?
| sp332 wrote:
| You can smell your drink this way.
| hetspookjee wrote:
| Makes me wonder in how far you can actually. Wouldn't the
| smell molecules also more or less stay roughly in the same
| space without convection and gravity playing their part?
| sp332 wrote:
| They still have airflow on the space station. And since
| brownian motion does a fine job of spreading smells up
| against gravity on earth, I would guess that it works ok in
| space too.
| TeMPOraL wrote:
| On a space station this size, I'm not sure it's a feature -
| especially if it starts being used for a more varied
| selection of consumable liquids than just coffee.
|
| Speaking of, how _do_ they manage smells up there? Is "ISS
| smell management" someone's job at NASA?
| jjk166 wrote:
| What's the benefit of using a coffee mug on earth? We risk
| spilling hot coffee on ourselves and things that can stain, we
| allow heat to escape to the air, and there is potential for
| something to get into and contaminate our coffee. And yet most
| of us probably have a decent collection of coffee mugs.
| Ergonomics and aesthetics, while perhaps not the very highest
| priorities, are nevertheless important.
| deelowe wrote:
| My coffee doesn't come prepackaged ready to drink and when it
| does, I just drink it out of the bottle.
| jjk166 wrote:
| Do you make it in the mug, or do you pour it into the mug
| after you make it? Why not pour it into a thermos? And why
| don't you exclusively drink prepackaged coffee?
| deelowe wrote:
| I think you're missing a few things here.
|
| > Do you make it in the mug, or do you pour it into the
| mug after you make it?
|
| The difference is that I make it. On the space station,
| their beverages are pre-made and pre-packaged. You can
| see the bags in the linked article.
|
| > Why not pour it into a thermos?
|
| Huh? I generally drink out of a mug, not a thermos, but
| I've used thermoses as well. Again, this situation is
| different because I generally make my coffee. It's not
| pre-made and prepackaged.
|
| > And why don't you exclusively drink prepackaged coffee?
|
| Again, huh? Because the coffee I buy comes as beans. I
| have to add water, heat it up, etc. I sometimes I drink
| pre-made coldbrew and I do often drink that out of the
| package it comes in (the bottle/can).
| TeMPOraL wrote:
| s/coffee/wine/ then.
| rtkwe wrote:
| By having it open to the air you get a lot more of the aroma of
| the drink which is a bit part of how we experience taste.
| Mostly it's just a neat trick to demonstrate zero-/micro-G
| fluid handling and dynamics packed into a relatable form.
|
| Principals like this are used in fuel/liquid handling in space
| already to make sure your tanks aren't pure chaos and your
| pumps don't run dry. A lot of rockets just do ullage burns with
| different motors to settle their fuel into the bottom of tanks
| but that's not possible for all fluids if you need to have them
| moving continuously or can't do burns just to settle them.
| Waterluvian wrote:
| I'd love to read more about inventions astronauts developed as a
| side-effect of being in space. Ie. Not because it was a scheduled
| project but because they had a problem and hacked together a
| utility for the problem.
| kraig911 wrote:
| Random question. Why haven't we made a spinning space station yet
| to simulate gravity? Would fluids still work? Does the spinning
| actually work?
| asperous wrote:
| https://www.popularmechanics.com/space/rockets/a8965/why-don...
| jylam wrote:
| Not a specialist, but that:
|
| 1/ is hard to build in space (big pieces that need to be
| assembled)
|
| 2/ needs to be big enough not to make everyone sick (the
| diameter must be quite large for the gradient of gravity not to
| be too noticeable)
|
| 3/ Not very useful when one of the main points of having a
| space station is to do ~zero g experiments
| jylam wrote:
| That's very neat, but it seems that if you handle it a bit to
| harshly the liquid will come out and make a mess, unlike the bag.
| If you are careful enough I guess that's a more flavorful and
| natural way to drink tho, I like this kind of stuff <3
| TeMPOraL wrote:
| Wonder if it would make sense to add a lid to this cup, such
| that when put on, the only open part would be the drinking
| "beak".
| r3trohack3r wrote:
| Capillary Action is my favorite Wikipedia article:
| https://en.wikipedia.org/wiki/Capillary_action
|
| Leonardo da Vinci observed Capillary Action making him remark
| that the paint brush was a gift from the gods. He rightfully
| observed paint brush has an unnatural, given our understanding at
| the time, attraction for paint. If you place the brush in a cup
| of paint, and come back some time later, the brush will have
| _pulled_ the paint into itself noticeably above the surface of
| the paint in the cup.
|
| It wasn't until the early 1800s that we had the early versions of
| the Young-Laplace equation which attempted to quantitatively
| explain the phenomenon.
|
| Fast forward to 1900, Albert Einstein's first paper was still
| exploring Leonardo's paint brush:
| https://web.archive.org/web/20171025203011/http://gallica.bn...
|
| The wikipedia entry reminds me that this world is full of magic
| and wonder, everywhere you look. Something as simple as a
| paintbrush can reveal something peculiar that takes generations
| of study by the brightest of human minds to try and explain.
|
| Go outside and turn over a rock, any rock, and there is a
| lifetime of wonder and mystery under it.
|
| And, just because we can explain it now, doesn't mean Leonardo's
| paint brush isn't magic. It just means that the magic is real.
| peheje wrote:
| beautiful
| CamperBob2 wrote:
| Argues for a 'news.ycombinator.com/bestof' category.
| JanSolo wrote:
| Don Pettit is my favorite astronaut. I loved watching all his ISS
| videos where he did wacky experiments and nerded-out about
| capillary flows, static attraction and similar stuff. He's also a
| renowned photographer and has taken some of the coolest space
| pictures from the ISS. He actually refined the guidelines for
| shooting pictures thru the glass windows of the station. I hope
| that they fly him again soon; I can't wait to see what he'll come
| up with next!
| eh_why_not wrote:
| He's active as u/astro_pettit on reddit.
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