I apologize for the narration of The Mat Sci Guy. His voice certainly lacks those nice, pear-shaped tones that are so valuable on the radio - or maybe he just needs a better microphone or a decongestant or processing software.
But...his content is interesting and educational, well laid out and thoroughly researched, so I recommend watching the video but maybe not showing it in class.
Today's video sees him exploring the formation, properties, and applications of aerogels in their various forms.
I'm thrilled that I know something about sol-gel chemistry from a summer of research I did at Miami University some twenty five years ago. I wasn't making aerogels, but I did spend the summer making sol-gels and exploring their applications in chromatography columns.
I also have a little experience with aerogels...or at least I did until my favorite coworker shattered my large sample. Now I have multiple, smaller samples.
The first four minutes or so of this video are about the economics of 3d printing with metal and why it is - for now, anyway - restricted mostly to just prototyping rather than mass production.
Then there's a bit of coverage about testing 3d printed parts - particularly in fatigue strength - as compared to traditional machined parts and a bit of explanation as to why their fatigue strengths tend to be significantly lower - including a micrograph exploration of metals while they are sintered . It's surprising to me that there isn't - at least shown - an example of a sintered piece of metal being tested.
Overall, the video is a nice exploration of why mass produced engines will likely not be made by 3d printing experts in the immediate future.
That's my first takeaway from watching these videos of young people doing amazing things to better their world and decrease the pollution and waste around them.
At 3:05, the creator states that, "this is the lowest carbon footprint way of making a tile," but I'm curious about that. I've come to understand that cement is a very carbon-intensive material, requiring large amounts of carbon dioxide to be released as the calcium carbonate raw material is heated to produce the calcium oxide for the cement.
I love the grey/black/white color scheme of the tiles. I'd happily buy those tiles.
The squishy black mess looks really gross, but I'm impressed at the ingenuity of turning the coconut husk waste into a usable fuel that can replace wood.
Anything that can be done to get rid of waste in landfills is a good thing.
This is another overly long video that is filled with a massive amount of science in all sorts of disciplines: physics, material science, chemistry, engineering, mechanics.
The video sees the Real Engineering host, Brian McManus, visit SpinLaunch's centrifuge being built to launch satellites into space primarily via kinetic energy rather than through rocket fuel combustion...which sounds totally bonkers but might work out.
One of the main technologies here involves a carbon fiber-reinforced polymer tether. At 3:00 that concept is explored with a laminated carbon fiber reinforcement mock-up of the thickness that they need the tether to be to hold the millions of pounds of force that would be necessary.
Then - 8:00 - they look at the need to spin up that tether in a vacuum chamber so that it doesn't melt the carbon fiber from the friction due to air resistance. They also describe how truly low pressure vacuum chamber pumps work and why the SpinLaunch people don't need a vacuum chamber with quite that low a pressure. The idea of outgassing from the metallic parts - 10:25 - was amazing to me. It makes sense to me that there would be small amounts of oxygen gas 'dissolved' in any steel parts, but I had certainly never thought about it before. It's an equilibrium problem, I guess, as oxygen is removed from the atmosphere around the part.
At 16:20 they take a look at the challenges of opening a low pressure chamber at near vacuum to the atmospheric pressure outside without destroying the chamber inside when the air rushes in. They've used a pairing of mylar layers that are broken through and two incredibly quick closing doors.
From 21:30 they explain how they address and minimize vibrations - especially once the payload is let go, leaving a highly unbalanced weight on the arm.
The next section - from 26:45 - they look into the ballistic coefficient of the projectile and why a heavier vehicle might be better for their launch process - something that is very well against the traditional method of launch's goals. With rockets, lighter is better. With the SpinLaunch, heavier and denser is somewhat better because it allows the projectile to gain more momentum without corresponding drag and heating due to friction with the lower atmosphere.
The whole process is fascinating, and I'm hopeful that it turns out to be feasible because I would love to see a full scale SpinLaunch facility built and functioning - for the science and novelty if for nothing else.
This is NOT another post about Naica's crystal cave in Mexico. I've already posted a few of those.
This post is about the Pulpí Geode, supposedly the world's largest geode, found near the town of Pulpí, Spain.
The crystals are - like those in Naica's cave - gypsum, and they're admittedly not as large as those in Naica's cave. In the above video, they refer to the Naica crystals as being up to 15m in length and those in the Pulpí Geode as being up to 2m in length. In the video, however, they state - without much explanation - that the Pulpí Geode is a geode - a cavity in rock completely covered with crystals - and the Naica cave as not a geode.
I don't know if that means the Naica cave just has some un-covered surfaces or what, but the video above doesn't go into that detail, admittedly.
But this cave is available for people to walk through - for now, anyway - whereas Naica is flooded again. You just need to get to Pulpí.
